Science.gov

Sample records for gigantic bivalve alatoconchidae

  1. Gigantism

    MedlinePlus

    Gigantism; Pituitary giant; Overproduction of growth hormone; Growth hormone - excess production ... The most common cause of too much growth hormone release is a noncancerous (benign) tumor of the ...

  2. Protobranch bivalves.

    PubMed

    Zardus, John D

    2002-01-01

    The subclass Protobranchia comprises more than 600 species of bivalves that occur throughout the world ocean. Mostly deposit feeders in soft sediments, they are abundant in the deep sea. Apomorphies that unite them as a group include gill structure, hinge conformation, shell microstructure, larval development, foot morphology, respiratory pigments, trophic mode and digestion. They are relatively small and highly conserved in form, originating in the Cambrian era. They may represent an ancestral, derived or paraphylectic group of the Bivalvia. The protobranchs include two orders, the Nuculoida and Solemyoida, which previously were classified separately in the subclasses Paleotaxodonta and Cryptodonta, respectively. They are of ecological interest and have a unique functional morphology. They feed mostly under the surface of the sediment with highly modified labial palps, but the degree to which they are selective in diet remains difficult to determine. They are important bioturbators in many soft-sediment assemblages; their feeding and locomotion affects sediment structure and community development. Solemyoids are unusual in inhabiting reducing environments and hydrocarbon seeps and in deriving their nutrition from endosymbiotic chemosynthetic bacteria. A variety of species of protobranchs are found in oceanic trenches, near hydrothermal vents, and in submarine caves. Protobranchs produce a lecithotrophic larval stage, the pericalymma, making their development unique among bivalves. The pericalymma remains in the plankton for a short time and presumably has low dispersal ability. Recruitment may be intermittent. Growth is rapid in post-larvae but decreases with age, though rates may not necessarily be slow, especially in continental shelf species. Life spans are commonly 1 to 2 decades, but deep-sea representatives may grow more slowly and live longer. Bottom fish, seastars and gastropods are their major predators and a few parasites and commensals have been

  3. Dwarfism and gigantism in historical picture postcards.

    PubMed

    Enderle, A

    1998-05-01

    A collection of 893 historical picture postcards from 1900 to 1935, depicting dwarfs and giants, was analysed from medical and psychosocial viewpoints. In conditions such as 'bird headed dwarfism', achondroplasia, cretinism, so-called Aztecs or pinheads, Grebe chondrodysplasia, and acromegalic gigantism, the disorder could be diagnosed easily. In hypopituitary dwarfism, exact diagnosis was more difficult because of heterogeneity. The most common conditions depicted were pituitary dwarfism and achondroplasia. Most of those with gigantism had pituitary gigantism and acromegaly. Brothers and sisters or parents and their children provided evidence of mendelian inheritance of some of these disorders. The cards suggest that being put on show provided, at least in some cases, social benefits. PMID:9764085

  4. Gigantic Suprapubic Lymphedema: A Case Study

    PubMed Central

    Tanhaeivash, Roozbeh; Franiel, Tobias; Grimm, Marc-Oliver

    2016-01-01

    We present the first case study of idiopathic gigantic suprapubic lymphedema and buried penis treated with puboscrotal reconstruction in a patient with initial extreme obesity after an extensive weight reduction (120 kg). Massive localized lymphedema of the suprapubic region should be differentiated from the scrotal type. Severe lymphedema could not resolve on its own and weight reduction does not seem to be helpful in such cases. PMID:27574599

  5. Gigantic Suprapubic Lymphedema: A Case Study.

    PubMed

    Tanhaeivash, Roozbeh; Franiel, Tobias; Grimm, Marc-Oliver; Horstmann, Marcus

    2016-08-01

    We present the first case study of idiopathic gigantic suprapubic lymphedema and buried penis treated with puboscrotal reconstruction in a patient with initial extreme obesity after an extensive weight reduction (120 kg). Massive localized lymphedema of the suprapubic region should be differentiated from the scrotal type. Severe lymphedema could not resolve on its own and weight reduction does not seem to be helpful in such cases. PMID:27574599

  6. Evolution of Gigantism in Amphiumid Salamanders

    PubMed Central

    Bonett, Ronald M.; Chippindale, Paul T.; Moler, Paul E.; Van Devender, R. Wayne; Wake, David B.

    2009-01-01

    The Amphiumidae contains three species of elongate, permanently aquatic salamanders with four diminutive limbs that append one, two, or three toes. Two of the species, Amphiuma means and A. tridactylum, are among the largest salamanders in the world, reaching lengths of more than one meter, whereas the third species (A. pholeter), extinct amphiumids, and closely related salamander families are relatively small. Amphiuma means and A. tridactylum are widespread species and live in a wide range of lowland aquatic habitats on the Coastal Plain of the southeastern United States, whereas A. pholeter is restricted to very specialized organic muck habitats and is syntopic with A. means. Here we present analyses of sequences of mitochondrial and nuclear loci from across the distribution of the three taxa to assess lineage diversity, relationships, and relative timing of divergence in amphiumid salamanders. In addition we analyze the evolution of gigantism in the clade. Our analyses indicate three lineages that have diverged since the late Miocene, that correspond to the three currently recognized species, but the two gigantic species are not each other's closest relatives. Given that the most closely related salamander families and fossil amphiumids from the Upper Cretaceous and Paleocene are relatively small, our results suggest at least two extreme changes in body size within the Amphuimidae. Gigantic body size either evolved once as the ancestral condition of modern amphiumas, with a subsequent strong size reduction in A. pholeter, or gigantism independently evolved twice in the modern species, A. means and A. tridactylum. These patterns are concordant with differences in habitat breadth and range size among lineages, and have implications for reproductive isolation and diversification of amphiumid salamanders. PMID:19461997

  7. Sotos syndrome: An interesting disorder with gigantism

    PubMed Central

    Nalini, A.; Biswas, Arundhati

    2008-01-01

    We report the case of a 16-year-old boy diagnosed to have Sotos syndrome, with rare association of bilateral primary optic atrophy and epilepsy. He presented with accelerated linear growth, facial gestalt, distinctive facial features, seizures and progressive diminution of vision in both eyes. He had features of gigantism from early childhood. An MRI showed that brain and endocrine functions were normal. This case is of interest, as we have to be aware of this not so rare disorder. In addition to the classic features, there were two unusual associations with Sotos syndrome in the patient. PMID:19893668

  8. Butterflied bivalves as paleoenvironmental indicators

    SciTech Connect

    Allmon, R.A.

    1985-01-01

    Fossil bivalves are seldom preserved in a flat-open, yet still articulated position, or butterflied. A study of butterflied bivalves in the Delphi Station of the Hamilton Fm. suggests that this preservation mode is limited to one or possibly two sedimentary environments: deltaic and fluvial. Three parameters control the mode of preservation of fossil bivalves: 1) rate of sedimentation, 2) depth of bioturbation, and 3) time of ligament failure. Using these three parameters a model for the occurrence of butterflied bivalves can be constructed: bioturbation depth divided by sedimentation rate gives the disturbance time (DST), during which shells on one bedding plane would be subject to reworking. This can be seen as a time window into which ligament failure times - or disarticulation time (DAT) - can be fitted. If DATbivalves may be used as partial indicators of conditions prevailing in environments of deposition.

  9. Mechanisms of viral persistence within bivalves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fecal bacteria and waterborne enteric viruses bioconcentrate within bivalve shellfish. However while bacteria are readily purged, viruses tend to be retained within shellfish when bivalves are depurated. The US. Department of Agriculture Seafood Safety Laboratory has recently demonstrated that pha...

  10. Gigantism and Its Implications for the History of Life.

    PubMed

    Vermeij, Geerat J

    2016-01-01

    Gigantism-very large body size-is an ecologically important trait associated with competitive superiority. Although it has been studied in particular cases, the general conditions for the evolution and maintenance of gigantism remain obscure. I compiled sizes and dates for the largest species in 3 terrestrial and 7 marine trophic and habitat categories of animals from throughout the Phanerozoic. The largest species (global giants) in all categories are of post-Paleozoic age. Gigantism at this level appeared tens to hundreds of millions of years after mass extinctions and long after the origins of clades in which it evolved. Marine gigantism correlates with high planktic or seafloor productivity, but on land the correspondence between productivity and gigantism is weak at best. All global giants are aerobically active animals, not gentle giants with low metabolic demands. Oxygen concentration in the atmosphere correlates with gigantism in the Paleozoic but not thereafter, likely because of the elaboration of efficient gas-exchange systems in clades containing giants. Although temperature and habitat size are important in the evolution of very large size in some cases, the most important (and rare) enabling circumstance is a highly developed ecological infrastructure in which essential resources are abundant and effectively recycled and reused, permitting activity levels to increase and setting the stage for gigantic animals to evolve. Gigantism as a hallmark of competitive superiority appears to have lost its luster on land after the Mesozoic in favor of alternative means of achieving dominance, especially including social organization and coordinated food-gathering. PMID:26771527

  11. Analysis of lightning development associated with gigantic jets

    NASA Astrophysics Data System (ADS)

    Lu, G.; Cummer, S. A.; Lyons, W. A.; Krehbiel, P. R.; Li, J.; Beasley, W. H.; Rison, W.; Thomas, R. J.; Edens, H. E.; Stanley, M. A.; MacGorman, D. R.; Van Der Velde, O. A.; Cohen, M.; Lang, T. J.; Rutledge, S. A.

    2011-12-01

    We have examined two negative gigantic jets that occurred sufficiently near a very high-frequency (VHF) lightning mapping network that the associated lightning development is well characterized. Remote sensing of broadband (<1 Hz to 400 kHz) magnetic fields provides extra insights into the charge transfer and detailed sequence of fast discharge events associated with these gigantic jets. In both cases the jet-producing flash began with an upward negative leader that first exaggerated the charge imbalance in the upper part of the storm by dissipating upper positive cloud charge, making conditions more favorable for subsequent negative leaders to emanate from the cloud top and develop into a gigantic jet. Neither flash developed cloud-to-ground strokes, confirming the notion that the major charge transfer during gigantic jets occurred between the cloud and the ionosphere. One of these two jets yielded high-altitude VHF sources above 20 km and up to ~35 km, suggesting that VHF techniques are applicable to detect and track the lower portion of negative jet phenomena. Several gigantic jets observed near Duke University, including one appearing to be of positive polarity, are examined to see if the underlying lightning-gigantic jet correlation as inferred from remote magnetic fields generally fits the picture described above.

  12. Gigantism and Its Implications for the History of Life

    PubMed Central

    Vermeij, Geerat J.

    2016-01-01

    Gigantism—very large body size—is an ecologically important trait associated with competitive superiority. Although it has been studied in particular cases, the general conditions for the evolution and maintenance of gigantism remain obscure. I compiled sizes and dates for the largest species in 3 terrestrial and 7 marine trophic and habitat categories of animals from throughout the Phanerozoic. The largest species (global giants) in all categories are of post-Paleozoic age. Gigantism at this level appeared tens to hundreds of millions of years after mass extinctions and long after the origins of clades in which it evolved. Marine gigantism correlates with high planktic or seafloor productivity, but on land the correspondence between productivity and gigantism is weak at best. All global giants are aerobically active animals, not gentle giants with low metabolic demands. Oxygen concentration in the atmosphere correlates with gigantism in the Paleozoic but not thereafter, likely because of the elaboration of efficient gas-exchange systems in clades containing giants. Although temperature and habitat size are important in the evolution of very large size in some cases, the most important (and rare) enabling circumstance is a highly developed ecological infrastructure in which essential resources are abundant and effectively recycled and reused, permitting activity levels to increase and setting the stage for gigantic animals to evolve. Gigantism as a hallmark of competitive superiority appears to have lost its luster on land after the Mesozoic in favor of alternative means of achieving dominance, especially including social organization and coordinated food-gathering. PMID:26771527

  13. Toxic responses of bivalves to metal mixtures

    SciTech Connect

    Mathew, P.; Menon, N.R. )

    1992-02-01

    Although there is a growing body of information on the toxicity of individual heavy metals to economically important on the toxicity of individual heavy metals to economically important species of bivalves, literature on the lethal toxicity of metal mixtures to bivalves under controlled conditions is rather limited. In the present investigation the toxic effects of combinations of copper - mercury and copper - mercury and copper - cadmium at lethal levels of two marine bivalve species, Perna indica and Donax incarnatus, have been delineated.

  14. Ependimoma myxopapilar sacro gigante con osteolisis

    PubMed Central

    Ajler, Pablo; Landriel, Federico; Goldschmidt, Ezequiel; Campero, Álvaro; Yampolsky, Claudio

    2014-01-01

    Objetivo: la presentación de un caso de una paciente con un ependimoma sacro con extensa infiltración y destrucción ósea local. Descripción del caso: una mujer de 53 años acudió a la consulta por dolor lumbosacro y alteraciones sensitivas perineales y esfinterianas. La imágenes por Resonancia Magnética (IRM) y la Tomografía Axial Computada (TAC) mostraron una lesión expansiva gigante a nivel S2-S4 con extensa osteólisis e invasión de tejidos adyacentes. Se realizó una exéresis tumoral completa con mejoría del estatus funcional. La anatomía patológica informó ependimoma mixopapilar. Discusión: la extensión de la resección quirúrgica es el mejor predictor de buen pronóstico. El tratamiento radiante se reserva como opción adyuvante para las resecciones incompletas y recidiva tumoral. La quimioterapia sólo debería utilizarse en casos en que la cirugía y la radioterapia estén contraindicadas. Conclusión: Los ependimomas mixopapilares sacros con destrucción ósea y presentación intra y extradural son muy infrecuentes y deben ser tenidos en cuenta entre los diagnósticos diferenciales preoperatorios. Su resección total, siempre que sea posible, es la mejor alternativa terapéutica. PMID:25165615

  15. Macrodystrophia Lipomatosa: An Unusual Cause of Localized Gigantism

    PubMed Central

    Maheswari, S Uma; Sampath, V; Ramesh, A; Manoharan, K

    2016-01-01

    Macrodystrophia lipomatosa (MDL) is a rare congenital form of localized gigantism characterized by progressive overgrowth of all mesenchymal elements with a disproportionate increase in fibro adipose tissue. Here we report a case of 20 years old male who presented with history of painless gradual enlargement of entire left upper limb since childhood. Magnetic resonance imaging and histopathology confirmed the diagnosis of macrodystrophia lipomatosa. This condition has to be differentiated from other causes of localized gigantism, since these conditions differ in their course, prognosis, complications and treatment. PMID:27293271

  16. Neoplastic diseases of marine bivalves.

    PubMed

    Carballal, María J; Barber, Bruce J; Iglesias, David; Villalba, Antonio

    2015-10-01

    Two types of prevalent neoplastic diseases have been described in marine bivalves of commercial interest: disseminated neoplasia (DN) and gonadal neoplasia. The first involves the excessive proliferation of abnormal cells with unknown origin (probably of hemic source in some cases/species), disseminating through the circulatory system and infiltrating the connective tissue of various organs; the second consists of an abnormal proliferation of undifferentiated germinal cells of the gonad. These two types of bivalve neoplasia fit the criteria of malignant tumors: pleomorphic and undifferentiated cells, rapid and invasive growth, abundance of mitotic figures, metastasis and progressive development often resulting in the death of the affected individual. Different causes have been suggested regarding etiology: genetic alterations, virus, retrotranspons, and contaminants, although it could depend on the mollusk species; evidence of horizontal transmission of clonal cancer cells as the cause of DN spreading in clam Mya arenaria populations has been recently reported. In some species and populations, the neoplastic disorders affect only a few individuals, but in others reach high prevalence. Among the diagnostic methods, DN has been detected by histology and cytologic examination of hemolymph, and with developed specific antibodies. Recently, flow cytometry has also been applied, allowing detecting DNA quantity alteration. Several studies reported many genes and pathways critically involved in neoplastic transformation in Mya arenaria, Mytilus spp. and Ostrea edulis. These genetic studies will allow the development of diagnosis by PCR which can be used in biomonitoring studies. PMID:26146225

  17. First observations of Gigantic Jets from Monsoon Thunderstorms over India

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Maurya, Ajeet; Chanrion, Olivier; Neubert, Torsten; Cummer, Steven; Mlynarczyk, Janusz; Bór, József; Siingh, Devendraa; Cohen, Morris; Kumar, Sushil

    2016-04-01

    Gigantic Jets are electric discharges from thunderstorm cloud tops to the bottom of the ionosphere at ~80 km altitude. After their first discovery in 2001, relatively few observations have been reported. Most of these are from satellites at large distances and a few tens from the ground at higher spatial resolution. Here we report the first Gigantic Jets observed in India from two thunderstorm systems that developed over the land surface from monsoon activity, each storm producing two Gigantic Jets. The jets were recorded by a video camera system at standard video rate (20 ms exposure) at a few hundred km distance. ELF measurements suggest that the jets are of the usual negative polarity and that they develop in less than 40 ms, which is faster than most jets reported in the past. The jets originate from the leading edge of a slowly drifting convective cloud complex close to the highest regions of the clouds and carry ~25 Coulomb of charge to the ionosphere. One jet has a markedly horizontal displacement that we suggest is caused by a combination of close-range cloud electric fields at inception, and longer-range cloud fields at larger distances during full development. The Gigantic Jets are amongst the few that have been observed over land.

  18. Twin Explosions In Gigantic Dusty Potato Crisp

    NASA Astrophysics Data System (ADS)

    2006-05-01

    ESO's Very Large Telescope, equipped with the multi-mode FORS instrument, took an image of NGC 3190, a galaxy so distorted that astronomers gave it two names. And as if to prove them right, in 2002 it fired off, almost simultaneously, two stellar explosions, a very rare event. This beautiful edge-on spiral galaxy with tightly wound arms and a warped shape that makes it resemble a gigantic potato crisp lies in the constellation Leo ('the Lion') [1] and is approximately 70 million light years away. It is the dominant member of a small group of galaxies known as Hickson 44, named after the Canadian astronomer, Paul Hickson. In addition to NGC 3190 [2], Hickson 44 consists of one elliptical and two spiral galaxies. These are, however, slightly out of the field of view and therefore not visible here. ESO PR Photo 17/06 ESO PR Photo 17/06 The Spiral Galaxy NGC 3190 In 1982, Hickson published a catalogue of over 400 galaxies found in compact, physically-related groups of typically 4 to 5 galaxies per group (see the image of Robert's Quartet in ESO PR Photo 34/05 as another example). Such compact groups allow astronomers to study how galaxies dynamically affect each other, and help them test current ideas on how galaxies form. One idea is that compact groups of galaxies, such as Hickson 44, merge to form a giant elliptical galaxy, such as NGC 1316 (see ESO PR 17/00). Indeed, signs of tidal interactions are visible in the twisted dust lane of NGC 3190. This distortion initially misled astronomers into assigning a separate name for the southwestern side, NGC 3189, although NGC 3190 is the favoured designation. NGC 3190 has an 'Active Galactic Nucleus', and as such, the bright, compact nucleus is thought to host a supermassive black hole. In March 2002, a new supernova (SN 2002bo) was found in between the 'V' of the dust lanes in the southeastern part of NGC 3190. It was discovered independently by the Brazilian and Japanese amateur astronomers, Paulo Cacella and Yoji Hirose

  19. A Study in Bivalve Aging and Growth.

    ERIC Educational Resources Information Center

    Schlenker, Karl R.; Schlenker, Richard M.

    1998-01-01

    Describes how high school biology students use the clam to study the bivalve body plan anatomy. Employs an open-ended investigation format that is rich with measurement opportunities including body mass, valve mass, and volume. (DDR)

  20. Rostroconchia: A new class of bivalved mollusks

    USGS Publications Warehouse

    Pojeta, J., Jr.; Runnegar, B.; Morris, N.J.; Newell, N.D.

    1972-01-01

    Four Paleozoic bivalved genera are assigned to the new molluscan class Rostroconchia: Eopteria, Euchasma, Conocardium, and Pseudoconocardium. These mollusks have an uncoiled univalved larval shell; an untorted bivalved adult shell; no hinge teeth, ligament, or adductor muscles; and a fused, almost inflexible, hinge. Rostroconchians developed separately from the pelecypods through the ribeirioids, but are regarded as more closely related to the Pelecypoda and Scaphopoda than to other known classes of molllusks.

  1. Hereditary Gigantism-the biblical giant Goliath and his brothers.

    PubMed

    Donnelly, Deirdre E; Morrison, Patrick J

    2014-05-01

    The biblical giant Goliath has an identifiable family tree suggestive of autosomal dominant inheritance. We suggest that he had a hereditary pituitary disorder possibly due to the AIP gene, causing early onset and familial acromegaly or gigantism. We comment on the evidence within the scriptures for his other relatives including a relative with six digits and speculate on possible causes of the six digits. Recognition of a hereditary pituitary disorder in the biblical Goliath and his family sheds additional information on his and other family members' battles with David and his relatives. PMID:25075136

  2. Proteus syndrome: A rare cause of gigantic limb

    PubMed Central

    Chakrabarti, Nandini; Chattopadhyay, Chandan; Bhuban, Majhi; Pal, Salil Kumar

    2014-01-01

    A congenital disorder with variable manifestations, including partial gigantism of the hands and feet with hypertrophy of soles, nevi, hemihypertrophy, gynecomastia, macrocephaly and other skull abnormalities, and abdominal lipomatosis. The cause is unknown, although a genetic origin, generally of autosomal-dominant transmission, has been conjectured. Symptoms can be treated, but there is no known cure. We present the case of a young male with grotesque overgrowth of the right lower limb, splenomegaly and multiple nevi. Angiography revealed venous malformation within the limb. The findings are in conformity to the criteria for the Proteus syndrome. PMID:24860761

  3. Microplastics in commercial bivalves from China.

    PubMed

    Li, Jiana; Yang, Dongqi; Li, Lan; Jabeen, Khalida; Shi, Huahong

    2015-12-01

    We investigated microplastic pollution in 9 commercial bivalves from a fishery market in China. Multiple types of microplastics, including fibers, fragments and pellets, occurred in the tissue of all bivalves. The number of total microplastics varied from 2.1 to 10.5 items/g and from 4.3 to 57.2 items/individual for bivalves. Scapharca subcrenata contained on average 10.5 items/g and exhibited the highest levels of microplastics by weight. Fibers were the most common microplastics and consisted of more than half of the total microplastics in each of the 8 species. In Alectryonella plicatula, pellets accounted for 60% of the total microplastics. The most common size class was less than 250 μm and accounted for 33-84% of the total microplastics calculated by species. Our results suggest that microplastic pollution was widespread and exhibited a relatively high level in commercial bivalves from China. More intensive investigations on microplastics should be conducted in seafood. PMID:26386204

  4. A study of model bivalve siphonal currents

    USGS Publications Warehouse

    Monismith, Stephen G.; Koseff, Jeffrey R.; Thompson, Janet K.; O'Riordan, Catherine A.; Nepf, Heidi M.

    1990-01-01

    We carried out experiments studying the hydrodynamics of bivalve siphonal currents in a laboratory flume. Rather than use living animals, we devised a simple, model siphon pair connected to a pump. Fluorescence-based flow visualization was used to characterize siphon-jet flows for several geometric configurations and flow speeds. These measurements show that the boundary-layer velocity profile, siphon height, siphon pair orientation, and size of siphon structure all affect the vertical distribution of the excurrent flow downstream of the siphon pair and the fraction of excurrent that is refiltered. The observed flows may effect both the clearance rate of an entire population of siphonate bivalves as well as the efficiency of feeding of any individual. Our results imply that field conditions are properly represented in laboratory flume studies of phytoplankton biomass losses to benthic bivalves when the shear velocity and bottom roughness are matched to values found in the field. Numerical models of feeding by a bivalve population should include an effective sink distribution which is created by the combined incurrent-excurrent flow field. Near-bed flows need to be accounted for to properly represent these benthic-pelagic exchanges. We also present velocity measurements made with a laser-Doppler anemometer (LDA) for a single configuration (siphons flush with bed, inlet downstream) that show that the siphonal currents have a significant local effect on the properties of a turbulent boundary layer.

  5. Gigantic jets between a thundercloud and the ionosphere.

    PubMed

    Su, H T; Hsu, R R; Chen, A B; Wang, Y C; Hsiao, W S; Lai, W C; Lee, L C; Sato, M; Fukunishi, H

    2003-06-26

    Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites. PMID:12827198

  6. Bivalve grazing can shape phytoplankton communities

    USGS Publications Warehouse

    Lucas, Lisa; Cloern, James E.; Thompson, Janet K.; Stacey, Mark T.; Koseff, Jeffrey K.

    2016-01-01

    The ability of bivalve filter feeders to limit phytoplankton biomass in shallow waters is well-documented, but the role of bivalves in shaping phytoplankton communities is not. The coupled effect of bivalve grazing at the sediment-water interface and sinking of phytoplankton cells to that bottom filtration zone could influence the relative biomass of sinking (diatoms) and non-sinking phytoplankton. Simulations with a pseudo-2D numerical model showed that benthic filter feeding can interact with sinking to alter diatom:non-diatom ratios. Cases with the smallest proportion of diatom biomass were those with the fastest sinking speeds and strongest bivalve grazing rates. Hydrodynamics modulated the coupled sinking-grazing influence on phytoplankton communities. For example, in simulations with persistent stratification, the non-sinking forms accumulated in the surface layer away from bottom grazers while the sinking forms dropped out of the surface layer toward bottom grazers. Tidal-scale stratification also influenced vertical gradients of the two groups in opposite ways. The model was applied to Suisun Bay, a low-salinity habitat of the San Francisco Bay system that was transformed by the introduction of the exotic clam Potamocorbula amurensis. Simulation results for this Bay were similar to (but more muted than) those for generic habitats, indicating that P. amurensis grazing could have caused a disproportionate loss of diatoms after its introduction. Our model simulations suggest bivalve grazing affects both phytoplankton biomass and community composition in shallow waters. We view these results as hypotheses to be tested with experiments and more complex modeling approaches.

  7. Gigantic enhancement of spin Seebeck effect by phonon drag

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroto; Uchida, Ken-Ichi; Saitoh, Eiji; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

    2011-03-01

    We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect [K. Uchida et al., Nature 455, 778 (2008); C. M. Jaworski et al., Nature Mater. 9, 898 (2010); K. Uchida et al., Nature Mater. 9, 894 (2010)] in a prototypical magnet La Y2 Fe 5 O12 at low temperatures. Our theoretical analysis sheds light on the important role of phonons; the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag the low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.

  8. Methodology of growing gigantic sapphire for GSLW project

    NASA Astrophysics Data System (ADS)

    Abgaryan, Artoush A.; Hartounian, Gomidas

    2005-09-01

    In our present world the Crystal Growth Technology does not have the necessary and sufficient conditions to manufacture large sizes; especially in the Sapphire Crystal world. We have a theoretical and methodological development for growing gigantic Sapphire Crystal Lenses. Our gigantic Sapphire Crystal Lenses have a unique optical characteristic which will be used in the Global System of Laser Weapons (GSLW); hence solving one of the crucial problems in the Relay Mirror System; where it captures the Laser beam from the earth surface, cleaning the beam in the Satellite and redirecting the laser energy to the precise desired target. Developed and solution for the temperature and heat-elasticity fields in growth systems are considered theoretical, in order to assess their effects on the optical symmetry of the growing crystal. The process is modeled using three-dimensional curvilinear coordinates to describe a closed, low-strain heat-elasticity system, with allowance made for the temperature variations of the thermal properties of the multilayer growth system, and nonlinear and unsteady-state process with arbitrary boundary conditions. The results presented as plots of the strain, stress, displacement, and temperature fields; demonstrate the potential of the method for designing new growth units and improving the existing ones and suggesting that crystals, in general, without frustration of optical symmetry can, in principle, be grown. In order to solve generalized problem for large optics. It is required to have super and correct mathematical computing calculations, and using basic fundamental laws of nature regarding optical symmetry in the crystal, and discovering the radical "new wave method" for crystal growth technology.

  9. Fabricational morphology of oblique ribs in bivalves.

    PubMed

    Checa, Antonio G

    2002-11-01

    The formation of oblique ribs of bivalve shells usually has been attributed to processes of reaction-diffusion of morphogens from cell to cell at the mantle margin or neural activation and lateral inhibition in the mantle. In particular, such ribs appear with high rates of lateral diffusion. Nevertheless, theoretical models fail to explain either partially or wholly some varieties of oblique ribs. After surveying the modes of formation of the shell and oblique ribs by the bivalve mantle and associated fabricational defects, I have determined that the mantle is able to develop an elaborate behavior in order to displace the rib in a particular direction during growth. The mantle margin is, therefore, not only the shell-secreting organ, but also the main morphogenetic unit. In particular, there are two main fabricational strategies. In forms with strict contact guidance (SCG) the mantle is able to project far enough beyond the shell margins so as to feel the already formed reliefs and to align new growth increments of the ribs in the appropriate directions. The shell margin is always strongly reflected. In bivalves with reduced contact guidance plus constant lateral shift (RCG), the margin is usually acute and the information about ribs available to the mantle is reduced. During rib construction the mantle extrudes slightly from the shell edge and then pushes laterally by muscular action; in this way, the new growth increment of the rib is displaced laterally on a small scale. The contact-guidance model is supported also by the homogeneous structure of the shell-secreting mantle. From the morphogenetic standpoint, oblique ribs are related to commarginal ones and both differ completely from other ribbing patterns of bivalves. PMID:12353301

  10. In-situ bioassays using caged bivalves

    SciTech Connect

    Salazar, M.H.; Salazar, S.M.

    1995-12-31

    It is important to make the distinction between chemical measurements to assess bioaccumulation potential versus biological measurements to assess potential bioeffects because bioaccumulation is not a bioeffect. Caging provides a unique opportunity to make synoptic measurements of each and facilitates making these measurements over space and time. Measuring bioaccumulation in resident and transplanted bivalves has probably been the most frequently used form of an in-situ bioassay because bivalves concentrate chemicals in their tissues. They are also easy to collect, cage, and measure. The authors have refined bivalve bioassay methods by minimizing the size range of test animals, making repetitive measurements of the same individuals, and standardizing test protocols for a variety of applications. They are now attempting to standardize criteria for accepting and interpreting data in the same way that laboratory bioassays have been standardized. Growth measurements can serve two purposes in this assessment strategy: (1) An integrated biological response endpoint that is easily quantifiable and with significance to the population, and (2) A means of calibrating bioaccumulation by assessing the relative health and physiological state of tissues that have accumulated the chemicals. In general, the authors have found the highest bioconcentration factors associated with the highest growth rates, the highest concentrations ({micro}g/g) of chemicals in juvenile mussels, and the highest chemical content ({micro}g/animal) in adult mussels. Without accounting for possible dilution of chemical concentrations by tissue growth or magnification through degrowth, contaminant concentrations can be misleading. Examples are provided for the Sudbury River in Massachusetts (Elliptio complanata), San Diego Bay (Mytilus galloprovincialis), and the Harbor Island Superfund Site in Puget Sound (Mytilus trossulus).

  11. Atmospheric oxygen and the evolution of insect gigantism

    NASA Astrophysics Data System (ADS)

    Dudley, R.

    2003-04-01

    Geophysical analyses suggest the presence of a late Paleozoic oxygen pulse beginning in the late Devonian and continuing through to the late Carboniferous. During this time, atmospheric oxygen levels increased to values potentially as high as 35% relative to the contemporary value of 21%. Widespread gigantism in late Paleozoic insects and other arthropods is consistent with enhanced oxygen flux within diffusion-limited tracheal systems, and thus with relaxation of constraints on maximum insect body size. Because total atmospheric pressure increases with increased oxygen partial pressure, concurrently hyperdense conditions would have augmented aerodynamic force production in early forms of flying insects. Hyperoxia of the late Paleozoic atmosphere may also have physiologically facilitated the initial evolution of insect flight metabolism. By the late Permian, evolution of decompositional microbial and fungal communities together with disequilibrium in rates of carbon deposition gradually reduced oxygen concentrations to values possibly as low as 15%. The disappearance of giant insects by the end of the Permian is consistent with extinction of these taxa for reasons of asphyxiation on a geological time scale. In modern selection experiments with Drosophila flies, substantial plasticity in body size can be evoked under conditions of variable oxygen. In particular, moderate hyperbaria (and thus hyperoxia) evokes a 20% increase in adult body size over merely five generations, suggesting ready capacity for evolutionary responses by insects to fluctuating atmospheric oxygen.

  12. LTR Retrotransposons Contribute to Genomic Gigantism in Plethodontid Salamanders

    PubMed Central

    Sun, Cheng; Shepard, Donald B.; Chong, Rebecca A.; López Arriaza, José; Hall, Kathryn; Castoe, Todd A.; Feschotte, Cédric; Pollock, David D.; Mueller, Rachel Lockridge

    2012-01-01

    Among vertebrates, most of the largest genomes are found within the salamanders, a clade of amphibians that includes 613 species. Salamander genome sizes range from ∼14 to ∼120 Gb. Because genome size is correlated with nucleus and cell sizes, as well as other traits, morphological evolution in salamanders has been profoundly affected by genomic gigantism. However, the molecular mechanisms driving genomic expansion in this clade remain largely unknown. Here, we present the first comparative analysis of transposable element (TE) content in salamanders. Using high-throughput sequencing, we generated genomic shotgun data for six species from the Plethodontidae, the largest family of salamanders. We then developed a pipeline to mine TE sequences from shotgun data in taxa with limited genomic resources, such as salamanders. Our summaries of overall TE abundance and diversity for each species demonstrate that TEs make up a substantial portion of salamander genomes, and that all of the major known types of TEs are represented in salamanders. The most abundant TE superfamilies found in the genomes of our six focal species are similar, despite substantial variation in genome size. However, our results demonstrate a major difference between salamanders and other vertebrates: salamander genomes contain much larger amounts of long terminal repeat (LTR) retrotransposons, primarily Ty3/gypsy elements. Thus, the extreme increase in genome size that occurred in salamanders was likely accompanied by a shift in TE landscape. These results suggest that increased proliferation of LTR retrotransposons was a major molecular mechanism contributing to genomic expansion in salamanders. PMID:22200636

  13. Gigantic surface lifetime of an intrinsic topological insulator.

    PubMed

    Neupane, Madhab; Xu, Su-Yang; Ishida, Yukiaki; Jia, Shuang; Fregoso, Benjamin M; Liu, Chang; Belopolski, Ilya; Bian, Guang; Alidoust, Nasser; Durakiewicz, Tomasz; Galitski, Victor; Shin, Shik; Cava, Robert J; Hasan, M Zahid

    2015-09-11

    The interaction between light and novel two-dimensional electronic states holds promise to realize new fundamental physics and optical devices. Here, we use pump-probe photoemission spectroscopy to study the optically excited Dirac surface states in the bulk-insulating topological insulator Bi_{2}Te_{2}Se and reveal optical properties that are in sharp contrast to those of bulk-metallic topological insulators. We observe a gigantic optical lifetime exceeding 4  μs (1  μs=10^{-6}  s) for the surface states in Bi_{2}Te_{2}Se, whereas the lifetime in most topological insulators, such as Bi_{2}Se_{3}, has been limited to a few picoseconds (1  ps=10^{-12}  s). Moreover, we discover a surface photovoltage, a shift of the chemical potential of the Dirac surface states, as large as 100 mV. Our results demonstrate a rare platform to study charge excitation and relaxation in energy and momentum space in a two-dimensional system. PMID:26406846

  14. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs.

    PubMed

    Erickson, Gregory M; Makovicky, Peter J; Currie, Philip J; Norell, Mark A; Yerby, Scott A; Brochu, Christopher A

    2004-08-12

    How evolutionary changes in body size are brought about by variance in developmental timing and/or growth rates (also known as heterochrony) is a topic of considerable interest in evolutionary biology. In particular, extreme size change leading to gigantism occurred within the dinosaurs on multiple occasions. Whether this change was brought about by accelerated growth, delayed maturity or a combination of both processes is unknown. A better understanding of relationships between non-avian dinosaur groups and the newfound capacity to reconstruct their growth curves make it possible to address these questions quantitatively. Here we study growth patterns within the Tyrannosauridae, the best known group of large carnivorous dinosaurs, and determine the developmental means by which Tyrannosaurus rex, weighing 5,000 kg and more, grew to be one of the most enormous terrestrial carnivorous animals ever. T. rex had a maximal growth rate of 2.1 kg d(-1), reached skeletal maturity in two decades and lived for up to 28 years. T. rex's great stature was primarily attained by accelerating growth rates beyond that of its closest relatives. PMID:15306807

  15. Cambrian bivalved arthropod reveals origin of arthrodization

    PubMed Central

    Legg, David A.; Sutton, Mark D.; Edgecombe, Gregory D.; Caron, Jean-Bernard

    2012-01-01

    Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans (‘great-appendage’ arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids). PMID:23055069

  16. Cambrian bivalved arthropod reveals origin of arthrodization.

    PubMed

    Legg, David A; Sutton, Mark D; Edgecombe, Gregory D; Caron, Jean-Bernard

    2012-12-01

    Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans ('great-appendage' arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids). PMID:23055069

  17. Nanostructure and composition of bivalve shells

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Soldati, A. L.; Wirth, R.; Huth, J.; Wehrmeister, U.; Hofmeister, W.

    2009-04-01

    Shells and pearls of unionid mussels (Hyriopsis cumingii, Margaritifera margaritifera, Diplodon chilensis patagonicus) were studied by high resolution microbeam methods and -computer tomography to gather insight into the nanostructure and chemical composition of nacre and prism layers. Natural and cultured pearls are formed by many mollusc species and their generation is very similar to that of shells resulting in identical prismatic and nacreous structures of shells and pearls. Basic difference is, however that pearl culturing methods induce biomineralisation of CaCO3 around a crystalline bead which results in a reverse structural organisation compared to bivalve shells. Bivalve shell growth starts from a thick organic matrix (the periostracum; Eyster and Morse, 1984) which is followed towards the inside by two variously thick layers consisting of prismatic CaCO3 aggregations and layers of CaCO3 platelets, respectively. Platelets and prisms are individually covered by a chitinous organic matrix which lends structural support and is thought to exert control over the mineralization process. The minerals within the organic sheaths are highly-aligned poly-twinned crystals with a slightly distorted lattice due to inclusions of organic molecules (Pokroy et al., 2006). Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Raman Microscopy analyses of the shells and pearls show that both structures, prisms and platelets, consist of nanometre-sized organic membrane-coated granules of CaCO3 (Jacob et al., 2008). In the vicinity of the periostracum, the granules consist of amorphous calcium carbonate (ACC), but the crystallinity increases with increasing distance from the periostracum. The transition from disordered (amorphous) to crystalline CaCO3 is gradual within a few micrometers and coincides with a decrease in porosity. Concentrations of sulphur and phosphorus are higher in ACC than in aragonite indicating a

  18. Biology of the sauropod dinosaurs: the evolution of gigantism

    PubMed Central

    Sander, P Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jürgen; Mallison, Heinrich; Perry, Steven F; Preuschoft, Holger; Rauhut, Oliver W M; Remes, Kristian; Tütken, Thomas; Wings, Oliver; Witzel, Ulrich

    2011-01-01

    The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability. There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism. We review the biology of sauropod dinosaurs in detail and posit that sauropod gigantism was made possible by a specific combination of plesiomorphic characters (phylogenetic heritage) and evolutionary innovations at different levels which triggered a remarkable evolutionary cascade. Of these key innovations, the most important probably was the very long neck, the most conspicuous feature of the sauropod bauplan. Compared to other herbivores, the long neck allowed more efficient food uptake than in other large herbivores by covering a much larger feeding envelope and making food accessible that was out of the reach of other herbivores. Sauropods thus must have been able to take up more energy from their environment than other herbivores. The long neck, in turn, could only evolve because of the small head and the extensive pneumatization of the sauropod axial skeleton, lightening the neck. The small head was possible because food was ingested without mastication. Both mastication and a gastric mill would have limited food uptake rate. Scaling relationships between gastrointestinal tract size and basal metabolic rate (BMR) suggest that sauropods compensated for the lack of particle reduction with long retention times, even at high uptake rates. The

  19. Genomic gigantism: DNA loss is slow in mountain grasshoppers.

    PubMed

    Bensasson, D; Petrov, D A; Zhang, D X; Hartl, D L; Hewitt, G M

    2001-02-01

    Several studies have shown DNA loss to be inversely correlated with genome size in animals. These studies include a comparison between Drosophila and the cricket, Laupala, but there has been no assessment of DNA loss in insects with very large genomes. Podisma pedestris, the brown mountain grasshopper, has a genome over 100 times as large as that of Drosophila and 10 times as large as that of Laupala. We used 58 paralogous nuclear pseudogenes of mitochondrial origin to study the characteristics of insertion, deletion, and point substitution in P. pedestris and Italopodisma. In animals, these pseudogenes are "dead on arrival"; they are abundant in many different eukaryotes, and their mitochondrial origin simplifies the identification of point substitutions accumulated in nuclear pseudogene lineages. There appears to be a mononucleotide repeat within the 643-bp pseudogene sequence studied that acts as a strong hot spot for insertions or deletions (indels). Because the data for other insect species did not contain such an unusual region, hot spots were excluded from species comparisons. The rate of DNA loss relative to point substitution appears to be considerably and significantly lower in the grasshoppers studied than in Drosophila or Laupala. This suggests that the inverse correlation between genome size and the rate of DNA loss can be extended to comparisons between insects with large or gigantic genomes (i.e., Laupala and Podisma). The low rate of DNA loss implies that in grasshoppers, the accumulation of point mutations is a more potent force for obscuring ancient pseudogenes than their loss through indel accumulation, whereas the reverse is true for Drosophila. The main factor contributing to the difference in the rates of DNA loss estimated for grasshoppers, crickets, and Drosophila appears to be deletion size. Large deletions are relatively rare in Podisma and Italopodisma. PMID:11158383

  20. Hemocyanin respiratory pigment in bivalve mollusks

    SciTech Connect

    Morse, M.P.; Meyhoefer, E.; Otto, J.J.; Kuzirian, A.M.

    1986-03-14

    Hemocyanins, high molecular weight oxygen-binding proteins, were identified in two species of protobranch bivalve mollusks, Acila castrensis and Yoldia limatula. Although hemocyanins have been reported in chitons, gastropods, and cephalopods, they have not been observed in the Class Bivalvia. In A. castrensis the dissociation products of hemocyanin, characterized by gel electrophoresis, had a subunit molecular weight of approximately 250K. Negatively stained preparations of extracted hemocyanin formed protein aggregates in the shape of cylinders measuring 35 by 38 nanometers. X-ray microanalysis of hemocyanin aggregates in thin sections of Y. limatula demonstrated the presence of copper in the molecules. The discovery of hemocyanin in the protobranchs reinforces the primitive nature of the taxon and is further evidence that the major molluscan classes have a common ancestry. 14 references, 3 figures.

  1. Evidence for variable crystallinity in bivalve shells

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Wehrmeister, U.

    2012-04-01

    Bivalve shells are used as important palaeoclimate proxy archives and monitor regional climate variations. The shells mostly exist of two crystalline polymorphic phases of calcium carbonate calcite (rombohedric) and aragonite (orthorhombic). Calcite is the most stable polymorph at standard conditions, whereas vaterite (hexagonal) is the least stable and only rarely found in these structures. Shells are characterized by organized structures and several micro architectures of mollusc shell structures have been identified: Nacre shows different types: columnar and bricked forms and consists of composite inorganic- organic at the nano-scale. They are well known to display a "brick and mortar" structure. By AFM and FIB/TEM methods it could be shown, that its nanostructure consists of the structures in the range of 50 - 100 nm [1, 2]. These structures are vesicles, consisting of CaCO3 and are individually coated by a membrane. Most probably, the mantle epithelian cells of the bivalve extrude CaCO3 vesicles. By Raman spectroscopic investigations the crystalline CaCO3 polymorphs calcite, aragonite and vaterite, as well as ACC were determined. For some species (Diplodon chilensis patagonicus, Hyriopsis cumingii) pure ACC (i.e. not intermingled with a crystalline phase) could be identified. The presence of an amorphous phase is generally deduced from the lack of definite lattice modes, whereas a broad Raman band in this region is to observe. In most of the cultured pearls (Pinctada maxima and genus Hyriopsis) the ν1-Raman band of ACC clearly displays an asymmetric shape and splits into two different bands according to a nanocrystalline and an amorphous fraction. The FWHMs of most of the crystalline fractions are too high for well crystallized materials and support the assumption of nanocrystalline calcium carbonate polymorph clusters in ACC. They are primarily composed of amorphous calcium carbonate (ACC) which is later transformed into a crystalline modification [3

  2. Dynamics of sheet nacre formation in bivalves.

    PubMed

    Rousseau, Marthe; Meibom, Anders; Gèze, Marc; Bourrat, Xavier; Angellier, Martine; Lopez, Evelyne

    2009-03-01

    Formation of nacre (mother-of-pearl) is a biomineralization process of fundamental scientific as well as industrial importance. However, the dynamics of the formation process is still not understood. Here, we use scanning electron microscopy and high spatial resolution ion microprobe depth-profiling to image the full three-dimensional distribution of organic materials around individual tablets in the top-most layer of forming nacre in bivalves. Nacre formation proceeds by lateral, symmetric growth of individual tablets mediated by a growth-ring rich in organics, in which aragonite crystallizes from amorphous precursors. The pivotal role in nacre formation played by the growth-ring structure documented in this study adds further complexity to a highly dynamical biomineralization process. PMID:19121399

  3. Gigantism and Acromegaly Due to Xq26 Microduplications and GPR101 Mutation

    PubMed Central

    Trivellin, G.; Daly, A.F.; Faucz, F.R.; Yuan, B.; Rostomyan, L.; Larco, D.O.; Schernthaner-Reiter, M.H.; Szarek, E.; Leal, L.F.; Caberg, J.-H.; Castermans, E.; Villa, C.; Dimopoulos, A.; Chittiboina, P.; Xekouki, P.; Shah, N.; Metzger, D.; Lysy, P.A.; Ferrante, E.; Strebkova, N.; Mazerkina, N.; Zatelli, M.C.; Lodish, M.; Horvath, A.; de Alexandre, R. Bertollo; Manning, A.D.; Levy, I.; Keil, M.F.; de la Luz Sierra, M.; Palmeira, L.; Coppieters, W.; Georges, M.; Naves, L.A.; Jamar, M.; Bours, V.; Wu, T.J.; Choong, C.S.; Bertherat, J.; Chanson, P.; Kamenický, P.; Farrell, W.E.; Barlier, A.; Quezado, M.; Bjelobaba, I.; Stojilkovic, S.S.; Wess, J.; Costanzi, S.; Liu, P.; Lupski, J.R.; Beckers, A.; Stratakis, C.A.

    2015-01-01

    BACKGROUND Increased secretion of growth hormone leads to gigantism in children and acromegaly in adults; the genetic causes of gigantism and acromegaly are poorly understood. METHODS We performed clinical and genetic studies of samples obtained from 43 patients with gigantism and then sequenced an implicated gene in samples from 248 patients with acromegaly. RESULTS We observed microduplication on chromosome Xq26.3 in samples from 13 patients with gigantism; of these samples, 4 were obtained from members of two unrelated kindreds, and 9 were from patients with sporadic cases. All the patients had disease onset during early childhood. Of the patients with gigantism who did not carry an Xq26.3 microduplication, none presented before the age of 5 years. Genomic characterization of the Xq26.3 region suggests that the microduplications are generated during chromosome replication and that they contain four protein-coding genes. Only one of these genes, GPR101, which encodes a G-protein–coupled receptor, was overexpressed in patients’ pituitary lesions. We identified a recurrent GPR101 mutation (p.E308D) in 11 of 248 patients with acromegaly, with the mutation found mostly in tumors. When the mutation was transfected into rat GH3 cells, it led to increased release of growth hormone and proliferation of growth hormone–producing cells. CONCLUSIONS We describe a pediatric disorder (which we have termed X-linked acrogigantism [X-LAG]) that is caused by an Xq26.3 genomic duplication and is characterized by early-onset gigantism resulting from an excess of growth hormone. Duplication of GPR101 probably causes X-LAG. We also found a recurrent mutation in GPR101 in some adults with acromegaly. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.) PMID:25470569

  4. An Evolutionary Cascade Model for Sauropod Dinosaur Gigantism - Overview, Update and Tests

    PubMed Central

    Sander, P. Martin

    2013-01-01

    Sauropod dinosaurs are a group of herbivorous dinosaurs which exceeded all other terrestrial vertebrates in mean and maximal body size. Sauropod dinosaurs were also the most successful and long-lived herbivorous tetrapod clade, but no abiological factors such as global environmental parameters conducive to their gigantism can be identified. These facts justify major efforts by evolutionary biologists and paleontologists to understand sauropods as living animals and to explain their evolutionary success and uniquely gigantic body size. Contributions to this research program have come from many fields and can be synthesized into a biological evolutionary cascade model of sauropod dinosaur gigantism (sauropod gigantism ECM). This review focuses on the sauropod gigantism ECM, providing an updated version based on the contributions to the PLoS ONE sauropod gigantism collection and on other very recent published evidence. The model consist of five separate evolutionary cascades (“Reproduction”, “Feeding”, “Head and neck”, “Avian-style lung”, and “Metabolism”). Each cascade starts with observed or inferred basal traits that either may be plesiomorphic or derived at the level of Sauropoda. Each trait confers hypothetical selective advantages which permit the evolution of the next trait. Feedback loops in the ECM consist of selective advantages originating from traits higher in the cascades but affecting lower traits. All cascades end in the trait “Very high body mass”. Each cascade is linked to at least one other cascade. Important plesiomorphic traits of sauropod dinosaurs that entered the model were ovipary as well as no mastication of food. Important evolutionary innovations (derived traits) were an avian-style respiratory system and an elevated basal metabolic rate. Comparison with other tetrapod lineages identifies factors limiting body size. PMID:24205267

  5. Geography of end-Cretaceous marine bivalve extinctions

    NASA Technical Reports Server (NTRS)

    Raup, David M.; Jablonski, David

    1993-01-01

    Analysis of the end-Cretaceous mass extinction, based on 3514 occurrences of 340 genera of marine bivalves (Mollusca), suggests that extinction intensities were uniformly global; no latitudinal gradients or other geographic patterns are detected. Elevated extinction intensities in some tropical areas are entirely a result of the distribution of one extinct group of highly specialized bivalves, the rudists. When rudists are omitted, intensities at those localities are statistically indistinguishable from those of both the rudist-free tropics and extratropical localities.

  6. Ecological drivers and habitat associations of estuarine bivalves

    PubMed Central

    Tunberg, Björn G.; Johnston, Cora A.; Barshis, Daniel J.

    2015-01-01

    Community composition of the infaunal bivalve fauna of the St. Lucie Estuary and southern Indian River Lagoon, eastern Florida was sampled quarterly for 10 years as part of a long-term benthic monitoring program. A total of 38,514 bivalves of 137 taxa were collected and identified. We utilized this data, along with sediment samples and environmental measurements gathered concurrently, to assess the community composition, distribution, and ecological drivers of the infaunal bivalves of this estuary system. Salinity had the strongest influence on bivalve assemblage across the 15 sites, superseding the influences of sediment type, water turbidity, temperature and other environmental parameters. The greatest diversity was found in higher salinity euhaline sites, while the greatest abundance of individual bivalves was found in medium salinity mixohaline sites, the lowest diversity and abundances were found in the low salinity oligohaline sites, demonstrating a strong positive association between salinity and diversity/abundance. Water management decisions for the estuary should incorporate understanding of the role of salinity on bivalve diversity, abundance, and ecosystem function. PMID:26587338

  7. Isotopic fingerprints of bacterial chemosymbiosis in the bivalve Loripes lacteus

    NASA Astrophysics Data System (ADS)

    Dreier, A.; Stannek, L.; Blumenberg, M.; Taviani, M.; Sigovini, M.; Wrede, C.; Thiel, V.; Hoppert, M.

    2012-04-01

    Metazoans with chemosynthetic bacterial endosymbionts are widespread in marine habitats and respective endosymbioses are known from seven recent animal phyla. However, little is known about endosymbioses in fossil settings and, hence, ecological significance in earth history. In the presented project, we investigate the ancient and recent bivalve fauna living at marine sedimentary oxic/anoxic interfaces. Two bivalve species collected from the same benthic environment - a Mediterranean lagoon - were studied in detail. The diet of Loripes lacteus is based on thiotrophic gill symbionts whereas Venerupis aureus is a filter feeding bivalve without symbionts. The presence of three key enzymes from sulfur oxidation (APS-reductase), carbon fixation (RubisCO) and assimilation of nitrogen (glutamine synthetase [GS]) were detected by immunofluorescence in symbionts of Loripes and/or by activity tests in living specimens. In search of biosignatures associated with thiotrophic chemosymbionts that might be suitable for detection of chemosymbiotic diets in recent and fossil bivalve shells, we analyzed the isotopic composition of shell lipids (δ13C) and the bulk organic matrix of the shell (δ13C, δ15N, δ34S). We could show that the combined δ15N and δ13C values from shell extracts are stable in subfossil (Pleistocene) bivalve specimens, as long as the isotopic data is "calibrated" with respective signatures from a filter feeding bivalve sampled from the same site or lithostratigraphic bed.

  8. Gigantic self-confined pahoehoe inflated lava flows in Argentina

    NASA Astrophysics Data System (ADS)

    Pasquare', G.; Bistacchi, A.

    2007-05-01

    The largest lava flows on Earth are pahoehoe basalts emplaced by inflation, a process which can change lava lobes initially a few decimetres thick into large lava sheets several metres thick. Inflation involves the initial formation of a thin, solidified, viscoelastic crust, under which liquid lava is continually added. This thermally efficient endogenous growth process explains the spread of huge volumes of lava over large, almost flat areas, as in the sheet flows which characterise the distal portions of Hawaiian volcanoes or some continental flood basalt provinces. Long, narrow, inflated pahoehoe flows have occasionally been described, either emplaced along pre-existing river channels or confined within topographic barriers. In this contribution we present previously unknown inflated pahoehoe lava flows following very long, narrow pathways over an almost flat surface, with no topographic confinement. Lava, which erupted in Late Quaternary times from the eastern tip of a 60 km long volcanic fissure in Argentina, formed several discrete flows extending as far as 180 km from the source. This fissure was characterized by a long-lasting and complex activity. Alkali-basaltic lava flows were emitted at the two extremities of the fissure system. In the intermediate section of the fissure, the Payun Matru, a great trachitic composite volcano, developed, giving rise to a large caldera which produced large pyroclastic flows. Alkali-basalts predate and postdate the trachitic activity, in fact at the end of the trachitic activity, new basaltic lava flows (mainly aa) were emitted from both ends of the fissure. We studied in details the youngest of the gigantic flows (Pampas Onduladas lava flow), which progressively develops through differing thermally-efficient flow mechanisms. The flow created a large shield volcanic structure at the eastern tip of the E-W fissure and spread to the E forming a very large and thick inflated pahoehoe sheet flow. Leaving the flanks of the

  9. Discharge processes, electric field, and electron energy in ISUAL-recorded gigantic jets

    NASA Astrophysics Data System (ADS)

    Kuo, Cheng-Ling; Chou, J. K.; Tsai, L. Y.; Chen, A. B.; Su, H. T.; Hsu, R. R.; Cummer, S. A.; Frey, H. U.; Mende, S. B.; Takahashi, Y.; Lee, L. C.

    2009-04-01

    This article reports the first high time resolution measurements of gigantic jets from the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) experiment. The velocity of the upward propagating fully developed jet stage of the gigantic jets was ˜107 m s-1, which is similar to that observed for downward sprite streamers. Analysis of spectral ratios for the fully developed jet emissions gives a reduced E field of 400-655 Td and average electron energy of 8.5-12.3 eV. These values are higher than those in the sprites but are similar to those predicted by streamer models, which implies the existence of streamer tips in fully developed jets. The gigantic jets studied here all contained two distinct photometric peaks. The first peak is from the fully developed jet, which steadily propagates from the cloud top (˜20 km) to the lower ionosphere at ˜90 km. We suggest that the second photometric peak, which occurs ˜1 ms after the first peak, is from a current wave or potential wave-enhanced emissions that originate at an altitude of ˜50 km and extend toward the cloud top. We propose that the fully developed jet serves as an extension of the local ionosphere and produces a lowered ionosphere boundary. As the attachment processes remove the charges, the boundary of the local ionosphere moves up. The current in the channel persists and its contact point with the ionosphere moves upward, which produces the upward surging trailing jets. Imager and photometer data indicate that the lightning activity associated with the gigantic jets likely is in-cloud, and thus the initiation of the gigantic jets is not directly associated with cloud-to-ground discharges.

  10. Marine diatoms sustain growth of bivalves in a Mediterranean lagoon

    NASA Astrophysics Data System (ADS)

    Pernet, Fabrice; Malet, Nathalie; Pastoureaud, Annie; Vaquer, André; Quéré, Claudie; Dubroca, Laurent

    2012-02-01

    Carbon stable isotopes and fatty acids were measured in the suspended particulate organic matter (POM) of the Thau lagoon to study its qualitative temporal changes in relation to environmental factors and to identify the food sources of bivalves over a one-yr-cycle in relation to their growth. Reciprocally, the impact of shellfish farming on POM was also studied. Oysters and mussels were sampled and measured for biometry, stable isotopes and fatty acid composition. Water samples were collected at two sites, both inside and outside of the shellfish farming area, to determine concentrations in POM, chlorophyll a (Chl a) and stable isotopes. Carbon isotopes and fatty acids in bivalves reflected seasonal changes in food sources, which varied consistently with the environment. Seasonal changes in δ13C and fatty acids in the bivalves suggested that dietary phytoplankton contribution varied according to season. Terrestrial organic matter and bacteria can contribute to the diet of bivalves during non-bloom periods. Mussels seemed to rely more on diatoms and less on terrestrial organic matter and bacteria than oysters did, particularly when phytoplankton biomass was low during the summer. Although one- and two-yr-old oysters showed similar δ13C, their fatty acid dynamics differed slightly. Periods of high growth rate in bivalves were mainly fuelled by diatoms, thus highlighting the importance of seasonal blooms of microphytoplankton during the critical period of bivalve growth and gamete production. Although there was no significant effect of shellfish farms on Chl a and POM δ13C, consistent differences indicate that stable isotopes could be used successfully to investigate the effects of bivalve aquaculture.

  11. Analysis of marine bivalves and sediments

    SciTech Connect

    Zeisler, R.; Stone, S.F.

    1986-01-01

    Recently, environmental monitoring has been complemented by programs for systematic and controlled long-term storage of environmental samples; i.e., environmental specimen banking (ESB). In the US a pilot ESB program is currently expanding to become past of several environmental and human health monitoring projects. The National Status and Trends (NS and T) program on the marine environment, administrated by the National Oceanic and Atmospheric Administration (NOAA), is one of these projects and has initialized new investigations within the ESB research program. This research includes all steps of the ESB operation, with special emphasis on quality assurance in the selection, collection, preparation, storage, and analysis of marine samples according to validated procedures. A unique sequence of instrumental analytical methods involving x-ray fluorescence and neutron activation analysis procedures has been employed for the determination of 44 elements in marine bivalves. The individual procedures are an x-ray fluorescence method based on backscatter with fundamental parameter corrections, prompt gamma activation analysis, and neutron activation analysis with instrumental and radiochemical procedures. This analytical approach has been expanded to include the analysis of sediments and fish tissues.

  12. Bivalves: From individual to population modelling

    NASA Astrophysics Data System (ADS)

    Saraiva, S.; van der Meer, J.; Kooijman, S. A. L. M.; Ruardij, P.

    2014-11-01

    An individual based population model for bivalves was designed, built and tested in a 0D approach, to simulate the population dynamics of a mussel bed located in an intertidal area. The processes at the individual level were simulated following the dynamic energy budget theory, whereas initial egg mortality, background mortality, food competition, and predation (including cannibalism) were additional population processes. Model properties were studied through the analysis of theoretical scenarios and by simulation of different mortality parameter combinations in a realistic setup, imposing environmental measurements. Realistic criteria were applied to narrow down the possible combination of parameter values. Field observations obtained in the long-term and multi-station monitoring program were compared with the model scenarios. The realistically selected modeling scenarios were able to reproduce reasonably the timing of some peaks in the individual abundances in the mussel bed and its size distribution but the number of individuals was not well predicted. The results suggest that the mortality in the early life stages (egg and larvae) plays an important role in population dynamics, either by initial egg mortality, larvae dispersion, settlement failure or shrimp predation. Future steps include the coupling of the population model with a hydrodynamic and biogeochemical model to improve the simulation of egg/larvae dispersion, settlement probability, food transport and also to simulate the feedback of the organisms' activity on the water column properties, which will result in an improvement of the food quantity and quality characterization.

  13. Bivalve mollusks in metal pollution studies: from bioaccumulation to biomonitoring.

    PubMed

    Zuykov, Michael; Pelletier, Emilien; Harper, David A T

    2013-09-01

    Contemporary environmental challenges have emphasized the need to critically assess the use of bivalve mollusks in chemical monitoring (identification and quantification of pollutants) and biomonitoring (estimation of environmental quality). Many authors, however, have considered these approaches within a single context, i.e., as a means of chemical (e.g. metal) monitoring. Bivalves are able to accumulate substantial amounts of metals from ambient water, but evidence for the drastic effects of accumulated metals (e.g. as a TBT-induced shell deformation and imposex) on the health of bivalves has not been documented. Metal bioaccumulation is a key tool in biomonitoring; bioavailability, bioaccumulation, and toxicity of various metals in relation to bivalves are described in some detail including the development of biodynamic metal bioaccumulation model. Measuring metal in the whole-body or the tissue of bivalves themselves does not accurately represent true contamination levels in the environment; these data are critical for our understanding of contaminant trends at sampling sites. Only rarely has metal bioaccumulation been considered in combination with data on metal concentrations in parts of the ecosystem, observation of biomarkers and environmental parameters. Sclerochemistry is in its infancy and cannot be reliably used to provide insights into the pollution history recorded in shells. Alteration processes and mineral crystallization on the inner shell surface are presented here as a perspective tool for environmental studies. PMID:23751124

  14. Larviphagy in native bivalves and an introduced oyster

    NASA Astrophysics Data System (ADS)

    Troost, Karin; Kamermans, Pauline; Wolff, Wim J.

    2008-10-01

    Introduced Pacific oysters Crassostrea gigas have expanded rapidly in the Dutch Oosterschelde estuary, while stocks of native bivalves declined slightly. As a consequence, total filtration pressure increased significantly, which may affect the mortality of bivalve larvae. Better escape abilities in Pacific oyster larvae might be a contributing factor to their rapid geographic expansion. To study whether C. gigas larvae are filtered less than larvae of native bivalves, we investigated filtration and ingestion of the larvae of the native Mytilus edulis and introduced C. gigas by the adults of C. gigas and M. edulis as well as the native Cerastoderma edule. We measured filtration rates of C. gigas and M. edulis larvae by the adult bivalves ( C. gigas, M. edulis and C. edule), and compared these to filtration rates of algae. Additionally, we studied the fate of filtered larvae. All three adult species filtered both C. gigas and M. edulis larvae. M. edulis larvae were filtered by all three bivalve species with the same filtration rates as algae, whereas filtration rates of C. gigas larvae were roughly 50% lower than filtration rates of algae. This suggests that C. gigas larvae can somehow reduce their filtration risk, whereas larvae of M. edulis cannot. The majority of filtered C. gigas and M. edulis larvae were ingested.

  15. Gigantic Cosmic Corkscrew Reveals New Details About Mysterious Microquasar

    NASA Astrophysics Data System (ADS)

    2004-10-01

    Making an extra effort to image a faint, gigantic corkscrew traced by fast protons and electrons shot out from a mysterious microquasar paid off for a pair of astrophysicists who gained new insights into the beast's inner workings and also resolved a longstanding dispute over the object's distance. Microquasar SS 433 VLA Image of Microquasar SS 433 CREDIT: Blundell & Bowler, NRAO/AUI/NSF (Click on Image for Larger Version) The astrophysicists used the National Science Foundation's Very Large Array (VLA) radio telescope to capture the faintest details yet seen in the plasma jets emerging from the microquasar SS 433, an object once dubbed the "enigma of the century." As a result, they have changed scientists' understanding of the jets and settled the controversy over its distance "beyond all reasonable doubt," they said. SS 433 is a neutron star or black hole orbited by a "normal" companion star. The powerful gravity of the neutron star or black hole draws material from the stellar wind of its companion into an accretion disk of material tightly circling the dense central object prior to being pulled onto it. This disk propels jets of fast protons and electrons outward from its poles at about a quarter of the speed of light. The disk in SS 433 wobbles like a child's top, causing its jets to trace a corkscrew in the sky every 162 days. The new VLA study indicates that the speed of the ejected particles varies over time, contrary to the traditional model for SS 433. "We found that the actual speed varies between 24 percent to 28 percent of light speed, as opposed to staying constant," said Katherine Blundell, of the University of Oxford in the United Kingdom. "Amazingly, the jets going in both directions change their speeds simultaneously, producing identical speeds in both directions at any given time," Blundell added. Blundell worked with Michael Bowler, also of Oxford. The scientists' findings have been accepted by the Astrophysical Journal Letters. SS 433 New VLA

  16. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

    PubMed Central

    Liu, Jun; Hu, Shi-xue; Rieppel, Olivier; Jiang, Da-yong; Benton, Michael J.; Kelley, Neil P.; Aitchison, Jonathan C.; Zhou, Chang-yong; Wen, Wen; Huang, Jin-yuan; Xie, Tao; Lv, Tao

    2014-01-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic. PMID:25429609

  17. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Hu, Shi-Xue; Rieppel, Olivier; Jiang, Da-Yong; Benton, Michael J.; Kelley, Neil P.; Aitchison, Jonathan C.; Zhou, Chang-Yong; Wen, Wen; Huang, Jin-Yuan; Xie, Tao; Lv, Tao

    2014-11-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic.

  18. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery.

    PubMed

    Liu, Jun; Hu, Shi-Xue; Rieppel, Olivier; Jiang, Da-Yong; Benton, Michael J; Kelley, Neil P; Aitchison, Jonathan C; Zhou, Chang-Yong; Wen, Wen; Huang, Jin-Yuan; Xie, Tao; Lv, Tao

    2014-01-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic. PMID:25429609

  19. Ecotoxicological impact of engineered nanomaterials in bivalve molluscs: An overview.

    PubMed

    Rocha, Thiago Lopes; Gomes, Tânia; Sousa, Vânia Serrão; Mestre, Nélia C; Bebianno, Maria João

    2015-10-01

    The increasing production and application of engineered nanomaterials (ENMs) in consumer products over the past decade will inevitably lead to their release into aquatic systems and thereby cause the exposure to aquatic organisms, resulting in growing environmental and human health concern. Since bivalves are widely used in the monitoring of aquatic pollution, the aim of this review was to compile and analyse data concerning the ecotoxicity of ENMs using bivalve molluscs. The state of the art regarding the experimental approach, characterization, behaviour, fate, bioaccumulation, tissue and subcellular distribution and mechanisms of toxicity of ENMs in marine and freshwater bivalve molluscs is summarized to achieve a new insight into the mode of action of these nanoparticles in invertebrate organisms. This review shows that the studies about the toxic effects of ENMs in bivalves were conducted mainly with seawater species compared to freshwater ones and that the genus Mytilus is the main taxa used as a model system. There is no standardization of experimental approaches for toxicity testing and reviewed data indicate the need to develop standard protocols for ENMs ecotoxicological testing. In general, the main organ for ENM accumulation is the digestive gland and their cellular fate differs according to nano-specific properties, experimental conditions and bivalve species. Endosomal-lysosomal system and mitochondria are the major cellular targets of ENMs. Metal based ENMs mode of action is related mainly to the dissolution and/or release of the chemical component of the particle inducing immunotoxicity, oxidative stress and cellular injury to proteins, membrane and DNA damage. This review indicates that the aquatic environment is the potential ultimate fate for ENMs and confirms that bivalve molluscs are key model species for monitoring aquatic pollution by ENMs. PMID:26152602

  20. [Unique optical reflection spectra of bivalve nacre and its origin].

    PubMed

    Zhang, Wei-gang; Wang, Gang; Yan, Jun; Li, Hao-xuan; Zhang, Gang-sheng

    2009-05-01

    The structural color and microstructure of nacre in bivalve shells of Pinctada maxima were investigated by optical reflection spectra, scanning electron microscopy and theoretical simulation. The following results are obtained: (1) The thickness of aragonite tablets decreased significantly from growing to central region of nacre, which leads to a blue-shift of reflection peak wavelength with the same reflection order obviously; (2) The structural color of nacre in bivalve shells of Pinctada maxima is derived from the combination effects of aragonite-protein multilayer structure and yellow pigments in nacre. PMID:19650449

  1. Cope's Rule and Romer's theory: patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates

    PubMed Central

    Lamsdell, James C.; Braddy, Simon J.

    2010-01-01

    Gigantism is widespread among Palaeozoic arthropods, yet causal mechanisms, particularly the role of (abiotic) environmental factors versus (biotic) competition, remain unknown. The eurypterids (Arthropoda: Chelicerata) include the largest arthropods; gigantic predatory pterygotids (Eurypterina) during the Siluro-Devonian and bizarre sweep-feeding hibbertopterids (Stylonurina) from the Carboniferous to end-Permian. Analysis of family-level originations and extinctions among eurypterids and Palaeozoic vertebrates show that the diversity of Eurypterina waned during the Devonian, while the Placodermi radiated, yet Stylonurina remained relatively unaffected; adopting a sweep-feeding strategy they maintained their large body size by avoiding competition, and persisted throughout the Late Palaeozoic while the predatory nektonic Eurypterina (including the giant pterygotids) declined during the Devonian, possibly out-competed by other predators including jawed vertebrates. PMID:19828493

  2. Starvation reveals the cause of infection-induced castration and gigantism

    PubMed Central

    Cressler, Clayton E.; Nelson, William A.; Day, Troy; McCauley, Edward

    2014-01-01

    Parasites often induce life-history changes in their hosts. In many cases, these infection-induced life-history changes are driven by changes in the pattern of energy allocation and utilization within the host. Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them. Determining the causes and consequences of infection-induced life-history changes requires the ability to experimentally manipulate life history and a framework for connecting life history to host and parasite fitness. Here, we combine a novel starvation manipulation with energy budget models to provide new insights into castration and gigantism in the Daphnia magna–Pasteuria ramosa host–parasite system. Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration. These results are consistent with an energetic structure where the parasite uses growth energy as a resource. This finding gives us new understanding of the role of castration and gigantism in this system, and how life-history variation will affect infection outcome and epidemiological dynamics. The approach of combining targeted life-history manipulations with energy budget models can be adapted to understand life-history changes in other disease systems. PMID:25143034

  3. Ecological explanations to island gigantism: dietary niche divergence, predation, and size in an endemic lizard.

    PubMed

    Runemark, Anna; Sagonas, Kostas; Svensson, Erik I

    2015-08-01

    Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we investigate if selection for novel diets has contributed to the multiple independent cases of island gigantism in the Skyros wall lizard (Podarcis gaigeae) and if diet, predation, or both factors best explain island gigantism. We combined data on body size, shape, bite force, and realized and available diets to address this. Several lines of evidence suggest that diet has contributed to the island gigantism. The larger islet lizards have relatively wider heads and higher bite performance in relation to mainland lizards than would be expected from size differences alone. The proportions of consumed and available hard prey are higher on islets than mainland localities, and lizard body size is significantly correlated with the proportion of hard prey. Furthermore, the main axis of divergence in head shape is significantly correlated with dietary divergence. Finally, a model with only diet and one including diet and predation regime explain body size divergence equally well. Our results suggest that diet is an important ecological factor behind insular body size divergence, but could be consistent with an additional role for predation. PMID:26405734

  4. A Bivalve Proxy for Neogene Antarctic Shelf Marine Environments

    NASA Astrophysics Data System (ADS)

    Clark, N. A.; Williams, M.; Quilty, P. G.; Leng, M. J.; Zalasiewicz, J. A.; Smellie, J.; Dowsett, H. J.

    2012-12-01

    The Neogene shallow-marine successions of the Antarctic Peninsula and of the East Antarctic region preserve rich assemblages of bivalve molluscs. These bivalve molluscs provide a detailed record of palaeoseasonality in the chemical signature and morphology of their shells that can be used to assess sea temperatures and sea ice extent for the Antarctic shelf during the Pliocene. Analyses identify the following. 1) Neogene bivalves from James Ross Island, Antarctic Peninsula, comprise material of late Miocene through to late Pliocene age. Results identify warm (ca. 3-10 °C) early Pliocene sea temperatures, and cooler late Pliocene sea temperatures (ca. 0-4 °C), and flag a cooling trend which is consistent with the evolution of polar climate through this interval. 2) Neogene bivalves from the Larsemann Hills, East Antarctic, identify generally warmer than present sea temperatures (ca. 0-11 °C) in the early Pliocene consistent with data from other fossil groups of this age, including dolphins and silicoflagellates. The new data may provide significant ground truth for climate models assessing the Southern Ocean and Antarctic shelf climate.

  5. COMPARATIVE HISTOPATHOLOGY OF GONADAL NEOPLASMS IN MARINE BIVALVE MOLLUSCS

    EPA Science Inventory

    Comparative histology of gonadal neoplasms in 14 marine bivalve species or hybrids from 5 countries described in the literature and/or archived in the Registry of Tumors in Lower Animals (RTLA), Washington, DC, USA, revealed 3 basic histotypes. undreds of cases were of germ cell ...

  6. CHEMICAL CARCINOGENS IN BIVALVE MOLLUSKS FROM OREGON ESTUARIES

    EPA Science Inventory

    The research undertaken involved the use of indigenous populatons of bivalve mollusks as monitors for detecting and quantifying environmental benzo(s)pyrene (BAP) in Oregon estuaries. Short-term and long-term studies were conducted in order to establish baseline levels of BAP and...

  7. Vínculos observacionais para o processo-S em estrelas gigantes de Bário

    NASA Astrophysics Data System (ADS)

    Smiljanic, R. H. S.; Porto de Mello, G. F.; da Silva, L.

    2003-08-01

    Estrelas de bário são gigantes vermelhas de tipo GK que apresentam excessos atmosféricos dos elementos do processo-s. Tais excessos são esperados em estrelas na fase de pulsos térmicos do AGB (TP-AGB). As estrelas de bário são, no entanto, menos massivas e menos luminosas que as estrelas do AGB, assim, não poderiam ter se auto-enriquecido. Seu enriquecimento teria origem em uma estrela companheira, inicialmente mais massiva, que evolui pelo TP-AGB, se auto-enriquece com os elementos do processo-s e transfere material contaminado para a atmosfera da atual estrela de bário. A companheira evolui então para anã branca deixando de ser observada diretamente. As estrelas de bário são, portanto, úteis como testes observacionais para teorias de nucleossíntese pelo processo-s, convecção e perda de massa. Análises detalhadas de abundância com dados de alta qualidade para estes objetos são ainda escassas na literatura. Neste trabalho construímos modelos de atmosferas e, procedendo a uma análise diferencial, determinamos parâmetros atmosféricos e evolutivos de uma amostra de dez gigantes de bário e quatro normais. Determinamos seus padrões de abundância para Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu e Gd, concluindo que algumas estrelas classificadas na literatura como gigantes de bário são na verdade gigantes normais. Comparamos dois padrões médios de abundância, para estrelas com grandes excessos e estrelas com excessos moderados, com modelos teóricos de enriquecimento pelo processo-s. Os dois grupos de estrelas são ajustados pelos mesmos parâmetros de exposição de nêutrons. Tal resultado sugere que a ocorrência do fenômeno de bário com diferentes intensidades não se deve a diferentes exposições de nêutrons. Discutimos ainda efeitos nucleossintéticos, ligados ao processo-s, sugeridos na literatura para os elementos Cu, Mn, V e Sc.

  8. Formación y evolución de planetas gigantes

    NASA Astrophysics Data System (ADS)

    Benvenuto, O. G.; Brunini, A.

    Presentamos el estado actual del trabajo que estamos realizando en el estudio de la formación de planetas gigantes. Detallamos los algoritmos numéricos necesarios para realizar este tipo de cálculo. Presentamos algunos resultados de la formación de objetos con masas de hasta una docena de veces la del planeta Júpiter, resaltando las principales caracteríticas. Finalmente detallamos los problemas que pensamos abordar en un futuro cercano en este tema de investigación.

  9. Modeling the carbon isotope composition of bivalve shells (Invited)

    NASA Astrophysics Data System (ADS)

    Romanek, C.

    2010-12-01

    The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., <10%) in shells from aquatic organism and high (>90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions

  10. Sequential determination of biological and pollutant elements in marine bivalves

    SciTech Connect

    Zeisler, R.; Stone, S.F.; Sanders, R.W.

    1988-12-15

    A unique sequence of instrumental methods has been employed to obtain concentrations for 44 elements in marine bivalve tissue. The techniques used were (1) X-ray fluorescence, (2) prompt gamma activation analysis, and (3) neutron activation analysis. It is possible to use a single subsample and follow it nondestructively through the three instrumental analysis techniques. A final radiochemical procedure for tin was also applied after completing the instrumental analyses. Comparison of results for elements determined by more than one technique in sequence showed good agreement, as did results from certified reference material samples analyzed along with the samples. The concentrations found in the bivalve samples ranged from carbon at more than 50% dry weight down to gold at several microgram per kilogram.

  11. Comparative pathology in bivalves: Aetiological agents and disease processes.

    PubMed

    Carella, F; Feist, S W; Bignell, J P; De Vico, G

    2015-10-01

    Comparative pathology as a scientific discipline studies animal diseases in relation to their aetiology, pathogenesis and prognosis. Among the main aspects of this discipline, regressive changes, host defense responses with pathological implications and progressive changes, represent the majority of the possible responses of cells and tissues to pathogens and exposure to chemicals. One of the most persistent issues in the field of invertebrate pathology is the variability in terminology and definition, which has led to confusion in scientific communication. The aim of this paper is to provide an overview of the pathological basis of bivalve disease (defensive, regressive and progressive phenomena) and contribute to the standardised terminology for bivalve molluscan disease in the context of comparative pathology. PMID:26215472

  12. Ocean Acidification Has Multiple Modes of Action on Bivalve Larvae

    PubMed Central

    Waldbusser, George G.; Hales, Burke; Langdon, Chris J.; Haley, Brian A.; Schrader, Paul; Brunner, Elizabeth L.; Gray, Matthew W.; Miller, Cale A.; Gimenez, Iria; Hutchinson, Greg

    2015-01-01

    Ocean acidification (OA) is altering the chemistry of the world’s oceans at rates unparalleled in the past roughly 1 million years. Understanding the impacts of this rapid change in baseline carbonate chemistry on marine organisms needs a precise, mechanistic understanding of physiological responses to carbonate chemistry. Recent experimental work has shown shell development and growth in some bivalve larvae, have direct sensitivities to calcium carbonate saturation state that is not modulated through organismal acid-base chemistry. To understand different modes of action of OA on bivalve larvae, we experimentally tested how pH, PCO2, and saturation state independently affect shell growth and development, respiration rate, and initiation of feeding in Mytilus californianus embryos and larvae. We found, as documented in other bivalve larvae, that shell development and growth were affected by aragonite saturation state, and not by pH or PCO2. Respiration rate was elevated under very low pH (~7.4) with no change between pH of ~ 8.3 to ~7.8. Initiation of feeding appeared to be most sensitive to PCO2, and possibly minor response to pH under elevated PCO2. Although different components of physiology responded to different carbonate system variables, the inability to normally develop a shell due to lower saturation state precludes pH or PCO2 effects later in the life history. However, saturation state effects during early shell development will carry-over to later stages, where pH or PCO2 effects can compound OA effects on bivalve larvae. Our findings suggest OA may be a multi-stressor unto itself. Shell development and growth of the native mussel, M. californianus, was indistinguishable from the Mediterranean mussel, Mytilus galloprovincialis, collected from the southern U.S. Pacific coast, an area not subjected to seasonal upwelling. The concordance in responses suggests a fundamental OA bottleneck during development of the first shell material affected only by

  13. Bivalves build their shells from amorphous calcium carbonate

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Wirth, R.; Soldati, A. L.; Wehrmeister, U.

    2012-04-01

    One of the most common shell structures in the bivalve class is the prism and nacre structure. It is widely distributed amongst both freshwater and marine species and gives cultured pearls their sought-after lustre. In freshwater bivalves, both shell structures (prism and nacre) consist of aragonite. Formation of the shell form an amorphous precursor phase is a wide-spread strategy in biomineralization and presents a number of advantages for the organisms in the handling of the CaCO3 material. While there is already evidence that larval shells of some mollusk species use amorphous calcium carbonate (ACC) as a transient precursor phase for aragonite, the use of this strategy by adult animals was only speculated upon. We present results from in-situ geochemistry, Raman spectroscopy and focused-ion beam assisted TEM on three species from two different bivalve families that show that remnants of ACC can be found in shells from adult species. We show that the amorphous phase is not randomly distributed, but is systematically found in a narrow zone at the interface between periostracum and prism layer. This zone is the area where spherulitic CaCO3- structures protrude from the inner periostracum to form the initial prisms. These observations are in accordance with our earlier results on equivalent structures in freshwater cultured pearls (Jacob et al., 2008) and show that the original building material for the prisms is amorphous calcium carbonate, secreted in vesicles at the inner periostracum layer. Quantitative temperature calibrations for paleoclimate applications using bivalve shells are based on the Mg-Ca exchange between inorganic aragonite (or calcite) and water. These calibrations, thus, do not take into account the biomineral crystallization path via an amorphous calcium carbonate precursor and are therefore likely to introduce a bias (a so-called vital effect) which currently is not accounted for. Jacob et al. (2008) Geochim. Cosmochim. Acta 72, 5401-5415

  14. Relating Productivity Events to Holocene Bivalve Shell Growth Rates

    NASA Astrophysics Data System (ADS)

    Huntley, J. W.; Krause, R. A.; Kowalewski, M.; Romanek, C. S.; Kaufman, D. S.; Simoes, M. G.

    2007-12-01

    The growth rate of a bivalve can be influenced by many environmental factors that can change during the life of the organism. In this contribution we present initial data from a millennium scale chronology to assess the relationship between ontogenetic growth in the bivalve Semele casali and paleoenvironmental conditions preserved in the shell using growth increment analysis, radiocarbon-calibrated amino acid racemization dating techniques, stable isotopes (C and O) and high spatial resolution (125-150 samples per cm of shell profile) trace element (Ba, Mn) analysis (LA-ICPMS). Time-averaged specimens of S. casali were dredged from two sites at 10 meters and 30 meters depth along the inner continental shelf at Ubatuba Bay in the Southeast Brazilian Bight, an area influenced by productivity pulses triggered by coastal runoff events and coastal upwelling. Seventy-five individual valves were dated using amino acid racemization (aspartic acid). Dates were calculated using an expanded version of a previously published relationship (Barbour Wood et al., 2006 Quaternary Research 323- 331) between aspartic acid ratios and AMS radiocarbon dates of twelve S. casali individuals from the same sampling locations. The resulting time series has complete coverage for the past three thousand years at centennial resolution. From this time series, a sub-sample of dated valves was selected for more detailed growth increment, stable isotope and high-resolution trace element (Ba/Ca and Mn/Ca) analyses. Oceanic productivity is expressed differentially in the trace element profiles of S. casali with elevated Ba/Ca and Mn/Ca ratios capturing nutrient input through coastal runoff events while elevated Ba/Ca and depressed Mn/Ca ratios represent input through coastal upwelling. Fluctuations in Ba/Ca and Mn/Ca are not correlated to fluctuations in relative growth throughout the ontogeny of an individual bivalve, nor are they expected to be as periods of increased productivity are transient

  15. The small but clear gravity signal above the natural cave 'Grotta Gigante' (Trieste, Italy)

    NASA Astrophysics Data System (ADS)

    Braitenberg, Carla; Sampietro, Daniele; Zuliani, David; Barbagallo, Alfio; Fabris, Paolo; Fabbri, Julius; Rossi, Lorenzo; Handi Mansi, Ahmed

    2014-05-01

    Gravity observations are a powerful means for detecting underground mass changes. The Italian and Slovenian Karst has a number of explored caves, several are also touristic due to their size (e.g. Grotta Gigante in Italy; Skocjianske Jame and Postojnska Jama in Slovenia). Just a few years ago another big cave was discovered by chance close to Trieste when drilling a tunnel for a motor-highway, which shows that more caves are expected to be discovered in coming years. We have acquired the gravity field above the Grotta Gigante cave, a cave roughly 100 m high and 200 m long with a traditional spring-gravity meter (Lacoste&Romberg) and height measurements made with GPS and total station. The GPS was made with two different teams and processing algorithms, to cross-check accuracy and error estimate. Some stations had to be surveyed with a classical instrument due to the vegetation which concealed the satellite positioning signal. Here we present the results of the positioning acquisitions and the gravity field. The cave produces a signal of 1.5 mGal, with a clear elongated concentric symmetry. The survey shows that a systematic coverage of the Karst would have the benefit to recover the position of all of the greater existing caves. This will have a large impact on civil and environmental purposes, since it will for example allow to plan the urban development at a safety distance from subsurface caves.

  16. Pituitary gigantism presenting with depressive mood disorder and diabetic ketoacidosis in an Asian adolescent.

    PubMed

    Kuo, Sheng-Fong; Chuang, Wen-Yu; Ng, Sohching; Chen, Chih-Hung; Chang, Chen-Nen; Chou, Chi-Hsiang; Weng, Wei-Chieh; Yeh, Chih-Hua; Lin, Jen-Der

    2013-01-01

    Hyperglycemia is seldom described in young patients with pituitary gigantism. Here, we describe the case of a 17-year-old Taiwanese boy who developed depressive mood disorder and diabetic ketoacidosis (DKA) at the presentation of pituitary gigantism. The boy complained of lethargy and dysphoric mood in June 2008. He presented at the emergency department with epigastralgia and dyspnea in January 2009. Results of laboratory tests suggested type 1 diabetes mellitus with DKA. However, serum C-peptide level was normal on follow-up. Although he had no obvious features of acral enlargement, a high level of insulin-like growth factor 1 was detected, and a 75 g oral glucose suppression test showed no suppression of serum growth hormone levels. A pituitary macroadenoma was found on subsequent magnetic resonance imaging. The pituitary adenoma was surgically removed, followed by gamma-knife radiosurgery, and Sandostatin long-acting release treatment. He was then administered metformin, 500 mg twice daily, and to date, his serum glycohemoglobin has been <7%. PMID:23729615

  17. A gigantic coronal jet ejected from a compact active region in a coronal hole

    NASA Technical Reports Server (NTRS)

    Shibata, K.; Nitta, N.; Strong, K. T.; Matsumoto, R.; Yokoyama, T.; Hirayama, T.; Hudson, H.; Ogawara, Y.

    1994-01-01

    A gigantic coronal jet greater than 3 x 10(exp 5) km long (nearly half the solar radius) has been found with the soft X-ray telescope (SXT) on board the solar X-ray satellite, Yohkoh. The jet was ejected on 1992 January 11 from an 'anemone-type' active region (AR) appearing in a coronal hole and is one of the largest coronal X-ray jets observed so far by SXT. This gigantic jet is the best observed example of many other smaller X-ray jets, because the spatial structures of both the jet and the AR located at its base are more easily resolved. The range of apparent translational velocities of the bulk of the jet was between 90 and 240 km s(exp -1), with the corresponding kinetic energy estimated to be of order of 10(exp 28) ergs. A detailed analysis reveals that the jet was associated with a loop brightening (a small flare) that occurred in the active region. Several features of this observation suggest and are consistent with a magnetic reconnection mechanism for the production of such a 'jet-loop-brightening' event.

  18. A gigantic coronal jet ejected from a compact active region in a coronal hole

    NASA Astrophysics Data System (ADS)

    Shibata, K.; Nitta, N.; Strong, K. T.; Matsumoto, R.; Yokoyama, T.; Hirayama, T.; Hudson, H.; Ogawara, Y.

    1994-08-01

    A gigantic coronal jet greater than 3 x 105 km long (nearly half the solar radius) has been found with the soft X-ray telescope (SXT) on board the solar X-ray satellite, Yohkoh. The jet was ejected on 1992 January 11 from an 'anemone-type' active region (AR) appearing in a coronal hole and is one of the largest coronal X-ray jets observed so far by SXT. This gigantic jet is the best observed example of many other smaller X-ray jets, because the spatial structures of both the jet and the AR located at its base are more easily resolved. The range of apparent translational velocities of the bulk of the jet was between 90 and 240 km s-1, with the corresponding kinetic energy estimated to be of order of 1028 ergs. A detailed analysis reveals that the jet was associated with a loop brightening (a small flare) that occurred in the active region. Several features of this observation suggest and are consistent with a magnetic reconnection mechanism for the production of such a 'jet-loop-brightening' event.

  19. IMPORTANCE OF MATERNAL TRANSFER OF THE PHOTOREACTIVE POLYCYCLIC AROMATIC HYDROCARBON FLUORANTHENE FROM BENTHIC ADULT BIVALVES TO THEIR PELAGIC LARVAE

    EPA Science Inventory

    Laboratory experiments were conducted to determine if maternal transfer of polycyclic aromatic hydrocarbons (PAHs) from benthic adult bivalves could result in phototoxicity to their pelagic larvae when exposed to ultraviolet light (UV). In these experiments, adult bivalves were e...

  20. One-pot versus sequential reactions in the self-assembly of gigantic nanoscale polyoxotungstates.

    PubMed

    Gao, Jing; Yan, Jun; Beeg, Sebastian; Long, De-Liang; Cronin, Leroy

    2013-02-01

    By using a new type of lacunary tungstoselenite {Se(2)W(29)O(103)} (1), which contains a "defect" pentagonal {W(W)(4)} unit, we explored the assembly of clusters using this building block and demonstrate how this unit can give rise to gigantic nanomolecular species, using both a "one-pot" and "stepwise" synthetic assembly approach. Specifically, exploration of the one-pot synthetic parameter space lead to the discovery of {Co(2.5)(W(3.5)O(14))(SeW(9)O(33))(Se(2)W(30)O(107))} (2), {CoWO(H(2)O)(3)(Se(2)W(26)O(85))(Se(3)W(30)O(107))(2)} (3), and {Ni(2)W(2)O(2)Cl(H(2)O)(3)(Se(2)W(29)O(103)) (Se(3)W(30)O(107))(2)} (4), effectively demonstrating the potential of the {Se(2)W(29)} based building blocks, which was further extended by the isolation of a range of 3d transition metal doped tetramer family derivatives: {M(2)W(n)O(m)(H(2)O)(m)(Se(2)W(29)O(102))(4)} (M = Mn, Co, Ni or Zn, n = 2, m = 4; M = Cu, n = 3, m = 5) (5-9). To contrast the 'one-pot' approach, an optimized stepwise self-assembly investigation utilizing 1 as a precursor was performed showing that the high nuclearity clusters can condense in a more controllable way allowing the tetrameric clusters (5-8) to be synthesized with higher yield, but it was also shown that 1 can be used to construct a gigantic {W(174)} hexameric-cluster {Cu(9)Cl(3)(H(2)O)(18)(Se(2)W(29)O(102))(6)} (10). Further, 1 can also dimerize to {(Se(2)W(30)O(105))(2)} (11) by addition of extra tungstate under similar conditions. All the clusters were characterized by single-crystal X-ray crystallography, chemical analysis, infrared spectroscopy, thermogravimetric analysis, and electrospray ionization mass spectrometry, which remarkably showed that all the clusters, even the largest cluster, 10 (∼50 kD), could be observed as the intact cluster demonstrating the extraordinary potential of this approach to construct robust gigantic nanoscale polyoxotungstates. PMID:23244039

  1. A Novel Filtering Mutualism between a Sponge Host and Its Endosymbiotic Bivalves

    PubMed Central

    Tsubaki, Remi; Kato, Makoto

    2014-01-01

    Sponges, porous filter-feeding organisms consisting of vast canal systems, provide unique substrates for diverse symbiotic organisms. The Spongia (Spongia) sp. massive sponge is obligately inhabited by the host-specific endosymbiotic bivalve Vulsella vulsella, which benefits from this symbiosis by receiving protection from predators. However, whether the host sponge gains any benefit from this association is unclear. Considering that the bivalves exhale filtered water into the sponge body rather than the ambient environment, the sponge is hypothesized to utilize water exhaled by the bivalves to circulate water around its body more efficiently. We tested this hypothesis by observing the sponge aquiferous structure and comparing the pumping rates of sponges and bivalves. Observations of water currents and the sponge aquiferous structure revealed that the sponge had a unique canal system enabling it to inhale water exhaled from bivalves, indicating that the host sponge adapted morphologically to receive water from the bivalves. In addition, the volume of water circulating in the sponge body was dramatically increased by the water exhaled from bivalves. Therefore, this sponge-bivalve association can be regarded as a novel mutualism in which two filter-feeding symbionts promote mutual filtering rates. This symbiotic association should be called a “filtering mutualism”. PMID:25330073

  2. GREEN CRAB (CARCINUS MAENAS LINNAEUS) CONSUMPTION RATES ON AND PREY PREFERENCES AMONG FOUR BIVALVE PREY SPECIES

    EPA Science Inventory

    The European green crab, Carcinus maenas, is a recent invader to Pacific Northwest (PNW) estuaries with a voracious appetite, especially for bivalves. To assess their potential impact, we estimated green crab consumption rates on four PNW bivalve species, Yaquina oyster (Ostrea ...

  3. Lower Oligocene bivalves of Ramanian Stage from Kachchh, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Kachhara, R. P.; Jodhawat, R. L.; Devi, K. Bigyapati

    2012-04-01

    Marine Oligocene sequences in India outcrop only in western part of Kachchh. Earlier researchers have recognized the Oligocene strata under the Nari Series (Nagappa 1959; Chatterji and Mathur 1966). The Nari Series has a type area in Pakistan. It has two subdivisions - the Lower Nari (Lower Oligocene) and the Upper Nari (Upper Oligocene). It seems that there is no valid proof about the age of the Lower Nari due to lack of proper fauna (Eames 1975), and according to Pascoe (1962), the Upper Nari slightly transgress into Aquitanian (Lower Miocene), therefore, one has to be very cautious. Biswas and Raju (1971) reclassified the Oligocene strata of Kachchh and lithostratigraphically clubbed them as the Maniyara Fort Formation with type section along the Bermoti stream. This Formation has four members. The lower three members correspond to the Ramanian Stage (Lower Oligocene, Biswas 1971, 1973) while the uppermost to the Waiorian Stage (Upper Oligocene, Biswas 1965, 1971, 1973). The Ramanian Stage is characterized by large forams especially Nummulites fichteli, Nummulites fichteli intermedius, Lepidocyclina ( Eulepidina) dialata and Operculina sp. Several ostracods are also known to occur. Megafauna include bivalves, gastropods, echinoids, corals, mammals and reptiles. Concerning bivalves earlier researchers have recorded a few taxa namely Trisidos semitorta (Lamarck), Cubitostrea angulata (J de C Sowerby), Pecten ( Amussiopecten) labadyei d'Archiac and Haime, Periglypta puerpera (Linne') var. aglaurae Brongniart, Ostrea fraasi Mayer Eymer and listed Pecten laevicostatus J de C Sowerby, Callista pseudoumbonella Vredenburg and Clementia papyracea (Gray) from Kachchh as against overall 42 forms from the Nari Series as a whole (Vredenburg 1928). This tempted us to make an attempt to collect bivalve fauna systematically which are occurring prolifically in the Ramanian Stage. In the present work, for this purpose, sections are worked out around Lakhpat (23°50'N; 68°47'E

  4. [The Microsculpture of Glochidia of Some Anodontine Bivalves (Unionidae)].

    PubMed

    Sayenko, E M

    2016-01-01

    Glochidia of three freshwater anodontine bivalves: Kunashiria Starobogatov in Zatrawkin, 1983, Sinanodonta Modell, 1944, from the Far East, and Anodonta Lamarck, 1799, were investigated by scanning electron microscopy. Data on the microsculpture of the outer surface of glochidial valves are given. Among the three genera discussed, the glochidia of Anodonta are the largest, with a loose-looped outer microsculpture and numerous granules. The glochidia of Kunashiria and Sinanodonta differ by the valve height--length proportions and some details of the outer microsculpture: glochidia of Kunashiria have a tight-looped outer sculpture while the glochidia of Sinanodonta have a loose-net outer sculpture. PMID:27396177

  5. Intraspecific competition and high food availability are associated with insular gigantism in a lizard

    NASA Astrophysics Data System (ADS)

    Pafilis, Panayiotis; Meiri, Shai; Foufopoulos, Johannes; Valakos, Efstratios

    2009-09-01

    Resource availability, competition, and predation commonly drive body size evolution. We assess the impact of high food availability and the consequent increased intraspecific competition, as expressed by tail injuries and cannibalism, on body size in Skyros wall lizards ( Podarcis gaigeae). Lizard populations on islets surrounding Skyros (Aegean Sea) all have fewer predators and competitors than on Skyros but differ in the numbers of nesting seabirds. We predicted the following: (1) the presence of breeding seabirds (providing nutrients) will increase lizard population densities; (2) dense lizard populations will experience stronger intraspecific competition; and (3) such aggression, will be associated with larger average body size. We found a positive correlation between seabird and lizard densities. Cannibalism and tail injuries were considerably higher in dense populations. Increases in cannibalism and tail loss were associated with large body sizes. Adult cannibalism on juveniles may select for rapid growth, fuelled by high food abundance, setting thus the stage for the evolution of gigantism.

  6. Giants among larges: how gigantism impacts giant virus entry into amoebae.

    PubMed

    Rodrigues, Rodrigo Araújo Lima; Abrahão, Jônatas Santos; Drumond, Betânia Paiva; Kroon, Erna Geessien

    2016-06-01

    The proposed order Megavirales comprises the nucleocytoplasmic large DNA viruses (NCLDV), infecting a wide range of hosts. Over time, they co-evolved with different host cells, developing various strategies to penetrate them. Mimiviruses and other giant viruses enter cells through phagocytosis, while Marseillevirus and other large viruses explore endocytosis and macropinocytosis. These differing strategies might reflect the evolution of those viruses. Various scenarios have been proposed for the origin and evolution of these viruses, presenting one of the most enigmatic issues to surround these microorganisms. In this context, we believe that giant viruses evolved independently by massive gene/size gain, exploring the phagocytic pathway of entry into amoebas. In response to gigantism, hosts developed mechanisms to evade these parasites. PMID:27039270

  7. A gigantic, exceptionally complete titanosaurian sauropod dinosaur from southern Patagonia, Argentina.

    PubMed

    Lacovara, Kenneth J; Lamanna, Matthew C; Ibiricu, Lucio M; Poole, Jason C; Schroeter, Elena R; Ullmann, Paul V; Voegele, Kristyn K; Boles, Zachary M; Carter, Aja M; Fowler, Emma K; Egerton, Victoria M; Moyer, Alison E; Coughenour, Christopher L; Schein, Jason P; Harris, Jerald D; Martínez, Rubén D; Novas, Fernando E

    2014-01-01

    Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death. PMID:25186586

  8. Gigantic directional asymmetry of luminescence in multiferroic CuB 2O 4

    NASA Astrophysics Data System (ADS)

    Toyoda, S.; Abe, N.; Arima, T.

    2016-05-01

    In multiferroic materials, luminescence intensities can be direction dependent, i.e., different between the opposite propagating directions of emitted light. However, the effect has not been thought to be used for technological applications, since only small directional asymmetry has been reported so far. Here we show that the effect is robust in multiferroic CuB2O4 . The luminescence intensity changes by about 70 % between the opposite directions of the emission, which is about 100 times larger than the previously reported values. We demonstrate that such a gigantic directional asymmetry of luminescence can be applied to the imaging of canted antiferromagnetic domains. The observation of the effect and its application to magnetic domain imaging are important for a deeper understanding of light-matter interactions as well as technological applications such as optical reading techniques for magnetic memory devices.

  9. Gate-tunable gigantic lattice deformation in VO{sub 2}

    SciTech Connect

    Okuyama, D. E-mail: nakano@imr.tohoku.ac.jp Hatano, T.; Nakano, M. E-mail: nakano@imr.tohoku.ac.jp; Takeshita, S.; Ohsumi, H.; Tardif, S.; Shibuya, K.; Yumoto, H.; Koyama, T.; Ohashi, H.; Takata, M.; Kawasaki, M.; Tokura, Y.; Iwasa, Y. E-mail: nakano@imr.tohoku.ac.jp; Arima, T.

    2014-01-13

    We examined the impact of electric field on crystal lattice of vanadium dioxide (VO{sub 2}) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO{sub 2} decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature.

  10. Can Oxygen Set Thermal Limits in an Insect and Drive Gigantism?

    PubMed Central

    Verberk, Wilco C. E. P.; Bilton, David T.

    2011-01-01

    Background Thermal limits may arise through a mismatch between oxygen supply and demand in a range of animal taxa. Whilst this oxygen limitation hypothesis is supported by data from a range of marine fish and invertebrates, its generality remains contentious. In particular, it is unclear whether oxygen limitation determines thermal extremes in tracheated arthropods, where oxygen limitation may be unlikely due to the efficiency and plasticity of tracheal systems in supplying oxygen directly to metabolically active tissues. Although terrestrial taxa with open tracheal systems may not be prone to oxygen limitation, species may be affected during other life-history stages, particularly if these rely on diffusion into closed tracheal systems. Furthermore, a central role for oxygen limitation in insects is envisaged within a parallel line of research focussing on insect gigantism in the late Palaeozoic. Methodology/Principal Findings Here we examine thermal maxima in the aquatic life stages of an insect at normoxia, hypoxia (14 kPa) and hyperoxia (36 kPa). We demonstrate that upper thermal limits do indeed respond to external oxygen supply in the aquatic life stages of the stonefly Dinocras cephalotes, suggesting that the critical thermal limits of such aquatic larvae are set by oxygen limitation. This could result from impeded oxygen delivery, or limited oxygen regulatory capacity, both of which have implications for our understanding of the limits to insect body size and how these are influenced by atmospheric oxygen levels. Conclusions/Significance These findings extend the generality of the hypothesis of oxygen limitation of thermal tolerance, suggest that oxygen constraints on body size may be stronger in aquatic environments, and that oxygen toxicity may have actively selected for gigantism in the aquatic stages of Carboniferous arthropods. PMID:21818347

  11. The Early ULF Signal of the Gigantic Jets Revealed By Hilbert-Huang Transform

    NASA Astrophysics Data System (ADS)

    Huang, Po-Hsun; Bing-Chih Chen, Alfred

    2015-04-01

    The conventional Fourier analysis on the sferics in ULF and VLF bandpasses has been done for years. Several phenomena e.g. whistler and Schumann resonance have been well studied by the Fourier spectrum comprehensively. But the Fourier analysis is computed by an integration over time, therefore, the temporal resolution is smoothed, and limited not only by the sampling rate but also the size of the integration window. The instantaneous frequency can't be obtained through this conventional approach. We introduce the Hilbert-Huang transform (HHT) instead of Fourier transform to analyze the sferics of TLEs recorded at Lulin observatory. The Hilbert-Huang transform decomposes a signal into so-called intrinsic mode functions (IMF), and derive instantaneous frequency data by differentiating the phase angle yielded by Hilbert transform. Our analysis of HHT on several gigantic jets recorded by ground observation surprisingly revealed an early signal of frequency-change during the phase of the leading jet, and this early signal can not be identified by Fourier analysis. In the phase of leading jet, the amplitude of the sferics remains a constant and no significant features are recognized in the recorded waveform, but an obvious frequency change about 100-200 millisecond prior to the main discharge of the full development jets (FDJs), which can be clearly recognized in the HHT spectra of all observed gigantic jets. From a further simulation, this frequency change is confirmed to come from the nature of the discharge, not an alias or a false signal generated by the analysis method. This early signal may implies an in-cloud discharge process which is suggested by Krehbiel et al. [2008

  12. Conservation of Gbx genes from EHG homeobox in bivalve molluscs.

    PubMed

    Mesías-Gansbiller, Crimgilt; Sánchez, José L; Pazos, Antonio J; Lozano, Vanessa; Martínez-Escauriaza, Roi; Luz Pérez-Parallé, M

    2012-04-01

    Homeobox-containing genes encode a set of transcription factors that have been shown to control spatial patterning mechanisms in bilaterian organism development. The homeobox gene Gbx, included in the EHGbox cluster, is implicated in the development of the nervous system. In this study, we surveyed five different families of Bivalvia for the presence of Gbx genes by means of PCR with degenerate primers. We were able to recover seven Gbx gene fragments from five bivalve species: Solen marginatus, Mimachlamys varia, Venerupis pullastra, Ostrea edulis and Mytilus galloprovincialis (the derived amino acid sequence were designated Sma-Gbx, Cva-Gbx, Vpu-Gbx, Oed-Gbx and Mga-Gbx, respectively). These genes are orthologous to various Gbx genes present in bilaterian genomes. The Gbx genes in four Bivalvia families, namely Solenidae, Veneridae, Ostreidae and Mytilidae, are newly reported here and we also showed additional information of the Gbx genes of Pectinidae. The phylogenetic analyses by neighbour-joining, UPGMA, maximum parsimony and Bayesian analysis clearly indicated that the Gbx sequences formed a well supported clade and assigned these Gbx genes to the Gbx family. These data permit to confirm that the homeodomain of the Gbx family is highly conserved among these five distinct families of bivalve molluscs. PMID:22245384

  13. The miRNA biogenesis in marine bivalves.

    PubMed

    Rosani, Umberto; Pallavicini, Alberto; Venier, Paola

    2016-01-01

    Small non-coding RNAs include powerful regulators of gene expression, transposon mobility and virus activity. Among the various categories, mature microRNAs (miRNAs) guide the translational repression and decay of several targeted mRNAs. The biogenesis of miRNAs depends on few gene products, essentially conserved from basal to higher metazoans, whose protein domains allow specific interactions with dsRNA. Here, we report the identification of key genes responsible of the miRNA biogenesis in 32 bivalves, with particular attention to the aquaculture species Mytilus galloprovincialis and Crassostrea gigas. In detail, we have identified and phylogenetically compared eight evolutionary conserved proteins: DROSHA, DGCR8, EXP5, RAN, DICER TARBP2, AGO and PIWI. In mussels, we recognized several other proteins participating in the miRNA biogenesis or in the subsequent RNA silencing. According to digital expression analysis, these genes display low and not inducible expression levels in adult mussels and oysters whereas they are considerably expressed during development. As miRNAs play an important role also in the antiviral responses, knowledge on their production and regulative effects can shed light on essential molecular processes and provide new hints for disease prevention in bivalves. PMID:26989613

  14. The miRNA biogenesis in marine bivalves

    PubMed Central

    Rosani, Umberto; Pallavicini, Alberto

    2016-01-01

    Small non-coding RNAs include powerful regulators of gene expression, transposon mobility and virus activity. Among the various categories, mature microRNAs (miRNAs) guide the translational repression and decay of several targeted mRNAs. The biogenesis of miRNAs depends on few gene products, essentially conserved from basal to higher metazoans, whose protein domains allow specific interactions with dsRNA. Here, we report the identification of key genes responsible of the miRNA biogenesis in 32 bivalves, with particular attention to the aquaculture species Mytilus galloprovincialis and Crassostrea gigas. In detail, we have identified and phylogenetically compared eight evolutionary conserved proteins: DROSHA, DGCR8, EXP5, RAN, DICER TARBP2, AGO and PIWI. In mussels, we recognized several other proteins participating in the miRNA biogenesis or in the subsequent RNA silencing. According to digital expression analysis, these genes display low and not inducible expression levels in adult mussels and oysters whereas they are considerably expressed during development. As miRNAs play an important role also in the antiviral responses, knowledge on their production and regulative effects can shed light on essential molecular processes and provide new hints for disease prevention in bivalves. PMID:26989613

  15. Deployed bivalves (oysters and clams) as indicators of estuarine condition

    SciTech Connect

    Ringwood, A.H.; Holland, A.F.; Keppler, C.; Wert, M.; Hyland, J.

    1995-12-31

    Hatchery-reared bivalves, oysters (Crassostrea virginica) and clams (Mercenaria mercenaria), were deployed simultaneously at reference and degraded sites in SC estuaries for approximately 1 month. Juvenile bivalves with endogenously high growth rates were used because effects on growth can be detected in a short time frame. The effects on growth and bioaccumulation of metal contaminants, as well as two biochemical indices (expression of metallothioneins, MT, and multi-xenobiotic transporting proteins, {at}R) were evaluated. Metal concentrations of sediments were also measured. Adverse effects on growth of both species were observed at degraded sites. However, oysters tended to grow more rapidly than clams, and adverse effects on oysters were more pronounced than in clams. Many of the sediments were characterized by elevated concentrations of multiple metals (Cu, Pb, Cr, etc.). However, increases in metal concentrations of oyster tissues were observed primarily with Cu, suggesting that many of the other metals had low bioavailability. There was little evidence of bioconcentration of any metals in clams. There was a significant correlation between sediment Cu and Cu in oyster tissues, but not in clams. Alterations in MT and MXR expression were also observed in oysters deployed at degraded sites. These studies suggest that oysters may be better in-situ indicators of habitat condition because they have more rapid growth rates and greater bioaccumulation potentials.

  16. Metal levels in economically important bivalve species from Turkey.

    PubMed

    Colakoglu, S; Ulukoy, G; Ormanci, H B; Colakoglu, F A

    2012-01-01

    Concentrations of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were determined in economically important bivalve species: oyster (Ostrea edulis), wedge clam (Donax trunculus), manila clam (Ruditapes philippinarium) and warty clam (Venus verrucosa) from the Marmara and Aegean seas. Samples were collected seasonally between 2008 and 2009. Metal levels of bivalves were found in the following ranges: As 0.02-3.40, Cd 0.02-2.80, Cr 0.19-0.82, Cu 0.82-25.06, Hg < LOD-0.12, Ni 0.09-0.73, Pb 0.05-4.16 and Zn 6.85-899 mg kg(-1). The most abundant elements were Zn > Cu > As. In addition, the results showed that oysters had the highest concentrations of Zn in all seasons. The next abundant heavy metal detected was Cu in oyster and other clam species. It was concluded that in the future, these metals should be monitored regularly. PMID:24786409

  17. Flexible digestion strategies and trace metal assimilation in marine bivalves

    USGS Publications Warehouse

    Decho, Alan W.; Luoma, Samuel N.

    1996-01-01

    Pulse-chase experiments show that two marine bivalves take optimal advantage of different types of particulate food by varying food retention time in a flexible two-phase digestive system. For example, carbon is efficiently assimilated from bacteria by subjecting nearly all the ingested bacteria to prolonged digestion. Prolonging digestion also enhances assimilation of metals, many of which are toxic in minute quantities if they are biologically available. Detritus-feeding aquatic organisms have always lived in environments naturally rich in particle-reactive metals. We suggest that avoiding excess assimilation of metals could be a factor in the evolution of digestion strategies. We tested that suggestion by studying digestion of particles containing different Cr concentrations. We show that bivalves are capable of modifying the digestive processing of food to reduce exposure to high, biologically available, Cr concentrations. The evolution of a mechanism in some species to avoid high concentrations of metals in food could influence how effects of modern metal pollution are manifested in marine ecosystems.

  18. Metabolic dominance of bivalves predates brachiopod diversity decline by more than 150 million years

    PubMed Central

    Payne, Jonathan L.; Heim, Noel A.; Knope, Matthew L.; McClain, Craig R.

    2014-01-01

    Brachiopods and bivalves feed in similar ways and have occupied the same environments through geological time, but brachiopods were far more diverse and abundant in the Palaeozoic whereas bivalves dominate the post-Palaeozoic, suggesting a transition in ecological dominance 250 Ma. However, diversity and abundance data alone may not adequately describe key changes in ecosystem function, such as metabolic activity. Here, we use newly compiled body size data for 6066 genera of bivalves and brachiopods to calculate metabolic rates and revisit this question from the perspective of energy use, finding that bivalves already accounted for a larger share of metabolic activity in Palaeozoic oceans. We also find that the metabolic activity of bivalves has increased by more than two orders of magnitude over this interval, whereas brachiopod metabolic activity has declined by more than 50%. Consequently, the increase in bivalve energy metabolism must have occurred via the acquisition of new food resources rather than through the displacement of brachiopods. The canonical view of a mid-Phanerozoic transition from brachiopod to bivalve dominance results from a focus on taxonomic diversity and numerical abundance as measures of ecological importance. From a metabolic perspective, the oceans have always belonged to the clams. PMID:24671970

  19. A Gray-purple Mass on the Floor of the Mouth: Gigantic Mucogingival Pyogenic Granuloma in a Teenage Patient

    PubMed Central

    Brunet-LLobet, Lluís; Miranda-Rius, Jaume; Lahor-Soler, Eduard; Mrina, Ombeni; Nadal, Alfons

    2014-01-01

    Pyogenic granuloma is defined as a benign neoplasm of vascular phenotype. This case describes the clinical and histopathological features of a gigantic mucogingival pyogenic granuloma, in a 14-year-old healthy black boy. This exophytic gray-purple mass, related to a toothpick injury, had more than twelve-month evolution on the anterior mandible involving lingual area besides to the floor of the mouth pressing the right salivary duct. Conservative excision was performed, followed by uncomplicated healing with no recurrence in two years. The histopathological examination reported a pyogenic granuloma (lobular capillary haemangioma). The authors provide a discussion of the presurgical differential diagnosis of the lesion. This case report presents an extremely uncommon location of a gigantic pyogenic granuloma, involving mucogingival complex and affecting the salivary outflow. This clinical manuscript may shed light on the controversies about possible mechanisms inducing oral pyogenic granuloma. PMID:24987485

  20. A new Rosalina (foraminifera) parasitic on a bivalve

    USGS Publications Warehouse

    Todd, R.

    1965-01-01

    In a collection of pelecypods from deep water off the west coast of Africa, several specimens of a new species of the foraminifer, Rosalina, are attached to the umbonal area of the bivalve. In addition, numerous attachment scars are observed on the exterior surface with interconnected penetration scars on the interior surface of the valves. It is speculated that the foraminifer made the partial or complete penetration of the clam shell in connection with its search for calcium carbonate for shell-building. From the nature of the scars on the interior of the valves, it is clear that the clam was alive, because there are mounded up shell deposits around some of the openings and others are completely sealed shut by shell material deposited by the clam. ?? 1965.

  1. Selectivity of end-Cretaceous marine bivalve extinctions

    NASA Technical Reports Server (NTRS)

    Jablonski, D.; Raup, D. M.

    1995-01-01

    Analyses of the end-Cretaceous or Cretaceous-Tertiary mass extinction show no selectivity of marine bivalve genera by life position (burrowing versus exposed), body size, bathymetric position on the continental shelf, or relative breadth of bathymetric range. Deposit-feeders as a group have significantly lower extinction intensities than suspension-feeders, but this pattern is due entirely to low extinction in two groups (Nuculoida and Lucinoidea), which suggests that survivorship was not simply linked to feeding mode. Geographically widespread genera have significantly lower extinction intensities than narrowly distributed genera. These results corroborate earlier work suggesting that some biotic factors that enhance survivorship during times of lesser extinction intensities are ineffectual during mass extinctions.

  2. Selective extinction among Early Jurassic bivalves: A consequence of anoxia

    NASA Astrophysics Data System (ADS)

    Aberhan, Martin; Baumiller, Tomasz K.

    2003-12-01

    Analyses of taxonomically standardized data sets demonstrate several statistically robust extinction patterns in Early Jurassic bivalve species from northwest Europe and the Andean basins of South America. In both regions, extinction intensities were significantly enhanced in late Pliensbachian and early Toarcian time as compared to all other time intervals. The same intervals (except for the early Toarcian of South America) also represent times of unusual extinction selectivity, with infaunal taxa suffering distinctly more than epifaunal forms. As infaunal suspension feeders are extremely rare components of Early Jurassic oxygen-controlled macrofaunas, these results are entirely compatible with sedimentological and geochemical data suggesting that widespread anoxia was a principal cause of the diversity crisis. Although many biotic traits that enhance survivorship during background times seem to be irrelevant during major mass extinctions, patterns of survivorship selectivity may provide more distinct clues to the causes of less severe mass extinctions.

  3. Peculiarities of the geologic structure of gigantic gas fields of the western Siberian oil and gas province

    SciTech Connect

    Belyi, N.

    1991-03-01

    The Western Siberian Oil and Gas Province is a unique one regarding the concentration of natural gas resources in Mesozoic terrigenous formations. Discovery of gigantic natural gas fields makes it possible to provide high level of gas production for future prospects. The USSR has enormous potential possibilities for discoveries of new natural gas fields onshore, as well as offshore. At present, three gigantic gas fields have been developed, namely Medvezhie, Urongoi, and Yamburg. The first one has been in operation for 18 years. In the Mesozoic section, three productive complexes can be noticed: Upper Cretaceous, Lower Cretaceous, and Jurassic. The Upper Cretaceous production complex is mostly explored, with unique gas resources containing mainly methane having been discovered. The Lower Cretaceous production complex is characterized by considerable lithofaceous uniformity of reservoirs. Gas pools of this complex contain considerable quantities of condensate quite often having oil rims. The Jurassic production complex, which is characterized by its complicated structure and considerable changeability of the filtration properties, is less studied. Study of the geological structural peculiarities of the gigantic gas fields of Western Siberia gives us the possibility to find new approval for the development and exploration of gas fields.

  4. Gravity combined with laser-scan in Grotta Gigante: a benchmark cave for gravity studies

    NASA Astrophysics Data System (ADS)

    Pivetta, Tommaso; Braitenberg, Carla

    2014-05-01

    Laser scanning has become one of the most important topographic techniques in the last decades, due to its ability to reconstruct complex surfaces with high resolution and precision and due to its fast acquisition time. Recently a laser-scan survey has been acquired (Fingolo et al., 2011) in the "Grotta Gigante" cave near Trieste, Italy, the biggest cave worldwide according to the Guinness Awards. In this paper this survey is used to obtain a 3D discretization of the cave with prisms. Then through this new model, with the densities derived from campaign measurements, the exact gravimetric effect of the structure was computed (Nagy et al., 2000) and compared with the gravity observation at the surface. The transition from the cloud of laser-scan points to the prism model was carried out by different computer elaborations; first of all the reduction of the data density through an averaging process that allows to pass from over 10000 points/m2 to less than 10points/m2. Then the whole dataset was filtered from the outliers by the means of a simple quadratic surface that fit the data (Turner, 1999). The reduced data points should be divided into the 2 surfaces of top and bottom, that are used to define the prisms. This step was performed using the local regression method (Loess) to calculate a surface located halfway between top and bottom points. Once the top and bottom interfaces were obtained it was possible to get the final prism representation and calculate the gravity signal. The observed Bouguer field is explained very well by our model and the residuals are used to evaluate possible secondary caves. The final prism model together with the gravity database on surface and inside the cave form a perfect benchmark to test forward and inverse potential field algorithms. References Fingolo M., Facco L., Ceccato A., Breganze C., Paganini P., Cezza M., Grotta Gigante di Trieste. Tra realtà virtuale e rilievi 3D ad alta risoluzione, Veneto Geologi, 75, pp.21-25, 2011

  5. Protozoan parasites of bivalve molluscs: literature follows culture.

    PubMed

    Fernández Robledo, José A; Vasta, Gerardo R; Record, Nicholas R

    2014-01-01

    Bivalve molluscs are key components of the estuarine environments as contributors to the trophic chain, and as filter -feeders, for maintaining ecosystem integrity. Further, clams, oysters, and scallops are commercially exploited around the world both as traditional local shellfisheries, and as intensive or semi-intensive farming systems. During the past decades, populations of those species deemed of environmental or commercial interest have been subject to close monitoring given the realization that these can suffer significant decline, sometimes irreversible, due to overharvesting, environmental pollution, or disease. Protozoans of the genera Perkinsus, Haplosporidium, Marteilia, and Bonamia are currently recognized as major threats for natural and farmed bivalve populations. Since their identification, however, the variable publication rates of research studies addressing these parasitic diseases do not always appear to reflect their highly significant environmental and economic impact. Here we analyzed the peer- reviewed literature since the initial description of these parasites with the goal of identifying potential milestone discoveries or achievements that may have driven the intensity of the research in subsequent years, and significantly increased publication rates. Our analysis revealed that after initial description of the parasite as the etiological agent of a given disease, there is a time lag before a maximal number of yearly publications are reached. This has already taken place for most of them and has been followed by a decrease in publication rates over the last decade (20- to 30- year lifetime in the literature). Autocorrelation analyses, however, suggested that advances in parasite purification and culture methodologies positively drive publication rates, most likely because they usually lead to novel molecular tools and resources, promoting mechanistic studies. Understanding these trends should help researchers in prioritizing research

  6. Protozoan Parasites of Bivalve Molluscs: Literature Follows Culture

    PubMed Central

    Fernández Robledo, José A.; Vasta, Gerardo R.; Record, Nicholas R.

    2014-01-01

    Bivalve molluscs are key components of the estuarine environments as contributors to the trophic chain, and as filter –feeders, for maintaining ecosystem integrity. Further, clams, oysters, and scallops are commercially exploited around the world both as traditional local shellfisheries, and as intensive or semi–intensive farming systems. During the past decades, populations of those species deemed of environmental or commercial interest have been subject to close monitoring given the realization that these can suffer significant decline, sometimes irreversible, due to overharvesting, environmental pollution, or disease. Protozoans of the genera Perkinsus, Haplosporidium, Marteilia, and Bonamia are currently recognized as major threats for natural and farmed bivalve populations. Since their identification, however, the variable publication rates of research studies addressing these parasitic diseases do not always appear to reflect their highly significant environmental and economic impact. Here we analyzed the peer– reviewed literature since the initial description of these parasites with the goal of identifying potential milestone discoveries or achievements that may have driven the intensity of the research in subsequent years, and significantly increased publication rates. Our analysis revealed that after initial description of the parasite as the etiological agent of a given disease, there is a time lag before a maximal number of yearly publications are reached. This has already taken place for most of them and has been followed by a decrease in publication rates over the last decade (20– to 30– year lifetime in the literature). Autocorrelation analyses, however, suggested that advances in parasite purification and culture methodologies positively drive publication rates, most likely because they usually lead to novel molecular tools and resources, promoting mechanistic studies. Understanding these trends should help researchers in prioritizing

  7. Evolutionary implications of endosymbiont diversity within lucinid bivalves

    NASA Astrophysics Data System (ADS)

    Garcia, A. M.; Thiessen, M.; Aronowsky, A.; Anderson, L.; Bao, H.; Engel, A.

    2007-12-01

    Bacterial endosymbiosis is widespread among Bivalvia. Symbiosis between lucinid bivalves and sulfur-oxidizing (thiotrophic) bacteria has received recent attention, as lucinids are one of the geologically oldest extant bivalve clades to possess endosymbionts. However, the ecological and evolutionary relationships between host and symbiont are poorly understood, and reconstructing the evolutionary history and geological significance of lucinid endosymbiosis requires additional knowledge and characterization of endosymbiont ecology and taxonomic diversity. Our goal was to characterize the bacterial diversity of a modern lucinid habitat in order to evaluate possible lucinid endosymbiont diversity. Host organisms ( Lucinisca nassula and Phacoides pectinatus) and sediment cores were collected from geochemically reducing and sulfide-rich sea grass beds. PCR amplification and sequencing of bacterial 16S rRNA genes from the sediment cores retrieved 13 major taxonomic groups, including equally dominant Chloroflexi, Delta-, and Gammaproteobacteria, and rare Bacteroides, Acidobacteria, Spirochaetes, and Firmicutes. Less than 2% of the sequences were affiliated with uncultured gammaproteobacterial symbiont groups, but were not closely related to the sequences retrieved from the lucinid gills. Moreover, our analyses uncovered multiple gene sequence populations within an individual, as well as across individuals within the same sampling site. Additional habitat-host-symbiont diversity from three other lucinid taxa and from six geographically distinct habitat sites is also expanding the previously understood diversity of thiotrophic endosymbionts, and specifically that the lucinid symbionts are probably not a monophyletic species. These data suggest that thiotrophic bacteria are recruitable for endosymbiosis and are widely distributed in reducing marine environments. But, because of the diversity of bacteria in any one habitat, symbionts may be metabolically and physiologically

  8. Pinna nobilis: A big bivalve with big haemocytes?

    PubMed

    Matozzo, V; Pagano, M; Spinelli, A; Caicci, F; Faggio, C

    2016-08-01

    The fan mussel Pinna nobilis (Linnaeus, 1758) is one of the biggest bivalves worldwide. Currently, no updated information is available in the literature concerning the morpho-functional aspects of haemocytes from this bivalve species. Consequently, in this study, we characterised P. nobilis haemocytes from both a morphological and functional point of view. The mean number of haemocytes was about 5 (×10(5)) cells mL haemolymph(-1), and the cell viability was about 92-100%. Two haemocyte types were distinguished under the light microscope: granulocytes (51.6%), with evident cytoplasmic granules, and hyalinocytes (48.4%), with a few granules. The granules of the granulocytes were mainly lysosomes, as indicated by the in vivo staining with Neutral Red. Haemocytes were further distinguished in basophils (83.75%), acidophils (14.75%) and neutrophils (1.5%). After adhesion to slides and fixation, the cell diameter was approximately 10 μm for granulocytes and 7 μm for hyalinocytes. The granulocytes and hyalinocytes were both positive to the Periodic Acid-Schiff reaction for carbohydrates. Only granulocytes were able to phagocytise yeast cells. The phagocytic index (6%) increased significantly up to twofold after preincubation of yeast in cell-free haemolymph, suggesting that haemolymph has opsonising properties. In addition, haemocytes produce superoxide anion and acid and alkaline phosphatases. Summarising, this preliminary study indicates that both the granulocytes and hyalinocytes circulate in the haemolymph of P. nobilis and that they are active immunocytes. PMID:27346153

  9. The Late Triassic bivalve Monotis in accreted terranes of Alaska

    USGS Publications Warehouse

    Silberling, Norman J.; Grant-Mackie, J. A.; Nichols, K.M.

    1997-01-01

    Late Triassic bivalves of the genus Monotis occur in at least 16 of the lithotectonic terranes and subterranes that together comprise nearly all of Alaska, and they also occur in the Upper Yukon region of Alaska where Triassic strata are regarded as representing non-accretionary North America. On the basis of collections made thus far, 14 kinds of Monotis that differ at the species or subspecies level can be recognized from alaska. These are grouped into the subgenera Monotis (Monotis), M. (Pacimonotis), M. (Entomonotis), and M. (Eomonotis). In places, Monotis shells of one kind or another occur in rock-forming abundance. On the basis of superpositional data from Alaska, as well as from elsewhere in North America and Far Eastern Russia, at least four distince biostratigraphic levels can be discriminated utilizing Monotis species. Different species of M. (Eomonotis) characterize two middle Norian levels, both probably within the supper middle Norian Columbianus Ammonite Zone. Two additional levels are recognized in the lower upper Norian Cordilleranus Ammonite Zone utilizing species of M. (Monotis) or M. (Entomonotis), both of which subgenera are restricted to the late Norian. An attached-floating mode of life is commonly attributed to Monotis; thus, these bivalves would have been pseudoplanktonic surface dwellers that were sensitive to surface-water temperature and paleolatitude. Distinctly different kinds of Monotis occur at different paleolatitudes along the Pacific and Arctic margins of the North American craton inboard of the accreted terranes. Comparison between thse craton-bound Monotis faunas and those of the Alaskan terranes in southern Alaska south of the Denali fault were paleoequatorial in latitude during Late Triassic time. Among these terranes, the Alexander terrane was possibly in the southern hemisphere at that time. Terranes of northern Alaska, on the other hand, represent middle, possibly high-middle, northern paleolatitudes.

  10. Reproductive investment in the intertidal bivalve Macoma balthica

    NASA Astrophysics Data System (ADS)

    Honkoop, P. J. C.; Van der Meer, J.; Beukema, J. J.; Kwast, D.

    1999-05-01

    Bivalve eggs generally contain large amounts of lipids which, in comparison with proteins and carbohydrates, have high energy contents and are thus costly in energetic terms. As lipid contents vary between species, comparisons of reproductive investments should not only include numbers and sizes of eggs, but also their energy content. We estimated the investment in egg material of mature females of the Baltic tellin Macoma balthica (L.) in terms of both mass and energy content. All mass below a minimum body mass (below which no eggs are produced) was defined as structural mass. This threshold amounts to a body mass index (BMI) of 5.6 (ash-free dry mass per cubic shell length in mg cm -3). More than half (55%) of the mass above the structural mass was invested in egg material and 45% in extra somatic tissue and tissue for production and storage of gametes. This means that the amount of eggs spawned ranged from 0 (at BMI = 5.6 mg cm -3) to 33% of the total ash-free dry mass (at a high BMI value of 14 mg cm -3). Eggs contained a relatively large amount of lipids, about 30% of their ash-free dry mass, whereas non-egg material contained only about 7% lipids. Eggs of two other bivalves in the Wadden Sea, the cockle Cerastoderma edule and the mussel Mytilus edulis, were smaller and contained only about 11% and 20% lipids, respectively. Energy content of M. balthica eggs amounted to ˜0.006 J, in the other two species to ˜0.002 J. The function of the more expensive eggs in M. balthica may be related to its early spawning in spring, causing slower larval development until first feeding.

  11. Magnetosome-containing bacteria living as symbionts of bivalves

    PubMed Central

    Dufour, Suzanne C; Laurich, Jason R; Batstone, Rebecca T; McCuaig, Bonita; Elliott, Alexander; Poduska, Kristin M

    2014-01-01

    Bacteria containing magnetosomes (protein-bound nanoparticles of magnetite or greigite) are common to many sedimentary habitats, but have never been found before to live within another organism. Here, we show that octahedral inclusions in the extracellular symbionts of the marine bivalve Thyasira cf. gouldi contain iron, can exhibit magnetic contrast and are most likely magnetosomes. Based on 16S rRNA sequence analysis, T. cf. gouldi symbionts group with symbiotic and free-living sulfur-oxidizing, chemolithoautotrophic gammaproteobacteria, including the symbionts of other thyasirids. T. cf. gouldi symbionts occur both among the microvilli of gill epithelial cells and in sediments surrounding the bivalves, and are therefore facultative. We propose that free-living T. cf. gouldi symbionts use magnetotaxis as a means of locating the oxic–anoxic interface, an optimal microhabitat for chemolithoautotrophy. T. cf. gouldi could acquire their symbionts from near-burrow sediments (where oxic–anoxic interfaces likely develop due to the host's bioirrigating behavior) using their superextensile feet, which could transfer symbionts to gill surfaces upon retraction into the mantle cavity. Once associated with their host, however, symbionts need not maintain structures for magnetotaxis as the host makes oxygen and reduced sulfur available via bioirrigation and sulfur-mining behaviors. Indeed, we show that within the host, symbionts lose the integrity of their magnetosome chain (and possibly their flagellum). Symbionts are eventually endocytosed and digested in host epithelial cells, and magnetosomes accumulate in host cytoplasm. Both host and symbiont behaviors appear important to symbiosis establishment in thyasirids. PMID:24914799

  12. Magnetosome-containing bacteria living as symbionts of bivalves.

    PubMed

    Dufour, Suzanne C; Laurich, Jason R; Batstone, Rebecca T; McCuaig, Bonita; Elliott, Alexander; Poduska, Kristin M

    2014-12-01

    Bacteria containing magnetosomes (protein-bound nanoparticles of magnetite or greigite) are common to many sedimentary habitats, but have never been found before to live within another organism. Here, we show that octahedral inclusions in the extracellular symbionts of the marine bivalve Thyasira cf. gouldi contain iron, can exhibit magnetic contrast and are most likely magnetosomes. Based on 16S rRNA sequence analysis, T. cf. gouldi symbionts group with symbiotic and free-living sulfur-oxidizing, chemolithoautotrophic gammaproteobacteria, including the symbionts of other thyasirids. T. cf. gouldi symbionts occur both among the microvilli of gill epithelial cells and in sediments surrounding the bivalves, and are therefore facultative. We propose that free-living T. cf. gouldi symbionts use magnetotaxis as a means of locating the oxic-anoxic interface, an optimal microhabitat for chemolithoautotrophy. T. cf. gouldi could acquire their symbionts from near-burrow sediments (where oxic-anoxic interfaces likely develop due to the host's bioirrigating behavior) using their superextensile feet, which could transfer symbionts to gill surfaces upon retraction into the mantle cavity. Once associated with their host, however, symbionts need not maintain structures for magnetotaxis as the host makes oxygen and reduced sulfur available via bioirrigation and sulfur-mining behaviors. Indeed, we show that within the host, symbionts lose the integrity of their magnetosome chain (and possibly their flagellum). Symbionts are eventually endocytosed and digested in host epithelial cells, and magnetosomes accumulate in host cytoplasm. Both host and symbiont behaviors appear important to symbiosis establishment in thyasirids. PMID:24914799

  13. Life history traits to predict biogeographic species distributions in bivalves

    NASA Astrophysics Data System (ADS)

    Montalto, V.; Rinaldi, A.; Sarà, G.

    2015-10-01

    Organismal fecundity ( F) and its relationship with body size (BS) are key factors in predicting species distribution under current and future scenarios of global change. A functional trait-based dynamic energy budget (FT-DEB) is proposed as a mechanistic approach to predict the variation of F and BS as function of environmental correlates using two marine bivalves as model species ( Mytilus galloprovincialis and Brachidontes pharaonis). Validation proof of model skill (i.e., degree of correspondence between model predictions and field observations) and stationarity (i.e., ability of a model generated from data collected at one place/time to predict processes at another place/time) was provided to test model performance in predicting the bivalve distribution throughout the 22 sites in the Central Mediterranean Sea under local conditions of food density and body temperature. Model skill and stationarity were tested through the estimate of commission (i.e., proportion of species' absences predicted present) and omission (i.e., proportion of presences predicted absent) errors of predictions by comparing mechanistic predicted vs. observed F and BS values throughout the study area extrapolated by lab experiments and literature search. The resulting relationship was reliable for both species, and body size and fecundity were highly correlated in M. galloprovincialis compared to B. pharaonis; FT-DEB showed correct predictions of presence in more than 75 % of sites, and the regression between BS predicted vs. observed was highly significant in both species. Whilst recognising the importance of biotic interactions in shaping the distribution of species, our FT-DEB approach provided reliable quantitative estimates of where our species had sufficient F to support local populations or suggesting reproductive failure. Mechanistically, estimating F and BS as key traits of species life history can also be addressed within a broader, scale-dependent context that surpasses the

  14. Life history traits to predict biogeographic species distributions in bivalves.

    PubMed

    Montalto, V; Rinaldi, A; Sarà, G

    2015-10-01

    Organismal fecundity (F) and its relationship with body size (BS) are key factors in predicting species distribution under current and future scenarios of global change. A functional trait-based dynamic energy budget (FT-DEB) is proposed as a mechanistic approach to predict the variation of F and BS as function of environmental correlates using two marine bivalves as model species (Mytilus galloprovincialis and Brachidontes pharaonis). Validation proof of model skill (i.e., degree of correspondence between model predictions and field observations) and stationarity (i.e., ability of a model generated from data collected at one place/time to predict processes at another place/time) was provided to test model performance in predicting the bivalve distribution throughout the 22 sites in the Central Mediterranean Sea under local conditions of food density and body temperature. Model skill and stationarity were tested through the estimate of commission (i.e., proportion of species' absences predicted present) and omission (i.e., proportion of presences predicted absent) errors of predictions by comparing mechanistic predicted vs. observed F and BS values throughout the study area extrapolated by lab experiments and literature search. The resulting relationship was reliable for both species, and body size and fecundity were highly correlated in M. galloprovincialis compared to B. pharaonis; FT-DEB showed correct predictions of presence in more than 75 % of sites, and the regression between BS predicted vs. observed was highly significant in both species. Whilst recognising the importance of biotic interactions in shaping the distribution of species, our FT-DEB approach provided reliable quantitative estimates of where our species had sufficient F to support local populations or suggesting reproductive failure. Mechanistically, estimating F and BS as key traits of species life history can also be addressed within a broader, scale-dependent context that surpasses the

  15. Bioaccumulation of 210Po in common gastropod and bivalve species from the northern Gulf.

    PubMed

    Uddin, S; Bebhehani, M

    2014-06-01

    This study sets the baseline for the concentration of the natural-series radionuclide polonium-210 in two species of gastropods and four species of bivalves that are common to the Northern Arabian/Persian Gulf. (210)Po is primarily absorbed from water and via ingestion of detrital material by gastropoda and bivalves. This concentrated (210)Po can then be passed along to the next trophic level of the marine food web. The lowest (210)Po concentration was measured in the gastropod Stomatella auricular (10.36-12.39Bq kg(-1)dry) and the highest in the bivalve Marica marmorata (193.51-215.60Bq kg(-1)dry). The measured concentration factor for these molluscs in the northern Gulf varied between 4.8 and 115×10(3), values very similar to the IAEA recommended value for bivalves and gastropods of 2×10(4). PMID:24675441

  16. Draft Genome Sequence of the New Pathogen for Bivalve Larvae Vibrio bivalvicida

    PubMed Central

    Dubert, Javier; Spinard, Edward J.; Gomez-Chiarri, Marta

    2016-01-01

    Vibrio bivalvicida is a novel pathogen of bivalve larvae responsible for recent vibriosis outbreaks affecting shellfish hatcheries. Here, we announce the draft genome sequence of V. bivalvicida 605T and describe potential virulence factors. PMID:27056224

  17. Molecular and isotopic composition of lipids in modern and fossil bivalve shells: Records of paleoenvironmental change?

    SciTech Connect

    CoBabe, E.A.

    1995-12-31

    Suites of lipids residing in situ in modern and fossil bivalve shells offer new possibilities for the study of paleoecology and paleoclimatology. Distributions of carbon isotopic compositions of modem shell lipids suggests that many of these compounds, including alkanes, sterols, fatty acids, ketones and phytadienes, are derived from the bivalves and not directly from the surrounding environment. The occurrence of fatty acids in modem and fossil shell material opens up the possibility that saturation levels of these compounds may be used as paleothermometers. To date, the utility of fatty acids in paleoclimate studies has been limited because of the swift breakdown of these compounds in sediment. However, initial results indicate that fatty acids in bivalve shells retain their original structure for at least several million years. Comparison of modem bivalve shell fatty acids from tropical, temperate and polar nearshore marine systems will be presented, along with analogous fossil data.

  18. IMPLICATIONS FOR THE PRESENCE OF TRANSFORMING GENES IN GONADAL TUMORS IN TWO BIVALVE MOLLUSK SPECIES

    EPA Science Inventory

    Studies were initiated on oncogene activation in two bivalve species with high frequencies of histologically identifiable gonadal neoplasms. athological assessments identified epizootic seminomas and dysgerminomas in softshell clams (Mya arenaria) from three Maine estuarine sites...

  19. APPLICATION OF THE DNA ALKALINE UNWINDING ASSAY TO DETECT DNA STRAND BREAKS IN MARINE BIVALVES

    EPA Science Inventory

    DNA alkaline unwinding methods were used to detect DNA strand breaks in tissues of marine bivalves following field and laboratory exposures and subsequent recoveries in the laboratory. ield deployments of mussels (Mytilus edulis) or oysters (Crassostrea virginica) into two highly...

  20. POLYNUCLEAR AROMATIC HYDROCARBONS AND CELLULAR PROLIFERATIVE DISORDERS IN BIVALVE MOLLUSCS FROM OREGON ESTUARIES

    EPA Science Inventory

    Indigenous populations of economically important bivalve molluscs were used as monitors for detecting and quantifying environmental PNAH, including 11 compounds classified as carcinogens, 11 EPA Priority Pollutants and 11 Toxic Pollutants. Baseline levels of PNAH were determined ...

  1. High pressure processing of bivalve shellfish and HPP's potential use as a virus intervention

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bivalve shellfish readily bioconcentrate pathogenic microbes and substance, such as algal and dinoflagulate toxins, fecal viruses and bacteria, and naturally present vibrio bacteria. High pressure processing (HPP) is currently used as an intervention for Vibrio vulnificus bacteria within molluscan ...

  2. A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot.

    PubMed

    González Riga, Bernardo J; Lamanna, Matthew C; Ortiz David, Leonardo D; Calvo, Jorge O; Coria, Juan P

    2016-01-01

    Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus--seemingly adapted for bearing extraordinary weight--and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods. PMID:26777391

  3. A gigantic bird-like dinosaur from the Late Cretaceous of China.

    PubMed

    Xu, Xing; Tan, Qingwei; Wang, Jianmin; Zhao, Xijin; Tan, Lin

    2007-06-14

    An evolutionary trend of decreasing size is present along the line to birds in coelurosaurian theropod evolution, but size increases are seen in many coelurosaurian subgroups, in which large forms are less bird-like. Here we report on a new non-avian dinosaur, Gigantoraptor erlianensis, gen. et sp. nov., from the Late Cretaceous Iren Dabasu Formation of Nei Mongol, China. Although it has a body mass of about 1,400 kg, a phylogenetic analysis positions this new taxon within the Oviraptorosauria, a group of small, feathered theropods rarely exceeding 40 kg in body mass. A histological analysis suggests that Gigantoraptor gained this size by a growth rate considerably faster than large North American tyrannosaurs such as Albertosaurus and Gorgosaurus. Gigantoraptor possesses several salient features previously unknown in any other dinosaur and its hind limb bone scaling and proportions are significantly different from those of other coelurosaurs, thus increasing the morphological diversity among dinosaurs. Most significantly, the gigantic Gigantoraptor shows many bird-like features absent in its smaller oviraptorosaurian relatives, unlike the evolutionary trend seen in many other coelurosaurian subgroups. PMID:17565365

  4. Discovery of gigantic molecular nanostructures using a flow reaction array as a search engine

    PubMed Central

    Zang, Hong-Ying; de la Oliva, Andreu Ruiz; Miras, Haralampos N.; Long, De-Liang; McBurney, Roy T.; Cronin, Leroy

    2014-01-01

    The discovery of gigantic molecular nanostructures like coordination and polyoxometalate clusters is extremely time-consuming since a vast combinatorial space needs to be searched, and even a systematic and exhaustive exploration of the available synthetic parameters relies on a great deal of serendipity. Here we present a synthetic methodology that combines a flow reaction array and algorithmic control to give a chemical ‘real-space’ search engine leading to the discovery and isolation of a range of new molecular nanoclusters based on [Mo2O2S2]2+-based building blocks with either fourfold (C4) or fivefold (C5) symmetry templates and linkers. This engine leads us to isolate six new nanoscale cluster compounds: 1, {Mo10(C5)}; 2, {Mo14(C4)4(C5)2}; 3, {Mo60(C4)10}; 4, {Mo48(C4)6}; 5, {Mo34(C4)4}; 6, {Mo18(C4)9}; in only 200 automated experiments from a parameter space spanning ~5 million possible combinations. PMID:24770632

  5. Discovery of gigantic molecular nanostructures using a flow reaction array as a search engine.

    PubMed

    Zang, Hong-Ying; de la Oliva, Andreu Ruiz; Miras, Haralampos N; Long, De-Liang; McBurney, Roy T; Cronin, Leroy

    2014-01-01

    The discovery of gigantic molecular nanostructures like coordination and polyoxometalate clusters is extremely time-consuming since a vast combinatorial space needs to be searched, and even a systematic and exhaustive exploration of the available synthetic parameters relies on a great deal of serendipity. Here we present a synthetic methodology that combines a flow reaction array and algorithmic control to give a chemical 'real-space' search engine leading to the discovery and isolation of a range of new molecular nanoclusters based on [Mo(2)O(2)S(2)](2+)-based building blocks with either fourfold (C4) or fivefold (C5) symmetry templates and linkers. This engine leads us to isolate six new nanoscale cluster compounds: 1, {Mo(10)(C5)}; 2, {Mo(14)(C4)4(C5)2}; 3, {Mo(60)(C4)10}; 4, {Mo(48)(C4)6}; 5, {Mo(34)(C4)4}; 6, {Mo(18)(C4)9}; in only 200 automated experiments from a parameter space spanning ~5 million possible combinations. PMID:24770632

  6. Lower limb gigantism, lymphedema, and painful varicosities following a thigh vascular access graft.

    PubMed

    Thompson, Michael; Mathuram Thiyagarajan, Umasankar; Akoh, Jacob A

    2014-07-01

    Prosthetic arteriovenous grafts (AVGs) are associated with greater morbidity than autogenous arteriovenous fistulas (AVFs), but their use is indicated when AVF formation is not possible. This report adds to the literature a case of lower limb gigantism, painful varicosities, and lymphedema following long-term use of AVG in the upper thigh. The patient's past medical history included renal transplantation on the same side well before the AVG was inserted and right leg deep vein thrombosis. Suspicion of AVG thrombosis was excluded by Doppler ultrasound, which demonstrated an access flow of 1700 mL/min. A computed tomography (CT) scan of the abdomen and pelvis did not identify the cause of her symptoms. Whereas functional incompetence of the iliac vein valve might be responsible for the varicosities, the extent of hypertrophy in this case raises the suspicion of lymphatic blockage possibly secondary to groin dissection undertaken at the time of graft insertion, in addition to the previous dissection at the time of transplantation. This case highlights the need for minimal groin dissection during AVG insertion, particularly in patients with a history of previous abdominopelvic surgery. PMID:24467313

  7. The properties of a gigantic jet reflected in a simultaneous sprite: Observations interpreted by a model

    NASA Astrophysics Data System (ADS)

    Neubert, T.; Chanrion, O.; Arnone, E.; Zanotti, F.; Cummer, S.; Li, J.; Füllekrug, M.; Soula, S.; van der Velde, O.

    2011-12-01

    Thunderstorm clouds may discharge directly to the ionosphere in spectacular luminous jets - the largest electric discharges of our planet. The properties of these “giants,” such as their polarity, conductivity, and currents, have been predicted by models, but are poorly characterized by measurements. A recent observation of a giant, fortuitously illuminated by an unusual sprite discharge in the mesosphere, allows us to study their electric properties and effects on the atmosphere-ionosphere. We show from a first-principles model of the combined giant and sprite event that the observations are consistent with the nature of the giant being a leader in the stratosphere of line charge density ˜0.8 mCm-1 and of multiple streamers in the mesosphere. It is further shown that the giant modifies the free electron content of the lower ionosphere because of electric field-driven ionization, electron attachment and detachment processes. This is the first time that sprites are used for sounding the properties of the mesosphere. The results presented here will allow evaluation of theories for jet and gigantic jets and of their influence on the atmosphere and ionosphere.

  8. A Thermodynamic, kinematic and microphysical analysis of a jet and gigantic jet-producing Florida thunderstorm

    NASA Astrophysics Data System (ADS)

    Lazarus, S. M.; Splitt, M. E.; Brownlee, James; Spiva, Nicholas; Liu, Ningyu

    2015-08-01

    This paper presents a meteorological analysis of a storm that produced two jets, four gigantic jets (GJ), and a starter, which were observed by two radars as well as the Kennedy Space Center 4-Dimensional Lightning Surveillance System on 3 August 2013 in Central Florida. The work is the first application of dual polarization data to a jet-producing storm and is the fifth case related to a tropical disturbance. The storm environment is consistent with the moist tropical paradigm that characterizes about three quarters of the surface and aircraft observed jet and GJ events. The most unstable (MU) convective available potential energy is not unusual for Florida summer convection and is below the climatological mean for these events. An unusual speed shear layer is located near the storm equilibrium level (EL) and the storm exhibits a tilted structure with CGs displaced upshear. The turbulence, as measured by the eddy dissipation rate, is extreme near the storm top during the event window, consistent with the GJ mixing hypothesis. The individual events are collocated with, and track along, the center axis of the divergent outflow at the EL and occur within the region of the coldest GOES IR temperatures—placing the events within the overshoot. The dual polarization data indicate a deep graupel column, extending above the mixed phase layer, to a 13 km altitude.

  9. A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot

    PubMed Central

    González Riga, Bernardo J.; Lamanna, Matthew C.; Ortiz David, Leonardo D.; Calvo, Jorge O.; Coria, Juan P.

    2016-01-01

    Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus—seemingly adapted for bearing extraordinary weight—and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods. PMID:26777391

  10. Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism

    PubMed Central

    Claessens, Leon P. A. M.; O'Connor, Patrick M.; Unwin, David M.

    2009-01-01

    Pterosaurs, enigmatic extinct Mesozoic reptiles, were the first vertebrates to achieve true flapping flight. Various lines of evidence provide strong support for highly efficient wing design, control, and flight capabilities. However, little is known of the pulmonary system that powered flight in pterosaurs. We investigated the structure and function of the pterosaurian breathing apparatus through a broad scale comparative study of respiratory structure and function in living and extinct archosaurs, using computer-assisted tomographic (CT) scanning of pterosaur and bird skeletal remains, cineradiographic (X-ray film) studies of the skeletal breathing pump in extant birds and alligators, and study of skeletal structure in historic fossil specimens. In this report we present various lines of skeletal evidence that indicate that pterosaurs had a highly effective flow-through respiratory system, capable of sustaining powered flight, predating the appearance of an analogous breathing system in birds by approximately seventy million years. Convergent evolution of gigantism in several Cretaceous pterosaur lineages was made possible through body density reduction by expansion of the pulmonary air sac system throughout the trunk and the distal limb girdle skeleton, highlighting the importance of respiratory adaptations in pterosaur evolution, and the dramatic effect of the release of physical constraints on morphological diversification and evolutionary radiation. PMID:19223979

  11. Discovery of gigantic molecular nanostructures using a flow reaction array as a search engine

    NASA Astrophysics Data System (ADS)

    Zang, Hong-Ying; de La Oliva, Andreu Ruiz; Miras, Haralampos N.; Long, De-Liang; McBurney, Roy T.; Cronin, Leroy

    2014-04-01

    The discovery of gigantic molecular nanostructures like coordination and polyoxometalate clusters is extremely time-consuming since a vast combinatorial space needs to be searched, and even a systematic and exhaustive exploration of the available synthetic parameters relies on a great deal of serendipity. Here we present a synthetic methodology that combines a flow reaction array and algorithmic control to give a chemical ‘real-space’ search engine leading to the discovery and isolation of a range of new molecular nanoclusters based on [Mo2O2S2]2+-based building blocks with either fourfold (C4) or fivefold (C5) symmetry templates and linkers. This engine leads us to isolate six new nanoscale cluster compounds: 1, {Mo10(C5)}; 2, {Mo14(C4)4(C5)2}; 3, {Mo60(C4)10}; 4, {Mo48(C4)6}; 5, {Mo34(C4)4}; 6, {Mo18(C4)9}; in only 200 automated experiments from a parameter space spanning ~5 million possible combinations.

  12. Evolución de planetas gigantes y posibilidades de su detección directa

    NASA Astrophysics Data System (ADS)

    Brunini, A.; Benvenuto, O. G.

    Desde la reciente detección de planetas gigantes orbitando estrellas cercanas de tipo solar por medio de efecto Doppler, uno de los principales problemas, en cuanto al estudio de los sistemas planetarios extrasolares, se refiere a la posibilidad de obtener evidencia directa de su existencia. Esto parece ser factible gracias a que en un futuro cercano entrarán en operación algunos telescopios especialmente adecuados a estos propósitos. Por tal motivo, hemos comenzado desde hace un tiempo un esfuerzo en cuanto al estudio de la evolución planetaria. A tales efectos hemos adaptado el código de evolución estelar de nuestro Observatorio al caso planetario. Las principales diferencias entre el caso estelar y el planetario se encuentran en la ecuación de estado. A tales fines hemos incluído la reciente ecuación de estado de Saumon, Chabrier y Van Horn, las opacidades radiativas de Guillot et al., procesos de quema de Deuterio, etc. También se ha considerado la posible existencia de fases de hielo y roca en el interior planetario. Por el momento hemos despreciado los efectos de la rotación planetaria. Con este código hemos computado la evolución de planetas con masas desde 10 hasta 0.3 masas de Júpiter. Utilizando nuestros resultados numéricos discutimos la detectabilidad de estos objetos en condiciones realistas.

  13. Influence of intertidal recreational fisheries and 'bouchot' mussel culture on bivalve recruitment.

    PubMed

    Toupoint, Nicolas; Barbier, Pierrick; Tremblay, Réjean; Archambault, Philippe; McKindsey, Christopher W; Winkler, Gesche; Meziane, Tarik; Olivier, Frédéric

    2016-06-01

    In coastal environments, fishing and aquaculture may be important sources of disturbance to ecosystem functioning, the quantification of which must be assessed to make them more sustainable. In the Chausey Archipelago, France, recreational fishing and commercial shellfish farming are the only two evident anthropogenic activities, dominated by bivalve hand-raking and 'bouchot' mussel culture, respectively. This study evaluates the impact of both activities on bivalve recruitment dynamics by comparing primary recruitment intensity (short-term effect) and recruitment efficiency (medium-term effect) by sampling bivalves in reference (undisturbed) and disturbed (i.e. subjected to hand-raking or in 'bouchot' mussel culture areas) parcels throughout and at the end of the recruitment season, respectively. Specific hypotheses evaluated were that (H1) bivalve hand-raking negatively affects bivalve recruitment and that (H2) 'bouchot' mussel culture promotes bivalve recruitment. Patterns in bivalve community structure in reference parcels (i.e. natural pattern) differed between initial and final recruitment, underlining the great importance of early post-settlement processes, particularly secondary dispersal. Primary recruitment intensity was inhibited in hand-raking parcels whereas it was promoted in 'bouchot' mussel culture parcels, but the effect on recruitment efficiency was muted for both activities due to post-settlement processes. Nevertheless, the importance of effects that occur during the first step of recruitment should not be ignored as they may affect bivalve communities and induce immediate consequences on the trophic web through a cascade effect. Finally, it is highlighted that hand-raking damages all life stages of the common cockle Cerastoderma edule, one of the major target species, suggesting that this activity should be managed with greater caution than is currently done. PMID:27039134

  14. Assessing the potential of the European Atlantic sturgeon Acipenser sturio to control bivalve invasions in Europe.

    PubMed

    Ferreira-Rodriguez, N; Gessner, J; Pardo, I

    2016-08-01

    This pilot study explored the potential of juvenile European Atlantic sturgeon Acipenser sturio to feed on two invasive bivalve species, the Asian clam Corbicula fluminea and the Eurasian zebra mussel Dreissena polymorpha. Preliminary results indicate that native A. sturio were feeding on D. polymorpha at a very limited rate and their potential to prevent the establishment of invasive bivalve species, in new and previously invaded areas, is considered limited. PMID:27238016

  15. Detecting hot-spots of bivalve biomass in the south-western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Darr, Alexander; Gogina, Mayya; Zettler, Michael L.

    2014-06-01

    Bivalves are among the most important taxonomic groups in marine benthic communities in nutrient cycling via benthic-pelagic coupling and as food source for higher trophic levels. Additionally, bivalve species combine several autecological features with potential value for assessment and management purposes. Therefore, the demand for quantitative distribution maps of bivalves is high both in research with focus on functional ecology of marine benthos and in policy. In our study, we modelled and mapped the distribution of biomass of soft- and hard-bottom bivalves in the south-western Baltic Sea using Random Forest algorithms. Models were achieved for ten of the most frequent of overall 29 identified species. The distribution of bivalve biomass was mainly influenced by the abiotic parameters salinity, water depths, sediment characteristics and the amount of detritus as a proxy for food availability. Three hot-spots of bivalve biomass dominated by different species were detected: the oxygen-rich deeper parts of the Kiel Bay dominated by Arctica islandica, the shallow areas close to the mouth of the river Oder dominated by Mya arenaria and the hard-substrates around Rügen Island and the shallow Adlergrund dominated by Mytilus spp. The attained maps provide a good basis for further functional and applied analysis.

  16. Bivalve fouling of nuclear power plant service-water systems. Volume 1. Correlation of bivalve biological characteristics and raw-water system design

    SciTech Connect

    Neitzel, D.A.; Johnson, K.I.; Page, T.L.; Young, J.S.; Daling, P.M.

    1984-12-01

    Fouling of raw-water systems in nuclear power plants in the US can affect the safe operation of a power plant. This report describes correlations between the biology of bivalve organisms and the design and operation of power plants that allow bivalves to enter and reside in nuclear power plants. Discussions are focused on safety-related raw-water systems subject to fouling by the Asiatic clam (Corbicula fluminea), the blue mussel (Mytilus edulis), and the American oyster (Crassostrea virginica). Score sheets to rate fouling potential of power plant systems and components are provided.

  17. Strontium and barium incorporation into freshwater bivalve shells

    NASA Astrophysics Data System (ADS)

    Zhao, Liqiang; Schöne, Bernd R.

    2015-04-01

    Despite strong vital control, trace elements of bivalve shells can potentially serve as proxies of environmental change. However, to reconstruct past environments with the geochemical properties of the shells and determine the degree to which the element levels are biologically influenced, it is essential to experimentally determine the relationship between environmental variables and the element composition of the shells. In particular, the trace element geochemistry of freshwater bivalve shells has so far received little attention. Here, we present a controlled laboratory experiment that aimed at providing a better understanding of the influence of changing environmental variables on the incorporation of trace elements into freshwater bivalve shells. Under controlled conditions, Asian clams Corbicula fluminea were reared for 5 weeks in three sets of experiments: (1) different water temperature (10, 16, and 22° C) and different food levels (an equally mixed Scenedesmu quadricanda and Chlorella vulgaris at rations of 0.4, 2, 4, and 8 × 104 cells ml-1 d-1); (2) different water temperature (10, 16, and 22° C) and different element levels (Sr, Ba); (3) five sediment types (sand, slightly muddy sand, muddy sand, slightly sandy mud and mud). In the first set of experiments, shell Sr/Ca showed a significantly negative correlation with temperature, where Sr/Ca decreased linearly by about 1.6 to 2.1% per 1° C, but responded far more weakly to food availability. On the other hand, temperature and food availability affected shell Ba/Ca ratios, which potentially confounds the interpretation of Ba/Ca variations. Moreover, shell Sr/Ca and Ba/Ca exhibited a clearly negative dependence on shells growth rate that varied significantly among combinations of temperature and food availability. In the second set of experiments, shell Sr/Ca and Ba/Ca were positively and linearly related to water Sr/Ca and Ba/Ca for all temperatures. However, significantly negative effects of

  18. Trace Element Uptake in Marine Bivalve Shells Constraints from Field- and Laboratory Studies

    NASA Astrophysics Data System (ADS)

    Klünder, M.; Hippler, D.; Witbaard, R.; Frei, D.; Immenhauser, A.

    2006-12-01

    There is an increasing interest in the use of the trace element signatures recorded in calcium carbonate skeletons of marine organisms as archives of past and present environmental conditions, such as temperature, salinity or nutrition level. Because of their global occurrence in the modern and ancient oceans, the trace element chemistry of bivalve shells might be used as a potential proxy for present and past environmental conditions. If the composition of bivalve shells, for instance, can be shown to represent the environment in which they lived, then shells can be used to investigate conditions in the lifetime of the animal. And as the shell material is sequentially deposited, an understanding of the internal shell structure will enable time- resolution of the analyses. Therefore, the trace element signature of bivalve shells may provide an important record of climate changes and global geochemical cycles. One of the difficulties of using the trace element signatures of bivalve shells as proxies for environmental conditions is that little is known about the mechanisms by which the trace elements are incorporated into the shells. There has been quite an amount of research into the use of bivalve shell chemistry as proxy for one or more environmental parameters, but there are relatively few datasets in which both bivalve shells and the water in which the animals lived have been analysed. It is as yet not clear to what extent the trace element incorporation into bivalve shells is governed by biological processes, like growth rate and metabolism of the animals, or by physical and crystal chemical parameters. An added difficulty is that the existing data do suggest that trace element uptake in bivalve shells may be species specific. Therefore, studies that investigate the relationships between the content of these elements in the shells and the ambient water and the possible incorporation mechanisms are needed if the potential that bivalve shells offer as

  19. Multi-instrumental observations of a positive gigantic jet produced by a winter thunderstorm in Europe

    NASA Astrophysics Data System (ADS)

    van der Velde, Oscar A.; Bór, József; Li, Jingbo; Cummer, Steven A.; Arnone, Enrico; Zanotti, Ferruccio; Füllekrug, Martin; Haldoupis, Christos; Naitamor, Samir; Farges, Thomas

    2010-12-01

    At 2336:56 UTC on 12 December 2009, a bright gigantic jet (GJ) was recorded by an observer in Italy. Forty-nine additional sprites, elves, halos and two cases of upward lightning were observed that night. The location of the GJ corresponded to a distinct cloud top (-34°C) west of Ajaccio, Corsica. The GJ reached approximately 91 km altitude, with a "trailing jet" reaching 49-59 km, matching with earlier reported GJs. The duration was short at 120-160 ms. This is the first documented GJ which emerged from a maritime winter thunderstorm only 6.5 km tall, showing high cloud tops are not required for initiation of GJs. In the presence of strong vertical wind shear, the meteorological situation was different from typical outbreaks of fall and winter thunderstorms in the Mediterranean. During the trailing jet phase of the GJ, a sprite with halo triggered by a nearby cloud-to-ground lightning flash occurred at a relatively low altitude (<72 km). At the same time, the trailing jet and beads were reilluminated. Electromagnetic waveforms from Hungary, Poland, and the USA revealed this GJ is the first reported to transfer negative charge (approximately 136 C) from the ionosphere to the positively charged origins in the cloud (i.e., a positive cloud-to-ionosphere discharge, +CI), with a large total charge moment change of 11600 C km and a maximum current of 3.3 kA. Early VLF transmitter amplitude perturbations detected concurrently with the GJ confirm the production of large conductivity changes due to electron density enhancements in the D-region of the ionosphere.

  20. Optical and radio signatures of negative gigantic jets: Cases from Typhoon Lionrock (2010)

    NASA Astrophysics Data System (ADS)

    Huang, Sung-Ming; Hsu, Rue-Rou; Lee, Li-Jou; Su, Han-Tzong; Kuo, Cheng-Ling; Wu, Chun-Chieh; Chou, Jung-Kuang; Chang, Shu-Chun; Wu, Yen-Jung; Chen, Alfred B.

    2012-08-01

    On 31 August 2010, more than 100 transient luminous events were observed to occur over Typhoon Lionrock when it passed at ˜210 km to the southwest of the NCKU site in Taiwan. Among them, 14 negative gigantic jets (GJs) with clear recognizable morphologies and radio frequency signals are analyzed. These GJs are all found to have negative discharge polarity and thus are type I GJs. Morphologically, they are grouped into three forms: tree-like, carrot-like, and a new intermediate type called tree-carrot-like GJs. The ULF and ELF/VLF band signals of these events contain clear signatures associated with GJ development stages, including the initiating lightning, the leading jet, the fully developed jet, and the trailing jet. Though the radio waveform for each group of GJs always contains a fast descending pulse linked with the surge current upon the GJ-ionosphere contact, the detailed waveforms actually vary substantially. Cross analysis of the optical and radio frequency signals for these GJs indicates that a large surge current moment (CM) (>60 kA-km) appears to be essentially associated with the tree-like GJs. In contrast, the carrot-like and the tree-carrot-like GJs are both related to a surge CM less than 36 kA-km, and a continuing CM less than 27 kA-km further separates the carrot-like GJs from the tree-carrot-like GJs. Furthermore, on the peak CM versus charge moment change diagram for the initiating lightning, different groups of GJs seem to exhibit different trends. This feature suggests that the eventual forms of negative GJs may have been determined at the initiating lightning stage.

  1. New color images of sprites, halos and gigantic jets from the International Space Station

    NASA Astrophysics Data System (ADS)

    Yair, Y.; Rubanenko, L.; Mezuman, K.; Elhalel, G.; Pariente, M.; Glickman-Pariente, M.; Ziv, B.; Takahashi, Y.; Inoue, T.

    2012-12-01

    During July-August 2011, Expedition 28/29 JAXA astronaut Satoshi Furukawa conducted TLE observations from the International Space Station in conjunction with the "Cosmic Shore" program produced by NHK. An EMCCD normal video-rate color TV camera was used to conduct directed observations from the Earth-pointing Copula module. The target selection was based on the methodology developed for the MEIDEX sprite campaign on board the space shuttle Columbia in January 2003 (Ziv et al., 2004). We used the Aviation Weather Center (http://aviationweather.gov) daily significant weather forecast maps (SIGWX) to select regions with high probability for convective activity and thunderstorm such that they were within the camera FOV as deduced from the ISS trajectory and distance to the limb (2240 km). For increasing the chance for successful observations, only storms with predicted "Frequent Cb" and cloud tops above 45 Kft (~14 km) were selected. Additionally, we targeted tropical storms and hurricanes over the oceans. The observation geometry was pre-determined and uploaded daily to the ISS with pointing options to limb, oblique or nadir, based on the predicted location of the storm with regards to the ISS. The pointing angle was rotated in real-time according to visual eyesight by the astronaut. We present results of 10 confirmed TLEs: 8 sprites, 1 sprite halo and 1 gigantic jet, out of <2 hours of video. Sprites tend to appear in a single frame simultaneously with maximum lightning brightness. Unique images (a) from nadir of a sprite horizontally displaced form the lightning light and (b) from oblique view of a sprite halo, enable the calculation of dimensions and volumes occupied by these TLEs. Since time stamping on the ISS images was accurate within 1 s, matching with ELF and WWLLN data for the parent lightning location is limited. Nevertheless, the results prove that the ISS is an ideal platform for lightning and TLE observations, and careful operational procedures greatly

  2. Gigantic jets produced by an isolated tropical thunderstorm near Réunion Island

    NASA Astrophysics Data System (ADS)

    Soula, Serge; van der Velde, Oscar; Montanya, Joan; Huet, Patrice; Barthe, Christelle; Bór, József

    2011-10-01

    Five gigantic jets (GJs) have been recorded with video and photograph cameras on 7 March 2010 above an isolated tropical storm east of Réunion Island. Three of them were produced before the storm reached its coldest cloud top temperature (approximately -81°C), and two others occurred during the cloud extension. Thanks to the close distance of observation (˜50 km), the luminosity within the cloud was recorded, and the events are analyzed in unprecedented detail. The tops of the GJs are estimated between 80 and 90 km. All these GJs are accompanied by long, continuous cloud illumination, and they are preceded and followed by intermittent optical flashes from the cloud, most of time without any cloud-to-ground (CG) flash simultaneously detected, which suggests they originated mainly as intracloud discharges and without any charge transfer to Earth. The CG lightning activity is observed to cease a few tens of seconds before the jets. According to ELF data recorded at Nagycenk, Hungary, the five GJs serve to raise negative charge. Their duration ranges from 333 to 850 ms. The leading jet has the most variable duration (33-167 ms) and propagates faster at higher altitudes. The trailing jet exhibits a continuous decrease of luminosity in different parts of the jet (lower channel, transition zone and, for most events, carrot sprite-like top) and in the cloud, with possible rebrightening. The lower channels (˜20-40 km altitude) produce blue luminosity which decreases with altitude and become more and more diffuse with time. The transition zone (around 40-65 km) consists of bright red, luminous beads slowly going up (˜104 m s-1), retracing the initial leading jet channels.

  3. Changing restoration rules: exotic bivalves interact with residence time and depth to control phytoplankton productivity

    USGS Publications Warehouse

    Lucas, Lisa V.; Thompson, Janet K.

    2012-01-01

    Non-native species are a prevalent ecosystem stressor that can interact with other stressors to confound resource management and restoration. We examine how interactions between physical habitat attributes and a particular category of non-native species (invasive bivalves) influence primary production in aquatic ecosystems. Using mathematical models, we show how intuitive relationships between phytoplankton productivity and controllable physical factors (water depth, hydraulic transport time) that hold in the absence of bivalves can be complicated—and even reversed—by rapid bivalve grazing. In light-limited environments without bivalves, shallow, hydrodynamically “slow” habitats should generally have greater phytoplankton biomass and productivity than deeper, “faster” habitats. But shallower, slower environments can be less productive than deeper, faster ones if benthic grazing is strong. Moreover, shallower and slower waters exhibit a particularly broad range of possible productivity outcomes that can depend on whether bivalves are present. Since it is difficult to predict the response of non-native bivalves to habitat restoration, outcomes for new shallow, slow environments can be highly uncertain. Habitat depth and transport time should therefore not be used as indicators of phytoplankton biomass and production where bivalve colonization is possible. This study provides for ecosystem management a particular example of a broad lesson: abiotic ecosystem stressors should be managed with explicit consideration of interactions with other major (including biotic) stressors. We discuss the applicability and management implications of our models and results for a range of aquatic system types, with a case study focused on the Sacramento-San Joaquin Delta (California, USA). Simple mathematical models like those used here can illuminate interactions between ecosystem stressors and provide process-based guidance for resource managers as they develop strategies

  4. First Evidence of Immunomodulation in Bivalves under Seawater Acidification and Increased Temperature

    PubMed Central

    Matozzo, Valerio; Chinellato, Andrea; Munari, Marco; Finos, Livio; Bressan, Monica; Marin, Maria Gabriella

    2012-01-01

    Water acidification, temperature increases and changes in seawater salinity are predicted to occur in the near future. In such a global climate change (GCC) scenario, there is growing concern for the health status of both wild and farmed organisms. Bivalve molluscs, an important component of coastal marine ecosystems, are at risk. At the immunological level, the ability of an organism to maintain its immunosurveillance unaltered under adverse environmental conditions may enhance its survival capability. To our knowledge, only a few studies have investigated the effects of changing environmental parameters (as predicted in a GCC scenario) on the immune responses of bivalves. In the present study, the effects of both decreased pH values and increased temperature on the important immune parameters of two bivalve species were evaluated for the first time. The clam Chamelea gallina and the mussel Mytilus galloprovincialis, widespread along the coast of the Northwestern Adriatic Sea, were chosen as model organisms. Bivalves were exposed for 7 days to three pH values (8.1, 7.7 and 7.4) at two temperatures (22 and 28°C). Three independent experiments were carried out at salinities of 28, 34 and 40 PSU. The total haemocyte count, Neutral Red uptake, haemolymph lysozyme activity and total protein levels were measured. The results obtained demonstrated that tested experimental conditions affected significantly most of the immune parameters measured in bivalves, even if the variation pattern of haemocyte responses was not always linear. Between the two species, C. gallina appeared more vulnerable to changing pH and temperature than M. galloprovincialis. Overall, this study demonstrated that climate changes can strongly affect haemocyte functionality in bivalves. However, further studies are needed to clarify better the mechanisms of action of changing environmental parameters, both individually and in combination, on bivalve haemocytes. PMID:22479452

  5. Determining provenance of marine metal pollution in French bivalves using Cd, Zn and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Shiel, Alyssa E.; Weis, Dominique; Cossa, Daniel; Orians, Kristin J.

    2013-11-01

    Cadmium, Zn and Pb isotopic compositions (MC-ICP-MS) and elemental concentrations (HR-ICP-MS) have been used to distinguish between natural and anthropogenic sources of these metals in bivalves collected from the coastlines of France (English Channel, Atlantic and Mediterranean coasts). The Cd isotopic signatures (δ114Cd = -1.08‰ to -0.52‰) exhibited by bivalves from the coastlines of France, excluding those from NE France, are within the range of those exhibited by bivalves from the USA East coast (δ114Cd = -1.20‰ to -0.54‰). This indicates the high prevalence of industry, as well as the low natural contributions of Cd from North Atlantic waters in both regions. Thus, the significance of anthropogenic Cd sources is similar. These significant anthropogenic contributions are identified for bivalves with a large range in tissue Cd concentrations. Importantly, French bivalves from the Gironde estuary and Marennes-Oléron basin (regions of historic and modern importance for oyster farming, respectively) exhibited the highest Cd levels of the study. Their Cd isotopic signatures indicate historical smelting emissions remain the primary Cd source despite the cessation of local smelting activities in 1986 and subsequent remedial efforts. No significant variability is observed in the δ66Zn values of the French bivalves (∼0.53‰), with the exception of the much heavier compositions exhibited by oysters from the polluted Gironde estuary (1.19-1.27‰). Lead isotopes do not fractionate during processing like Cd and Zn. They can, therefore, be used to identify emissions from industrial processes and the consumption of unleaded gasoline and diesel fuel as metal sources to French bivalves. Cadmium and Zn isotopes are successfully used here as tracers of anthropogenic processing emissions and are combined with Pb isotope "fingerprinting" techniques to identify metal sources.

  6. Permian nonmarine bivalve zonation of the East European platform

    NASA Astrophysics Data System (ADS)

    Silantiev, V. V.

    2014-01-01

    New finds and revision of available collections of nonmarine bivalves provided grounds for development of a zonal scale for terrestrial sequences of the Permian System based on species belonging to the genus Palaeomutela Amalitzky, 1891, which are characterized by regular changes in the structure of the shell hinge. The scale includes two parallel zonal successions that are based on the stratigraphic distribution and evolutionary trends of two morphological lineages of the genus. The zonal succession based on development of the P. umbonata group (dwellers of mobile waters and silty-psammitic substrates) includes 11 range zones: stegocephalum, ovatiformis, umbonata, quadriangularis, krotowi, wohrmani, numerosa, ulemensis, keyserlingi, curiosa, golubevi. The zonal succession based on development of the P. castor group (dwellers of calm waters and silty-pelitic substrates) includes eight range zones: larae, castor, olgae, doratioformis, marposadica, fischeri, obunca, amalitzkyi. The proposed zonal units are correlated with scales based on ostracod, fish, and tetrapod fossils. New species Palaeomutela golubevi sp. nov. and P. amalitzkyi sp. nov. are described with the extended diagnosis of the genus Palaeomutela.

  7. Different carbon sources affect PCB accumulation by marine bivalves.

    PubMed

    Laitano, M V; Silva Barni, M F; Costa, P G; Cledón, M; Fillmann, G; Miglioranza, K S B; Panarello, H O

    2016-02-01

    Pampean creeks were evaluated in the present study as potential land-based sources of PCB marine contamination. Different carbon and nitrogen sources from such creeks were analysed as boosters of PCB bioaccumulation by the filter feeder bivalve Brachidontes rodriguezii and grazer limpet Siphonaria lessoni. Carbon of different source than marine and anthropogenic nitrogen assimilated by organisms were estimated through their C and N isotopic composition. PCB concentration in surface sediments and mollusc samples ranged from 2.68 to 6.46 ng g(-1) (wet weight) and from 1074 to 4583 ng g(-1) lipid, respectively, reflecting a punctual source of PCB contamination related to a landfill area. Thus, despite the low flow of creeks, they should not be underestimated as contamination vectors to the marine environment. On the other hand, mussels PCB bioaccumulation was related with the carbon source uptake which highlights the importance to consider this factor when studying PCB distribution in organisms of coastal systems. PMID:26606107

  8. Intracellular Oceanospirillales bacteria inhabit gills of Acesta bivalves.

    PubMed

    Jensen, Sigmund; Duperron, Sébastien; Birkeland, Nils-Kåre; Hovland, Martin

    2010-12-01

    A novel bacterium was discovered in the gills of the large bivalve Acesta excavata (Limidae) from coral reefs on the northeast Atlantic margin near the shelf break of the fishing ground Haltenbanken of Norway, and confirmed present in A. excavata from a rock-wall in the Trondheimsfjord. Purified gill DNA contained one dominant bacterial rRNA operon as indicated from analysis of broad range bacterial PCR amplicons in denaturant gradient gels, in clone libraries and by direct sequencing. The sequences originated from an unknown member of the order Oceanospirillales and its 16S rRNA gene fell within a clade of strictly marine invertebrate-associated Gammaproteobacteria. Visual inspection by fluorescent in situ hybridization and transmission electron microscopy indicated a pleomorphic bacterium with no visible cell wall, located in aggregates inside vacuoles scattered within the gill cells cytoplasm. Intracellular Oceanospirillales exist in bathymodiolin mussels (parasites), Osedax worms and whiteflies (symbionts). This bacterium apparently lives in a specific association with the Acesta. PMID:21044098

  9. Early Pliocene Weddell Sea climate and seasonality reconstructed from bivalves and bryozoans

    NASA Astrophysics Data System (ADS)

    Williams, M.; Clark, N.; Okamura, B.; Zalasiewicz, J.; Johnson, A.; Leng, M. J.; Smellie, J.; Haywood, A.; Nelson-Laloe, A.; Taylor, P.

    2010-12-01

    Early Pliocene marine cheilostome bryozoans and bivalves are preserved in glacigenic and interglacial marine deposits of James Ross Island and Cockburn Island, northern Antarctic Peninsula. Several different marine bryozoan genera were incorporated into diamictites during Pliocene ice advance(s). Bryozoan zooid-size Mean Annual Range of Temperature (zs-MART) analysis provides estimates of seasonality which suggest annual marine temperatures for the James Ross Island region varied by at least 4°C and possibly by as much as 10°C during Early Pliocene warm intervals (compared with ca 2°C for present day). Coupled with evidence from oxygen isotope data from bivalves, Early Pliocene Weddell Sea warm intervals were evidently much warmer than present, with summer sea temperatures probably exceeding 5°C. Morphological (growth-increment) and oxygen isotope data from bivalves in the marine interglacial Cockburn Island Formation (dated at 4.7 Ma) indicate little or no sea ice present, supporting the theory that Chlamys-like bivalves have retreated from the Antarctic as sea ice increased in the late Pliocene. We demonstrate that bivalve and bryozoan growth-related morphologies, interpreted in conjunction with stable oxygen and carbon isotope data, provide a powerful tool for tracking high latitude climate in the Pliocene.

  10. Dioxins/furans and PCBs in bivalves and sediments from NOAA national status and trends program

    SciTech Connect

    Wade, T.; Gardinali, P.; Jackson, T.; Sericano, J.; Chambers, L.

    1995-12-31

    As part of the National Oceanic and Atmospheric Administration (NOAA), National Status and Trends (NS and T) Mussel Watch Program 55 bivalves and 7 sediment samples were analyzed for 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD and PCDF) and planar PCBs. Bivalve samples were collected from selected US East Gulf and West coast sites, while the sediment samples were all from the Gulf coast. Sediment concentrations for 2,3,7,8-tetrachloro dibenzo-p-dioxin and dibenzofuran (TCDD and TCDF) ranged from 0.35 to 25 pg/g and 0.42 to 140 pg/g, respectively. The 2,3,7,8-TCDD and 2,3,7,8-TCDF represent only a small percentage of the total PCDD and PCDF in the sediments which is the case for most sediment. The concentration of TCDD and TCDF in bivalves ranged from not detected (ND) to 25 pg/g and ND to 140 pg/g, respectively. Most bivalve samples, in contrast to the sediment contained low proportions of the higher molecular weight PCDDs and PCDFs. The relative toxicological importance of 2,3,7,8-TCDD, 2,3,7,8-TCDF and dioxin-like PCB to the bivalves from different locations will be compared based on toxicity equivalency factors.

  11. Modification in digestive processing strategies to reduce toxic trace metal uptake in a marine bivalve

    SciTech Connect

    Decho, A.W.; Luoma, S.N.

    1994-12-31

    Bivalves possess two major digestion pathways for processing food particles: a rapid ``intestinal`` pathway where digestion is largely extracellular; and a slower ``glandular`` pathway where digestion is largely intracellular. The slower glandular pathway often results in more efficient absorption of carbon but also more efficient uptake of certain metals (e.g. Cr associated with bacteria). In the bivalve Potamocorbula amurensis, large portions (> 90%) of bacteria are selectively routed to the glandular pathway. This results in efficient C uptake but also efficient uptake of associated Cr. The authors further determined if prolonged exposure to Cr-contaminated bacteria would result in high Cr uptake by animals or whether mechanisms exist to reduce Cr exposure and uptake. Bivalves were exposed to natural food + added bacteria (with or without added Cr) for a 6-day period, then pulse-chase experiments were conducted to quantify digestive processing and % absorption efficiencies (%AE) of bacterial Cr. Bivalves compensate at low (2--5 ug/g sed) Cr by reducing overall food ingestion, while digestive processing of food remains statistically similar to controls. At high Cr (200--500 ug/g sed) there are marked decreases in % bacteria processed by glandular digestion. This results in lower overall %AE of Cr. The results suggest that bivalves under natural conditions might balance efficient carbon sequestration against avoiding uptake of potentially toxic metals associated the food.

  12. What's in a Shell? - Interactions of Chemistry and Structure at Submicron Levels in Bivalve Shells

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Piazolo, S.; Trimby, P.

    2014-12-01

    The wide geographical distribution of bivalve shells makes them much favoured paleoclimate proxy archives. However, they are amongst the materials most affected by physiological effects, making the correct deciphering of these archives a challenging task. Shell building plans are usually hierarchic, thus optimizing mechanical properties. However, different structures common to certain bivalve families, such as the prism-nacre or the crossed-lamellar structures, are assembled from very different building blocks. These structural differences coincide with chemical and crystallographic differences suggesting critically different formation mechanisms within the bivalve class. Most importantly some bivalves form their shells from amorphous calcium carbonate that crystallizes in situ once assembled into the shell. We present new correlated multi-scale structural and compositional data for different shell bivalve shell structures such as nacre-prism, cross-lamellar intermediate structures. Data are obtained using EBSD, FIB-assisted TEM and Transmission Kikuchi Diffraction combined with Nano-SIMS and Raman Microspectrometry and suggest that formation from amorphous phases is widespread and results in different calcium carbonate polymorphs to be present in the shell with distinct chemical compositions. The results highlight the complex nature of the biomaterials, which has consequences for the precision and accuracy of paleotemperature calculations.

  13. Organohalogenated contaminants in sediments and bivalves from the Northern Arabian Gulf.

    PubMed

    Ali, Nadeem; Ali, Lulwa Naseer; Eqani, Syed Ali Musstjab Akber Shah; Ismail, Iqbal Mohammad Ibrahim; Malarvannan, Govindan; Kadi, Mohammad W; Al-Badry Basahi, Jalal Mohammed; Covaci, Adrian

    2015-12-01

    Several classes of Organohalogenated contaminants (OHCs) were determined in sediments and bivalves collected from Kuwait coast. The levels and profile of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) were compared in both sediments and bivalves. PCB-153 and -138 were the major contributors towards total OHCs followed by DDT and its metabolites (DDTs). The higher contribution of DDTs (~40%) and BDE-47 (~15%) in bivalves as compared to that in associated sediments indicated high biota-sediment accumulation factors (BSAF). Higher BSAF (values for heavier PCBs, DDTs and PBDEs) also indicated their high accumulation potential from sediment into associated biota at most of the studied locations. Overall, OHCs in sediments and bivalves measured in current study were lower than those reported in the literature worldwide. Most of the sediment concentrations of OHCs (ng/g, dry weight) were in the range of permissible guideline values proposed by Canadian Sediment Quality Guidelines (CSQGs), with few exceptions for DDTs (5 ng/g) and PCBs (22.7 ng/g). Similarly, 10% of bivalve samples contained high levels (ng/g, lipid weight) of PCBs (300) and DDTs (150) and were above the set safety benchmarks. This study establishes baseline for future monitoring programs. PMID:26386334

  14. Modeling bivalve diversification: the effect of interaction on a macroevolutionary system

    NASA Technical Reports Server (NTRS)

    Miller, A. I.; Sepkoski, J. J. Jr; Sepkoski JJ, J. r. (Principal Investigator)

    1988-01-01

    The global diversification of the class Bivalvia has historically received two conflicting interpretations. One is that a major upturn in diversification was associated with, and a consequence of, the Lake Permian mass extinction. The other is that mass extinctions have had little influence and that bivalves have experienced slow but nearly steady exponential diversification through most of their history, unaffected by interactions with other clades. We find that the most likely explanation lies between these two interpretations. Through most of the Phanerozoic, the diversity of bivalves did indeed exhibit slow growth, which was not substantially altered by mass extinctions. However, the presence of "hyperexponential bursts" in diversification during the initial Ordovician radiation and following the Late Permian and Late Cretaceous mass extinctions suggests a more complex history in which a higher characteristic diversification rate was dampened through most of the Phanerozoic. The observed pattern can be accounted for with a two-phase coupled (i.e., interactive) logistic model, where one phase is treated as the "bivalves" and the other phase is treated as a hypothetical group of clades with which the "bivalves" might have interacted. Results of this analysis suggest that interactions with other taxa have substantially affected bivalve global diversity through the Phanerozoic.

  15. Distribution, abundance, and habitat associations of a large bivalve (Panopea generosa) in a eutrophic, fjord estuary

    USGS Publications Warehouse

    Mcdonald, P. Sean; Essington, Timothy E.; Davis, Jonathan P.; Galloway, Aaron W.E.; Stevick, Bethany C.; Jensen, Gregory C.; Vanblaricom, Glenn R.; Armstrong, David A.

    2015-01-01

    Marine bivalves are important ecosystem constituents and frequently support valuable fisheries. In many nearshore areas, human disturbance—including declining habitat and water quality—can affect the distribution and abundance of bivalve populations, and complicate ecosystem and fishery management assessments. Infaunal bivalves, in particular, are frequently cryptic and difficult to detect; thus, assessing potential impacts on their populations requires suitable, scalable methods for estimating abundance and distribution. In this study, population size of a common benthic bivalve (the geoduck Panopea generosa) is estimated with a Bayesian habitat-based model fit to scuba and tethered camera data in Hood Canal, a fjord basin in Washington state. Densities declined more than two orders of magnitude along a north—south gradient, concomitant with patterns of deepwater dissolved oxygen, and intensity and duration of seasonal hypoxia. Across the basin, geoducks were most abundant in loose, unconsolidated, sand substrate. The current study demonstrates the utility of using scuba, tethered video, and habitat models to estimate the abundance and distribution of a large infaunal bivalve at a regional (385-km2) scale.

  16. Zebra mussel infestation of unionid bivalves (Unionidae) in North America

    USGS Publications Warehouse

    Schloesser, Don W.; Nalepa, Thomas F.; Mackie, Gerald L.

    1996-01-01

    In 1989, zebra mussels received national attention in North America when they reached densities exceeding 750,000/m2 in a water withdrawal facility along the shore of western Lake Erie of the Laurentian Great Lakes. Although water withdrawal problems caused by zebra mussels have been of immediate concern, ecological impacts attributed to mussels are likely to be the more important long-term issue for surface waters in North America. To date, the epizoic colonization (i.e., infestation) of unionid bivalve mollusks by zebra mussels has caused the most direct and severe ecological impact. Infestation of and resulting impacts caused by zebra mussels on unionids in the Great Lakes began in 1988. By 1990, mortality of unionids was occurring at some locations; by 1991, extant populations of unionids in western Lake Erie were nearly extirpated; by 1992, unionid populations in the southern half of Lake St. Clair were extirpated; by 1993, unionids in widely separated geographic areas of the Great Lakes and the Mississippi River showed high mortality due to mussel infestation. All infested unionid species in the Great Lakes (23) have become infested and exhibited mortality within two to four years after heavy infestation began. Data indicate that mean zebra mussel densities >5,000–6,000/m2 and infestation intensities >100-200/unionid in the presence of heavy zebra mussel recruitment results in near total mortality of unionids. At present, all unionid species in rivers, streams, and akes that sympatrically occur with zebra mussels have been infested and, in many locations, negatively impacted by zebra mussels. We do not know the potential consequences of infestation on the 297 unionid species found in North America, but believe zebra mussels pose an immediate threat to the abundance and diversity of unionids.

  17. Persistent free radical ESR signals in marine bivalve tissues

    SciTech Connect

    Mehlorn, R.J.; Mendez, A.T.; Higashi, R.; Fan, T.

    1992-08-01

    Freeze-dried homogenates of the oyster Crassostrea rhizophorae collected from waters in Puerto Rico near urban and industrial sites as well as at relatively pristine locations yielded electron spin resonance (ESR) spectra characteristic of free radicals as well as spectral components of transition metal ions, dominated by manganese. The magnitudes of these ESR signals and the concentrations of trace elements (determined by X-ray fluorescence) varied considerably among oyster samples, masking any potential correlation with polluted waters. Laboratory studies were initiated to identify the factors controlling the magnitudes of the tissue free radical ESR signals. Another mollusc, Mytilus californianus collected at the Bodega Marine laboratory in northern California, was fractionated into goneds and remaining tissue. Freeze-dried homogenates of both fractions exhibited ESR signals that increased gradually with time. ESR signals were observed in freeze-dried perchloric acid (PCA) precipitates of the homogenates, delipidated PCA precipitates, and in chloroform extracts of these precipitates. Acid hydrolysis to degrade proteins to amino acids produced a residue, which yielded much larger ESR free radical signals after freeze-drying. Freshly thawed homogenates of Crassostrea rhizophorae also exhibited ESR signals. A laboratory model of copper stress in Crassostrea rhizophorae was developed to study the effect of this transition metal on dssue free radicals. Preliminary results suggested that sublethal copper exposure had little effect on tissue fire radicals, except possibly for a signal enhancement in an oyster fraction that was enriched in kidney granules. Since kidney granules are known to accumulate heavy metals in mussels and probably other marine bivalves, this signal enhancement may prove to be an indicator of free radical processes associated with heavy metal deposition in molluscs.

  18. Gigantic landslides versus glacial deposits: on origin of large hummock deposits in Alai Valley, Northern Pamir

    NASA Astrophysics Data System (ADS)

    Reznichenko, Natalya

    2015-04-01

    As glaciers are sensitive to local climate, their moraines position and ages are used to infer past climates and glacier dynamics. These chronologies are only valid if all dated moraines are formed as the result of climatically driven advance and subsequent retreat. Hence, any accurate palaeoenvironmental reconstruction requires thorough identification of the landform genesis by complex approach including geomorphological, sedimentological and structural landform investigation. Here are presented the implication of such approach for the reconstruction of the mega-hummocky deposits formation both of glacial and landslide origin in the glaciated Alai Valley of the Northern Pamir with further discussion on these and similar deposits validity for palaeoclimatic reconstructions. The Tibetan Plateau valleys are the largest glaciated regions beyond the ice sheets with high potential to provide the best geological record of glacial chronologies and, however, with higher probabilities of the numerous rock avalanche deposits including those that were initially considered of glacial origin (Hewitt, 1999). The Alai Valley is the largest intermountain depression in the upper reaches of the Amudarja River basin that has captured numerous unidentified extensive hummocky deposits descending from the Zaalai Range of Northern Pamir, covering area in more than 800 km2. Such vast hummocky deposits are usually could be formed either: 1) glacially by rapid glacial retreat due to the climate signal or triggered a-climatically glacial changes, such as glacial surge or landslide impact, or 2) during the landslide emplacement. Combination of sediment tests on agglomerates forming only in rock avalanche material (Reznichenko et al., 2012) and detailed geomorphological and sedimentological descriptions of these deposits allowed reconstructing the glacial deposition in the Koman and Lenin glacial catchments with identification of two gigantic rock avalanches and their relation to this glacial

  19. Gigantic lateral spreading of mountains in the epicentral area of the expected Tokai earthquake, central Japan

    NASA Astrophysics Data System (ADS)

    Chigira, Masahiro; Nakamura, Takeshi

    2010-05-01

    Lateral spreading of mountains is not only a degradation process itself but also it could become the background of a catastrophic landslide that occurs at its spreading rims. We found gigantic lateral spreading behind the Yui landsllide area, which is located along the Pacific Sea coast in the epicentral area of the expected Tokai earthquake, central Japan. The Yui landslide area is located on a socially very important place, where are major lifelines connecting east and west Japan: Tokaido railway, Tokaido Shinkansen, and Tomei highway. The Yui landslide area comprises many landslide units and has been causing many catastrophs. The lateral spreading is characterized by NS-trending multiple ridges and linear depressions as long as 1 to 2 km and up to 60 m deep. These features are observable on the aerial photographs and are clearly identified by using airborne laser scanner. Mountains subjected to the lateral spreading is 3 km wide in EW and 6 km long in NS and are 250 to 500 m high above sea level. These morphological features suggest that the NS trending ridges spread laterally to EW and their central parts settled down like the way by which horsts and grabens are made. The ridges are underlain by Miocene beds consisting of the alternating beds of mudstone and sandstone in the lower part and of sandstone and conglomerate in the upper part. The spreading ridge occupies the axial part of a NS-trending syncline, which has a half wave length longer than 2 km and comprises minor folds with a wavelength on the order of hundred meters. This structure, synclinorium, suggests that there could be decollements along the enveloping surface of the minor folds and that the lateral spreading could have a low-angle slip surface along the enveloping surface of the minor folds. There are many landslides along the side slopes of the laterally spread ridges and they have been moving many times by rainstorms and also by earthquakes. The movements are recorded since 1781, but the

  20. Approaches for evaluating the effects of bivalve filter feeding on nutrient dynamics in Puget Sound, Washington

    USGS Publications Warehouse

    Konrad, Christopher P.

    2014-01-01

    Marine bivalves such as clams, mussels, and oysters are an important component of the food web, which influence nutrient dynamics and water quality in many estuaries. The role of bivalves in nutrient dynamics and, particularly, the contribution of commercial shellfish activities, are not well understood in Puget Sound, Washington. Numerous approaches have been used in other estuaries to quantify the effects of bivalves on nutrient dynamics, ranging from simple nutrient budgeting to sophisticated numerical models that account for tidal circulation, bioenergetic fluxes through food webs, and biochemical transformations in the water column and sediment. For nutrient management in Puget Sound, it might be possible to integrate basic biophysical indicators (residence time, phytoplankton growth rates, and clearance rates of filter feeders) as a screening tool to identify places where nutrient dynamics and water quality are likely to be sensitive to shellfish density and, then, apply more sophisticated methods involving in-situ measurements and simulation models to quantify those dynamics.

  1. Arsenic and trace metals in commercially important bivalves, Anadara granosa and Paphia undulata

    SciTech Connect

    Mat, I. )

    1994-06-01

    The semi-culture of marine bivalves particularly Anadara granosa is of considerable economic importance in Malaysia. Currently, about 4-5000 ha of mudflats along the west coast are utilized for this purpose. Therefore, contamination of the highly productive mudflats with heavy metals tend to be accumulated in the filter feeding organisms such as bivalve molluscs which often serve as important environmental sinks of heavy metals. Bivalve molluscs, A. granosa and Paphia undulata are commercially important seafoods and popular among the locals in Malaysia. With this point in mind, it is intended to evaluate the concentration levels of arsenic as well as trace metals (Co, Cu, Ni, Cd, Zn, Cr and Pb) in both species derived from retail outlets in the city of Kuala Lumpur. Although this analysis may not indicate the site of capture but may act as a direct check on the contamination of seafoods available to the consumers. 17 refs., 2 tabs.

  2. Saturation-state sensitivity of marine bivalve larvae to ocean acidification

    NASA Astrophysics Data System (ADS)

    Waldbusser, George G.; Hales, Burke; Langdon, Chris J.; Haley, Brian A.; Schrader, Paul; Brunner, Elizabeth L.; Gray, Matthew W.; Miller, Cale A.; Gimenez, Iria

    2015-03-01

    Ocean acidification results in co-varying inorganic carbon system variables. Of these, an explicit focus on pH and organismal acid-base regulation has failed to distinguish the mechanism of failure in highly sensitive bivalve larvae. With unique chemical manipulations of seawater we show definitively that larval shell development and growth are dependent on seawater saturation state, and not on carbon dioxide partial pressure or pH. Although other physiological processes are affected by pH, mineral saturation state thresholds will be crossed decades to centuries ahead of pH thresholds owing to nonlinear changes in the carbonate system variables as carbon dioxide is added. Our findings were repeatable for two species of bivalve larvae could resolve discrepancies in experimental results, are consistent with a previous model of ocean acidification impacts due to rapid calcification in bivalve larvae, and suggest a fundamental ocean acidification bottleneck at early life-history for some marine keystone species.

  3. Characterization of the mantle transcriptome in bivalves: Pecten maximus, Mytilus edulis and Crassostrea gigas.

    PubMed

    Yarra, Tejaswi; Gharbi, Karim; Blaxter, Mark; Peck, Lloyd S; Clark, Melody S

    2016-06-01

    The calcareous shells secreted by bivalve molluscs display diverse and species specific structural compositions, which indicates possible divergent biomineralization processes. Thus, studying multiple mollusc species will provide a more comprehensive understanding of shell formation. Here, the transcriptomes of the mantle tissues responsible for shell deposition were characterized in three commercially relevant bivalve species. Using high-throughput sequencing and bioinformatics tools, de novo transcriptome assemblies of mantle tissues were generated for the mussel Mytilus edulis, the oyster Crassostrea gigas and the scallop Pecten maximus. These transcriptomes were annotated, and contigs with similarity to proteins known to have shell formation roles in other species were identified. Comparison of the shell formation specific proteins in the three bivalves indicates the possibility of species specific shell proteins. PMID:27160853

  4. Mussel watch - measurements of chemical pollutants in bivalves as one indicator of coastal environmental quality

    SciTech Connect

    Farrington, J.W.; Davis, A.C.; Tripp, B.W.; Phelps, D.K.; Galloway, W.B.

    1987-01-01

    The utility of the bivalve sentinel organism approach to monitoring for some chemicals of environmental concern in coastal and estuarine areas has been evaluated by regional and national programs and by smaller-scale research efforts during the past 15 years. The extent and severity of coastal contamination by chemicals such as polychlorinated biphenyls, chlorinated pesticides, trace metals, and plutonium was assessed in several bivalve sentinel organism programs. Advantages and limitations of this approach are presented and discussed briefly within the context of both national and international efforts.

  5. Arsenic in benthic bivalves of San Francisco Bay and the Sacramento/San Joaquin River Delta

    USGS Publications Warehouse

    Johns, C.; Luoma, S.N.

    1990-01-01

    Arsenic concentrations were determined in fine-grained, oxidized, surface sediments and in two benthic bivalves, Corbicula sp. and Macoma balthica, within San Francisco Bay, the Sacramento/San Joaquin River Delta, and selected rivers not influenced by urban or industrial activity. Arsenic concentrations in all samples were characteristic of values reported for uncontaminated estuaries. Small temporal fluctuations and low arsenic concentrations in bivalves and sediments suggest that most inputs of arsenic are likely to be minor and arsenic contamination is not widespread in the Bay.

  6. Bivalve effects on the food web supporting delta smelt—A long-term study of bivalve recruitment, biomass, and grazing rate patterns with varying freshwater outflow

    USGS Publications Warehouse

    Crauder, Jeff S.; Thompson, Janet K.; Parchaso, Francis; Anduaga, Rosa I.; Pearson, Sarah A.; Gehrts, Karen; Fuller, Heather; Wells, Elizabeth

    2016-01-01

    At the few stations where Potamocorbula and Corbicula co-occur, it appears that they did not hinder each other’s growth. Both bivalves had large animals at D4, where Corbicula size increased coincident with the presence of Potamocorbula in 1987. Corbicula were observed in wet years prior to Potamocorbula’sinvasion at D7 (Grizzly Bay) and were capable of growing to significant size in wet years (> 20 mm in 1986). 

  7. Shell growth and environmental control of methanophyllic Thyasirid bivalves from Svalbard cold seeps

    NASA Astrophysics Data System (ADS)

    Carroll, Michael; Åström, Emmelie; Ambrose, William; Locke, William; Oliver, Graham; Hong, Wei-Li; Carroll, JoLynn

    2016-04-01

    The analysis of molluscan shell material (sclerochronology) can provide information about an organism's age, growth history, and environmental conditions during its lifetime. Bivalve molluscs are common members of hydrothermal vents and methane cold seeps communities where, supported by chemosynthetic symbionts, they can reach high density and biomass. But little is known about methane-associated bivalve populations inhabiting high-Arctic cold seeps, and sclerochronological analysis of methane-influenced bivalves is rare. We measured growth rates and elemental and isotopic shell signatures in a newly discovered species of bivalve (Thyasiridae) from cold seeps at 350-390m depth southwest of Svalbard. First discovered in 2014, recently described shells of Thyasira capitanea sp.nov. were found at 2 independent seep systems in Storfjordrenna. Mean shell carbon isotopic ratios from inorganic δ13C (mean = -4.8‰) and organic δ13C (mean = -26.9‰) fractions clearly indicate a methane influenced habitat and food source for these organisms. Shell mineral ratios (Li/Ca, Mg/Ca, Mn/Ca, Fe/Ca, Sr/Ca, Ba/Ca, Pb/Ca) sampled along the axis of growth with laser-ablated ICP-MS exhibit variability through time and between sites, suggesting that concentrations of these elements that may be affected by methane emissions. The mineralogical data also elucidates the internal pattern of shell deposition and growth checks, and combined with the isotopic and growth rate data, enables us to interpret the temporal history of methane release from these locations.

  8. Bacillary Necrosis, a Disease of Larval and Juvenile Bivalve Mollusks I. Etiology and Epizootiology

    PubMed Central

    Tubiash, Haskell S.; Chanley, Paul E.; Leifson, Einar

    1965-01-01

    Tubiash, Haskell S. (U.S. Bureau of Commercial Fisheries, Milford, Conn.), Paul E. Chanley, and Einar Leifson. Bacillary necrosis, a disease of larval and juvenile bivalve mollusks. I. Etiology and epizootiology. J. Bacteriol. 90:1036–1044. 1965.—Lethal bacterial infections of a variety of hatchery-spawned bivalve mollusk larvae and juveniles have been studied. The symptoms of the disease and the course of the infection are described. Four biotypes and five antigenic types of bacteria, pathogenic for the larvae of five species of bivalve mollusks, were isolated and described in some detail. All are gram-negative motile rods. Comparative studies were made of a fairly large number of similar bacteria isolated from presumably normal marine fauna. None of these was pathogenic for the bivalve larvae nor did they have antigens in common with the pathogenic group. The four biotypes had a number of characteristics in common that rarely were present in other cultures from marine fauna. Several antibiotic preparations proved to be of value in the treatment and control of the infection. Images PMID:5847794

  9. Consumption of freshwater bivalves by muskrats in the Green River, Kentucky

    USGS Publications Warehouse

    Hersey, Kimberly Asmus; Clark, Joseph D.; Layzer, James B.

    2013-01-01

    Muskrats (Ondatra zibethicus) are known to prey on freshwater bivalves (mussels and clams) and can negatively impact imperiled mussel species. However, factors that influence muskrat predation on bivalves are poorly understood. We evaluated the feeding ecology of muskrats in the Green River, Kentucky, by using stable isotope analysis of muskrat hair samples and by monitoring bivalve shell deposition at muskrat middens. Bayesian mixing-model analysis of stable isotope δ15N and δ13C ratios revealed that the median muskrat biomass derived from bivalves was 51.4% (5th and 95th percentiles were 39.1 to 63.4%, respectively), a much higher dietary proportion than previously reported. Shell depositions by muskrats at middens decreased with the availability of seasonal emergent vegetation, suggesting that the consumption of animal matter is in response to a scarcity of plant foods, perhaps exacerbated by the altered flow regimes on the Green River. Our results add to the growing body of evidence that muskrats have the potential to impact mussel population growth and recovery in some environments.

  10. A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China.

    PubMed

    Yang, Jie; Ortega-Hernández, Javier; Lan, Tian; Hou, Jin-Bo; Zhang, Xi-Guang

    2016-01-01

    Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp. nov., recovered from the Cambrian (Stage 3) Hongjingshao Formation in Kunming, southern China, is characterized by having a robust first pair of raptorial appendages that bear well-developed ventral-facing spines, paired dorsal spines on the trunk, and posteriorly oriented serrations on the anteroventral margins of both valves. The raptorial limbs of C. serrata were adapted for grasping prey employing a descending stroke for transporting it close the mouth, whereas the backwards-facing marginal serrations of the bivalved carapace may have helped to secure the food items during feeding. The new taxon offers novel insights on the morphology of the enigmatic genus Clypecaris, and indicates that the possession of paired dorsal spines is a diagnostic trait of the Family Clypecarididae within upper stem-group Euarthropoda. C. serrata evinces functional adaptations for an active predatory lifestyle within the context of Cambrian bivalved euarthropods, and contributes towards the better understanding of feeding diversity in early ecosystems. PMID:27283406

  11. Estimating the distribution of harvested estuarine bivalves with natural-history-based habitat suitability models

    EPA Science Inventory

    Habitat suitability models are useful to forecast how environmental change may affect the abundance or distribution of species of concern. In the case of harvested bivalves, those models may be used to estimate the vulnerability of this valued ecosystem good to natural or human-...

  12. Filter-feeding bivalves can remove avian influenza viruses from water and reduce infectivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Avian influenza (AI) viruses are transmitted within wild aquatic bird populations through an indirect fecal-oral route involving fecal-contaminated water. In this study, the influence of filter-feeding bivalves, Corbicula fluminea, on the infectivity of AI virus in water was examined. A single cla...

  13. EFFECTS OF ENVIRONMENTAL FACTORS ON RADIOCADMIUM UPTAKE BY FOUR SPECIES OF MARINE BIVALVES

    EPA Science Inventory

    Temperature, salinity, bottom-sediment type, and zinc concentration all influenced Cd uptake by 4 marine bivalves (Mya arenaria, Mytilus edulis, Mulinia lateralis and Nucula proxima) in short-term static assay systems using 109Cd as a tracer. The experimental system consisted of ...

  14. Estimation of Density-Dependent Mortality of Juvenile Bivalves in the Wadden Sea

    PubMed Central

    Andresen, Henrike; Strasser, Matthias; van der Meer, Jaap

    2014-01-01

    We investigated density-dependent mortality within the early months of life of the bivalves Macoma balthica (Baltic tellin) and Cerastoderma edule (common cockle) in the Wadden Sea. Mortality is thought to be density-dependent in juvenile bivalves, because there is no proportional relationship between the size of the reproductive adult stocks and the numbers of recruits for both species. It is not known however, when exactly density dependence in the pre-recruitment phase occurs and how prevalent it is. The magnitude of recruitment determines year class strength in bivalves. Thus, understanding pre-recruit mortality will improve the understanding of population dynamics. We analyzed count data from three years of temporal sampling during the first months after bivalve settlement at ten transects in the Sylt-Rømø-Bay in the northern German Wadden Sea. Analyses of density dependence are sensitive to bias through measurement error. Measurement error was estimated by bootstrapping, and residual deviances were adjusted by adding process error. With simulations the effect of these two types of error on the estimate of the density-dependent mortality coefficient was investigated. In three out of eight time intervals density dependence was detected for M. balthica, and in zero out of six time intervals for C. edule. Biological or environmental stochastic processes dominated over density dependence at the investigated scale. PMID:25105293

  15. Estimation of density-dependent mortality of juvenile bivalves in the Wadden Sea.

    PubMed

    Andresen, Henrike; Strasser, Matthias; van der Meer, Jaap

    2014-01-01

    We investigated density-dependent mortality within the early months of life of the bivalves Macoma balthica (Baltic tellin) and Cerastoderma edule (common cockle) in the Wadden Sea. Mortality is thought to be density-dependent in juvenile bivalves, because there is no proportional relationship between the size of the reproductive adult stocks and the numbers of recruits for both species. It is not known however, when exactly density dependence in the pre-recruitment phase occurs and how prevalent it is. The magnitude of recruitment determines year class strength in bivalves. Thus, understanding pre-recruit mortality will improve the understanding of population dynamics. We analyzed count data from three years of temporal sampling during the first months after bivalve settlement at ten transects in the Sylt-Rømø-Bay in the northern German Wadden Sea. Analyses of density dependence are sensitive to bias through measurement error. Measurement error was estimated by bootstrapping, and residual deviances were adjusted by adding process error. With simulations the effect of these two types of error on the estimate of the density-dependent mortality coefficient was investigated. In three out of eight time intervals density dependence was detected for M. balthica, and in zero out of six time intervals for C. edule. Biological or environmental stochastic processes dominated over density dependence at the investigated scale. PMID:25105293

  16. A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China

    PubMed Central

    Yang, Jie; Ortega-Hernández, Javier; Lan, Tian; Hou, Jin-bo; Zhang, Xi-guang

    2016-01-01

    Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp. nov., recovered from the Cambrian (Stage 3) Hongjingshao Formation in Kunming, southern China, is characterized by having a robust first pair of raptorial appendages that bear well-developed ventral-facing spines, paired dorsal spines on the trunk, and posteriorly oriented serrations on the anteroventral margins of both valves. The raptorial limbs of C. serrata were adapted for grasping prey employing a descending stroke for transporting it close the mouth, whereas the backwards-facing marginal serrations of the bivalved carapace may have helped to secure the food items during feeding. The new taxon offers novel insights on the morphology of the enigmatic genus Clypecaris, and indicates that the possession of paired dorsal spines is a diagnostic trait of the Family Clypecarididae within upper stem-group Euarthropoda. C. serrata evinces functional adaptations for an active predatory lifestyle within the context of Cambrian bivalved euarthropods, and contributes towards the better understanding of feeding diversity in early ecosystems. PMID:27283406

  17. EMBATTLED BIVALVES: BIOGEOGRAPHIC DISTRIBUTIONS AND ABUNDANCES FROM THE BEAUFORT SEA TO THE GULF OF CALIFORNIA

    EPA Science Inventory

    As part of an EPA/USGS project to predict the relative vulnerability of near-coastal species to climate change, we have synthesized in a web-based tool, the Coastal Biogeographic Risk Analysis Tool (CBRAT), the biogeographic distributions and abundances of bivalves, found in dept...

  18. 76 FR 65200 - Risk Assessment on Norovirus in Bivalve Molluscan Shellfish: Request for Comments and for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-20

    ...The Food and Drug Administration (FDA) is undertaking a collaboration with Health Canada, the Canadian Food Inspection Agency, Environment Canada, and Fisheries and Oceans Canada, to conduct a quantitative food safety risk assessment on norovirus in bivalve molluscan shellfish, specifically, oysters, clams, and mussels. FDA, on behalf of the collaborative team, is requesting submission of......

  19. Forever competent: deep-sea bivalves are colonized by their chemosynthetic symbionts throughout their lifetime.

    PubMed

    Wentrup, Cecilia; Wendeberg, Annelie; Schimak, Mario; Borowski, Christian; Dubilier, Nicole

    2014-12-01

    Symbiotic bivalves at hydrothermal vents and cold seeps host chemosynthetic bacteria intracellularly in gill cells. In bivalves, the gills grow continuously throughout their lifetime by forming new filaments. We examined how newly developed gill tissues are colonized in bivalves with horizontal and vertical symbiont transmission (Bathymodiolus mussels versus a vesicoymid clam) using fluorescence in situ hybridization and transmission electron microscopy. Symbiont colonization was similar in mussels and clams and was independent of the transmission modes. Symbionts were absent in the growth zones of the gills, indicating that symbionts colonize newly formed gill filaments de novo after they are formed and that gill colonization is a continuous process throughout the host's lifetime. Symbiont abundance and distribution suggested that colonization is shaped by the developmental stage of host cells. Self-infection, in which new gill cells are colonized by symbionts from ontogenetically older gill tissues, may also play a role. In mussels, symbiont infection led to changes in gill cell structure similar to those described from other epithelial cells infected by intracellular pathogens, such as the loss of microvilli. A better understanding of the factors that affect symbiont colonization of bivalve gills could provide new insights into interactions between intracellular bacteria and epithelial tissues. PMID:25142549

  20. Characterization of the endosymbiont of a deep-sea bivalve, Calyptogena soyoae.

    PubMed Central

    Kim, Y W; Yasuda, M; Yamagishi, A; Oshima, T; Ohta, S

    1995-01-01

    We have purified DNA from gill tissue of a marine bivalve, Calyptogena soyoae, collected from the deep-sea cold seep communities in Sagami Bay, Japan. An rRNA gene was amplified, cloned, and sequenced. In situ hybridization revealed that the sequence is that of a bacterial endosymbiont within the gill of C. soyoae. PMID:7574622

  1. Dynamic Energy Budget model parameter estimation for the bivalve Mytilus californianus: Application of the covariation method

    NASA Astrophysics Data System (ADS)

    Matzelle, A.; Montalto, V.; Sarà, G.; Zippay, M.; Helmuth, B.

    2014-11-01

    Dynamic Energy Budget (DEB) models serve as a powerful tool for describing the flow of energy through organisms from assimilation of food to utilization for maintenance, growth and reproduction. The DEB theory has been successfully applied to several bivalve species to compare bioenergetic and physiological strategies for the utilization of energy. In particular, mussels within the Mytilus edulis complex (M. edulis, M. galloprovincialis, and M. trossulus) have been the focus of many studies due to their economic and ecological importance, and their worldwide distribution. However, DEB parameter values have never been estimated for Mytilus californianus, a species that is an ecological dominant on rocky intertidal shores on the west coast of North America and which likely varies considerably from mussels in the M. edulis complex in its physiology. We estimated a set of DEB parameters for M. californianus using the covariation method estimation procedure and compared these to parameter values from other bivalve species. Model parameters were used to compare sensitivity to environmental variability among species, as a first examination of how strategies for physiologically contending with environmental change by M. californianus may differ from those of other bivalves. Results suggest that based on the parameter set obtained, M. californianus has favorable energetic strategies enabling it to contend with a range of environmental conditions. For instance, the allocation fraction of reserve to soma (κ) is among the highest of any bivalves, which is consistent with the observation that this species can survive over a wide range of environmental conditions, including prolonged periods of starvation.

  2. MUSSEL WATCH--MEASUREMENTS OF CHEMICAL POLLUTANTS IN BIVALVES AS ONE INDICATOR OF COASTAL ENVIRONMENTAL QUALITY

    EPA Science Inventory

    The utility of the bivalve sentinel organism approach to monitoring for some chemicals of environmental concern in coastal and estuarine areas has been evaluated by regional and national programs and by smaller scale research efforts during the past 15 years. The extent and sever...

  3. BIVALVE BIOGEOGRAPHIC DISTRIBUTIONS, ABUNDANCES, AND CLIMATE VULNERABILITY FROM THE BEAUFORT SEA TO THE GULF OF CALIFORNIA

    EPA Science Inventory

    As part of an U.S. EPA/USGS project to predict the relative vulnerability of near-coastal species to climate change along the Pacific Coast, we have synthesized the biogeographic distributions and abundances of bivalves found in depths <200 m. We have included the twelve &ldqu...

  4. Freshwater bivalve mollusca (unionidae, sphaeriidae, corbiculidae) of the Savannah River Plant, South Carolina

    SciTech Connect

    Britton, J.C.; Fuller, S.L.H.

    1980-11-01

    A guide to freshwater bivalve molluscs found at the Savannah River Plant is presented. A dichotomous taxonomic key is provided to common forms and to unreported species whose geographic distributions include nearby localities. Discussions of ecology, life history, larval hosts, and other pertinent information is provided. (ACR)

  5. Draft Genome Sequence of the Emerging Bivalve Pathogen Vibrio tubiashii subsp. europaeus

    PubMed Central

    Spinard, Edward J.; Dubert, Javier; Gomez-Chiarri, Marta; Barja, Juan L.

    2016-01-01

    Vibrio tubiashii subsp. europaeus is a bivalve pathogen isolated during episodes of mortality affecting larval cultures in different shellfish hatcheries. Here, we announce the draft genome sequence of the type strain PP-638 and describe potential virulence factors, which may provide insight into the mechanism of pathogenicity. PMID:27469949

  6. DETERMINATION OF LETHAL DISSOLVED OXYGEN LEVELS FOR SELECTED MARINE AND ESTUARINE FISHES, CRUSTACEANS AND A BIVALVE

    EPA Science Inventory

    The objective of this study was to provide a database of the incipient lethal concentrations for reduced dissolved oxygen (DO) for selected marine and estuarine species including 12 species of fish, 9 crustaceans, and 1 bivalve. All species occur in the Virginian Province, USA, w...

  7. Uptake of contaminants of emerging concern by the bivalves Anodonta californiensis and Corbicula fluminea.

    PubMed

    Ismail, Niveen S; Müller, Claudia E; Morgan, Rachel R; Luthy, Richard G

    2014-08-19

    Uptake of seven contaminants regularly detected in surface waters and spanning a range of hydrophobicities (log D(ow) -1 to 5) was studied for two species of freshwater bivalves, the native mussel Anodonta californiensis and the invasive clam Corbicula fluminea. Batch systems were utilized to determine compound partitioning, and flow-through systems, comparable to environmental conditions in effluent dominated surface waters, were used to determine uptake and depuration kinetics. Uptake of compounds was independent of bivalve type. Log bioconcentration factor (BCF) values were correlated with log D(ow) for nonionized compounds with the highest BCF value obtained for triclocarban (TCC). TCC concentrations were reduced in the water column due to bivalve activity. Anionic compounds with low D(ow) values, i.e., clofibric acid and ibuprofen, were not removed from water, while the organic cation propranolol showed biouptake similar to that of TCC. Batch experiments supported compound uptake patterns observed in flow-through experiments. Contaminant removal from water was observed through accumulation in tissue or settling as excreted pseudofeces or feces. The outcomes of this study indicate the potential utility of bivalve augmentation to improve water quality by removing hydrophobic trace organic compounds found in natural systems. PMID:25017714

  8. Larval supply of predator and prey: temporal mismatch between crabs and bivalves after a severe winter in the Wadden Sea

    NASA Astrophysics Data System (ADS)

    Strasser, Matthias; Günther, Carmen-Pia

    2001-08-01

    Enhanced bivalve recruitment after severe winters is a well-known phenomenon in the coastal North Sea. By comparing the bivalve larval abundances in the northern Wadden Sea after a severe (1995/96), a moderate (1996/97) and a mild (1997/98) winter we found no evidence for the hypothesis that high bivalve recruitment after severe winters is caused by enhanced larval supply. Total and peak abundances of all bivalve larvae as well as of each of four separate species Ensis americanus, Mytilus edulis, Cerastoderma edule and Mya arenaria were three to six times lower after the severe than after the mild winter. In Macoma balthica total and peak abundances after the severe winter were only slightly higher than after the moderate winter. The larvae of the epibenthic predator Carcinus maenas appeared in lower numbers and six to eight weeks later after the severe winter than after the moderate and the mild winter. Since the bivalve larvae appeared without, or with less, delay after the severe winter, there was a temporal mismatch between Carcinus and the bivalves, supporting the hypothesis that reduced epibenthic predation is an important factor in high bivalve recruitment after severe winters.

  9. Cellular physiological assessment of bivalves after chronic exposure to spilled Exxon Valdez crude oil using a novel molecular diagnostic biotechnology.

    PubMed

    Downs, Craig A; Shigenaka, Gary; Fauth, John E; Robinson, Charles E; Huang, Arnold

    2002-07-01

    The objective of this study was to determine the cellular physiological status of the bivalves Mya arenaria and Mytilus trossulus in an area experiencing a 10-yr chronic exposure of spilled Exxon Valdez crude oil in Prince William Sound. Bivalves were collected from well-characterized oiled and unoiled sites. We used a novel biotechnology (Environmental Cellular Diagnostic System) to determine (i) if bivalves were physiologically stressed, (ii) the nature of the altered physiological state, and (iii) whether the bivalves were responding to an exposure of polyaromatic hydrocarbons (PAH). Molecular diagnostic analysis indicated that bivalves at the oiled site were experiencing both oxidative and xenobiotic stress, resulting in increased protein turnover and chaperone activity. Bivalves from the impacted area were responding specifically to a PAH-xenobiotic exposure and accumulating protein-PAH adducts. Finally, species-specific responses were observed that could be related to the habitat preferences of each species. We conclude that bivalves inhabiting a site impacted by crude oil from the 1989 Exxon Valdez spill showed clear indications of cellular physiological stress. PMID:12144276

  10. Burrowing Criteria and Burrowing Mode Adjustment in Bivalves to Varying Geoenvironmental Conditions in Intertidal Flats and Beaches

    PubMed Central

    Sassa, Shinji; Watabe, Yoichi; Yang, Soonbo; Kuwae, Tomohiro

    2011-01-01

    The response of bivalves to their abiotic environment has been widely studied in relation to hydroenvironmental conditions, sediment types and sediment grain sizes. However, the possible role of varying geoenvironmental conditions in their habitats remains poorly understood. Here, we show that the hardness of the surficial intertidal sediments varies by a factor of 20–50 due to suction development and suction-induced void state changes in the essentially saturated states of intertidal flats and beaches. We investigated the response of two species of bivalves, Ruditapes philippinarum and Donax semigranosus, in the laboratory by simulating such prevailing geoenvironmental conditions in the field. The experimental results demonstrate that the bivalve responses depended strongly on the varying geoenvironmental conditions. Notably, both bivalves consistently shifted their burrowing modes, reducing the burrowing angle and burial depth, in response to increasing hardness, to compensate for the excessive energy required for burrowing, as explained by a proposed conceptual model. This burrowing mode adjustment was accompanied by two burrowing criteria below or above which the bivalves accomplished vertical burrowing or failed to burrow, respectively. The suitable and fatal conditions differed markedly with species and shell lengths. The acute sensitivities of the observed bivalve responses to geoenvironmental changes revealed two distinctive mechanisms accounting for the adult–juvenile spatial distributions of Ruditapes philippinarum and the behavioral adaptation to a rapidly changing geoenvironment of Donax semigranosus. The present results may provide a rational basis by which to understand the ensuing, and to predict future, bivalve responses to geoenvironmental changes in intertidal zones. PMID:21957474

  11. Depth-related gradients in community structure and relatedness of bivalves and isopods in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Brandt, Angelika; Linse, Katrin; Ellingsen, Kari E.; Somerfield, Paul J.

    2016-05-01

    Despite increased research over the last decade, diversity patterns in Antarctic deep-sea benthic taxa and their driving forces are only marginally known. Depth-related patterns of diversity and distribution of isopods and bivalves collected in the Atlantic sector of the Southern Ocean are analysed. The data, sampled by epibenthic sledge at 40 deep-sea stations from the upper continental slope to the hadal zone (774-6348 m) over a wide area of the Southern Ocean, comprises 619 species of isopods and 81 species of bivalves. There were more species of isopods than bivalves in all samples, and species per station varied from 2 to 85 for isopods and from 0 to 18 for bivalves. Most species were rare, with 72% of isopod species restricted to one or two stations, and 45% of bivalves. Among less-rare species bivalves tended to have wider distributions than isopods. The species richness of isopods varied with depth, showing a weak unimodal curve with a peak at 2000-4000 m, while the richness of bivalves did not. Multivariate analyses indicate that there are two main assemblages in the Southern Ocean, one shallow and one deep. These overlap over a large depth-range (2000-4000 m). Comparing analyses based on the Sørensen resemblance measure and Γ+ (incorporating relatedness among species) indicates that rare species tend to have other closely related species within the same depth band. Analysis of relatedness among species indicates that the taxonomic variety of bivalves tends to decline at depth, whereas that of isopods is maintained. This, it is speculated, may indicate that the available energy at depth is insufficient to maintain a range of bivalve life-history strategies.

  12. Exploring the symmetry, structure, and self-assembly mechanism of a gigantic seven-fold symmetric {Pd₈₄} wheel.

    PubMed

    Scullion, Rachel A; Surman, Andrew J; Xu, Feng; Mathieson, Jennifer S; Long, De-Liang; Haso, Fadi; Liu, Tianbo; Cronin, Leroy

    2014-09-15

    The symmetry, structure and formation mechanism of the structurally self-complementary {Pd84} = [Pd84O42(PO4)42(CH3CO2)28](70-) wheel is explored. Not only does the symmetry give rise to a non-closest packed structure, the mechanism of the wheel formation is proposed to depend on the delicate balance between reaction conditions. We achieve the resolution of gigantic polyoxopalladate species through electrophoresis and size-exclusion chromatography, the latter has been used in conjunction with electrospray mass spectrometry to probe the formation of the ring, which was found to proceed by the stepwise aggregation of {Pd6}(-) = [Pd6O4(CH3CO2)2(PO4)3Na(6-n)H(n)](-) building blocks. Furthermore, the higher-order assembly of these clusters into hollow blackberry structures of around 50 nm has been observed using dynamic and static light scattering. PMID:25044792

  13. System of gigantic valleys northwest of Tharsis, Mars: Latent catastrophic flooding, northwest watershed, and implications for northern plains ocean

    USGS Publications Warehouse

    Dohm, J.M.; Anderson, R.C.; Baker, V.R.; Ferris, J.C.; Hare, T.M.; Strom, R.G.; Rudd, L.P.; Rice, J. W., Jr.; Casavant, R.R.; Scott, D.H.

    2000-01-01

    Mars Orbiter Laser Altimeter (MOLA) reveals a system of gigantic valleys to the northwest of the huge martian shield volcano, Arsia Mons, in the western hemisphere of Mars. These newly identified northwestern slope valleys (NSVs) potentially signify previously undocumented martian catastrophic floods and may corroborate the northern ocean hypotheses. These features, which generally correspond spatially to gravity lows, were previously obscurred in Mariner and Viking Orbiter imagery by veneers of materials, including volcanic lava flows and air fall deposits. Geologic investigations of the Tharsis region suggest that the NSVs were mainly carved prior to the construction of Arsia Mons and its associated Late Hesperian and Amazonian age lava flows, concurrent with the early development of the outflow channels that debouch into Chryse Planitia.

  14. An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Duperron, S.; Gaudron, S. M.; Rodrigues, C. F.; Cunha, M. R.; Decker, C.; Olu, K.

    2013-05-01

    Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria that ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, eastern Americas, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous, more easily accessible shallow marine species have been studied. Herein we provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to the Sea of Marmara, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 53 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae). Comparisons are made between the families, with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions. However, relatively little is known regarding their diversity and functioning, apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on oceans, we advocate a better assessment of the diversity of bivalve symbioses in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change.

  15. An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Duperron, S.; Gaudron, S. M.; Rodrigues, C. F.; Cunha, M. R.; Decker, C.; Olu, K.

    2012-11-01

    Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria which ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, East America, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous more easily accessible shallow marine species were studied. We here provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to Marmara Sea, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 51 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae), and compared among families with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions, yet relatively little is known regarding their diversity and functioning apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on Oceans, we advocate for a better assessment of bivalve symbioses diversity in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change

  16. The use of bivalves as rapid, real-time indicators of aquatic pollution

    SciTech Connect

    Markich, S.J.

    1995-12-31

    The ability of bivalves to filter large volumes of water on a daily basis, combined with the relatively high permeability of their cell membranes, make them valuable organisms to use in the contemporary detection of pollution. Bivalves are well known to respond to chemical contaminants by isolating their soft tissues from the aquatic medium by valve closure. The sensory acuity (via specialized sensory regions including the osphradium) and associated repertoire of this behavioral response can be employed to assess subtle effects exerted by chemical contaminants, such as complex effluents, that may ultimately influence the survival of these organisms. As hazard assessment tools, behavioral studies reflect sublethal toxicity and often yield a highly sensitive estimate of the lowest observable effect concentration (LOEC). Moreover, valve movement behavior has been identified as one of the more sensitive biological early warning measures to a variety of aquatic contaminants, in comparison with those used in other aquatic animal phyla. Therefore, the valve movement behavior of both freshwater (Hyridella depressa, Velesunio angasi and V. ambiguus) and marine (Mytilus edulis) bivalves was continuously monitored, using an on-line computer based data acquisition system, during exposure to either trace metals (e.g. Cu, Cd, Mn and U) or complex effluents (ie treated sewage effluent and acid leachate derived from contaminated Sydney Harbour sediments), in the context of using the valve movement behavior of the bivalve species to indicate the biological significance of exposure to the above-mentioned pollutants. The results indicate that several components of the valve movement behavior of each bivalve provide quantifiable and ecologically interpretable sub-lethal endpoints for the rapid and sensitive evaluation of waters containing either complex effluents or elevated levels of trace metals.

  17. First respiration estimates of cold-seep vesicomyid bivalves from in situ total oxygen uptake measurements.

    PubMed

    Decker, Carole; Caprais, Jean-Claude; Khripounoff, Alexis; Olu, Karine

    2012-04-01

    Vesicomyid bivalves are one of the most abundant symbiont-bearing species inhabiting deep-sea reducing ecosystems. Nevertheless, except for the hydrothermal vent clam Calyptogena magnifica, their metabolic rates have not been documented, and only assessed with ex situ experiments. In this study, gathering benthic chamber measurements and biomass estimation, we give the first in situ assessment of the respiration rate of these bivalves. The giant pockmark Regab, located at 3160m depth along the Congo-Angola margin, is a cold-seep site characterised by dense assemblages of two species of vesicomyids: Christineconcha regab and Laubiericoncha chuni with high dominance of C. regab. Two sites with dense aggregates of vesicomyids were selected to measure total oxygen uptake (TOU), and methane fluxes using IFREMER's benthic chamber CALMAR deployed by the ROV Quest 4000 (MARUM). Photographs were taken and bivalves were sampled using blade corers to estimate density and biomass. Total oxygen uptake was higher at Site 2 compared to Site 1 (respectively 492 mmol.m(-2).d(-1) and 332 mmol.m(-2).d(-1)). However, given vesicomyid densities and biomass, mean oxygen consumption rates were similar at both sites (1.9 to 2.5 μmol.g total dry mass(-1).h(-1) at the Site 1 and 1.8 to 2.3 μmol.g total dry mass(-1).h(-1) at Site 2). These respiration rates are higher than published ex situ estimates for cold-seep or hydrothermal vent bivalves. Although methane fluxes at the base of sulphide production were clearly higher at Site 2 (14.6 mmol.m(-2).d(-1)) than at Site 1 (0.3 mmol.m(-2).d(-1)), they do not seem to influence the respiration rates of these bivalves associated to sulphide-oxidizing symbionts. PMID:22578572

  18. Occurrence of gigantic biogenic magnetite during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Schumann, D.; Raub, T. D.; Kopp, R. E.; Guerquin-Kern, J. L.; Wu, T. D.; Rouiller, I.; Smirnov, A. V.; Sears, S. K.; Lücken, U.; Tikoo, S. M.; Hesse, R.; Kirschvink, J. L.; Vali, H.

    2009-04-01

    et al. 2008] to other PETM locations of the Atlantic margin and to a possible modern analog environment. High surface productivity with low-organic carbon density sediments and meter-scale sedimentary suboxic zones are provided by tropical shelves fed by energetic river systems, such as the Amazon. We inverstigated several magnetic extracts of samples taken from the meter-scale suboxic zones of the Amazone delta system. Sluijs A, Brinkhuis H, Schouten S, Bohaty SM, John CM, Zachos JC, Reichart GJ, Damste JSS, Crouch EM, Dickens GR. 2007. Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary. Nature 450:1218-1221. Kopp RE, Raub TD, Schumann D, Vali H, Smirnov AV, Kirschvink JL 2007. Magnetofossil spike during the Paleocene-Eocene thermal maximum: Ferromagnetic resonance, rock magnetic, and electron microscopy evidence from Ancora, New Jersey, United States. Paleoceanography, doi:10.1029/2007pa001473. Lipper PC, Zachos JC 2007. A biogenic origin for anomalous fine-grained magnetic material at the Paleocone-Eocene booundary at Wilson Lake, New Jesery. Paleoceanography, doi:10.1029/2007pa001471. Schumann D, Raub TD, Kopp RE, Guerquin-Kern JL, Wu TD, Rouiller I, Smirnov AV, Sears K, Lücken U, Tikoo SM, Hesse R, Kirschvink JL, Vali H 2008. Gigantism in unique biogenic magnetite at the Paleocene-Eocene Thermal Maximum. PNAS, 105:17648-17653.

  19. New records and a new species of bivalve (Mollusca: Bivalvia) from Miocene hydrocarbon seep deposits, North Island, New Zealand.

    PubMed

    Saether, Kristian P; Jingeng, Sha; Little, Crispin T S; Campbell, Kathleen A

    2016-01-01

    Fourteen bivalve taxa belonging to 11 families are present in at least 13 early to middle Miocene hydrocarbon seep deposits in the East Coast Basin, North Island, New Zealand. Among these are at least three new species, one of which, Semeloidea (s. l.) bexhavenensis sp. nov. (Lasaeidae), is described here. New distribution data are recorded for bivalve species in the families Limidae, Propeamussiidae, Malleidae and Solemyidae. Additional morphological details of Gigantidas coseli (Mytilidae) and Pratulum quinarium (Cardiidae) are provided based upon previously unrecorded internal shell features. Palaeoecological analysis indicates that bivalves utilized a broad range of modes of life and niches within the New Zealand Miocene seep environment, and no more than ca. 30% of these bivalve species were likely to have been obligate to seeps. PMID:27615822

  20. Trophic Dynamics of Filter Feeding Bivalves in the Yangtze Estuarine Intertidal Marsh: Stable Isotope and Fatty Acid Analyses

    PubMed Central

    Wang, Sikai; Jin, Binsong; Qin, Haiming; Sheng, Qiang; Wu, Jihua

    2015-01-01

    Benthic bivalves are important links between primary production and consumers, and are essential intermediates in the flow of energy through estuarine systems. However, information on the diet of filter feeding bivalves in estuarine ecosystems is uncertain, as estuarine waters contain particulate matter from a range of sources and as bivalves are opportunistic feeders. We surveyed bivalves at different distances from the creek mouth at the Yangtze estuarine marsh in winter and summer, and analyzed trophic dynamics using stable isotope (SI) and fatty acid (FA) techniques. Different bivalve species had different spatial distributions in the estuary. Glauconome chinensis mainly occurred in marshes near the creek mouth, while Sinonovacula constricta preferred the creek. Differences were found in the diets of different species. S. constricta consumed more diatoms and bacteria than G. chinensis, while G. chinensis assimilated more macrophyte material. FA markers showed that plants contributed the most (38.86 ± 4.25%) to particular organic matter (POM) in summer, while diatoms contributed the most (12.68 ± 1.17%) during winter. Diatoms made the largest contribution to the diet of S. constricta in both summer (24.73 ± 0.44%) and winter (25.51 ± 0.59%), and plants contributed no more than 4%. This inconsistency indicates seasonal changes in food availability and the active feeding habits of the bivalve. Similar FA profiles for S. constricta indicated that the bivalve had a similar diet composition at different sites, while different δ13C results suggested the diet was derived from different carbon sources (C4 plant Spartina alterniflora and C3 plant Phragmites australis and Scirpus mariqueter) at different sites. Species-specific and temporal and/or spatial variability in bivalve feeding may affect their ecological functions in intertidal marshes, which should be considered in the study of food webs and material flows in estuarine ecosystems. PMID:26261984

  1. Proteomic Profiling of Cytosolic Glutathione Transferases from Three Bivalve Species: Corbicula fluminea, Mytilus galloprovincialis and Anodonta cygnea

    PubMed Central

    Martins, José Carlos; Campos, Alexandre; Osório, Hugo; da Fonseca, Rute; Vasconcelos, Vítor

    2014-01-01

    Suspension-feeding bivalves are considered efficient toxin vectors with a relative insensitivity to toxicants compared to other aquatic organisms. This fact highlights the potential role of detoxification enzymes, such as glutathione transferases (GSTs), in this bivalve resistance. Nevertheless, the GST system has not been extensively described in these organisms. In the present study, cytosolic GSTs isoforms (cGST) were surveyed in three bivalves with different habitats and life strategies: Corbicula fluminea, Anodonta cygnea and Mytilus galloprovincialis. GSTs were purified by glutathione-agarose affinity chromatography, and the collection of expressed cGST classes of each bivalve were identified using a proteomic approach. All the purified extracts were also characterized kinetically. Results reveal variations in cGST subunits collection (diversity and properties) between the three tested bivalves. Using proteomics, four pi-class and two sigma-class GST subunits were identified in M. galloprovincialis. C. fluminea also yielded four pi-class and one sigma-class GST subunits. For A. cygnea, two mu-class and one pi-class GST subunits were identified, these being the first record of GSTs from these freshwater mussels. The affinity purified extracts also show differences regarding enzymatic behavior among species. The variations found in cGST collection and kinetics might justify diverse selective advantages for each bivalve organism. PMID:24473139

  2. Growth rates of the infaunal bivalve Soletellina alba (Lamarck, 1818) (Bivalvia: Psammobiidae) in an intermittent estuary of southern Australia

    NASA Astrophysics Data System (ADS)

    Matthews, Ty G.; Fairweather, Peter G.

    2003-12-01

    Caging and a mark-recapture design were used to estimate the growth rate of the brittle, infaunal bivalve Soletellina alba in the Hopkins River estuary. The growth of both caged and uncaged individuals was monitored at three sites near the mouth of the estuary over 180 days. Growth rates did not differ for caged and uncaged bivalves, or for bivalves subject to different amounts of handling, or between sites. Growth did differ between consecutive time intervals, which was attributable to negligible growth occurring during the colder months of autumn/winter. Comparisons of the condition (as indicated by total mass for length 3) of S. alba were inconsistent between sites for caged and uncaged bivalves and for those subject to different amounts of handling. Soletellina alba is a rapidly growing bivalve with mean growth rates for the three time intervals being 0.04±0.002 mm day-1 in summer, 0.02±0.001 mm day-1 in autumn and 0.03±0.001 mm day-1 from summer to winter. Using existing literature, it was shown that a significant relationship exists between maximum shell length and onset of sexual maturity in bivalve molluscs. This relationship predicts that S. alba should reach the onset of sexual maturity at 15.8 mm length. Therefore, it appears that it may be possible for juvenile S. alba (<1 mm) to grow, reach sexual maturity and reproduce in between annual mass-mortality events caused by winter flooding.

  3. Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX.

    PubMed

    Novoa, Anai; Talley, Theresa S; Talley, Drew M; Crooks, Jeffrey A; Reyns, Nathalie B

    2016-01-01

    A combination of historical bivalve surveys spanning 30-50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration. PMID:26840744

  4. Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX

    PubMed Central

    Crooks, Jeffrey A.; Reyns, Nathalie B.

    2016-01-01

    A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration. PMID:26840744

  5. Proteomic profiling of cytosolic glutathione transferases from three bivalve species: Corbicula fluminea, Mytilus galloprovincialis and Anodonta cygnea.

    PubMed

    Martins, José Carlos; Campos, Alexandre; Osório, Hugo; da Fonseca, Rute; Vasconcelos, Vítor

    2014-01-01

    Suspension-feeding bivalves are considered efficient toxin vectors with a relative insensitivity to toxicants compared to other aquatic organisms. This fact highlights the potential role of detoxification enzymes, such as glutathione transferases (GSTs), in this bivalve resistance. Nevertheless, the GST system has not been extensively described in these organisms. In the present study, cytosolic GSTs isoforms (cGST) were surveyed in three bivalves with different habitats and life strategies: Corbicula fluminea, Anodonta cygnea and Mytilus galloprovincialis. GSTs were purified by glutathione-agarose affinity chromatography, and the collection of expressed cGST classes of each bivalve were identified using a proteomic approach. All the purified extracts were also characterized kinetically. Results reveal variations in cGST subunits collection (diversity and properties) between the three tested bivalves. Using proteomics, four pi-class and two sigma-class GST subunits were identified in M. galloprovincialis. C. fluminea also yielded four pi-class and one sigma-class GST subunits. For A. cygnea, two mu-class and one pi-class GST subunits were identified, these being the first record of GSTs from these freshwater mussels. The affinity purified extracts also show differences regarding enzymatic behavior among species. The variations found in cGST collection and kinetics might justify diverse selective advantages for each bivalve organism. PMID:24473139

  6. Measurement of filtration rates by infaunal bivalves in a recirculating flume

    USGS Publications Warehouse

    Cole, B.E.; Thompson, J.K.; Cloern, J.E.

    1992-01-01

    A flume system and protocol for measuring the filtration rate of infaunal bivalves is described. Assemblages of multi-sized clams, at natural densities and in normal filter-feeding positions, removed phytoplankton suspended in a unidirectional flow of water. The free-stream velocity and friction velocity of the flow, and bottom roughness height were similar to those in natural estuarine waters. Continuous variations in phytoplankton (Chroomonas salinay) cell density were used to measure the filtration rate of the suspension-feeding clam Potamocorbula amurensis for periods of 2 to 28 h. Filtration rates of P. amurensis varied from 100 to 580 liters (gd)-1 over a free-stream velocity range of 9 to 25 cm s-1. Phytoplankton loss rates were usually constant throughout the experiments. Our results suggest that suspension-feeding by infaunal bivalves is sensitive to flow velocity. ?? 1992 Springer-Verlag.

  7. Paleoenvironmental and paleoclimatic significance of freshwater bivalves in the Upper Jurassic Morrison Formation, Western Interior, USA

    NASA Astrophysics Data System (ADS)

    Good, Steven C.

    2004-05-01

    Freshwater unionid bivalves are spatially and temporally distributed throughout the Morrison depositional basin, and locally dominate the biomass of many aquatic depositional environments. Two bivalve assemblages are identified. Within-channel assemblages are death assemblages that have been transported and may represent mixed assemblages from multiple communities. These assemblages are predominately disarticulated, in current stable orientations, and composed of higher stream velocity ecophenotypes (medium size, lanceolate form, and very thick shells). The floodplain-pond assemblages are disturbed neighborhood assemblages in the mudstones inhabited during life. The bivalves are predominately articulated, variable in size, and composed of low stream velocity ecophenotypes (large maximum sizes, ovate shell shapes, and thinner shells). The glochidial parasitic larval stage of unionid bivalves provides an effective means of dispersing species throughout drainage basins. These larvae attach to fish and are carried through the fluvial drainage where the larvae detach and establish new bivalve communities. Preliminary paleobiogeographic analyses are drawn at the genus level because of the need to reevaluate bivalve species of the Morrison. Unio spp. and Vetulonaia spp. are widespread throughout the Morrison depositional basin, but Hadrodon spp. are restricted to the eastern portion of the Colorado Plateau during Salt Wash Member deposition, suggesting that Salt Wash drainage was isolated from other contemporaneous regions of the basin. Bivalves from five localities in the Morrison Formation were thin-sectioned for growth band analysis. Growth bands of modern unionid bivalves are produced when the valves are forced to close. Closure can produce annual growth bands in response to seasonal variation, such as temperature-induced hibernation, or precipitation-induced aestivation or turbidity. Pseudoannual growth bands form from non-cyclical events such as predation attacks or

  8. [Participation of insulin in regulating the metabolism of marine bivalve mollusks].

    PubMed

    Plisetskaia, E M; Soltitskaia, L P; Leĭbson, L G

    1979-01-01

    Marine bivalve molluscs, the mussel Mytilus galloprovincialis aud the scallop Chlamys (Flexopecten) glaber ponticus, have been injected (intramuscularly or in the haemolymph) with glucose, mammalian insulin, insulin (or insulin-like substance) from molluscs, and anti-insulin serum, checking changes in glucose and fatty acid content of the haemolymph as well as in the content of glycogen and the activity of glycogen synthetase in muscles. After glucose injections, studies were also made on the level of IRI in the haemolymph. Comparison of the data obtained in the present work with those reported earlier for freshwater bivalve molluscs suggests that: 1) metabolic shifts induced by anti-insulin serum are more rapid in vigorous scallops than in sedentary mussels; 2) molluscan insulin (or insulin-like substance) exerts the same effect on metabolic parameters of the molluscs, as mammalian insulin exerts in vertebrates. PMID:473986

  9. Role of bivalve mollusks in the sediment balance of the Anapa Bay Bar

    NASA Astrophysics Data System (ADS)

    Kosyan, A. R.; Kucheruk, N. V.; Flint, M. V.

    2012-02-01

    The sandy beaches of Anapa Bay Bar are a unique natural resource, but they are gradually being degrade under both natural and anthropogenic factors. The emissions of sand and shelly ground from the adjacent sea bottom partly compensate for this process. The concentration of carbonates may reach up to 50% in the beach sands, and most of these carbonates are of mollusk origin. The major deposit formation role belongs to the key bivalve species: Chamelea gallina (Linnaeus, 1758). The average biomass of this mollusk species reaches up to 450 g/m2 at the depths of 5-10 m. The other two subdominating mollusk species, the bivalve Donax trunculus (Linnaeus, 1758) and the gastropod Rapana venosa (Valenciennes, 1846), may impact as 16 g/m2 and 6 g/m2, respectively. Annually, 350 kg of shelly ground per running meter are newly deposited on Anapa beach.

  10. p53 Superfamily proteins in marine bivalve cancer and stress biology.

    PubMed

    Walker, Charles W; Van Beneden, Rebecca J; Muttray, Annette F; Böttger, S Anne; Kelley, Melissa L; Tucker, Abraham E; Thomas, W Kelley

    2011-01-01

    The human p53 tumour suppressor protein is inactivated in many cancers and is also a major player in apoptotic responses to cellular stress. The p53 protein and the two other members of this protein family (p63, p73) are encoded by distinct genes and their functions have been extensively documented for humans and some other vertebrates. The structure and relative expression levels for members of the p53 superfamily have also been reported for most major invertebrate taxa. The functions of homologous proteins have been investigated for only a few invertebrates (specifically, p53 in flies, nematodes and recently a sea anemone). These studies of classical model organisms all suggest that the gene family originally evolved to mediate apoptosis of damaged germ cells or to protect germ cells from genotoxic stress. Here, we have correlated data from a number of molluscan and other invertebrate sequencing projects to provide a framework for understanding p53 signalling pathways in marine bivalve cancer and stress biology. These data suggest that (a) the two identified p53 and p63/73-like proteins in soft shell clam (Mya arenaria), blue mussel (Mytilus edulis) and Northern European squid (Loligo forbesi) have identical core sequences and may be splice variants of a single gene, while some molluscs and most other invertebrates have two or more distinct genes expressing different p53 family members; (b) transcriptional activation domains (TADs) in bivalve p53 and p63/73-like protein sequences are 67-69% conserved with human p53, while those in ecdysozoan, cnidarian, placozoan and choanozoan eukaryotes are ≤33% conserved; (c) the Mdm2 binding site in the transcriptional activation domain is 100% conserved in all sequenced bivalve p53 proteins (e.g. Mya, Mytilus, Crassostrea and Spisula) but is not present in other non-deuterostome invertebrates; (d) an Mdm2 homologue has been cloned for Mytilus trossulus; (e) homologues for both human p53 upstream regulatory and

  11. Trace metals in water, sediment and bivalves of a tropical estuary, west coast of India.

    PubMed

    Parvez Al-Usmani, S M; Jagtap, T G; Patil, D N

    2015-10-15

    Trace metal pollution was studied in water, sediment and three selected bivalves in Mandovi and Chapora estuaries of Goa. The trace metal in water and sediment of Mandovi was higher than in Chapora. The concentration in the tissues was in the range of 1205.2-2506.7 ppm for Paphia malabarica, 1906.2-2802.6 ppm for Perna viridis and 778.7-1607.5 ppm for Saccostrea cucullata in Mandovi estuary. Tha values for Chapora were 199.4-625.8 ppm for P. malabarica, 812.6-1220.2 for P. viridis and 392.5-418.6 ppm for S. cucullata. The anthropogenic input of metal in Mandovi estuary appears to be mainly responsible for the high accumulation of trace metals. These bivalves have potential to serve as indicator for metal contamination in seafood of Goa. PMID:26228069

  12. Cytotoxicity assessment of antibiofouling compounds and by-products in marine bivalve cell cultures.

    PubMed

    Domart-Coulon, I; Auzoux-Bordenave, S; Doumenc, D; Khalanski, M

    2000-06-01

    Short-term primary cell cultures were derived from adult marine bivalve tissues: the heart of oyster Crassostrea gigas and the gill of clam Ruditapes decussatus. These cultures were used as experimental in vitro models to assess the acute cytotoxicity of an organic molluscicide, Mexel-432, used in antibiofouling treatments in industrial cooling water systems. A microplate cell viability assay, based on the enzymatic reduction of tetrazolium dye (MTT) in living bivalve cells, was adapted to test the cytotoxicity of this compound: in both in vitro models, toxicity thresholds of Mexel-432 were compared to those determined in vivo with classic acute toxicity tests. The clam gill cell model was also used to assess the cytotoxicity of by-products of chlorination, a major strategy of biofouling control in the marine environment. The applications and limits of these new in vitro models for monitoring aquatic pollutants were discussed, in reference with the standardized Microtox test. PMID:10806375

  13. Ultrafast gigantic photo-response in charge-ordered organic salt (EDO-TTF)2PF6 on 10-fs time scales

    SciTech Connect

    Itatani, J.; Rini, M.; Cavalleri, A.; Onda, K.; Ishikawa, T.; Ogihara, S.; Koshihara, S.; Shao, X.; Nakano, Y.; Yamochi, H.; Saito, G.; Schoenlein, R.W.

    2008-08-01

    The initial dynamics of photo-induced phase transition in charge-ordered organic salt (EDO-TTF){sub 2}PF{sub 6} was investigated using 10-fs near-infrared laser pulses. We observed sub-20-fs gigantic photo-responses (|{Delta}R/R|>100%) due to intra-molecular vibration and a clear signature of a structural bottleneck ({approx}50 fs) for the first time.

  14. Bivalves and gastropods from the middle Campanian Anacacho limestone, South Central Texas

    USGS Publications Warehouse

    Elder, W.P.

    1996-01-01

    The Anacacho Limestone was deposited during the Campanian and represents two depositional intervals, one of early Campanian and one of middle Campanian age. These two intervals correspond to periods of major eustatic sea level rise. This study focuses on the molluscan paleontology of the middle Campanian interval in the eastern part of the Anacacho exposure belt in Medina County, Texas. Molluscan assemblages in this area are indicative of inner to mid-shelf environments. No significant reef components are present. These eastern Anacacho deposits are interpreted to represent more offshore, deeper water environments than those to the southwest, where reef and lagoonal deposits have been reported. Analysis of the macrofossil components from these eastern localities has expanded the number of invertebrate species known from the Anacacho Limestone by nearly three-fold. This increase in diversity, based on a small amount of new work, suggests that many more taxa are yet to be identified, particularly in the western part of the exposure belt in Uvalde and Kinney Counties. This paper documents the bivalve and gastropod fauna, discussing and illustrating 24 bivalve taxa and 11 gastropod species. Two new bivalve species are named, Panopea anacachoensis new species and Spondylus siccus new species, and two potentially new gastropod species are identified but not named herein due to inadequate material. This paper expands the distribution of many eastern Gulf Coast and Atlantic Coast taxa westward into Texas and shows strong ties between the Anacacho fauna and that of the Campanian Tar Heel and Bladen Formations of the Black Creek Group in North Carolina. The taxonomic ties between these two areas probably reflect the thorough documentation of the North Carolina fauna, which is the best documented Campanian bivalve fauna in the Gulf or Atlantic Coast regions.

  15. Dinophysis caudata generated lipophilic shellfish toxins in bivalves from the Nanji Islands, East China Sea

    NASA Astrophysics Data System (ADS)

    Jiang, Tao; Xu, Yixiao; Li, Yang; Qi, Yuzao; Jiang, Tianjiu; Wu, Feng; Zhang, Fan

    2014-01-01

    A 12-month program of monitoring potentially toxic microalgae (that produce lipophilic shellfish toxins; LSTs) and their toxins in bivalves was conducted from April 2006 to March 2007 in the Nanji Islands, East China Sea. Two Dinophysis species, D. caudata and D. acuminata, were identified, and D. caudata was found to be the dominant species. D. caudata was detected in water samples between April and June 2006, and between February and March 2007. It reached its highest abundances in May, with a mean abundance of 1.38×102 cells/L in surface water and 1.25×102 cells/L in bottom water (<10 m deep). The temporal distribution of D. caudata was associated with the occurrence of LSTs in bivalve samples, which mostly occurred at the same time as D. caudata blooms, between April and July 2006. All of the cultured bivalves sampled between April and June were contaminated with LSTs, with an average toxicity of 85 μg okadaic acid (OA) eq./100 g meat, which was four times higher than the Chinese regulatory limit (20 μg OA eq./100 g meat). Ten out of fifteen wild samples (66.7%) collected during the same period were positive for LSTs, and contained an average LST toxicity of 45 μg OA eq./100 g meat (more than twice the regulatory value). Cultured Patinopecten yessoensis collected on 15 May 2006 had the highest toxicity, 320 μg OA eq./100 g meat, and relatively high toxicities (80 to 160 μg OA eq./100 g meat) were found in bivalves until the end of July.

  16. Species composition and distribution of bivalves in bathyal and abyssal depths of the Sea of Japan

    NASA Astrophysics Data System (ADS)

    Kamenev, Gennady M.

    2013-02-01

    Twenty-six bivalve species collected by four Russian (1972, 1976, 1985, 2005) and Russian-German (2010) expeditions in the bathyal and abyssal depths of the Sea of Japan (465-3435 m) are listed with the material examined and illustrated. Taxonomic decisions herein: Robaia habei Scarlato, 1981 is synonymized with Nuculana (Robaia) robai (Kuroda, 1929); following Scarlato (1981) and Coan et al. (2000)Dacrydium nipponicum Okutani, 1975 and Dacrydium minimum Okutani and Izumidate, 1992 are synonymized with Dacrydium vitreum (Möller, 1842); Maorithyas yamatotaensis Okutani and Izumidate, 1992 is synonymized with Adontorhina cyclia Berry, 1947; Axinopsida rubiginosa Okutani and Izumidate, 1992 is synonymized with Mendicula ferruginosa (Forbes, 1844); Cardiomya lindbergi batialis Scarlato, 1972 is synonymized with Cardiomya tosaensis (Kuroda, 1948); Cuspidaria sadoensis Okutani and Ito, 1983 is synonymized with Cuspidaria ascoldica Scarlato, 1972; Cyclocardia rjabininae (Scarlato, 1955) recognized as valid and distinct from Cyclocardia ovata (Rjabinina, 1952). The deep-water bivalve fauna of the Sea of Japan is characterized by an impoverished shelf fauna and consists of eurybathic species that extend from the shelf to the bathyal and abyssal zones. Most of them have a wide geographic distribution and inhabit cold water regions of the Northern Atlantic, Northern Pacific, and Arctic Ocean. Only five species are endemic to the Sea of Japan. With increase in depth, the species richness of bivalves decreases. In the depth range from 200 to 1600 m, all species (26) found in the deep Sea of Japan were recorded, while only 10 species were recorded in the lower bathyal slope (1700-3000 m). At depths below 3000 m, only D. vitreum, Delectopecten vancouverensis (Whiteaves, 1893), and Thyasira (Parathyasira) sp. were found. The lack of typical abyssal species of bivalves in the deep Sea of Japan is probably connected with the isolation of this body of water from the Pacific abyssal

  17. Investigation of Nematopsis spp. oocysts in 7 species of bivalves from Chonburi province, Gulf of Thailand.

    PubMed

    Tuntiwaranuruk, C; Chalermwat, K; Upatham, E S; Kruatrachue, M; Azevedo, C

    2004-01-28

    This is the first detailed report of Nematopsis spp. in Thai bivalves. A monthly survey was conducted on 7 species of commercial bivalves from Chonburi province, on the eastern seaboard of Thailand, from November 2000 to November 2001 to investigate the prevalence of the apicomplexan parasite Nematopsis Schneider, 1892. Nematopsis spp. sporozoites were found in the cultivated bivalves Arcuatula arcuatula, Anadara granosa and Perna viridis as well as the locally harvested Paphia undulata. They were not found in Donax faba, Meretrix meretrix or Saccostrea cucullata. Using light microscopy, we were able to identiby 4 oocyst morphotypes of the gregarine Nematopsis spp. Prevalence of Nematopsis spp. during the 13 mo sampling period was highest in A. arcuatula (91.8%; n = 110) and lowest in A. granosa (59.2%; n = 130). The morphology of the oocysts differed between hosts, with an average (x +/- SD) length/width of 16.28 +/- 0.64/12.01 +/- 0.35 microm (n = 50) for A. arcuatula, 16.90 +/- 0.71/12.69 +/- 0.33 microm (n = 50) for A. granosa, 17.61 +/- 0.69/12.72 +/- 0.36 microm (n = 50) for P. viridis, and 11.21 +/- 0.62/8.55 +/- 0.52 microm (n = 50) for P. undulata. Identification of oocysts of these apicomplexan gregarines to species was not attempted. The prevalence of infection in relation to habitat and time of sampling is discussed. PMID:15038451

  18. Analysis of synonymous codon usage patterns in sixty-four different bivalve species

    PubMed Central

    De Moro, Gianluca; Venier, Paola; Pallavicini, Alberto

    2015-01-01

    Synonymous codon usage bias (CUB) is a defined as the non-random usage of codons encoding the same amino acid across different genomes. This phenomenon is common to all organisms and the real weight of the many factors involved in its shaping still remains to be fully determined. So far, relatively little attention has been put in the analysis of CUB in bivalve mollusks due to the limited genomic data available. Taking advantage of the massive sequence data generated from next generation sequencing projects, we explored codon preferences in 64 different species pertaining to the six major evolutionary lineages in Bivalvia. We detected remarkable differences across species, which are only partially dependent on phylogeny. While the intensity of CUB is mild in most organisms, a heterogeneous group of species (including Arcida and Mytilida, among the others) display higher bias and a strong preference for AT-ending codons. We show that the relative strength and direction of mutational bias, selection for translational efficiency and for translational accuracy contribute to the establishment of synonymous codon usage in bivalves. Although many aspects underlying bivalve CUB still remain obscure, we provide for the first time an overview of this phenomenon in this large, commercially and environmentally important, class of marine invertebrates. PMID:26713259

  19. Lincoln Park shoreline erosion control project: Monitoring for surface substrate, infaunal bivalves and eelgrass, 1993

    SciTech Connect

    Antrim, L.D.; Thom, R.M.; Gardiner, W.W.

    1993-09-01

    In 1988, the US Army Corps of Engineers and the City of Seattle placed material on the upper beach at Lincoln Park, in West Seattle, Washington. The fill served to mitigate shoreline erosion that had caused undercutting and collapse of the seawall in several places. A series of pre- and post-construction studies have been conducted to assess the impacts to marine biota of fill placement and movement of surface substrate. This study was designed to monitor infaunal bivalves and eelgrass from intertidal areas in and adjacent to the area of original fill placement. Findings from this survey were compared to previous survey results to determine (1) if recruitment of infaunal bivalves to the fill area has occurred, (2) if infaunal bivalve densities outside the fill area are stable, and (3) if eelgrass distribution and abundance have remained stable along the adjacent shoreline. To maximize comparability of findings from this survey with previous studies, sampling techniques, transects, and tidal elevations were consistent with previous studies at this site.

  20. Pathogenic marine microbes influence the effects of climate change on a commercially important tropical bivalve.

    PubMed

    Turner, Lucy M; Alsterberg, Christian; Turner, Andrew D; Girisha, S K; Rai, Ashwin; Havenhand, Jonathan N; Venugopal, M N; Karunasagar, Indrani; Godhe, Anna

    2016-01-01

    There is growing evidence that climate change will increase the prevalence of toxic algae and harmful bacteria, which can accumulate in marine bivalves. However, we know little about any possible interactions between exposure to these microorganisms and the effects of climate change on bivalve health, or about how this may affect the bivalve toxin-pathogen load. In mesocosm experiments, mussels, Perna viridis, were subjected to simulated climate change (warming and/or hyposalinity) and exposed to harmful bacteria and/or toxin-producing dinoflagellates. We found significant interactions between climate change and these microbes on metabolic and/or immunobiological function and toxin-pathogen load in mussels. Surprisingly, however, these effects were virtually eliminated when mussels were exposed to both harmful microorganisms simultaneously. This study is the first to examine the effects of climate change on determining mussel toxin-pathogen load in an ecologically relevant, multi-trophic context. The results may have considerable implications for seafood safety. PMID:27576351

  1. Direct and indirect effects of biological factors on extinction risk in fossil bivalves.

    PubMed

    Harnik, Paul G

    2011-08-16

    Biological factors, such as abundance and body size, may contribute directly to extinction risk and indirectly through their influence on other biological characteristics, such as geographic range size. Paleontological data can be used to explicitly test many of these hypothesized relationships, and general patterns revealed through analysis of the fossil record can help refine predictive models of extinction risk developed for extant species. Here, I use structural equation modeling to tease apart the contributions of three canonical predictors of extinction--abundance, body size, and geographic range size--to the duration of bivalve species in the early Cenozoic marine fossil record of the eastern United States. I find that geographic range size has a strong direct effect on extinction risk and that an apparent direct effect of abundance can be explained entirely by its covariation with geographic range. The influence of geographic range on extinction risk is manifest across three ecologically disparate bivalve clades. Body size also has strong direct effects on extinction risk but operates in opposing directions in different clades, and thus, it seems to be decoupled from extinction risk in bivalves as a whole. Although abundance does not directly predict extinction risk, I reveal weak indirect effects of both abundance and body size through their positive influence on geographic range size. Multivariate models that account for the pervasive covariation between biological factors and extinction are necessary for assessing causality in evolutionary processes and making informed predictions in applied conservation efforts. PMID:21808004

  2. Improving data resolution and statistical rigor in the analysis of bivalve shells as environmental archives.

    PubMed

    Shoults-Wilson, W Aaron; Seymour, Lynne; Unrine, Jason M; Wisniewski, Jason M; Black, Marsha C

    2014-02-01

    Bivalves secrete their shells in an annual fashion, resulting in discrete bands of growth within each shell. In doing so, they may incorporate trace elements in concentrations reflecting exposure. This may make it possible to use them as archives of environmental information, such as contamination events. In this study, we used laser ablation inductively coupled plasma-mass spectrometry to analyze trace elements (Cd, Cu, Mn, Pb and Zn) on a fly-scanning transect perpendicular to the growth annuli of the freshwater bivalve Elliptio hopetonensis collected from the Altamaha river system. Concentrations of Mn from multiple shells at each site were correlated and average Mn data series were formed. Periodicity of Mn data was determined and sampling errors removed using an autoregression model. The Mn data series at each site were shown to have regular fluctuations of high and low concentrations. Fluctuations were similar between the shells from the same site but different between shells from different sites, demonstrating that Mn deposition in the shells of E. hopetonensis follows a regular, seasonal pattern but that growth differs between sites with different environments. Cd, Cu, Pb and Zn could not be analyzed in a statistically robust manner. This is the first study to attempt to improve data resolution by using the fly-scanning approach and, additionally, the first to apply an autoregression model to Mn data from bivalve annuli. Further study is required to develop this approach for environmental monitoring. PMID:24305745

  3. Bivalve larvae testing of ocean and in-bay sediments using porewater and elutriates

    SciTech Connect

    Griffin, D.; Targgart, L.

    1995-12-31

    Toxicity of marine sediments is commonly tested using bivalve larval tests. The tests are performed on elutriates, which are prepared by mixing the sediment sample with seawater, and allowing the mixture to settle. The supernatant is separated and tested. Test results appeared to vary depending on the grain-size of the sediments. A study was performed to compare the effects of sediment grain-size on elutriate and porewater toxicity using the bivalve larvae test. Sediments were sampled from two sites: one in San Francisco Bay and one off the coast of San Francisco in the open ocean. From each site, two areas were sampled, one that was potentially impacted by a point-source discharge and another that was free from any discharge impacts. The bay sediments were fine-grained, and the ocean sediments were coarse grained. Porewater from each sample was extracted by centrifugation, and elutriates were prepared using a 4:1 sediment: seawater ratio. Each of the porewater and elutriate samples were tested using the ASTM Standard Guide for Conducting Static Acute Toxicity Tests with Saltwater Bivalves. The results show differences in toxicity that appear to be related to sediment grain-size. The results of this study further imply that dredge material test results should be interpreted with caution when fine-grained sediments are tested. Normalization of the results to grain-size may be appropriate.

  4. Impact of particulate pollutant metals on larval and adult bivalve molluscs

    SciTech Connect

    Gilbert, T.R.; Robinson, W.E. ); Morse, M.P. . Marine Science Lab.)

    1982-10-25

    Our investigations of the effects of pollutants on bivalve molluscs have continued with studies with in the following areas: bioaccumulation of trace metals in adult sea scallops exposed to dissolved and particulate forms of the metals, SEM/EDXA studies of phosphoritic concretions in the kidneys of adult sea scallops (Placopecten magellanicus), documentation of the normal embryonic and larval development, including shell formation, in surf clams (Spisula solidissima), evaluation of the toxicity of dissolved silver to the gametes and larvae of surf clams at several stages of development, and examination of the effects of turbid suspensions on the feeding efficiency of larval Mercenaria mercenaria. The overall goal of our work is twofold. First, we are striving to gain an understanding of the pathways by which metals are transported within bivalve molluscs. The production of metallothioneins and metal-rich inorganic concretions have been documented for a number of bivalves. The ways in which of metal-rich matrices in membrane-limited vesicles as an intermediate step, is one area of investigation. Second, we are examining the relative sensitivities of the gamete and of early life stages of these organisms to stresses induced by exposure to energy-related pollutants. 46 refs., 12 figs., 8 tabs.

  5. Environmental regulation of bivalve growth in the southern Barents Sea: A combined ecological and geochemical approach

    NASA Astrophysics Data System (ADS)

    Carroll, M. L.; Johnson, B. J.; Henkes, G. A.; McMahon, K. W.; Voronkov, A.; Ambrose, W. G., Jr.; Denisenko, S. G.

    2009-04-01

    Ecological and geochemical analyses of bivalve shells provide potentially complimentary information on patterns and drivers of natural variability in Arctic marine populations, yet are rarely considered together. We analyzed growth rates and shell geochemistry of the Greenland Smooth Cockle (Serripes groenlandicus) from the southern Barents Sea between 1882 and 1968. Growth, stable isotope (oxygen and carbon), and trace elemental (Mg, Sr, Ba, Mn) patterns were linked to environmental variations on weekly to decadal scales. Standardized growth rates exhibited multi-year periodicity inversely related to the North Atlantic Oscillation Index (NAO) and positively related to river discharge. Up to 60% of the interannual variability in Ba/Ca could be explained by variations in river discharge at stations closest to the rivers, but the relationship disappeared at a more distant location. Stable isotope data (18O, 13C), and Sr/Ca patterns suggest that bivalve growth ceases at elevated temperatures during the fall and recommences at the coldest temperatures in the early spring, implying that food, rather than temperature, is the primary driver of the annual growth cycle. Combining annually-integrated growth results and higher resolution geochemical results thus elucidated the annual growth cycle of an Arctic bivalve and mechanisms of biophysical coupling over a range of temporal and spatial scales.

  6. Synchronous barium peaks in high-resolution profiles of calcite and aragonite marine bivalve shells

    NASA Astrophysics Data System (ADS)

    Gillikin, David Paul; Lorrain, Anne; Paulet, Yves-Marie; André, Luc; Dehairs, Frank

    2008-10-01

    Barium/calcium profiles of bivalve shells are characterized by flat background signals periodically interrupted by sharp peaks, with the background signals correlated with water Ba/Ca. To test if the peaks are an environmental signal related to productivity, we analyzed high-resolution Ba/Ca profiles in bivalve shells that grew adjacent to one another. Two aragonitic Saxidomus giganteus show remarkable similarity over a decade of growth, clearly indicating an environmental forcing. Four calcitic Pecten maximus shells also record synchronous Ba/Ca peaks, again indicating an exogenous control. The Ba/Ca peaks, however, start ~40 days after the crash of a bloom, while sedimentation takes place immediately following the bloom. Barite formation in settling phytoplankton flocs, as has been previously proposed, is clearly not the cause of these peaks. Other possible causes, such as dissolved Ba in ambient water, spawning, shell organic matter content, and kinetic growth rate effects are also discussed, but none provide satisfactory explanations. Background shell Ba partition coefficients (Ba/Cacarbonate/Ba/Cawater) for both the calcitic shells (0.18) and aragonitic shells (0.16) are similar to that previously reported for the calcitic Mytilus edulis (~0.1). We suggest that Ba/Ca peaks in bivalve shells are caused by an as yet undetermined environmental forcing, while background Ba/Ca levels are a good indication of dissolved Ba/Ca in the water; both are independent of shell mineralogy.

  7. Explosive demographic expansion by dreissenid bivalves as a possible result of astronomical forcing

    NASA Astrophysics Data System (ADS)

    Harzhauser, M.; Mandic, O.; Kern, A. K.; Piller, W. E.; Neubauer, T. A.; Albrecht, C.; Wilke, T.

    2013-12-01

    Human induced range expansions of invasive dreissenid bivalves are of great concern. However, the underlying biological processes are only poorly understood, partly due to the lack of information on natural expansion events. Here we use the extinct bivalve species Sinucongeria primiformis as a model organism for testing natural (i.e. pre-Anthropocene) blooms of dreissenid species in a lacustrine system of Lake Pannon during the Tortonian (~ 10.5 Myr; late Miocene). A total of 600 samples from a consecutive core were evaluated for the relative abundance of this pavement-forming mollusc, which cover about eight millennia of late Miocene time with a decadal resolution. Our data indicate that the settlement by bivalves in the offshore environment was limited mainly by bottom water oxygenation, which follows predictable and repetitive patterns through time. These population fluctuations might be related to solar cycles: successful dreissenid settlement is recurring in a frequency known as the lower and upper Gleissberg cycles with 50-80 and 90-120 yr periods. These cycles appear to control regional wind patterns, which are directly linked to water mixing of the lake. This is modulated by the even more prominent 500 yr cycle, which seems to be the most important pacemaker for Lake Pannon hydrology.

  8. Explosive demographic expansion by dreissenid bivalves as a possible result of astronomical forcing

    NASA Astrophysics Data System (ADS)

    Harzhauser, M.; Mandic, O.; Kern, A. K.; Piller, W. E.; Neubauer, T. A.; Albrecht, C.; Wilke, T.

    2013-07-01

    Human induced range expansions of invasive dreissenid bivalves are of great concern. However, the underlying biological processes are only poorly understood, partly due to the lack of information on natural expansion events. Here we use the extinct bivalve species Sinucongeria primiformis as a model organism for testing natural (i.e. non-Anthropocene) blooms of dreissenid species in a lacustrine system of Lake Pannon during the Tortonian (~10.5 Myr; Late Miocene). 600 samples from a consecutive core were evaluated for the relative abundance of this pavement-forming mollusc, which cover about 8 millennia of Late Miocene time with a decadal resolution. Our data indicate that the settlement by bivalves in the offshore environment was limited mainly by bottom water oxygenation, which follows predictable and repetitive patterns through time. These population fluctuations might be related to solar cycles: successful dreissenid settlement is re-occurring in a frequency known as the lower and upper Gleissberg cycles with a 50-80 and 90-120 yr period. These cycles appear to control regional wind patterns, which are directly linked to water mixing of the lake. This is modulated by the even more prominent 500 yr cycle, which seems to be the most important pacemaker for Lake Pannon hydrology.

  9. Estimation of food limitation of bivalve larvae in coastal waters of north-western Europe

    NASA Astrophysics Data System (ADS)

    Bos, Oscar G.; Hendriks, Iris E.; Strasser, Matthias; Dolmer, Per; Kamermans, Pauline

    2006-04-01

    Marine invertebrate recruitment may be affected by food limitation during the pelagic larval life stages. In the present study, field data on abundance of bivalve larvae along with their prey (small phytoplankton) were examined to see whether they were consistent with predictions made by an energetic model of larval requirements. Bivalve larvae were monitored during 2000 at ten different study sites in four different areas (Limfjorden, Sylt-Rømø bight, Western Wadden Sea and Delta area) along the coast of north-western Europe. Calculation of the energetic requirements of the larvae at 15 °C indicated maintenance costs of a 200-μm bivalve larva to be 1.9 × 10 - 5 J larva - 1 d - 1 , while the maximum assimilation rate, resulting in maximum growth, would amount to 6.2 × 10 - 3 J larva - 1 d - 1 . Calculation of potential assimilation rates of larvae in the field resulted in estimates between 10 - 5 and 10 - 3 J larva - 1 d - 1 . Maximum larval concentrations in the field occurred from May to September and ranged between 17 and 392 larvae dm - 3 . Most larvae were able to cover their maintenance costs, but not to attain maximum growth rates. Between April and September, the potential assimilation rate averaged 7-26% of the maximum assimilation rate. Under the assumptions made for the present study, it is suggested that growth of larvae in north-west European waters is often food-limited.

  10. Bivalve and barnacle larvae distribution driven by water temperature in a Mediterranean lagoon.

    PubMed

    Ziadi, Boutheina; Dhib, Amel; Turki, Souad; Aleya, Lotfi

    2015-05-01

    The objective of this study was to explore the relationships between the distribution of some meroplanktonic species and water temperature. Meroplankton larvae abundance of bivalves, and barnacles and water temperature fluctuations were studied from February 2011 to January 2012 at five stations in Ghar El Melh lagoon (GML) Mediterranean Sea, northern Tunisia). According to redundancy analysis (RDA), a significant difference was found in the distribution of larvae among the seasons (F = 10.28, p < 0.001); summer and autumn appear to be the period of bivalve larvae development, whereas the arrival of barnacle larvae coincided with winter and spring. The generalized additive models (GAMs) show strong correlation of bivalve larvae with high temperature (F = 23.2; p < 0.001) and the affinity of barnacle larvae to low temperature values (F = 8.41; p = 0.004). This environmental parameter accounted for 26 % of the deviance in variability in larvae abundance. The development process of many generations of larvae may therefore have been predetermined by temperature. PMID:25483975

  11. Pathogenic marine microbes influence the effects of climate change on a commercially important tropical bivalve

    PubMed Central

    Turner, Lucy M.; Alsterberg, Christian; Turner, Andrew D.; Girisha, S. K.; Rai, Ashwin; Havenhand, Jonathan N.; Venugopal, M. N.; Karunasagar, Indrani; Godhe, Anna

    2016-01-01

    There is growing evidence that climate change will increase the prevalence of toxic algae and harmful bacteria, which can accumulate in marine bivalves. However, we know little about any possible interactions between exposure to these microorganisms and the effects of climate change on bivalve health, or about how this may affect the bivalve toxin-pathogen load. In mesocosm experiments, mussels, Perna viridis, were subjected to simulated climate change (warming and/or hyposalinity) and exposed to harmful bacteria and/or toxin-producing dinoflagellates. We found significant interactions between climate change and these microbes on metabolic and/or immunobiological function and toxin-pathogen load in mussels. Surprisingly, however, these effects were virtually eliminated when mussels were exposed to both harmful microorganisms simultaneously. This study is the first to examine the effects of climate change on determining mussel toxin-pathogen load in an ecologically relevant, multi-trophic context. The results may have considerable implications for seafood safety. PMID:27576351

  12. Predicting growth and mortality of bivalve larvae using gene expression and supervised machine learning.

    PubMed

    Bassim, Sleiman; Chapman, Robert W; Tanguy, Arnaud; Moraga, Dario; Tremblay, Rejean

    2015-12-01

    It is commonly known that the nature of the diet has diverse consequences on larval performance and longevity, however it is still unclear which genes have critical impacts on bivalve development and which pathways are of particular importance in their vulnerability or resistance. First we show that a diet deficient in essential fatty acid (EFA) produces higher larval mortality rates, a reduced shell growth, and lower postlarval performance, all of which are positively correlated with a decline in arachidonic and eicosapentaenoic acids levels, two EFAs known as eicosanoid precursors. Eicosanoids affect the cell inflammatory reactions and are synthesized from long-chain EFAs. Second, we show for the first time that a deficiency in eicosanoid precursors is associated with a network of 29 genes. Their differential regulation can lead to slower growth and higher mortality of Mytilus edulis larvae. Some of these genes are specific to bivalves and others are implicated at the same time in lipid metabolism and defense. Several genes are expressed only during pre-metamorphosis where they are essential for muscle or neurone development and biomineralization, but only in stress-induced larvae. Finally, we discuss how our networks of differentially expressed genes might dynamically alter the development of marine bivalves, especially under dietary influence. PMID:26282335

  13. Stress detection in bivalve mollusk using non-invasive bioelectric monitoring of myoneural behavior

    SciTech Connect

    Morgan, E.L.; Hardison, B.S.; Dawson, V.K.; Waller, D.; Waller, W.T.; Dickson, K.L.; Allen, H.J.

    1995-12-31

    Few studies have demonstrated cause-and-effect linkages between extrinsic environmental factors and intrinsic bioelectric action potentials of bivalve mollusk using non-invasive, non-destructive approaches. A non-invasive, external probe configuration and detection system, similar to one used previously with native unionids, was developed for continuously monitoring bioelectric activities of clams and mussels. Using remote probes and differential amplifiers, bioelectric activities were recorded for cardiac, adductor, siphon and foot responses using a computer equipped with integrating software. To test if remote, non-invasive probes would detect similar information to that recorded by invasive needle electrodes, two individuals of zebra mussel (Dreissenia polymorpha), and Asiatic clam (Corbicula fluminea) were each configured with two sets of probes. One set was inserted between the valves and along the inside surface of the shelf; the other set was positioned remotely about the outside margins of the valves. Signal validation was made by simultaneously recording bioelectric responses for the same animal from both sets of probes. In preliminary stress tests monitored bivalves were subjected to changes in temperatures over 2 to 3 hr intervals from ambient to potentially lethal levels (20 to 30 C for zebra, 25 C to 40 C for corbicula). Dramatic increases resulted in both number and amplitude of cardiac events as temperature increased. Planned studies will use this approach to evaluate bivalve myoneural behavior patterns in response to chemical and non-chemical stimuli.

  14. Soft-shell clam, Mya arenaria, a convenient laboratory animal for screening pathogens of bivalve mollusks.

    PubMed

    Tubiash, H S

    1971-09-01

    Attempts to introduce infectious or foreign material into oysters and other bivalve mollusks usually involve force or trauma because of immediate, prolonged adduction of the tightly closing valves. The soft-shell clam, Mya arenaria, is unable to seal its valves completely and relaxes readily, exposing soft tissue and a large siphon. This species is free from fouling organisms and is readily available at all seasons in the New England and mid-Atlantic areas. Suspensions of five strains of Vibrio sp. that cause bacillary necrosis in larval and juvenile bivalve mollusks were injected into the heart, siphon tissue, and the incurrent and excurrent siphon lumina of soft-shell clams. All vibrio strains caused significant mortality, usually within 2 days. Heaviest losses resulted from heart and excurrent siphon injections. No mortality occurred in control clams injected with seawater, broth, Serratia sp., and Escherichia coli. The soft-shell clam appears to be a useful animal for testing the pathogenicity of marine microorganisms for bivalve mollusks. PMID:4940871

  15. Environmental changes and shallow marine fossil bivalve assemblages of the Lower Cretaceous Miyako Group, NE Japan

    NASA Astrophysics Data System (ADS)

    Fujino, Shigehiro; Maeda, Haruyoshi

    2013-03-01

    We reconstructed the environmental changes recorded in the Lower Cretaceous Miyako Group via facies analysis and delineated the relationship between depositional facies and the occurrence of diverse marine invertebrate macrofossils. The Miyako Group consists of deposits from alluvial bay-head delta, bay-head delta front, central bay, and lower shoreface to inner shelf depositional settings. Fossil bivalve assemblages responded to shifts in these sedimentary environments. We defined three fossil bivalve assemblages from the central bay and lower shoreface to inner shelf deposits. The assemblages in the inner shelf and central bay deposits are clearly different, even though they occur within similar depositional facies. This contrast in assemblages results from environmental differences between closed and open settings; this interpretation is supported by the occurrence of stenohaline crinoids. We defined a fourth bivalve assemblage in a tsunami deposit intercalated within the bay-head delta front deposits. It consists of polygenic allochthonous shells, some that were derived from an estuarine environment or the shallow seafloor and others that were torn from small reefs.

  16. Uncharted waters: Bivalves of midway atoll and integrating mathematics into biology education

    NASA Astrophysics Data System (ADS)

    McCully, Kristin M.

    To protect and conserve the Earth's biodiversity and ecosystem services, it is important not only to understand and conserve species and ecosystems, but also to instill an understanding and appreciation for biodiversity and ecosystem services in the next generations of both scientists and citizens. Thus, this dissertation combines research into the ecology and identity of large bivalves at Midway Atoll in the Northwestern Hawaiian Islands (NWHI) with research on pedagogical strategies for integrating mathematics into undergraduate biology education. The NWHI is one of the few remaining large, mainly intact, predator-dominated coral reef ecosystems and one of the world's largest marine protected areas. Previous bivalve studies focused on the black-lipped pearl oyster, Pinctada margaritifera, which was heavily harvested in the late 1920s, has not recovered, and is now a candidate species for restoration. First, I combined remote sensing, geographic information systems, SCUBA, and mathematical modeling to quantify the abundance, spatial distributions, and filtration capacity of large epifaunal bivalves at Midway Atoll. These bivalves are most abundant on the forereef outside the atoll, but densities are much lower than reported on other reefs, and Midway's bivalves are unlikely to affect plankton abundance and productivity inside the lagoon. Second, I used molecular techniques and phylogenetic reconstructions to identify pearl oysters (Pinctada) from Midway Atoll as P. maculata , a species not previously reported in Hawaii. As a small morphologically cryptic species, P. maculata may be a native species that has not been collected previously, a native species that has been identified incorrectly as the morphologically similar P. radiata, or it may be a recent introduction or natural range extension from the western Pacific. Finally, I review science education literature integrating mathematics into undergraduate biology curricula, and then present and evaluate a

  17. Size, distribution and sediment biodeposition of prolific bivalves in small estuaries

    NASA Astrophysics Data System (ADS)

    Callaway, Ruth; Grenfell, Suzanne; Bertelli, Chiara; Mendzil, Anouska; Moore, Jon

    2014-10-01

    The growth and distribution of bivalves in estuaries is generally driven by access to food, hydrodynamic forces and sedimentary conditions that facilitate recruitment and allow persistent settlement. Factors such as site elevation or sediment properties have a significant impact, but there are few studies quantifying the relative importance of different factors in an entire estuary. We carried out an estuary-wide survey of the cockle Cerastoderma edule L. by sampling 343 sites in a small estuary, the Burry Inlet in South Wales, UK. We determined the extent to which site elevation, as an indicator for the duration of feeding, sediment properties and position inside the estuary, explained variation in the size and density of the bivalve. We also analysed the production of faeces and pseudo-faeces per cockle. The population consisted almost entirely of 1-year old cockles, the average size was 14.7 ± 2.7 mm and the average density was 56 ± 189 cockles 0.1 m-2 (mean ± SD). Altogether 37% of the variation in size was explained by two factors: elevation of site (15%) and amount of clay & silt in sediments (22%). Variation in density appeared to play no significant role in determining size. Density was significantly linked to sediment properties (32%) and position inside the estuary (4%). Sediment biodeposition, the amount of material discharged per cockle, was 0.032 ± 0.017 g dry weight, the whole population thereby producing an estimated 387 tonnes of faeces and pseudo-faeces in the entire estuary per day. The study confirmed that access to food is a principal driver of growth, but the relatively small proportion of the variation in size explained by site elevation highlights that other factors play an important role. Sediment characteristics in particular were of importance to variation in size as well as density. It seems plausible that sediment properties were a proxy for factors such as bedload movement and exposure, which are more likely causal factors for

  18. Museum Preserved Bivalves as Indicators of Long-term Trends in Methylmercury Concentrations

    NASA Astrophysics Data System (ADS)

    Luengen, A. C.; Foslund, H. M.; Greenfield, B. K.

    2015-12-01

    Despite the many efforts to reduce mercury concentrations in the environment, there are relatively few datasets on long-term trends in mercury in biota, especially for the bioavailable form, methylmercury (MeHg). This study used museum preserved bivalves (stored in ethanol) to look at MeHg trends in the Asian date mussel Musculista senhousia and the Asian clam Potamocorbula amurensis, collected from San Francisco Bay, California between 1975 and 2012. For each sampling date, 4 to 15 individuals were obtained from museum collections (N = 156 total specimens), freeze-dried, weighed, homogenized, digested, and individually analyzed for MeHg using trace metal clean techniques. The bivalves were also analyzed for δ13C and δ15N to look for changes in food web structure. P. amurensis specimens were only available from 1988 to 2012, and an increase in MeHg was observed during that time. In contrast, M. senhousia specimens were available for the entire 37 year period and exhibited a significant decline in MeHg in the southern reach of the estuary (South Bay). The median MeHg concentration in M. senhousia was highest at 239 ng/g dw in October 1975. That year was the last year of operations for the New Almaden Mercury Mining District, which drained into South Bay. By the 1990s, MeHg concentrations in M. senhousia dropped significantly to a median of 37 ng/g dw. Isotopic δ15N values did not support a hypothesis of reduced trophic position causing the MeHg decline. Over the study duration, δ15N increased in M. senhousia, which we attributed to a baseline shift. We also observed a decline in δ13C since 2000, which may represent a shift in bivalve carbon towards greater utilization of planktonic sources. To validate the use of museum specimens, we ran a preservation study, where we collected fresh bivalves, fixed them in ethanol or formalin, and then transferred them to ethanol for long-term storage. Although MeHg concentrations increased after 1 week, they stabilized over

  19. Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda

    PubMed Central

    Olson, Storrs L.; Hearty, Paul J.

    2010-01-01

    During the last half million years, pulses of gigantism in the anagenetic lineage of land snails of the subgenus Poecilozonites on Bermuda were correlated with glacial periods when lower sea level resulted in an island nearly an order of magnitude larger than at present. During those periods, the island was colonized by large vertebrate predators that created selection pressure for large size and rapid growth in the snails. Extreme reduction in land area from rising seas, along with changes in ecological conditions at the onset of interglacial episodes, marked extinction events for large predators, after which snails reverted to much smaller size. The giant snails were identical in morphology during the last two glacials when the predators included a large flightless rail Rallus recessus (marine isotope stages (MIS) 4-2) and a crane Grus latipes and a duck Anas pachysceles (MIS 6). In a preceding glacial period (MIS 10), when the fauna also included the tortoise Hesperotestudo bermudae, the snails were not only large, but the shells were much thicker, presumably to prevent crushing by tortoises. Evolution of Poecilozonites provides an outstanding example of dramatic morphological change in response to environmental pressures in the absence of cladogenesis. PMID:20554560

  20. Herbivory and body size: allometries of diet quality and gastrointestinal physiology, and implications for herbivore ecology and dinosaur gigantism.

    PubMed

    Clauss, Marcus; Steuer, Patrick; Müller, Dennis W H; Codron, Daryl; Hummel, Jürgen

    2013-01-01

    Digestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differentiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM. PMID:24204552

  1. Herbivory and Body Size: Allometries of Diet Quality and Gastrointestinal Physiology, and Implications for Herbivore Ecology and Dinosaur Gigantism

    PubMed Central

    Clauss, Marcus; Steuer, Patrick; Müller, Dennis W. H.; Codron, Daryl; Hummel, Jürgen

    2013-01-01

    Digestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differentiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM. PMID:24204552

  2. Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda.

    PubMed

    Olson, Storrs L; Hearty, Paul J

    2010-12-23

    During the last half million years, pulses of gigantism in the anagenetic lineage of land snails of the subgenus Poecilozonites on Bermuda were correlated with glacial periods when lower sea level resulted in an island nearly an order of magnitude larger than at present. During those periods, the island was colonized by large vertebrate predators that created selection pressure for large size and rapid growth in the snails. Extreme reduction in land area from rising seas, along with changes in ecological conditions at the onset of interglacial episodes, marked extinction events for large predators, after which snails reverted to much smaller size. The giant snails were identical in morphology during the last two glacials when the predators included a large flightless rail Rallus recessus (marine isotope stages (MIS) 4-2) and a crane Grus latipes and a duck Anas pachysceles (MIS 6). In a preceding glacial period (MIS 10), when the fauna also included the tortoise Hesperotestudo bermudae, the snails were not only large, but the shells were much thicker, presumably to prevent crushing by tortoises. Evolution of Poecilozonites provides an outstanding example of dramatic morphological change in response to environmental pressures in the absence of cladogenesis. PMID:20554560

  3. Assessment of ametryn contamination in river water, river sediment, and mollusk bivalves in São Paulo state, Brazil.

    PubMed

    Jacomini, Analu Egydio; de Camargo, Plínio Barbosa; Avelar, Wagner Eustáquio Paiva; Bonato, Pierina Sueli

    2011-04-01

    São Paulo state, Brazil, is one of the main areas of sugar cane agriculture in the world. Herbicides, in particular, ametryn, are extensively used in this extensive area, which implies that this herbicide is present in the environment and can contaminate the surface water by running off. Thereby, residues of ametryn were analyzed in samples of river water an river sediment and in freshwater bivalves obtained from the rivers Sapucaí, Pardo and Mogi-Guaçu in São Paulo State, Brazil. Samples were taken in the winter of 2003 and 2004 in two locations in each river. The specimens of freshwater bivalves collected and analyzed were Corbicula fluminea, an exotic species, and Diplodon fontaineanus, a native species. Additionally, the evaluation of the ability of bioconcentration and depuration of ametryn by the freshwater bivalve Corbicula fluminea was also performed. Ametryn concentrations in the samples were measured by liquid chromatography coupled to mass spectrometry. Residues of ametryn in water (50 ng/L) and in freshwater bivalves (2-7 ng/g) were found in the Mogi-Guaçu River in 2004, and residues in river sediments were found in all rivers in 2003 and 2004 (0.5-2 ng/g). The observation of the aquatic environment through the analysis of these matrixes, water, sediment, and bivalves, revealed the importance of the river sediment in the accumulation of the herbicide ametryn, which can contaminate the biota. PMID:20567812

  4. Validating the Incorporation of 13C and 15N in a Shorebird That Consumes an Isotopically Distinct Chemosymbiotic Bivalve.

    PubMed

    van Gils, Jan A; Ahmedou Salem, Mohamed Vall

    2015-01-01

    The wealth of field studies using stable isotopes to make inferences about animal diets require controlled validation experiments to make proper interpretations. Despite several pleas in the literature for such experiments, validation studies are still lagging behind, notably in consumers dwelling in chemosynthesis-based ecosystems. In this paper we present such a validation experiment for the incorporation of 13C and 15N in the blood plasma of a medium-sized shorebird, the red knot (Calidris canutus canutus), consuming a chemosymbiotic lucinid bivalve (Loripes lucinalis). Because this bivalve forms a symbiosis with chemoautotrophic sulphide-oxidizing bacteria living inside its gill, the bivalve is isotopically distinct from 'normal' bivalves whose food has a photosynthetic basis. Here we experimentally tested the hypothesis that isotope discrimination and incorporation dynamics are different when consuming such chemosynthesis-based prey. The experiment showed that neither the isotopic discrimination factor, nor isotopic turnover time, differed between birds consuming the chemosymbiotic lucinid and a control group consuming a photosynthesis-based bivalve. This was true for 13C as well as for 15N. However, in both groups the 15N discrimination factor was much higher than expected, which probably had to do with the birds losing body mass over the course of the experiment. PMID:26458005

  5. Validating the Incorporation of 13C and 15N in a Shorebird That Consumes an Isotopically Distinct Chemosymbiotic Bivalve

    PubMed Central

    van Gils, Jan A.; Ahmedou Salem, Mohamed Vall

    2015-01-01

    The wealth of field studies using stable isotopes to make inferences about animal diets require controlled validation experiments to make proper interpretations. Despite several pleas in the literature for such experiments, validation studies are still lagging behind, notably in consumers dwelling in chemosynthesis-based ecosystems. In this paper we present such a validation experiment for the incorporation of 13C and 15N in the blood plasma of a medium-sized shorebird, the red knot (Calidris canutus canutus), consuming a chemosymbiotic lucinid bivalve (Loripes lucinalis). Because this bivalve forms a symbiosis with chemoautotrophic sulphide-oxidizing bacteria living inside its gill, the bivalve is isotopically distinct from ‘normal’ bivalves whose food has a photosynthetic basis. Here we experimentally tested the hypothesis that isotope discrimination and incorporation dynamics are different when consuming such chemosynthesis-based prey. The experiment showed that neither the isotopic discrimination factor, nor isotopic turnover time, differed between birds consuming the chemosymbiotic lucinid and a control group consuming a photosynthesis-based bivalve. This was true for 13C as well as for 15N. However, in both groups the 15N discrimination factor was much higher than expected, which probably had to do with the birds losing body mass over the course of the experiment. PMID:26458005

  6. Differential reproductive strategies of two bivalves in the Dutch Wadden Sea

    NASA Astrophysics Data System (ADS)

    Cardoso, Joana F. M. F.; Witte, Johannes IJ.; van der Veer, Henk W.

    2009-08-01

    Cerastoderma edule and Mya arenaria are two common bivalve species in European waters. Longevity and maximum size are much greater in the latter species. Because comparison of species life-history strategies states that a long life span (i.e. high annual survival) generally goes with lower fecundity, we hypothesise that reproductive output would be lower in M. arenaria than in C. edule. In the present paper, we studied the reproductive strategies of these two species in an intertidal and a subtidal area of the western Dutch Wadden Sea, by following seasonal changes in absolute and relative weights of somatic and gonadal tissues in these bivalves. Starting of spawning was similar in the two species, around May, except for intertidal M. arenaria, which initiated spawning in August. Individual energy investment in reproduction was similar for the two species but, unlike M. arenaria, C. edule spawned completely, releasing all energy of gonadal mass in the form of gametes. Mya arenaria used the gonad not only for reproduction but also for storage. In the intertidal area, we found a trade-off between longevity and reproduction, i.e. maximum reproductive output (expressed as a proportion of body mass) was higher in C. edule than in M. arenaria. However, since body size is larger and life span longer in M. arenaria than in C. edule, mean lifetime reproductive output per individual must be higher in the first than in the latter. Based on the differences in reproductive strategies of these two species, we hypothesise that the negative effects of warming climate on bivalve population dynamics in the Wadden Sea will be stronger in C. edule than in M. arenaria.

  7. How does the metallothionein induction in bivalves meet the criteria for biomarkers of metal exposure?

    PubMed

    Le, T T Yen; Zimmermann, Sonja; Sures, Bernd

    2016-05-01

    Metallothionein (MT) concentrations in the whole soft tissue or in a particular tissue of bivalves have widely been used in ecotoxicological studies and biomonitoring programmes. This approach is based on the reported results on the enhancement of MT induction in bivalves in response to metal exposure. The validity of using MT induction as a biomarker is briefly assessed in the present study. The sensitivity of MT induction in these organisms is questionable due to the high basal MT level as well as the high natural variability related to the effects of a number of biotic and abiotic factors, which are not well described yet. Moreover, the relationship between exposure to metals, the toxic effects of that exposure, and the appearance of MT in soft tissue, is not well characterized. A variety of factors may influence the appearance and distribution of MT: 1) the uneven distribution of metals in particular portions of the soft tissue and in particular subcellular compartments; 2) pre-exposure to metals, perhaps at non-toxic levels; 3) metal-metal competition and metal-protein interactions; and 4) tissue-specific induction, functions, and isoforms of MT. Therefore, attention is required when using MT induction in bivalves for assessment of metal exposure or consequent toxic effects. The MT concentration can be a reliable indicator only when it is considered in relation with metal uptake kinetics and subcellular partitioning while specifying the isoform of MT synthesised and considering various confounding factors. The kinetic turnover of MT may provide useful information on metal exposure and biological effects since it covers both the synthesis and breakdown of MT as well as the chemical species of metals accumulated and MT. PMID:26854695

  8. Effects of toxic dinoflagellate Alexandrium tamarense on the energy budgets and growth of two marine bivalves.

    PubMed

    Li, Siu-Chung; Wang, Wen-Xiong; Hsieh, Dennis P H

    2002-03-01

    Harmful algal blooms (HAB) may impose a serious threat to aquatic lives and human health. We determined the effects of a toxic dinoflagellate Alexandrium tamarense (clone ATCIO1, isolated from Hong Kong coastal waters) on the energy budget, quantified as scope for growth (SFG), and the growth rate of the manila clam Ruditapes philippinarum and the green-lipped mussel Perna viridis. To quantify the SFG, clams and mussels were dosed with different amounts of toxic A. tamarense for 6 days, resulting in different toxin burdens in the tissues. Clearance rate, absorption efficiency, and respiration rate were subsequently measured in these toxin containing bivalves. Clearance rate significantly declined at the highest toxin burden in the clams only, while there was no significant difference in the clearance rate among different treatments for the mussels. The respiration rate of either bivalve was not significantly affected by toxin accumulation in the tissues. In contrast, the absorption efficiency of both clams and mussels decreased, in a concentration-dependent manner for mussels but not for clams, when the tissue accumulated the toxins. With an increase in paralytic shellfish poisoning (PSP) toxin burden, SFG in both clams and mussels was significantly reduced, primarily because of the decrease of absorption efficiency. The growth rate of juvenile clam R. philippinarum, measured as an increment in tissue dry weight over a 15 d exposure period, was significantly lower during their feeding on toxic dinoflagellate than the growth rate of clams feeding on the diatom Thalassiosira pseudonana. The juvenile mussel P. viridis, however, exhibited similar growth rates after feeding on the toxic dinoflagellates and the nontoxic diatom. This study showed that SFG can provide a sensitive and integrated measure of the effect of HAB on the physiology of bivalves. Clam R. philippinarum may be more sensitive, in terms of their energy budget, to PSP toxin accumulation than the mussel P

  9. P-glycoprotein and its inducible expression in three bivalve species after exposure to Prorocentrum lima.

    PubMed

    Huang, Lu; Liu, Su-Li; Zheng, Jian-Wei; Li, Hong-Ye; Liu, Jie-Sheng; Yang, Wei-Dong

    2015-12-01

    P-glycoprotein (P-gp or ABCB1) belongs to the family of ATP-binding cassette (ABC) transporters responsible for multixenobiotic resistance (MXR) in aquatic organisms. To provide more information of P-gp in shellfish, in this study, complete cDNA of P-gp in three bivalve species including Ruditapes philippinarum, Scapharca subcrenata and Tegillarca granosa were cloned and its expressions in gill, digestive gland, adductor muscle and mantle of the three bivalves were detected after exposure to Prorocentrum lima, a toxogenic dinoflagellate. The complete sequences of R. philippinarum, S. subcrenata and T. granosa P-gp showed high homology with MDR/P-gp/ABCB proteins from other species, having a typical sequence organization as full transporters from the ABCB family. Phylogenetic analyses revealed that the amino acid sequences of P-gp from S. subcrenata and T. granosa had a closest relationship, forming an independent branch, then grouping into the other branch with Mytilus californianus, Mytilus galloprovincialis and Crassostrea gigas. However, P-gp sequences from R. philippinarum were more similar to the homologs from the more distantly related Aplysia californica than to homologs from S. subcrenata and T. granosa, suggesting that bivalves P-gp might have different paralogs. P-glycoprotein expressed in all detected tissues but there were large differences between them. After exposure to P. lima, the expression of P-gp changed in the four tissues in varying degrees within the same species and between different species, but the changes in mRNA and protein level were not always synchronous. PMID:26539802

  10. PBDEs, hydroxylated PBDEs and methoxylated PBDEs in bivalves from Beijing markets.

    PubMed

    Liu, Xitao; Jiao, Ying; Lin, Chunye; Sun, Ke; Zhao, Ye

    2014-09-01

    The structural analogues of polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) have been attracting increasing concern in recent years. Five bivalve species (blue mussel, short-necked clam, surf clam, ark shell and razor clam) were collected from Beijing markets, and the concentrations of seven PBDEs, four OH-PBDEs and fourteen MeO-PBDEs in the bivalves were measured. The seasonal variations of these three types of polybrominated compound in blue mussels were also monitored. The results indicate that the levels of ΣPBDEs in this study were comparable to those in short-necked clams from Liaodong Bay, China, with BDE47 as the dominant congener. For the ortho-MeO-PBDEs, 6-MeO-BDE47 was found at higher concentrations than the others, while for the meta- and para-MeO-PBDEs, 4'-MeO-BDE17 was found at higher concentrations. 6-OH-BDE-47 was the most abundant congener among the 4 measured OH-PBDEs, followed by 6-OH-BDE-137 and 6-OH-BDE-85. The levels of OH-PBDEs and MeO-PBDEs in bivalves from Beijing markets were much lower than the corresponding compounds in blue mussels from the Baltic Sea. In the blue mussels collected in April, June and September of 2012, apparent seasonal variations were observed for these three types of polybrominated compounds, but the acidic components displayed different trends from the neutral components, with PBDEs and MeO-PBDEs showing the highest concentrations in June, while OH-PBDEs had the lowest concentrations in June. This difference in seasonal variations between the neutral components and the acidic components may be explained by their different sources and transformation/elimination mechanisms. PMID:24636323