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Mesodermal Gene Expression in the Acoel Isodiametra pulchra Indicates a Low Number of Mesodermal Cell Types and the Endomesodermal Origin of the Gonads  

PubMed Central

Acoelomorphs are bilaterally symmetric small marine worms that lack a coelom and possess a digestive system with a single opening. Two alternative phylogenetic positions of this group within the animal tree are currently debated. In one view, Acoelomorpha is the sister group to all remaining Bilateria and as such, is a morphologically simple stepping stone in bilaterian evolution. In the other, the group is a lineage within the Deuterostomia, and therefore, has derived a simple morphology from a more complex ancestor. Acoels and the closely related Nemertodermatida and Xenoturbellida, which together form the Acoelomorpha, possess a very limited number of cell types. To further investigate the diversity and origin of mesodermal cell types we describe the expression pattern of 12 orthologs of bilaterian mesodermal markers including Six1/2, Twist, FoxC, GATA4/5/6, in the acoel Isodiametra pulchra. All the genes are expressed in stem cells (neoblasts), gonads, and at least subsets of the acoel musculature. Most are expressed in endomesodermal compartments of I. pulchra developing embryos similar to what has been described in cnidarians. Our molecular evidence indicates a very limited number of mesodermal cell types and suggests an endomesodermal origin of the gonads and the stem cell system. We discuss our results in light of the two prevailing phylogenetic positions of Acoelomorpha. PMID:23405161

Chiodin, Marta; Børve, Aina; Berezikov, Eugene; Ladurner, Peter; Martinez, Pedro; Hejnol, Andreas



Posterior regeneration in Isodiametra pulchra (Acoela, Acoelomorpha)  

PubMed Central

Introduction Regeneration is a widespread phenomenon in the animal kingdom, but the capacity to restore damaged or missing tissue varies greatly between different phyla and even within the same phylum. However, the distantly related Acoelomorpha and Platyhelminthes share a strikingly similar stem-cell system and regenerative capacity. Therefore, comparing the underlying mechanisms in these two phyla paves the way for an increased understanding of the evolution of this developmental process. To date, Isodiametra pulchra is the most promising candidate as a model for the Acoelomorpha, as it reproduces steadily under laboratory conditions and is amenable to various techniques, including the silencing of gene expression by RNAi. In order to provide an essential framework for future studies, we report the succession of regeneration events via the use of cytochemical, histological and microscopy techniques, and specify the total number of cells in adult individuals. Results Isodiametra pulchra is not capable of regenerating a new head, but completely restores all posterior structures within 10 days. Following amputation, the wound closes via the contraction of local muscle fibres and an extension of the dorsal epidermis. Subsequently, stem cells and differentiating cells invade the wound area and form a loosely delimited blastema. After two days, the posterior end is re-patterned with the male (and occasionally the female) genital primordium being apparent. Successively, these primordia differentiate into complete copulatory organs. The size of the body and also of the male and female copulatory organs, as well as the distance between the copulatory organs, progressively increase and by nine days copulation is possible. Adult individuals with an average length of 670 ?m consist of approximately 8100 cells. Conclusion Isodiametra pulchra regenerates through a combination of morphallactic and epimorphic processes. Existing structures are “re-modelled” and provide a framework onto which newly differentiating cells are added. Growth proceeds through the intercalary addition of structures, mirroring the embryonic and post-embryonic development of various organ systems. The suitability of Isodiametra pulchra for laboratory techniques, the fact that its transcriptome and genome data will soon be available, as well as its small size and low number of cells, make it a prime candidate subject for research into the cellular mechanisms that underlie regeneration in acoelomorphs. PMID:24160844



The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications  

PubMed Central

Introduction Acoels are microscopic marine worms that have become the focus of renewed debate and research due to their placement at the base of the Bilateria by molecular phylogenies. To date, Isodiametra pulchra is the most promising “model acoel” as it can be cultured and gene knockdown can be performed with double-stranded RNA. Despite its well-known morphology data on the nervous system are scarce. Therefore we examined this organ using various microscopic techniques, including histology, conventional histochemistry, electron microscopy, and immunocytochemistry in combination with CLSM and discuss our results in light of recently established phylogenies. Results The nervous system of Isodiametra pulchra consists of a bilobed brain with a dorsal posterior commissure, a frontal ring and tracts, four pairs of longitudinal neurite bundles, as well as a supramuscular and submuscular plexus. Serotonin-like immunoreactivity (SLI) is displayed in parts of the brain, the longitudinal neurite bundles and a large part of the supramuscular plexus, while FMRFamide-like immunoreactivity (RFLI) is displayed in parts of the brain and a distinct set of neurons, the longitudinal neurite bundles and the submuscular plexus. Despite this overlap SLI and RFLI are never colocalized. Most remarkable though is the presence of a distinct functional neuro-muscular system consisting of the statocyst, tracts, motor neurons and inner muscles, as well as the presence of various muscles that differ with regard to their ultrastructure and innervation. Conclusions The nervous system of Isodiametra pulchra consists of an insunk, bilobed brain, a peripheral part for perception and innervation of the smooth body-wall musculature as well as tracts and motor neurons that together with pseudostriated inner muscles are responsible for steering and quick movements. The insunk, bilobed brains with two to three commissures found in numerous acoels are homologous and evolved from a ring-commissural brain that was present in the stem species of acoelomorphs. The acoelomorph brain is bipartite, consisting of a Six3/6-dependend animal pole nervous system that persists throughout adulthood and an axial nervous system that does not develop by exhibiting a staggered pattern of conserved regulatory genes as in other bilaterians but by a nested pattern of these genes. This indicates that acoelomorphs stem from an ancestor with a simple brain or with a biphasic life cycle. PMID:23072457



Embryonic Muscle Development of Convoluta pulchra (Turbellaria–Acoelomorpha, Platyhelminthes)  

Microsoft Academic Search

We studied the embryonic development of body-wall musculature in the acoel turbellarian Convoluta pulchra by fluorescence microscopy using phalloidin-bound stains for F-actin. During stage 1, which we define as development prior to 50% of the time between egg-laying and hatching, actin was visible only in zonulae adhaerentes of epidermal cells. Subsequent development of muscle occurred in two distinct phases: first,

Peter Ladurner; Reinhard Rieger



The Effect of Light on Rates of Cloning of the Symbiont-Bearing Acoel Convolutriloba longifissura  

Microsoft Academic Search

The acoel turbellarian Convolutriloba longifissura reproduces primarily by asexual fission and engages in an obligate symbiotic relationship with unicellular algae belonging to the genus Tetraselrnis. The obligate nature of the symbiosis between these species suggests that algal photosynthesis may influence rates of flatworm asexual reproduction. To test this hypothesis we explored the effect of light on C. longifissura 's ability

Rahim Sara



Graptemys pulchra Baur 1893: Alabama Map Turtle  

USGS Publications Warehouse

The Alabama Map Turtle, Graptemys pulchra (Family Emydidae), is a moderately large riverine species endemic to the Mobile Bay drainage system of Alabama, Georgia, and Mississippi. Sexual size dimorphism is pronounced, with adult females (carapace length [CL] to 273 mm) attaining more than twice the size of adult males (CL to 117 mm). The species is an inhabitant of relatively large, swift creeks and rivers, often with wide sandbars. Stream sections open to the sun and with abundant basking sites in the form of logs and brush are preferred. Six to seven clutches of 4–7 eggs are laid each year on river sandbars. Although the species is locally abundant, populations are threatened by habitat destruction, declines in their prey base, commercial collection, and vandalism. It is listed as a Species of Special Concern in Alabama.

Lovich, Jeffrey E.; Godwin, James C.; McCoy, C.J.



Whole-body acoel regeneration is controlled by Wnt and Bmp-Admp signaling.  


Whole-body regeneration is widespread in the Metazoa, yet little is known about how underlying molecular mechanisms compare across phyla. Acoels are an enigmatic phylum of invertebrate worms that can be highly informative about many questions in bilaterian evolution, including regeneration. We developed the three-banded panther worm, Hofstenia miamia, as a new acoelomorph model system for molecular studies of regeneration. Hofstenia were readily cultured, with accessible embryos, juveniles, and adults for experimentation. We developed molecular resources and tools for Hofstenia, including a transcriptome and robust systemic RNAi. We report the identification of molecular mechanisms that promote whole-body regeneration in Hofstenia. Wnt signaling controls regeneration of the anterior-posterior axis, and Bmp-Admp signaling controls regeneration of the dorsal-ventral axis. Perturbation of these pathways resulted in regeneration-abnormal phenotypes involving axial feature duplication, such as the regeneration of two heads following Wnt perturbation or the regeneration of ventral cells in place of dorsal ones following bmp or admp RNAi. Hofstenia regenerative mechanisms are strikingly similar to those guiding regeneration in planarians. However, phylogenetic analyses using the Hofstenia transcriptome support an early branching position for acoels among bilaterians, with the last common ancestor of acoels and planarians being the ancestor of the Bilateria. Therefore, these findings identify similar whole-body regeneration mechanisms in animals separated by more than 550 million years of evolution. PMID:24768051

Srivastava, Mansi; Mazza-Curll, Kathleen L; van Wolfswinkel, Josien C; Reddien, Peter W



Coordinated spatial and temporal expression of Hox genes during embryogenesis in the acoel Convolutriloba longifissura  

PubMed Central

Background Hox genes are critical for patterning the bilaterian anterior-posterior axis. The evolution of their clustered genomic arrangement and ancestral function has been debated since their discovery. As acoels appear to represent the sister group to the remaining Bilateria (Nephrozoa), investigating Hox gene expression will provide an insight into the ancestral features of the Hox genes in metazoan evolution. Results We describe the expression of anterior, central and posterior class Hox genes and the ParaHox ortholog Cdx in the acoel Convolutriloba longifissura. Expression of all three Hox genes begins contemporaneously after gastrulation and then resolves into staggered domains along the anterior-posterior axis, suggesting that the spatial coordination of Hox gene expression was present in the bilaterian ancestor. After early surface ectodermal expression, the anterior and central class genes are expressed in small domains of putative neural precursor cells co-expressing ClSoxB1, suggesting an evolutionary early function of Hox genes in patterning parts of the nervous system. In contrast, the expression of the posterior Hox gene is found in all three germ layers in a much broader posterior region of the embryo. Conclusion Our results suggest that the ancestral set of Hox genes was involved in the anterior-posterior patterning of the nervous system of the last common bilaterian ancestor and were later co-opted for patterning in diverse tissues in the bilaterian radiation. The lack of temporal colinearity of Hox expression in acoels may be due to a loss of genomic clustering in this clade or, alternatively, temporal colinearity may have arisen in conjunction with the expansion of the Hox cluster in the Nephrozoa. PMID:19796382

Hejnol, Andreas; Martindale, Mark Q



Coordinated spatial and temporal expression of Hox genes during embryogenesis in the acoel Convolutriloba longifissura  

Microsoft Academic Search

Background  \\u000a Hox genes are critical for patterning the bilaterian anterior-posterior axis. The evolution of their clustered genomic arrangement\\u000a and ancestral function has been debated since their discovery. As acoels appear to represent the sister group to the remaining\\u000a Bilateria (Nephrozoa), investigatingHox gene expression will provide an insight into the ancestral features of theHox genes in metazoan evolution.\\u000a \\u000a \\u000a \\u000a \\u000a Results  We describe the

Andreas Hejnol; Mark Q Martindale



Stable Photosymbiotic Relationship under CO2-Induced Acidification in the Acoel Worm Symsagittifera Roscoffensis  

PubMed Central

As a consequence of anthropogenic CO2 emissions, oceans are becoming more acidic, a phenomenon known as ocean acidification. Many marine species predicted to be sensitive to this stressor are photosymbiotic, including corals and foraminifera. However, the direct impact of ocean acidification on the relationship between the photosynthetic and nonphotosynthetic organism remains unclear and is complicated by other physiological processes known to be sensitive to ocean acidification (e.g. calcification and feeding). We have studied the impact of extreme pH decrease/pCO2 increase on the complete life cycle of the photosymbiotic, non-calcifying and pure autotrophic acoel worm, Symsagittifera roscoffensis. Our results show that this species is resistant to high pCO2 with no negative or even positive effects on fitness (survival, growth, fertility) and/or photosymbiotic relationship till pCO2 up to 54 K µatm. Some sub-lethal bleaching is only observed at pCO2 up to 270 K µatm when seawater is saturated by CO2. This indicates that photosymbiosis can be resistant to high pCO2. If such a finding would be confirmed in other photosymbiotic species, we could then hypothesize that negative impact of high pCO2 observed on other photosymbiotic species such as corals and foraminifera could occur through indirect impacts at other levels (calcification, feeding). PMID:22253736

Dupont, Sam; Moya, Aurélie; Bailly, Xavier



Structure of the central nervous system of a juvenile acoel, Symsagittifera roscoffensis  

PubMed Central

The neuroarchitecture of Acoela has been at the center of morphological debates. Some authors, using immunochemical tools, suggest that the nervous system in Acoela is organized as a commissural brain that bears little resemblance to the central, ganglionic type brain of other flatworms, and bilaterians in general. Others, who used histological staining on paraffin sections, conclude that it is a compact structure (an endonal brain; e.g., Raikova 2004; von Graff 1891; Delage Arch Zool Exp Gén 4:109-144, 1886). To address this question with modern tools, we have obtained images from serial transmission electron microscopic sections of the entire hatchling of Symsagittifera roscoffensis. In addition, we obtained data from wholemounts of hatchlings labeled with markers for serotonin and tyrosinated tubulin. Our data show that the central nervous system of a juvenile S. roscoffensis consists of an anterior compact brain, formed by a dense, bilobed mass of neuronal cell bodies surrounding a central neuropile. The neuropile flanks the median statocyst and contains several types of neurites, classified according to their types of synaptic vesicles. The neuropile issues three pairs of nerve cords that run at different dorso-ventral positions along the whole length of the body. Neuronal cell bodies flank the cords, and neuromuscular synapses are abundant. The TEM analysis also reveals different classes of peripheral sensory neurons and provides valuable information about the spatial relationships between neurites and other cell types within the brain and nerve cords. We conclude that the acoel S. roscoffensis has a central brain that is comparable in size and architecture to the brain of other (rhabditophoran) flatworms. PMID:20549514

Cardona, Albert; Martinez, Pedro



Development and metamorphosis of the planktotrophic larvae of Rostanga pulchra (Mollusca: Nudibranchia)  

Microsoft Academic Search

Rostanga pulchra MacFarland, a small (1 to 2 cm) dorid nudibranch, lays an average of 7000 eggs in the laboratory during a period of 30 days in the summer. The veligers hatch 15 to 16 days after oviposition and it takes another 35 to 40 days to become competent for metamorphosis at a temperature of 10° to 15°C. Larval cultures

F. S. Chia; R. Koss



Infection Process of Erysiphe Pulchra on Flowering Dogwood Leaves and Glass Slides  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spore germination, infection structure formation, and colony development of Erysiphe pulchra, the causal agent of powdery mildew of dogwood, were examined on glass slides and leaf disks of a susceptible flowering dogwood line using light and scanning electron microscopy. On both glass slides and lea...


A new species of Centris ( Centris) (Fabricius) from northeastern Brazil, with taxonomic notes on C. ( C.) pulchra Moure, Oliveira & Viana (Hymenoptera, Apidae)  

PubMed Central

Abstract We describe a new species of the bee genus Centris, Centris (Centris) byrsonimae Mahlmann & Oliveira sp. n., whose name has appeared as a nomen nudum in the literature since 1985. Further, a new species group of Centris s.str. is proposed, the pulchra group, based on morphological characters, which comprises the species Centris pulchra Moure, Oliveira & Viana, 2003 and Centris byrsonimae sp. n..Based on information from specimen labels studied and data from the literature, a list of plant species visited by the pulchra group is presented. The male genitalia and hidden metasomal sterna 7 and 8 of Centris pulchra are described for the first time. Typographic errors pertaining to the paratype labels reported in the original description of Centris pulchra are corrected. One female paratype of Centris pulchra is designated herein as a paratype of Centris byrsonimae sp. n. An updated list of species of Centris s.str. from northeastern Brazil is provided including references about geographic distributions as well as an identification key to the pulchra species group. PMID:23459508

Mahlmann, Thiago; de Oliveira, Favízia Freitas





In this study, the effect of the methanol extract of Indigofera pulchra Willd. (Papillionaceae) was investigated against castor oil induced diarrheoa. Its effects on perfused isolated rabbit jejunum and guinea pig ileum were also evaluated. The extract produced a dose-dependent protection against the castor oil-induced diarrheoa in mice with the highest protection (100%), obtained at 200 mgkg-1 comparable to that of loperamide (5 mgkg-1), a standard antidiarrhoeal drug. The extract (0.4 - 6.4 mgml-1) produced a concentration relaxation of the rabbit jejunum. However, no observable effect was noticed when the guinea pig ileum was treated. The extract blocked the contractile effect of acetylcholine (2 × 10-8 gml-1) and histamine (4 × 10-7 gml-1) on both rabbit jejunum and guinea pig ileum. Phytochemical screening revealed the presence of flavonoids, tannins, saponins and steroids. The intraperitoneal median lethal dose (LD50) value for the extract was found to be 2154.0 mgkg-1. The results obtained revealed that the extract possesses pharmacologically active compounds with gastrointestinal relaxant and antidiarrhoeal activities and may possibly explain the use of the plant in traditional medicine for the treatment of gastrointestinal disorder. PMID:21197141

Musa, A M; Sule, M I; Haruna, A K; Ilyas, M; Iliya, I; Yaro, A H; Magaji, M G



Complete mitochondrial genome of the mottled skate: Raja pulchra (Rajiformes, Rajidae).  


Abstract The complete sequence of mitochondrial DNA of a mottled skate, Raja pulchra was sequenced as being circular molecules of 16,907?bp including 2 rRNA, 22 tRNA, 13 protein-coding genes (PCGs), and an AT-rich control region. The organization of the PCGs is the same as those found in other Rajidae species. The nucleotide of L-strand is composed of 29.8% A, 28.0% C, 27.9% T, and 14.3% G with a bias toward A?+?T slightly. Twelve of 13 PCGs are initiated by the ATG codon while COX1 starts with GTG. Only ND4 harbors the incomplete termination codon, TA. All tRNA genes have a typical clover-leaf structure of mitochondrial tRNA with the exception of [Formula: see text] which has a reduced DHU arm. This mitogenome will provide essential information for better phylogenetic resolution and precision of the family Rajidae and the genus Raja as well as for establishment of a fish stock recovery plan of the species. PMID:25317638

Jeong, Dageum; Kim, Sung; Kim, Choong-Gon; Myoung, Jung-Goo; Lee, Youn-Ho



Genomes and Virulence Factors of Novel Bacterial Pathogens Causing Bleaching Disease in the Marine Red Alga Delisea pulchra  

PubMed Central

Nautella sp. R11, a member of the marine Roseobacter clade, causes a bleaching disease in the temperate-marine red macroalga, Delisea pulchra. To begin to elucidate the molecular mechanisms underpinning the ability of Nautella sp. R11 to colonize, invade and induce bleaching of D. pulchra, we sequenced and analyzed its genome. The genome encodes several factors such as adhesion mechanisms, systems for the transport of algal metabolites, enzymes that confer resistance to oxidative stress, cytolysins, and global regulatory mechanisms that may allow for the switch of Nautella sp. R11 to a pathogenic lifestyle. Many virulence effectors common in phytopathogenic bacteria are also found in the R11 genome, such as the plant hormone indole acetic acid, cellulose fibrils, succinoglycan and nodulation protein L. Comparative genomics with non-pathogenic Roseobacter strains and a newly identified pathogen, Phaeobacter sp. LSS9, revealed a patchy distribution of putative virulence factors in all genomes, but also led to the identification of a quorum sensing (QS) dependent transcriptional regulator that was unique to pathogenic Roseobacter strains. This observation supports the model that a combination of virulence factors and QS-dependent regulatory mechanisms enables indigenous members of the host alga's epiphytic microbial community to switch to a pathogenic lifestyle, especially under environmental conditions when innate host defence mechanisms are compromised. PMID:22162749

Fernandes, Neil; Case, Rebecca J.; Longford, Sharon R.; Seyedsayamdost, Mohammad R.; Steinberg, Peter D.; Kjelleberg, Staffan; Thomas, Torsten



Tibouchina pulchra (Cham.) Cogn., a native Atlantic Forest species, as a bio-indicator of ozone: visible injury.  


Tibouchina pulchra saplings were exposed to carbon filtered air (CF), ambient non-filtered air (NF) and ambient non-filtered air+40 ppb ozone (NF+O3) 8 h per day during two months. The AOT40 values at the end of the experiment were 48, 910 and 12,895 ppb h(-1), respectively, for the three treatments. After 25 days of exposure (AOT40=3871 ppb h(-1)), interveinal red stippling appeared in plants in the NF+O3 chamber. In the NF chamber, symptoms were observed only after 60 days of exposure (AOT40=910 ppb h(-1)). After 60 days, injured leaves per plant corresponded to 19% in NF+O3 and 1% in the NF treatment; and the average leaf area injured was 7% within the NF+O3 and 0.2% within the NF treatment. The extent of leaf area injured (leaf injury index) was mostly explained by the accumulated exposure of ozone (r2=0.89; p<0.05). PMID:17683837

Furlan, Cláudia M; Moraes, Regina M; Bulbovas, Patricia; Sanz, Maria J; Domingos, Marisa; Salatino, Antonio



Establishing the redox potential of Tibouchina pulchra (Cham.) Cogn., a native tree species from the Atlantic Rain Forest, in the vicinity of an oil refinery in SE Brazil.  


The present study aimed to establish the seasonal variations in the redox potential ranges of young Tibouchina pulchra plants growing in the Cubatão region (SE Brazil) under varying levels of oxidative stress caused by air pollutants. The plants were exposed to filtered air (FA) and non-filtered air (NFA) in open-top chambers installed next to an oil refinery in Cubatão during six exposure periods of 90 days each, which included the winter and summer seasons. After exposure, several analyses were performed, including the foliar concentrations of ascorbic acid and glutathione in its reduced (AsA and GSH), total (totAA and totG) and oxidized forms (DHA and GSSG); their ratios (AsA/totAA and GSH/totG); the enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR); and the content of malondialdehyde (MDA). The range of antioxidant responses in T. pulchra plants varied seasonally and was stimulated by high or low air pollutant concentrations and/or air temperatures. Glutathione and APX were primarily responsible for increasing plant tolerance to oxidative stress originating from air pollution in the region. The high or low air temperatures mainly affected enzymatic activity. The content of MDA increased in response to increasing ozone concentration, thus indicating that the pro-oxidant/antioxidant balance may not have been reached. PMID:24407781

Esposito, Marisia Pannia; Domingos, Marisa



Response of stress indicators and growth parameters of Tibouchina pulchra Cogn. exposed to air and soil pollution near the industrial complex of Cubatão, Brazil.  


The present study was performed in the vicinity of the industrial complex of Cubatão, São Paulo, Brazil, in order to evaluate the response of 'manaca da serra' Tibouchina pulchra Cogn. (Melastomataceae), a common species of secondary Atlantic Rain Forest vegetation, to the impact of complex air pollution. Emphasis was given to changes of biochemical parameters such as ascorbic acid concentration, peroxidase activity, contents of water-soluble thiols, pH of leaf extract and buffering capacity. These plant factors are often used as early indicators of air pollution stress. Field experiments included sampling of leaves from mature trees in areas with different air pollution load (passive monitoring), exposure of saplings cultivated in uniform soil at these areas (active monitoring) and a study on the combined effects of contaminated soil and air pollution. In general, metabolic response of saplings was more accentuated than that of mature trees. Leaf extract pH and buffering capacity showed no or only small alterations in plants exposed to industrial emissions. In contrast, air pollution resulted in a distinct decrease in ascorbic acid contents and an increase in peroxidase activity and thiol concentrations in leaves. Cultivation of saplings in soil types from contaminated regions frequently caused the same modifications or enhanced the effects produced by air pollution. Growth analysis of exposed saplings demonstrated that a change of the relationship between above-ground and below-ground plant parts was the most obvious effect of air pollution and soil contamination. The experiments showed that even T. pulchra, a species considered resistant to air pollution, suffers metabolic disturbances by the present ambient air and soil quality. Although biochemical and physiological alterations were not related to a certain air pollution type, they could be used to estimate the overall pollution load and to map zones with different air quality. PMID:10682379

Klumpp, G; Furlan, C M; Domingos, M; Klumpp, A



The redifferentiation of nutritive cells in galls induced by Lepidoptera on Tibouchina pulchra (Cham.) Cogn. reveals predefined patterns of plant development.  


Insect galls may present nutritive tissues with distinct cytological features related to the order of the gall inducer. Galling Lepidoptera larvae chew plant cells and induce the redifferentiation of parenchymatic cells into nutritive ones. The nutritive cells in the galls induced by a microlepidoptera on the leaves of Tibouchina pulchra (Cham.) Cogn. (Melastomataceae) are organelle-rich, with developed Golgi apparatus, endoplasmic reticulum, ribosomes, polyribosomes, mitochondria, plastids, and one great central or several fragmented vacuoles. The nonobservance of the nuclei in the nutritive cells deserves special attention, and confers a similarity between the nutritive cells and the vascular conductive ones. The great amount of rough endoplasmic reticulum, ribosomes, polyribosomes, and mitochondria is indicative of the high metabolic status of these cells. They are vascular cambium-like, with high protein synthesis and lipid storage. The proteins are essential to enzymatic metabolism, and secondarily, to larvae nutrition, similarly to the lipid droplets which confer energetic profile to these nutritive cells. The living enucleated cells receive mRNA from their neighbor ones, which may support the high metabolic profile of endoplasmic reticulum and ribosomes observed in galls. Thus, the nutritive cells are stimulated by the galling larvae activity, generating a new cell type, whose redifferentiation includes a mix of intrinsic and common plant pathways. PMID:23779213

Vecchi, Claudia; Menezes, Nanuza Luiza; Oliveira, Denis Coelho; Ferreira, Bruno Garcia; Isaias, Rosy Mary Santos



Physiological responses of the tropical tree Tibouchina pulchra Cogn under the influence of combustion of crude oil and natural gas at an oil refinery.  


A refinery located on the slopes of a mountain range in the city of Cubatão (SE-Brazil) is the main source of sulfur dioxide (SO(2)) in the region. For this reason, the refinery replaced a system in which energy was produced from crude oil combustion in boilers with a system of energy and vapor co-generation in a thermoelectric power plant fueled by natural gas. The aim of this study was to investigate the responses of Tibouchina pulchra to the fuel switching. Saplings planted in pots were distributed throughout monitoring sites around the polluting source (sites I, II, III and IV) and in a site (V) far from emissions. Changes on the plants responses occur along the three fuel switching phases. During the last phase, increased carbon assimilation (Asat) and decreased stomatal conductance (gs) were observed in plants growing in sites II and III; as a consequence, intrinsic water use efficiency (iWUE) increased. However, the increase in Asat did not promote growth increase suggesting that changes at the refinery did not result in better air quality, but only in a change in the main contaminants. PMID:23352657

Silva, Daiane T; Moraes, Regina M



Four new species of Acoela from Chile.  


Acoels are with few exceptions marine worms and a common component of the interstitial meiofauna. In this study we present new species to science belonging to Isodiametridae and Solenofilomorphidae. The new species, Isodiametra finkei n. sp., Postaphanostoma nilssoni n. sp., Pseudaphanostoma hyalinorhabdoida n. sp. and Solenofilomorpha pellucida n. sp. were all collected in Chile during March 2012. Nucleotide sequences for the ribosomal genes 18S rDNA and 28S rDNA as well as COI mtDNA have been determined for the new species and used in a maximum likelihood analysis to further support their classification. PMID:25112642

Kånneby, Tobias; Jondelius, Ulf



Determination of five flavonoids in different parts of Fordia cauliflora by ultra performance liquid chromatography/triple-quadrupole mass spectrometry and chemical comparison with the root of Millettia pulchra var. laxior  

PubMed Central

Background The root of Fordia cauliflora Hemsl (FC) has long been used in southern China for the treatment of rheumatism, bruises, dementia in children, and valetudinarianism. However, sometimes it is mixed with other parts. And it has always been confused with the root of Millettia pulchra (Benth.) Kurz var. laxior (Dunn) Z. Wei (MP) by the local people. The chemical differences between the two ethnic drugs are not clear until now. The aim of this study is to develop a precise and accurate method to characterize and quantify multiple chemical components of FC, which is helpful for the quality evaluation and identification of FC. Results A method coupling ultra performance liquid chromatography (UPLC) with triple-quadrupole mass spectrometry (QqQ-MS) was first developed for simultaneous determination of five flavonoids in different parts of FC and the root of MP, based on a UPLC-diode array detection (DAD) fingerprint method. All calibration curves showed good linearity (R2>0.99) within test ranges. The overall LOD and LOQ were lower than 2.5 ng/mL and 5.0 ng/mL, respectively. The RSDs for intra- and inter-day of five analytes were less than 2.83% and 3.04%, respectively. Recovery studies for the quantified compounds were found to be within the range 93.6-99.8% with RSD less than 5.73%. The results suggest that the root, traditionally used medicinal part, yields the highest flavanoid content in FC. Pachycarin A, 3?,4?-dimethoxy(2??,3??:7,8) furanoflavone, karanjachromene and isoderricin A can be used to differentiate between FC and MP samples. Conclusions The present method is specific, precise and reliable, and is suitable for characterizing and quantifying multiple chemical components of FC. PMID:23870070



Steps towards a centralized nervous system in basal bilaterians: insights from neurogenesis of the acoel Symsagittifera roscoffensis.  


Due to its proposed basal position in the bilaterian Tree of Life, Acoela may hold the key to our understanding of the evolution of a number of bodyplan features including the central nervous system. In order to contribute novel data to this discussion we investigated the distribution of ?-tubulin and the neurotransmitters serotonin and RFamide in juveniles and adults of the sagittiferid Symsagittifera roscoffensis. In addition, we present the expression pattern of the neuropatterning gene SoxB1. Adults and juveniles exhibit six serotonergic longitudinal neurite bundles and an anterior concentration of serotonergic sensory cells. While juveniles show an "orthogon-like" arrangement of longitudinal neurite bundles along the anterior-posterior axis, it appears more diffuse in the posterior region of adults. Commissures between the six neurite bundles are present only in the anterior body region of adults, while irregularly distributed individual neurites, often interconnected by serotonergic nerve cells, are found in the posterior region. Anti-RFamide staining shows numerous individual neurites around the statocyst. The orthogon-like nervous system of S. roscoffensis is confirmed by ?-tubulin immunoreactivity. In the region of highest neurotransmitter density (i.e., anterior), the HMG-box gene SrSoxB1, a transcription factor known to be involved in neurogenesis in other bilaterians, is expressed in juvenile specimens. Accordingly, SoxB1 expression in S. roscoffensis follows the typical pattern of higher bilaterians that have a brain. Thus, our data support the notion that Urbilateria already had the genetic toolkit required to form brain-like neural structures, but that its morphological degree of neural concentration was still low. PMID:20874714

Semmler, Henrike; Chiodin, Marta; Bailly, Xavier; Martinez, Pedro; Wanninger, Andreas



Interception of nutrient rich submarine groundwater discharge seepage on European temperate beaches by the acoel flatworm, Symsagittifera roscoffensis.  


Submarine groundwater discharge (SGD) occurs in intertidal areas, representing a largely unquantified source of solute fluxes to adjacent coastal zones, with nitrogen being constantly the keynote chemical of concern. In Olhos de Água SGD is present as groundwater springs or merely sub-aerial runoff. The occurrence of the flatworm Symsagittifera roscoffensis is described for the first time in Olhos de Água in connection to seepage flows. To assess the impact of this symbiotic flatworm on the nitrogen associated to groundwater discharge flow at the beach, nitrate uptake experiments were conducted in laboratory microcosms. Our results show that S. roscoffensis actively uptakes nitrate at different rates depending on light availability, with rates ? 10 times higher than that of its symbiotic microalgae alone. This supports the hypothesis that S. roscoffensis could be an important in situ nitrate interceptor, potentially playing a biological role on the transformation of groundwater-borne nitrate loads at the land-ocean boundary. PMID:23948093

Carvalho, Liliana F; Rocha, Carlos; Fleming, Alexandra; Veiga-Pires, Cristina; Aníbal, Jaime



Mating systems and interfertility of swamp milkweed (Asclepias incarnata ssp. incarnata and ssp. pulchra)  

Microsoft Academic Search

We investigated the breeding system and interfertility of both subspecies of Asclepias incarnata. We performed hand-pollinations in the glasshouse to compare fruit-set from self- vs. cross-pollinations and to assess interfertility in crosses between the subspecies. We also used horizontal starch-gel electrophoresis to infer mating-system parameters from open-pollinated progeny arrays in three natural populations over two consecutive years. Plants of ssp.




The effects of oxalates produced by Salsola tragus on the phosphorus nutrition of Stipa pulchra  

Microsoft Academic Search

Oxalic acid is produced by some species of plants and mycorrhizal fungi and it may solubilize unavailable soil phosphorus (P) bound by cations (Ca++, Al++, Fe+++). Field and greenhouse experiments were conducted to show whether oxalate produced by the annual Salsola tragus or added oxalic acid would solubilize P from the inorganic-bound soil P pool, making it available for uptake

J. P. Cannon; E. B. Allen; M. F. Allen; L. M. Dudley; J. J. Jurinak



DOI: 10.1126/science.283.5409.1923 , 1923 (1999);283Science  

E-print Network

(deuterostomes; ecdysozoans, with the exception of Nematoda; and lophotrochozoans, with the exception of Platyhel (Platyhelminthes including acoels, Nematoda, Chaetognata, Mesozoa, Gnathostomulida, Rotifera, and Acanthocephala

Sereno, Martin


Radial Dispersion of Neighbors and the Small-Scale Competitive Impact of Two Annual Grasses on a  

E-print Network

's grasslands. Small gaps and patchy speci's Mediterranean type grasslands, native perennial grasses such as Nassella pulchra are surrounded by introduced of the grassland with potential for N. pulchra restoration. We hypothesized that competitor species differences

Rice, Kevin


Molecular systematics of the Acoela (Acoelomorpha, Platyhelminthes) and its concordance with morphology  

Microsoft Academic Search

The phylogenetic relationships of the lower worm group Acoela were investigated using newly obtained nuclear 18S rDNA sequences from 16 acoels in combination with 16 acoel sequences available on GenBank from other laboratories. Parsimony and maximum likelihood analyses of the molecular data supported the concept that the Acoela is monophyletic; however, the gene tree produced by these analyses conflicts with

Matthew D. Hooge; Pilar A. Haye; Seth Tyler; Marian K. Litvaitis; Irv Kornfield



How the worm got its pharynx: phylogeny, classification and Bayesian assessment of character evolution in Acoela.  


Acoela are marine microscopic worms currently thought to be the sister taxon of all other bilaterians. Acoels have long been used as models in evolutionary scenarios, and generalized conclusions about acoel and bilaterian ancestral features are frequently drawn from studies of single acoel species. There is no extensive phylogenetic study of Acoela and the taxonomy of the 380 species is chaotic. Here we use two nuclear ribosomal genes and one mitochondrial gene in combination with 37 morphological characters in an analysis of 126 acoel terminals (about one-third of the described species) to estimate the phylogeny and character evolution of Acoela. We present an estimate of posterior probabilities for ancestral character states at 31 control nodes in the phylogeny. The overall reconstruction signal based on the shape of the posterior distribution of character states was computed for all morphological characters and control nodes to assess how well these were reconstructed. The body-wall musculature appears more clearly reconstructed than the reproductive organs. Posterior similarity to the root was calculated by averaging the divergence between the posterior distributions at the nodes and the root over all morphological characters. Diopisthoporidae is the sister group to all other acoels and has the highest posterior similarity to the root. Convolutidae, including several "model" acoels, is most divergent. Finally, we present a phylogenetic classification of Acoela down to the family level where six previous family level taxa are synonymized. PMID:21828080

Jondelius, Ulf; Wallberg, Andreas; Hooge, Matthew; Raikova, Olga I



Mitochondrial genome data support the basal position of acoelomorpha and the polyphyly of the platyhelminthes  

SciTech Connect

We determined 9.7, 5.2, and 6.8 kb, respectively, of the mitochondrial genomes of the acoel Paratomella rubra, the nemertodermatid Nemertoderma westbladi and the free-living rhabditophoran platyhelminth Microstomum lineare. The identified gene arrangements are unique among metazoans, including each other, sharing no more than one or two single gene boundaries with a few distantly related taxa. Phylogenetic analysis of the amino acid sequences inferred from the sequenced genes confirms that the acoelomorph flatworms (acoels + nemertodermatids) do not belong to the Platyhelminthes, but are, instead, the most basal extant bilaterian group. Therefore, the Platyhelminthes, as traditionally constituted, is a polyphyletic phylum.

Ruiz-Trillo, Inaki; Riutort, Marta; Fourcade, H. Matthew; Baguna, Jaume; Boore, Jeffrey L.



Back in time: a new systematic proposal for the Bilateria  

Microsoft Academic Search

Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body axis and no mesoderm. The two main hypotheses on how this transformation took place consider either a simple organism akin to the planula larva of extant cnidarians or the acoel Platyhelminthes (planuloid-acoeloid theory), or a rather complex organism

Pere Martinez; Jordi Paps; Marta Riutort



Variation in Rates of Asexual Reproduction By Convolutriloba retrogemma  

Microsoft Academic Search

Convolutriloba retrogemma, an acoel turbellarian (phylum Platyhelminthes), engages in an obligate symbiotic relationship with unicellular algae, This species reproduces asexually by budding from the posterior end of the parent individual. The rate of reproduction of 24 newly budded flatworms of various sizes was studied over a period of six weeks, Flatworms were individually placed into 6 mL of 0.2 ?m

Rahim Sara



Determination of total sulfur in lichens and plants by combustion-infrared analysis. [Medicago sativa L. ; Vitis labruscana Bailey; Festuca sp. ; Fraxinum pennsylvanica Marsh. ; Paremelia chlorochroa Tuck. ; P. sulcata Tayl. ; Juniperus scopulorum Sarg. ; Artemisia tridentata Nuttl; Lycopersicum esculentum Mill. ; Triticum compactum Host; Agropyron smithii Rydb. ; Salix pulchra Cham  

Microsoft Academic Search

Sulfur was determined in plants and lichens by combustion of the sample and infrared detection of evolved sulfur dioxide using an automated sulfur analyzer. Vanadium pentaoxide was used as a combustion accelerator. Pelletization of the sample prior to combustion was not found to be advantageous. Washing studies showed that leaching of sulfur was not a major factor in the sample

L. L. Jackson; E. E. Engleman; J. L. Peard



Determination of total sulfur in lichens and plants by combustion-infrared analysis. [Medicago sativa L. ; Vitis labruscana Bailey; Festuca sp. ; Fraxinum pennsylvanica Marsh. ; Paremelia chlorochroa Tuck. ; P. sulcata Tayl. ; Juniperus scopulorum Sarg. ; Artemisia tridentata Nuttl; Lycopersicum esculentum Mill. ; Triticum compactum Host; Agropyron smithii Rydb. ; Salix pulchra Cham  

SciTech Connect

Sulfur was determined in plants and lichens by combustion of the sample and infrared detection of evolved sulfur dioxide using an automated sulfur analyzer. Vanadium pentaoxide was used as a combustion accelerator. Pelletization of the sample prior to combustion was not found to be advantageous. Washing studies showed that leaching of sulfur was not a major factor in the sample preparation. The combustion-IR analysis usually gave higher sulfur content than the turbidimetric analysis as well as shorter analysis time. Relative standard deviations of less than 7% were obtained by the combustion-IR technique when sulfur levels in plant material range from 0.05 to 0.70%. Determination of sulfur in National Bureau of Standards botanical reference materials showed good agreement between the combustion-IR technique and other instrumental procedures. Seven NBS botanical reference materials were analyzed.

Jackson, L.L.; Engleman, E.E.; Peard, J.L.



The Acoela: on their kind and kinships, especially with nemertodermatids and xenoturbellids (Bilateria incertae sedis)  

PubMed Central

Acoels are among the simplest worms and therefore have often been pivotal in discussions of the origin of the Bilateria. Initially thought primitive because of their “planula-like” morphology, including their lumenless digestive system, they were subsequently dismissed by many morphologists as a specialized clade of the Platyhelminthes. However, since molecular phylogenies placed them outside the Platyhelminthes and outside all other phyla at the base of the Bilateria, they became the focus of renewed debate and research. We review what is currently known of acoels, including information regarding their morphology, development, systematics, and phylogenetic relationships, and put some of these topics in a historical perspective to show how the application of new methods contributed to the progress in understanding these animals. Taking all available data into consideration, clear-cut conclusions cannot be made; however, in our view it becomes successively clearer that acoelomorphs are a “basal” but “divergent” branch of the Bilateria. PMID:24098090

Chiodin, Marta; Salvenmoser, Willi; Tyler, Seth



Mitochondrial genome data support the basal position of Acoelomorpha and the polyphyly of the Platyhelminthes  

Microsoft Academic Search

We determined 9.7, 5.2, and 6.8kb, respectively, of the mitochondrial genomes of the acoel Paratomella rubra, the nemertodermatid Nemertoderma westbladi, and the free-living rhabditophoran platyhelminth Microstomum lineare. The identified gene arrangements are unique among metazoans, including each other, sharing no more than one or two single gene boundaries with a few distantly related taxa. Phylogenetic analysis of the amino acid

Iñaki Ruiz-Trillo; Marta Riutort; H. Matthew Fourcade; Jaume Baguñà; Jeffrey L. Boore



Combined large and small subunit ribosomal RNA phylogenies support a basal position of the acoelomorph flatworms.  

PubMed Central

The phylogenetic position of the phylum Platyhelminthes has been re-evaluated in the past decade by analysis of diverse molecular datasets. The consensus is that the Rhabditophora + Catenulida, which includes most of the flatworm taxa, are not primitively simple basal bilaterians but are related to coelomate phyla such as molluscs. The status of two other groups of acoelomate worms, Acoela and Nemertodermatida, is less clear. Although many characteristics unite these two groups, initial molecular phylogenetic studies placed the Nemertodermatida within the Rhabditophora, but placed the Acoela at the base of the Bilateria, distant from other flatworms. This contradiction resulted in scepticism about the basal position of acoels and led to calls for further data. We have sequenced large subunit ribosomal RNA genes from 13 rhabditophorans + catenulids, three acoels and one nemertodermatid, tripling the available data. Our analyses strongly support a basal position of both acoels and nemertodermatids. Alternative hypotheses are significantly less well supported by the data. We conclude that the Nemertodermatida and Acoela are basal bilaterians and, owing to their unique body plan and embryogenesis, should be recognized as a separate phylum, the Acoelomorpha. PMID:12803898

Telford, Maximilian J; Lockyer, Anne E; Cartwright-Finch, Chloë; Littlewood, D Timothy J



Recent Records of Alien Anurans on the Pacific Island of Guam  

Microsoft Academic Search

Eight anuran species were recorded for the first time in Guam in the period May 2003-December 2005, all apparently the result of arrivals to the island since 2000. Three of the eight species (Rana guentheri, Polypedates megacephalus, and Eleutherodactylus planirostris) had well-established breeding populations by 2005. A further three (Fejervarya cf. limnocharis, Fejervarya cancri- vora, and Microhyla pulchra) were recorded

Michelle T. Christy; Craig S. Clark; David E. Gee II; Diane Vice; Daniel S. Vice; Mitchell P. Warner; Claudine L. Tyrrell; Gordon H. Rodda; Julie A. Savidge




Technology Transfer Automated Retrieval System (TEKTRAN)

Differences in resistance to powdery mildew were observed on detached leaf disks of six flowering dogwood lines inoculated with conidia of Erysiphe pulchra. Significant differences (P < 0.02) in germinated conidia with branched hyphae, infection efficiency, latent period and sporulation were detect...


Reworking of fusulinids and calcisphaerids in the Lercara Formation (Sicily, Italy); geological implications  

Microsoft Academic Search

Different fusulinids have been identified in the Lercara Formation (Sicily). They are: Reichelina sp., Schubertella paramelonica, Toriyamaia (?) sp., Neofusulinella lantenoisi, Yangchienia compressa, Rauserella staffi, Darvasites contractus, Chalaroschwagerina (Taiyuanella?) aff. davalensis, Levenella aff. evoluta, Pamirina darvasica, and Neoschwagerina ex gr. craticulifera. Small Permian foraminifers, as well as the calcispherid Asterosphaera pulchra also exist. The microfossils indicate reworking of different Permian

Lucia Carcione; Daniel Vachard; Rossana Martini; Louisette Zaninetti; Benedetto Abate; Giovanna Lo Cicero; Loris Montanari




Microsoft Academic Search

We studied the effects of soil fungi on interactions between Centaurea mel- itensis, an exotic invasive weed in central California, and two co-occurring grasses, Nassella pulchra and Avena barbata. The fungicide benomyl reduced the abundance of arbuscular mycorrhizal (AM) fungi in plant roots but did not affect non-AM fungi. Centaurea plants grown alone were .50% smaller with the resident microbial

Ragan M. Callaway; Bruce E. Mahall; Chris Wicks; Joel Pankey; Catherine Zabinski



Compensatory growth and competitive ability of an invasive weed are enhanced by soil fungi and native neighbours  

Microsoft Academic Search

Compensatory responses to herbivory by invasive weeds may foil attempts to arrest their spread with biological controls. We conducted an experiment to study the effects of defoliation and soil fungi on interactions between Centaurea melitensis, an invasive annual from Eurasia, and Nassella pulchra, a native Californian bunchgrass. Defoliation of C. melitensis reduced its final biomass in all species-fungicide treatments, except

Ragan M. Callaway; Beth Newingham; Cathy A. Zabinski; Bruce E. Mahall



Effects of Simulated Climate Change on Plant Phenology and Nitrogen Mineralization in Alaskan Arctic Tundra  

Microsoft Academic Search

This study was part of the International Tundra Experiment (ITEX) and examined the effects of increased winter snow depth and decreased growing season lengt ho n the phenology of four arctic plant species (Betula nana, Salix pulchra, Eriophorum vaginatum ,a ndVaccinium vitis-idaea) and seasonal nitrogen availability in arctic snowbed communities. Increased snow depth had a large effect on the temporal

Andrew P. Borner; Knut Kielland; Marilyn D. Walker



A phylogenetic analysis of myosin heavy chain type II sequences corroborates that Acoela and Nemertodermatida are basal bilaterians  

PubMed Central

Bilateria are currently subdivided into three superclades: Deuterostomia, Ecdysozoa, and Lophotrochozoa. Within this new taxonomic frame, acoelomate Platyhelminthes, for a long time held to be basal bilaterians, are now considered spiralian lophotrochozoans. However, recent 18S rDNA [small subunit (SSU)] analyses have shown Platyhelminthes to be polyphyletic with two of its orders, the Acoela and the Nemertodermatida, as the earliest extant bilaterians. To corroborate such position and avoid the criticisms of saturation and long-branch effects thrown on the SSU molecule, we have searched for independent molecular data bearing good phylogenetic information at deep evolutionary nodes. Here we report a phylogenetic analysis of DNA sequences from the myosin heavy chain type II (myosin II) gene from a large set of metazoans, including acoels and nemertodermatids. Our study demonstrates, both for the myosin II data set alone and for a combined SSU + myosin II data set, that Platyhelminthes are polyphyletic and that acoels and nemertodermatids are the extant earliest bilaterians. Hence, the common bilaterian ancestor was not, as currently held, large and complex but small, simple, and likely with direct development. This scenario has far-reaching implications for understanding the evolution of major body plans and for perceptions of the Cambrian evolutionary explosion. PMID:12177440

Ruiz-Trillo, I.; Paps, J.; Loukota, M.; Ribera, C.; Jondelius, U.; Baguñà, J.; Riutort, M.



Development and juvenile anatomy of the nemertodermatid Meara stichopi (Bock) Westblad 1949 (Acoelomorpha)  

PubMed Central

Introduction Nemertodermatida is the sister group of the Acoela, which together form the Acoelomorpha, a taxon that comprises bilaterally symmetric, small aquatic worms. While there are several descriptions of the embryology of acoel species, descriptions of nemertodermatid development are scarce. To be able to reconstruct the ground pattern of the Acoelomorpha it is crucial to gain more information about the development of several nemertodermatid species. Here we describe the development of the nemertodermatid Meara stichopi using light and fluorescent microscopic methods. Results We have collected Meara stichopi during several seasons and reconstruct the complex annual reproductive cycle dependent on the sea cucumber Parastichopus tremulus. Using common fluorescent markers for musculature (BODIPY FL-phallacidin) and neurons (antibodies against FMRFamide, serotonin, tyrosinated-tubulin) and live imaging techniques, we followed embryogenesis which takes approximately 9–10 weeks. The cleavage pattern is stereotypic up to the 16-cell stage. Ring- and longitudinal musculature start to develop during week 6, followed by the formation of the basiepidermal nervous system. The juvenile is hatching without mouth opening and has a basiepidermal nerve net with two dorsal neurite bundles and an anterior condensation. Conclusions The development of Meara stichopi differs from the development of Acoela in that it is less stereotypic and does not follow the typical acoel duet cleavage program. During late development Meara stichopi does not show a temporal anterior to posterior gradient during muscle and nervous system formation. PMID:25024737



Results of Surveys for Special Status Reptiles at the Site 300 Facilities of Lawrence Livermore National Laboratory  

SciTech Connect

The purpose of this report is to present the results of a live-trapping and visual surveys for special status reptiles at the Site 300 Facilities of Lawrence Livermore National Laboratory (LLNL). The survey was conducted under the authority of the Federal recovery permit of Swaim Biological Consulting (PRT-815537) and a Memorandum of Understanding issued from the California Department of Fish and Game. Site 300 is located between Livermore and Tracy just north of Tesla road (Alameda County) and Corral Hollow Road (San Joaquin County) and straddles the Alameda and San Joaquin County line (Figures 1 and 2). It encompasses portions of the USGS 7.5 minute Midway and Tracy quadrangles (Figure 2). Focused surveys were conducted for four special status reptiles including the Alameda whipsnake (Masticophis lateralis euryxanthus), the San Joaquin Whipsnake (Masticophis Hagellum ruddock), the silvery legless lizard (Anniella pulchra pulchra), and the California horned lizard (Phrynosoma coronanum frontale).

Woollett, J J



Karyotype and DNA-content evolution in ten species of Crepis (Asteraceae) distributed in Bulgaria  

Microsoft Academic Search

Ten Crepis species from Bulgaria—five perennials (C. viscidula, C. paludosa, C. conyzaefolia, C. bithynica, C. schachtii), four annuals (C. pulchra, C. sancta, C. setosa, C. zacintha) and one biennial (C. biennis)—were analysed karyologically using haematoxylin staining, Feulgen cytophotometry (scanning densitometry and video-based image analysis), and DNA flow cytometry with propidium iodide. All taxa but the biennial are diploids with descending




Halogenated furanones inhibit quorum sensing through accelerated LuxR turnover  

Microsoft Academic Search

N-acyl-L-homoserine lactones (AHLs) are co-regulatory ligands required for control of the expression of genes encoding virulence traits in many Gram- negative bacterial species. Recent studies have indicated that AHLs modulate the cellular concentrations of LuxR-type regulatory proteins by binding and fortifying these proteins against proteolytic degradation (Zhu & Winans, 2001). Halogenated furanones produced by the macroalga Delisea pulchra inhibit AHL-dependent

Michael Manefield; Thomas Bovbjerg Rasmussen; Morten Henzter; Jens Bo Andersen; Peter Steinberg; Staffan Kjelleberg; Michael Givskov



Responses of a Remnant California Native Bunchgrass Population to Grazing, Burning and Climatic Variation  

Microsoft Academic Search

This study examined the interactive effects of grazing intensity and burning on a remnant population of the California native\\u000a bunchgrass Nassella pulchra. We measured growth, reproduction and mortality of permanently marked bunchgrasses and measured bunchgrass seedling recruitment\\u000a and density in permanent quadrats. We burned half of the treatment plots in late spring 1998. Grazing treatments were implemented\\u000a in 1998, 1999

Jaymee T. Marty; Sharon K. Collinge; Kevin J. Rice



Moose herbivory, browse quality, and nutrient cycling in an Alaskan treeline community  

Microsoft Academic Search

Moose (Alces alces) browsing on diamondleaf willow (Salix planifolia pulchra) caused significant increases in subsequent growth of stems and leaves in treeline plant communities in central Alaska, USA.\\u000a Willows growing in the shade were significantly more palatable for moose than those growing in the sun. Moose density had\\u000a strong effects on rates of nutrient cycling, ostensibly through effects of browsing

Erik M. Molvar; R. Terry Bowyer; Victor Van Ballenberghe



Differential gene expression shows natural brominated furanones interfere with the autoinducer-2 bacterial signaling system ofEscherichia coli  

Microsoft Academic Search

The quorum sensing disrupter (5Z)-4-bromo- 5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) of the alga Delisea pulchra was previously found by us (En- viron Microbiol 3:731-736, 2001) to inhibit quorum sensing in Escherichia coli via autoinducer-2 (AI-2, pro- duced by LuxS). In this study, DNA microarrays were used to study the genetic basis of this natural furanone inhibi- tion of AI-2 signaling (significant values with

Dacheng Ren; Laura A. Bedzyk; Rick W. Ye; Stuart M. Thomas; Thomas K. Wood



Compensatory growth and competitive ability of an invasive weed are enhanced by soil fungi and native neighbours  

Microsoft Academic Search

Abstract Compensatory,responses to herbivory by invasive weeds may foil attempts to arrest their spread with biological controls. We conducted,an experiment,to study the effects of defoliation and soil fungi on interactions between Centaurea melitensis, an invasive annual from Eurasia, and Nassella pulchra, a native Californian bunchgrass. Defoliation of C. melitensis reduced its final biomass in all species?fungicide treatments, except when C.

Ragan M. Callaway; A Cathy; Bruce E. Mahall; Evolutionary Biology; Montana State


Myxozoa of deep-sea fishes in the northwestern Atlantic.  


The gall bladder of 5 species of deep-water fishes (Coryphaenoides armatus, Coryphaenoides rupestris, Macrourus berglax, Antimora rostrata, and Synaphobranchus kaupi) from the New York Bight and Carson Canyon areas in the northwest Atlantic were examined for myxozoan parasites. Myxidium coryphaenoidium was found in 4 fish species, whereas Auerbachia pulchra and Ceratomyxa sp. were each observed in 1 fish species. Prevalence of myxozoan infections was greater in fishes taken off the New York Bight than from the Carson Canyon. PMID:2319435

Threlfall, W; Khan, R A



High resistance of Acropora coral gametes facing copper exposure.  


Pollution by heavy metals remains today an important threat to the health of humans and ecosystems, but there is still a paucity of data on the response of early life stages of key organisms. In this context, the present work assessed the fertilization success rate of two Acropora species (A. cytherea and A. pulchra) from the French Polynesia reefs exposed to six increasing copper concentrations in seawater. The two species showed a relatively high tolerance to copper (4h30-EC50 was 69.4±4.8?gL(-1) and 75.4±6.4?gL(-1) for A. cytherea and A. pulchra, respectively). As Cu concentration increases, an increasing proportion of deformed embryos was recorded (67.6% and 58.5% for A. cytherea and A. pulchra, respectively, at 220?gCuL(-1)). These results demonstrated thus, that high levels of copper could negatively impair the normal fertilization process of coral gametes and therefore alter the renewal of coral populations. Since the two Acropora species investigated in this study displayed a high resistance to copper, these results should be considered in the context of multiple stressors associated with climate change, where rising temperature or ocean acidification may significantly exacerbate copper toxicity. PMID:25462298

Puisay, Antoine; Pilon, Rosanne; Hédouin, Laetitia



Mortality of exotic and native seeds in invaded and uninvaded habitats  

NASA Astrophysics Data System (ADS)

We examined seed survival in exotic- and native-dominated grasslands by placing seeds of a once-pervasive native grass species, Nassella pulchra, and two of the most common, widespread exotic grass species, Avena fatua and Bromus hordeaceus, in mesh bags in the field for 3 months. Compared to germination of unexposed seeds not placed in the field, exotic species experienced an approximately 40% reduction in viability, whereas the mortality experienced by the native species was <20%. Despite these differences, germination rates of exposed seeds were similar between native and exotic species because native N. pulchra seeds had lower initial viability prior to entering the seed bank. Seed mortality did not differ based on whether seeds were placed in habitats dominated by exotic or native grasses. Rather, our results suggest that re-establishment of native N. pulchra must focus on maximizing seed viability and survival, and that A. fatua and B. hordeaceus overcome relatively higher losses of viable seeds in the seed bank, potentially by producing large numbers of highly viable seeds.

Orrock, John L.; Hoisington-López, Jessica L.



Acoelomorph flatworms are deuterostomes related to Xenoturbella  

PubMed Central

Xenoturbellida and Acoelomorpha are marine worms with contentious ancestry. Both were originally associated with the flatworms (Platyhelminthes), but molecular data haverevised their phylogenetic positions, generally linking Xenoturbellida to the deuterostomes1,2 and positioning the Acoelomorpha as the most basally branching bilaterian group(s)3–6. Recent phylogenomic data suggested that Xenoturbellida and Acoelomorpha are sister taxa and together constitute an early branch of Bilateria7. Here we assemble three independent data sets—mitochondrial genes, a phylogenomic data set of 38,330 amino-acid positions and new microRNA (miRNA) complements—and show that the position of Acoelomorpha is strongly affected by a long-branch attraction (LBA) artefact. When we minimize LBA we find consistent support for a position of both acoelomorphs and Xenoturbella within the deuterostomes. The most likely phylogeny links Xenoturbella and Acoelomorpha in a clade we call Xenacoelomorpha. The Xenacoelomorpha is the sister group of the Ambulacraria (hemichordates and echinoderms). We show that analyses of miRNA complements8 have been affected by character loss in the acoels and that both groups possess one miRNA and the gene Rsb66 otherwise specific to deuterostomes. In addition, Xenoturbella shares one miRNA with the ambulacrarians, and two with the acoels. This phylogeny makes sense of the shared characteristics of Xenoturbellida and Acoelomorpha, such as ciliary ultrastructure and diffuse nervous system, and implies the loss of various deuterostome characters in the Xenacoelomorpha including coelomic cavities, through gut and gill slits. PMID:21307940

Philippe, Hervé; Brinkmann, Henner; Copley, Richard R.; Moroz, Leonid L.; Nakano, Hiroaki; Poustka, Albert J.; Wallberg, Andreas; Peterson, Kevin J.; Telford, Maximilian J.



Ancestor-descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata.  


Ancestor-descendant relationships (ADRs), involving descent with modification, are the fundamental concept in evolution, but are usually difficult to recognize. We examined the cladistic relationship between the only reported fossil pygmy right whale, †Miocaperea pulchra, and its sole living relative, the enigmatic pygmy right whale Caperea marginata, the latter represented by both adult and juvenile specimens. †Miocaperea is phylogenetically bracketed between juvenile and adult Caperea marginata in morphologically based analyses, thus suggesting a possible ADR-the first so far identified within baleen whales (Cetacea: Mysticeti). The †Miocaperea-Caperea lineage may show long-term morphological stasis and, in turn, punctuated equilibrium. PMID:25589485

Tsai, Cheng-Hsiu; Fordyce, R Ewan



Competition and soil resource environment alter plant-soil feedbacks for a native and exotic grass.  


Feedbacks between plants and soil biota are increasingly identified as key determinants of species abundance patterns within plant communities. However, our understanding of how plant-soil feedbacks may contribute to invasions is limited by our understanding of how feedbacks may shift in the light of other ecological processes. Here we assess how the strength of plant-soil feedbacks may shift as soil microbial communities change along a gradient of soil Nitrogen (N) availability and how these dynamics may be further altered by the presence of a competitor. We conducted a greenhouse experiment where we grew native Stipa pulchra and exotic Avena fatua, alone and in competition, in soils inoculated with conspecific and heterospecific soil microbial communities conditioned in low, ambient, and high N environments. Stipa pulchra decreased in heterospecific soil and in the presence of a competitor, while the exotic Avena fatua's performance shifted with soil microbial communities from altered N environments. Morever, competition and soil microbial communities from high N environment eliminated Stipa's positive plant-soil feedbacks. Our results highlight the importance of examining how individual plant-soil feedbacks may interact in a broader community context and contribute to the establishment, spread, and dominance of invaders. PMID:25425557

Larios, Loralee; Suding, Katharine N



Differential ecophysiological response of deciduous shrubs and a graminoid to long-term experimental snow reductions and additions in moist acidic tundra, Northern Alaska.  


Changes in winter precipitation that include both decreases and increases in winter snow are underway across the Arctic. In this study, we used a 14-year experiment that has increased and decreased winter snow in the moist acidic tussock tundra of northern Alaska to understand impacts of variation in winter snow depth on summer leaf-level ecophysiology of two deciduous shrubs and a graminoid species, including: instantaneous rates of leaf gas exchange, and ?(13)C, ?(15)N, and nitrogen (N) concentrations of Betula nana, Salix pulchra, and Eriophorum vaginatum. Leaf-level measurements were complemented by measurements of canopy leaf area index (LAI) and depth of thaw. Reductions in snow lowered summer leaf photosynthesis, conductance, and transpiration rates by up to 40% compared to ambient and deep snow conditions for Eriophorum vaginatum, and reduced Salix pulchra conductance and transpiration by up to 49%. In contrast, Betula nana exhibited no changes in leaf gas exchange in response to lower or deeper snow. Canopy LAI increased with added snow, while reduced winter snow resulted in lower growing season soil temperatures and reduced thaw depths. Our findings indicate that the spatial and temporal variability of future snow depth will have individualistic consequences for leaf-level C fixation and water flux by tundra species, and that these responses will be manifested over the longer term by changes in canopy traits, depth of thaw, soil C and N processes, and trace gas (CO2 and H2O) exchanges between the tundra and the atmosphere. PMID:24052332

Pattison, Robert R; Welker, Jeffrey M



Polyphenol contents and antioxidant activities of five Indigofera species (Fabaceae) from Burkina Faso.  


Aqueous acetone extracts prepared from five Indigofera species of Burkina Faso, namely Indigofera colutea (Burm.) Murril., I. macrocalyx Guilld et Perr., I. nigritana Hook f., I. pulchra willd. and I. tinctoria L., were investigated for their phytochemical composition and their antioxidant activities. Standard methods and TLC were used to screen the phytochemical composition. The total phenolic and flavonoid content of extracts were assessed by Folin-Ciocalteu and AlCl3 methods, respectively. These extracts were also evaluated for their antioxidant potentials using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) (ABTS) assays. Flavonoids, saponins, quinones, sterols/triterpenes and tannins were present in all these species except for I. pulchra where quinones were not found. Gallic acid, caffeic acid, rutin and myricetin in I. colutea; gallic acid, quercitrin, myricetin in I. tinctoria; galangin and myricetin in I. macrocalyx were identified by thin layer chromatography. Among these, I. colutea, I. tinctoria, I. nigritana and I. macrocalyx, which had the highest phenolic content, were also found to possess the best antioxidant activities. The results indicated a good correlation between antioxidant activities and total phenolic content (p<0.05 for FRAP/DPPH and DPPH/ABTS and p<0.01 for FRAP/ABTS). These plants represent promising sources of natural antioxidants and these findings give scientific bases to their ethnopharmacological uses. PMID:18817242

Bakasso, S; Lamien-Meda, A; Lamien, C E; Kiendrebeogo, M; Millogo, J; Ouedraogo, A G; Nacoulma, O G



Expression pattern of Piwi-like genes in adult Myzostoma cirriferum (Annelida).  


Piwi-like genes are a subgroup of Argonaute genes which participate as gene regulators by gene silencing. In most bilaterians, such as mouse, human, insects, and zebrafish, their expression is mostly limited to gonadal stem cells. But there are some striking exceptions to this pattern; flatworms and acoels also express Piwi-like genes in somatic stem cells, due to their unique replacement system. Annelid species like Capitella teleta and Platynereis dumerilii express these genes in cells of the posterior growth zone as well as in gonadal stem cells. To investigate the expression pattern of Piwi-like genes in another annelid, we established in situ hybridization for adult Myzostoma cirriferum. Piwi-like gene transcripts recovered in an mRNA-seq library of pooled adult stages of M. cirriferum were expanded using RACE PCR, cloned and sequenced. ML analysis confirmed the identity of both transcripts as part of the Piwi1-like or Piwi2-like subfamily of Argonaute proteins. The results of in situ hybridization studies show that the expression of both Piwi-like genes, Mc-Piwi1 and Mc-Piwi2, is clearly located only in gonadal stem cells, and as such we did not find any evidence for the existence of a posterior growth zone nor expression in somatic stem cells. PMID:23609434

Weigert, Anne; Helm, Conrad; Hausen, Harald; Zakrzewski, Anne-C; Bleidorn, Christoph



Hyposalinity stress compromises the fertilization of gametes more than the survival of coral larvae.  


The life cycle of coral is affected by natural and anthropogenic perturbations occurring in the marine environment. In the context of global changes, it is likely that rainfall events will be more intense and that coastal reefs will be exposed to sudden drops in salinity. Therefore, a better understanding of how corals-especially during the pelagic life stages-are able to deal with declines in salinity is crucial. To fill this knowledge gap, this work investigated how gametes and larva stages of two species of Acropora (Acropora cytherea and Acropora pulchra) from French Polynesia cope with drops in salinity. An analysis of collected results highlights that both Acropora coral gametes displayed the same resistance to salinity changes, with 4h30-ES50 (effective salinity that decrease by 50% the fertilization success after 4h30 exposure) of 26.6 ± 0.1 and 27.5 ± 0.3‰ for A. cytherea and A. pulchra, respectively. This study also revealed that coral gametes were more sensitive to decreases in salinity than larvae, for which significant changes are only observed at 26‰ for A. cytherea after 14 d of exposure. Although rising seawater temperatures and ocean acidification are often perceived as the main threat for the survival of coral reefs, our work indicates that 70% of the gametes could be killed during a single night of spawning by a rainfall event that decreases salinity to 26‰. This suggests that changes in the frequency and intensity of rainfall events associated with climate changes should be taken seriously in efforts to both preserve coral gametes and ensure the persistence and renewal of coral populations. PMID:25562765

Hédouin, Laetitia; Pilon, Rosanne; Puisay, Antoine



Nutrient fluxes in litterfall of a secondary successional alluvial rain forest in Southern Brazil.  


During forest succession, litterfall nutrient fluxes increase significantly. The higher inputs of organic matter and nutrients through litterfall affects positively soil fertility and the species composition, which are essential components in forest restoration and management programs. In the present study, the input of nutrients to the forest soil via litterfall components was estimated for two sites of different development stages, in an early successional alluvial rain forest in Brazil. Litterfall returned to the soil, in kg/ha, ca. 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu and 11.2 Al, in the site where trees were more abundant and had higher values of basal area. In the other area, where trees where less abundant and values of basal area were comparatively low, litterfall returned < 50% of those amounts to the forest soil, except for Al. The amount of Al that returned to the soil was similar in both areas due to the high contribution of Tibouchina pulchra (82% of Al returned). Comparatively, high proportion of three dominant native tree species (Myrsine coriacea, T. pulchra and Cecropia pachystachya) explained better litter nutrient use efficiency (mainly N and P) in the site with the least advanced successional stage. Although litterfall of these species show lower nutrient concentrations than the other tree species, their nutrient fluxes were high in both sites, indicating a certain independence from soil essential nutrients. Such feature of the native species is very advantageous and should be considered in forest restoration programs. PMID:22208099

Scheer, Maurício Bergamini; Gatti, Gustavo; Wisniewski, Celina



Variability in the Effects of Macroalgae on the Survival and Growth of Corals: The Consumer Connection  

PubMed Central

Shifts in dominance from corals to macroalgae are occurring in many coral reefs worldwide. Macroalgal canopies, while competing for space with coral colonies, may also form a barrier to herbivorous and corallivorous fish, offering protection to corals. Thus, corals could either suffer from enhanced competition with canopy-forming and understorey macroalgae or benefit from predator exclusion. Here, we tested the hypothesis that the effects of the brown, canopy-forming macroalga, Turbinaria ornata, on the survival and growth of corals can vary according to its cover, to the presence or absence of herbivorous and corallivorous fish and to the morphological types of corals. Over a period of 66 days, two coral species differing in growth form, Acropora pulchra and Porites rus, were exposed to three different covers of T. ornata (absent versus medium versus high), in the presence or absence of fish. Irrespective of the cover of T. ornata, fish exclusion reduced mortality rates of A. pulchra. Following fish exclusion, a high cover of T. ornata depressed the growth of this branched coral, whilst it had no effect when fish species were present. P. rus suffered no damage from corallivorous fish, but its growth was decreased by high covers of T. ornata, irrespective of the presence or absence of fish. These results show that negative effects of T. ornata on some coral species are subordinate to those of fish predation and are, therefore, likely to manifest only on reefs severely depleted of predators. In contrast, space dominance by T. ornata may decrease the growth of other coral species regardless of predation intensity. In general, this study shows that susceptibility to predation may determine the severity of the effects of canopy-forming macroalgae on coral growth. PMID:24260290

Bulleri, Fabio; Couraudon-Réale, Marine; Lison de Loma, Thierry; Claudet, Joachim



Spatial polychaeta habitat potential mapping using probabilistic models  

NASA Astrophysics Data System (ADS)

The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats.

Choi, Jong-Kuk; Oh, Hyun-Joo; Koo, Bon Joo; Ryu, Joo-Hyung; Lee, Saro



Free-Nematodes in the NW Black Sea meiobenthos - diversity, abundance, distribution and importance as indicator of hypoxic waters  

NASA Astrophysics Data System (ADS)

The aim of this study performed within EU FP7 Hypox Project was to get deeper knowledge about species of nematodes that could be indicators for stressful biotic conditions as low oxygen concentration due to phenomena of seasonal hypoxia. The Nematodes come from meiobenthos sampling (using a multi corer with 4 tubes, Mark II type, lowered into the sea from R/V "Mare Nigrum" board) performed in May and September 2010 and April 2011 along four transects crossing the Romanian continental shelf from where 87 meiobenthos samples were collected. In the studied area 96 species of nematodes were found. The authors analyzed the nematodes populations' distribution on four profiles: Sf. Gheorghe, Portita, Constanta and Mangalia. The qualitative and quantitative structure of nematodes populations was compared. 41 species were found on Mangalia profile, 47 species on Portita profile, 48 species on Constanta profile and 85 species on Sf. Gheorghe profile. The greatest densities were found on Constanta profile with an average of 369.607indvs/m-2. The most frequent and abundant species were: Sabatieria pulchra, Sabatieria abyssalis, Terschellingia longicaudata, Viscosia cobbi, Axonolaimus ponticus. The species assemblages were assessed for depth gradient distribution, 7 depth intervals being set from 20 to 210 m. The greatest diversity was noted in 61-100 m depth interval, while the lowest between 0-20 m. On the contrary, in terms of density of individuals (indvs/m-2), highest densities were obtained in shallow waters between 21-30 m. As far as the depth increases, the species assemblages change, becoming more favorable to species like Halalaimus ponticus, Metachromadora macrouthera, Halanonchus bullatus, Linhomoneidae species. However, on the first place still remained Sabatieria abyssalis. The vertical distribution of nematodes in sediments was analyzed for the surface layer 0-5 cm and sub-surface layer 5-10 cm, the dominant species in both layers being: Sabatieria pulchra, S. abyssalis, Terschellingia longicaudata, Viscosia cobbi, Axonolaimus ponticus, Metalinhomoeus zosterae, Enoplus euxinus, Eleutherolaimus longus. The density decreases in 5-10 cm layer as compared to 0-5 cm layer. Results show that a dominant nematodes community tolerant to eutrophication conditions, organic loading and hypoxic conditions, made up of species of Sabatieria pulchra, Sabatieria abyssalis, Terschellingia longicaudata etc., is spread throughout the whole investigated area, from the shallow waters to the deepest bottoms at the limit of the metazoan life development. Literature confirms the ubiquitous distribution of these species, often found in areas of low O2 concentration. The taxonomic diversity increases with depth, which may suggest that the nematodes in the Black Sea, under unfavorable conditions, may have an adaptive strategy in response to the lack of resources or in the presence of physiological stress factors.

Muresan, M.; Gomoiu, M.-T.



Quantifying the physiology of structurally complex arctic vegetation and implications for carbon cycling in a shrubbier tundra  

NASA Astrophysics Data System (ADS)

The arctic is undergoing a warming trend that is more extreme compared to lower latitudes. As one major consequence, repeat aerial photographs reveal that in recent decades woody deciduous shrubs have increased in dominance in valley bottoms and riparian areas of northern Alaska. Advancing shrub canopies are growing taller and more structurally complex, presumably increasing self-shading and reducing light availability with canopy depth. According to canopy optimization theory, plants will preferentially allocate nutrient resources to sun-exposed canopy leaves to enhance photosynthetic efficiency in order to take advantage of greater light availability. While canopy optimization has been studied in other, mainly forested ecosystems, this theory has yet to be tested in the arctic tundra. We made a series of measurements on canopy leaves located in high to low light environments, from three common woody deciduous shrubs on the North Slope of Alaska: dwarf birch (Betula nana), tealeaf willow (Salix pulchra), and feltleaf willow (Salix alaxensis). For each selected leaf, we measured the canopy leaf area index at its canopy position in order to quantify the amount of light intercepted by the leaf surface, and in situ chlorophyll fluorescence to evaluate its photosynthetic efficiency through calculation of leaf maximum electron transport rate. The same leaves were then removed and measured for leaf area, dry mass, and carbon to nitrogen ratio. Our data show trends that are consistent with the development of canopy optimization. Leaf nitrogen decreases significantly from the upper to lower terciles of leaf area index values (56% in Salix alaxensis, 41% in Salix pulchra, 46% in Betula nana). Similarly, there were significant reductions in the leaf maximum electron transport rate for two species (44% in Salix alaxensis, 40% Betula nana). These findings suggest that structurally complex arctic shrubs may be redistributing leaf nitrogen to more exposed parts of the canopy where light is more abundant, which combined with higher photosynthetic efficiencies suggests that plants may be investing more nitrogen into photosynthetic machinery. Future work should focus on the relationship between chlorophyll fluorescence and leaf-level CO2 exchange in order to determine the relationship between the observed gradients in photosynthetic efficiency and measured carbon exchange. This study suggests that because the arctic tundra is becoming more structurally complex, ecosystem-level carbon models should include within-canopy gradients in light intensity and consequent gradients in leaf physiological traits.

Formica, A. F.; Griffin, K. L.; Boelman, N.



Characterizing Variation of Isotopic Markers in Northern Alaskan Caribou Forages  

NASA Astrophysics Data System (ADS)

Isotopic markers in feces and tissues are a potential tool for monitoring the importance of feeding areas for migratory herbivores such as caribou (Rangifer tarandus). Many of these techniques are currently limited by gaps in our knowledge of how these isotopic signatures vary over the landscape. We collected seven species of preferred caribou forages along a latitudinal gradient in the summer ranges of the Central Arctic (9 sites) and Teshekpuk Lake (4 sites) caribou herds during 2011 and 2012. We analyzed forages at peak protein content and at the end of the season to characterize temporal, species-specific, and spatial variation in isotopic markers. The availability of C and N was measured by digestion in vitro. Isotopic signatures of digested samples were used to calculate fractionation that would bias the isotopic signature of feces. The range of values for isotopes (all values ‰) of nitrogen (?15N -9.5 - +4.3), and sulfur (?34S -3.6 - +15.5) were greater than those for carbon (?13C -30.5 - -24.9). Small declines in forage ?13C with latitude (Carex aquatilis, Eriophorum vaginatum, Salix pulchra, and S. richardsonii [all P < 0.01]), season (all species except C. bigelowii [all P ? 0.01]), and season x year (S. richardsonii; P = 0.01) were probably associated with changes in water availability. Fractionation of ?13C in early season forages was 0.1 × 1.0 and positively related to C availability (58% × 15%; P < 0.01) with the greatest fractionation for the highly digestible forb Pedicularis langsdorfii (1.43 × 0.44; P < 0.01). Sedges (Carex and Eriophorum) were significantly higher in ?15N than Salix spp. and other dicots (2.0 × 1.1 vs. -2.9 × 2.2; P < 0.01). For Salix spp., ?15N was consistent over the season and between years. Fractionation of ?15N in early season forages was 0.2 × 1.8 and not related to N availability (60% × 17%). For S. pulchra, ?34S may indicate usage of coastal habitats over foothills because ?34S was higher on the coastal plain than in the foothills (11.1 × 3.3 and 3.1 × 2.6; P < 0.01). Isotopic ratios in N and S show the greatest promise for tracking diet and location of migratory caribou whereas the narrow range in ?13C is affected by species, season and location.

VanSomeren, L.; Barboza, P. S.; Gustine, D. D.; Parrett, L. S.; Stricker, C. A.



The Influence Of Water Tracks And Hillslope Position On The Physiology Of The Dominant Plant Species In The Imnavait Creek Watershed, Alaska  

NASA Astrophysics Data System (ADS)

Within a small arctic tundra watershed located on the north slope of Alaska, we asked if plant abundance and physiological performance are linked to hillslope position by the hydrologic processes controlling nutrient availability. Our prediction was that down slope sites and within water track sites should have the greatest nutrient availability resulting in the highest photosynthetic capacity and productivity. To examine these relationships, two transects were established in the Imnavait Creek watershed, running from the northern ridge crest to a beaded stream. In total, 16 sites, one water track (WT) and one non water track (NWT), from 8 locations, each 100 m apart were examined. At each site, soil moisture, thaw depth, canopy water status (from spectral reflectance) and species diversity were recorded. Chlorophyll fluorescence was used assess the maximum capacity of each species to transport electrons within the photosynthetic membranes of individual leaves (ETRMAX), a variable we expect to reflect both leaf N and general photosynthetic capacity. Significant differences were found within and among the major functional groups of plants growing in the watershed. In the two deciduous shrubs, Betula nana and Salix pulchra, ETRMAX generally decreased down slope but no significant difference were found between the WT and NWT sites. By contrast, ETRMAX in Rubus chamaemors, also a deciduous species, showed an initial decrease at the first two locations, but then remained constant further down slope and between WT and NWT sites. In the evergreen plants, Ledum palustre differed in that the maximum ETRMAX was found at the mid-slope locations while Vaccinium vitis-idaea had a characteristic decrease in ETRMAX down slope, with a large difference between WT and NWT at the first location. The forb Petasites frigidus displayed a unique pattern, with large difference in ETRMAX between WT and NWT at sites 4 and 5, the last two locations at which this species could be found. Finally, the only graminoid species studied, Eriophorum vaginatu, ETRMAX decrease down slope in a linear fashion and had the highest absolute ETRMAX. Additionally leaf gas-exchange was measured in Salix pulchra and leaf N and canopy reflectance was measured at each site. Together, our results demonstrate that while hillsope position has a significant effect on the physiology, growth and diversity of species, the relationships were not as hypothesized. Clearly other ecological, morphological or environmental factors are contributing to the productivity of the watershed and ultimately impacting the biogeochemistry of this important ecosystem.

Griffin, K. L.; Epstein, D. J.; Shapiro, J. B.; Boelman, N. T.; Stieglitz, M.



Shrub growth response to climate change and feedbacks of vegetation change to permafrost thaw in the Siberian arctic tundra (Invited)  

NASA Astrophysics Data System (ADS)

Background/Question/Methods The Siberian tundra is one of the key permafrost regions in the Arctic because of its large spatial extent and carbon-rich yedoma soils. Changes in permafrost thaw and concomitant carbon losses to the atmosphere can have large impacts on the global climate. Permafrost thaw is believed to strongly increase this century as a result of predicted increasing air temperature. At the same time, arctic vegetation growth and composition is predicted to respond to future climate change, which can have large implications for the stability of permafrost and can feedback to further vegetation changes. Deciduous shrubs are expected to benefit from climate warming by increasing growth and expanding their range to higher latitudes. However, observational evidence for recent increases in deciduous shrub cover in the arctic region is limited thus far to areas in Alaska. We examined if deciduous shrubs at our research site in Northeastern Siberia show a growth response to the main climate variables, temperature and precipitation. We constructed dendrochronological records for two key arctic deciduous shrub species, Betula nana and Salix pulchra, dating back roughly 60 years. The ring-width records are related to summer temperature and summer-precipitation data from the closest climate station in order to identify the main climate factor limiting shrub growth in this area. Remote sensing data are used to assess changes in panarctic vegetation productivity by vegetation type following the circumpolar arctic vegetation map (CAVM). Using a combined approach of dendrochronology and remote sensing provides the opportunity to study the vegetation response at different temporal and spatial scales. Results/Conclusions Our results indicate that growth of both Salix pulchra and Betula nana shrubs relates positively to summer temperature at our research site in Northeast Siberia. Secondary growth of both shrub species was most sensitive to early summer temperature (mid-June to mid-July). Annual shrub growth correlated positively with late-summer precipitation of the year preceding the ring formation. Panarctic vegetation productivity of the last 25 years shows a significant positive trend, especially in areas identified as shrub-dominated plant communities in the CAVM. Most climate model scenarios predict increasing summer temperature and precipitation in the arctic region. This implies that shrub growth will further increase. Finally, we present experimental evidence from a shrub removal experiment showing that shrub cover is negatively correlated with active layer thickness through shading of the soil surface. Expansion of deciduous shrubs, triggered by climate warming, may thus reduce summer permafrost thaw and partly offset the permafrost degradation expected to result from the air temperature rise predicted for the coming decades.

Blok, D.; Schaepman-Strub, G.; Sass-Klaassen, U.; Heijmans, M.; Bartholomeus, H.; Berendse, F.




PubMed Central

Distribution and occurrence of blow flies of forensic importance was performed during 2007 and 2008 in Chiang Mai and Lampang Provinces, northern Thailand. Surveys were conducted in forested areas for 30 minutes using a sweep net to collected flies attracted to a bait. A total of 2,115 blow flies belonging to six genera and 14 species were collected; Chrysomya megacephala (Fabricius) (44.7%), C. pinguis (Walker) (15.1%), C. chani Kurahashi (9.3%), C. thanomthini Kurahashi & Tumrasvin (0.3%); Achoetandrus rufifacies (Macquart) (10.5%), A. villeneuvi (Patton) (2.2%); Lucilia papuensis Macquart (2.2%), L. porphyrina (Walker) (12.4%), L. sinensis Aubertin (0.7%); Hemipyrellia ligurriens (Wiedemann) (1.3%), H. pulchra (Wiedemann) (0.1%); Hypopygiopsis infumata (Bigot) (0.6%), Hy. tumrasvini Kurahashi (0.2%) and Ceylonomyia nigripes Aubertin (0.4%). Among them, C. megacephala was the predominant species collected, particularly in the summer. The species likely to prevail in highland areas are C. pinguis, C. thanomthini, Hy. tumrasvini, L. papuensis and L. porphyrina. PMID:24626423

Moophayak, Kittikhun; Klong-Klaew, Tunwadee; Sukontason, Kom; Kurahashi, Hiromu; Tomberlin, Jeffery K.; Sukontason, Kabkaew L.



Morphological variability in tree root architecture indirectly affects coexistence among competitors in the understory.  


Interactions between plants can have strong effects on community structure and function. Variability in the morphological, developmental, physiological, and biochemical traits of plants can influence the outcome of plant interactions and thus have important ecological consequences. However, the ecological ramifications of trait variability in plants are poorly understood and have rarely been tested in the field. We experimentally tested the effects of morphological variation in root architecture of Quercus douglasii trees in the field on interactions between understory plants and community composition. Our results indicate that variability among Q. douglasii tree root systems initiates a striking reversal in the competitive effects of dominant understory grass species on a less common species. Trees with a deep-rooted morphology facilitated exotic annual grasses and these annual grasses, in turn, competitively excluded the native perennial bunchgrass, Stipapulchra. In contrast, Q. douglasii trees with shallow-rooted morphologies directly suppressed the growth of exotic annual grasses and indirectly released S. pulchra individuals from competition with these annual grasses. Morphological variation in the root architecture of Q. douglasii created substantial conditionality in the outcomes of competition among species which enhanced the potential for indirect interactions to sustain coexistence and increase community diversity. PMID:25163107

Aschehoug, Erik T; Callaway, Ragan M



Leaves of Lolium multiflorum 'Lema' and tropical tree species as biomonitors of polycyclic aromatic hydrocarbons.  


This study extends the current knowledge regarding the use of plants for the passive accumulation of anthropogenic PAHs that are present in the atmospheric total suspended particles (TSP) in the tropics and sub-tropics. It is of major relevance because the anthropic emissions of TSP containing PAHs are significant in these regions, but their monitoring is still scarce. We compared the biomonitor efficiency of Lolium multiflorum 'Lema' and tropical tree species (Tibouchina pulchra and Psidium guajava 'Paluma') that were growing in an intensely TSP-polluted site in Cubatão (SE Brazil), and established the species with the highest potential for alternative monitoring of PAHs. PAHs present in the TSP indicated that the region is impacted by various emission sources. L. multiflorum showed a greater efficiency for the accumulation of PAH compounds on their leaves than the tropical trees. The linear regression between the logBCF and logKoa revealed that L. multiflorum is an efficient biomonitor of the profile of light and heavy PAHs present in the particulate phase of the atmosphere during dry weather and mild temperatures. The grass should be used only for indicating the PAHs with higher molecular weight in warmer and wetter periods. PMID:22285658

Rinaldi, Mirian C S; Domingos, Marisa; Dias, Ana P L; Esposito, Jéssica B N; Pagliuso, Josmar D



Effects of initial climatic conditions on growth and accumulation of fluoride and nitrogen in leaves of two tropical tree species exposed to industrial air pollution.  


Saplings of Tibouchina pulchra and Psidium guajava, cultivated under standardized soil conditions, were placed in two sites at Cubatão (state of São Paulo, southeast Brazil) to study the effects of air pollution on growth, biomass allocation and foliar nitrogen and fluoride concentrations. Thirty-six potted plants were maintained over two periods of one year (Jul/00 to Jun/01; Dec/00 to Nov/01) at each of two experimental sites with distinct levels of air pollution: Pilões River Valley (PV) with vegetation virtually unaffected by air pollution; and Mogi River Valley (MV) severely affected by pollutants released mainly by chemical, fertilizer, iron and steel industries. For both species, saplings growing at MV showed alterations of growth and biomass allocation, as well as increased leaf concentrations of nitrogen and fluoride. Comparing both experimental periods, the one starting in winter (the driest season in Southeastern Brazil) seemed to affect the saplings more severely, the differences of the measured parameters between MV and PV being higher than in the second period. Multivariate analysis revealed two groups of data: one representing the MV and the other the PV saplings. For both species, saplings growing at MV showed differences in chemical composition, growth and biomass allocation, compared with the PV saplings. The results suggested that seasonal conditions of the first months of sapling exposure (summer or winter) modulate the intensity of responses to pollution stress. PMID:17289116

Furlan, Cláudia Maria; Domingos, Marisa; Salatino, Antonio



Gas exchange, growth, and chemical parameters in a native Atlantic forest tree species in polluted areas of Cubatão, Brazil.  


The Atlantic forest species near the industrial complex of Cubatão, Brazil have been subjected to heavy air pollution for decades. In this study, we used some physiological parameters (gas exchange, growth and chemical contents) to biomonitor the effects of air pollution on Tibouchina pulchra, one of the most common tree species in this forest. Under standardized conditions, saplings were exposed to the environment from April to July and from July to September of 1998, at three different sites in the vicinity of the industrial complex: the Valley of Pilões River (VP), the control area; the Valley of Mogi River (VM), near fertilizer, metallurgical, and cement industries sustaining high concentrations of fluorides, N and S oxides, and particulate materials; and Caminho do Mar (CM), near petrochemical industries under N and S oxides, photooxidants, and organic compounds. Plants exposed to CM and VM conditions presented visible injuries, reductions in net photosynthesis, growth parameters, and ascorbate concentrations, and increased F, N, and S foliar concentrations. These results indicate that the environmental conditions around these industries are still harmful to plants. PMID:12651190

Moraes, R M; Delitti, W B C; Moraes, J A P V



Revision of the genus Turris Batsch, 1789 (Gastropoda: Conoidea: Turridae) with the description of six new species  

PubMed Central

The taxonomy of the genus Turris Batsch, 1789, type genus of the family Turridae, widespread in shallow-water habitats of tropic Indo-Pacific, is revised. A total of 31 species of Turris, are here recognized as valid. New species described: Turris chaldaea, Turris clausifossata, Turris guidopoppei, Turris intercancellata, Turris kantori, T. kathiewayae. Homonym renamed: Turris bipartita nom. nov. for Pleurotoma variegata Kiener, 1839 (non Philippi, 1836). New synonymies: Turris ankaramanyensis Bozzetti, 2006 = Turris tanyspira Kilburn, 1975; Turris imperfecti, T. nobilis, T. pulchra and T. tornatum Röding, 1798, and Turris assyria Olivera, Seronay & Fedosov, 2010 = T. babylonia; Turris dollyi Olivera, 2000 = Pleurotoma crispa Lamarck, 1816; Turris totiphyllis Olivera, 2000 = Turris hidalgoi Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000; Turris kilburni Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000 = Turris pagasa Olivera, 2000; Turris (Annulaturris) munizi Vera-Peláez, Vega-Luz & Lozano-Francisco, 2000 = Gemmula lululimi Olivera, 2000. Revised status: Turris intricata Powell, 1964, Pleurotoma variegata Kiener, 1839 (non Philippi, 1836) and Pleurotoma yeddoensis Jousseaume, 1883, are regarded as full species (not subspecies of Turris crispa). Neotype designated: For Pleurotoma garnonsii Reeve, 1843, to distinguish it from Turris garnonsii of recent authors, type locality emended to Zanzibar. New combination: Turris orthopleura Kilburn, 1983, is transferred to genus Makiyamaia, family Clavatulidae. PMID:23847408

Kilburn, Richard N.; Fedosov, Alexander E.; Olivera, Baldomero M.



Species-level diversity of belowground structure in savanna woody plants  

NASA Astrophysics Data System (ADS)

Using compressed air, we excavated individual trees and shrubs and mapped their coarse root systems on a three-dimensional grid system up to 1.5 m depth. We excavated four woody savanna species at three sites spanning a climate gradient on the Kalahari Transect in southern Africa. Overall, species was more important than site in determining both large-scale and small-scale root system structure. The species excavated fell into two groups that coexisted across the climate gradient. Acacia mellifera and Terminalia sericea had straight roots in a laterally-extensive and relatively shallow system. Boscia albitrunca and Ochna pulchra had sinuous roots that were mostly concentrated beneath the canopy and were more prevalent in deep than near-surface soil layers, departing from the conventional model of decreasing root abundance with depth. The shallow-rooted species had small taproots, though it is unlikely that they reached the water table. Deep- and shallow-rootedness appear to correlate with other characteristics such as growth form (tree or shrub) and drought deciduousness. Acacia mellifera Boscia albitrunca

O'Donnell, F. C.; Caylor, K. K.; Bhattachan, A.; Dintwe, K.; D'Odorico, P.; Okin, G. S.



2(5H)-Furanone, epigallocatechin gallate, and a citric-based disinfectant disturb quorum-sensing activity and reduce motility and biofilm formation of Campylobacter jejuni.  


Brominated furanone and epigallocatechin gallate (EGCG) are naturally occurring polyphenolic compounds that can be derived from sources such as Delisea pulchra algae and green tea, respectively. These compounds may have potential health benefits and antimicrobial properties. Biofilm formation and bacterial motility are virulence factors that seem to be involved in the autoinducer 2 (AI-2)-mediated quorum sensing (QS) response of Campylobacter. In this study, the anti-QS activities of 2(5H)-furanone, EGCG, and a citric-based disinfectant were tested against Campylobacter jejuni. The minimal bactericidal concentration (MBC) was determined by a microdilution method, and the AI-2 activity was measured by bioluminescence. For motility tests, subinhibitory concentrations of each compound were mixed with semisolid Muller Hinton agar. Biofilm formation was quantified in broth-containing microplates after staining with safranin. The MBC of tested compounds ranged from 0.3 to 310 ?g/mL. Subinhibitory concentrations of all of the antimicrobial compounds significantly decreased (19 to 62 %) the bacterial motility and reduced biofilm formation. After treatment with EGCG, furanone, and the disinfectant, AI-2 activity was decreased by 60 to 99 % compared to control. In conclusion, 2(5H)-furanone, EGCG, and the disinfectant exert bactericidal effects against C. jejuni and disturb QS activity and reduce motility and biofilm formation. These compounds may be naturally occurring alternatives to control C. jejuni. PMID:25231135

Castillo, Sandra; Heredia, Norma; García, Santos



A new species of Moennigia (Trichostrongylina: Molineidae) a parasite of Chaetophractus spp. (Xenarthra: Dasypodidae) from Argentina.  


Moennigia celinae n. sp. collected from the small intestine of Chaetophractus vellerosus and Chaetophractus villosus (Xenarthra, Dasypodidae) from Argentina is herein described. This new species belongs to the genus Moennigia because it possesses a short uterus with few eggs, atrophied distal branch of the ovejector, vulva near the anus, and a conical tail. The new species has a synlophe with 17 symmetrical ridges and slight ventro-dorsal orientation. The spicule length:body length ratio is similar to that of the other species parasitic of Dasypodidae; however, Moennigia celinae n. sp. differs from Moennigia pintoi and Moennigia lutzi because the latter lack a gubernaculum, and from Moennigia complexus, Moennigia moennigi, Moennigia filamentosus, Moennigia intrusa, Moennigia littlei, Moennigia pulchra and Moennigia dessetae by the latter having very complex spicules with 2 or 3 points at the distal extremity. Moreover, Moennigia celinae n. sp. differs from Moennigia virilis by the length and shape of its spicules. Moennigia celinae n. sp. can be distinguished from Moennigia travassosi by the shape of the dorsal ray of the caudal bursa. Moennigia celinae n. sp. resembles Moennigia pseudopulchra but the gubernaculum of the latter is V-shaped. This is the second report of a species of Moennigia in Argentina and the first for the genus Chaetophractus. PMID:24552210

Ezquiaga, María C; Navone, Graciela T



Revision, cladistic analysis and biogeography of Typhochlaena C. L. Koch, 1850, Pachistopelma Pocock, 1901 and Iridopelma Pocock, 1901 (Araneae, Theraphosidae, Aviculariinae).  


Three aviculariine genera endemic to Brazil are revised. Typhochlaena C. L. Koch, 1850 is resurrected, including five species; Pachistopelma Pocock, 1901 includes two species; and Iridopelma Pocock, 1901, six species. Nine species are newly described: Typhochlaena ammasp. n., Typhochlaena costaesp. n., Typhochlaena curumimsp. n., Typhochlaena paschoalisp. n., Pachistopelma bromelicolasp. n., Iridopelma katiaesp. n., Iridopelma marcoisp. n., Iridopelma oliveiraisp. n. and Iridopelma vaninisp. n. Three new synonymies are established: Avicularia pulchra Mello-Leitão, 1933 and Avicularia recifiensis Struchen & Brändle, 1996 are junior synonyms of Pachistopelma rufonigrum Pocock, 1901 syn. n., and Avicularia palmicola Mello-Leitão, 1945 is a junior synonym of Iridopelma hirsutum Pocock, 1901 syn. n.Pachistopelma concolor Caporiacco, 1947 is transferred to Tapinauchenius Ausserer, 1871, making the new combination Tapinauchenius concolor (Caporiacco, 1947)comb. n. Lectotypes are newly designed for Pachistopelma rufonigrum Pocock, 1901 , Iridopelma hirsutum Pocock, 1901 and Pachistopelma concolor Caporiacco, 1947. Cladistic analyses using both equal and implied weights were carried out with a matrix comprising 62 characters and 38 terminal taxa. The chosen cladogram found with X-Pee-Wee and concavity 6 suggests they are monophyletic. All species are keyed and mapped and information on species habitat and area cladograms are presented. Discussion on biogeography and conservation is provided. PMID:23166476

Bertani, Rogério



Biogeochemical characterization of an undisturbed highly acidic, metal-rich bryophyte habitat, east-central Alaska, U.S.A.  

USGS Publications Warehouse

We report on the geochemistry of soil and bryophyte-laden sediment and on the biogeochemistry of willows growing in an undisturbed volcanogenic massive sulfide deposit in the Alaska Range ecoregion of east-central Alaska. We also describe an unusual bryophyte assemblage found growing in the acidic metal-rich waters that drain the area. Ferricrete-cemented silty alluvial sediments within seeps and streams are covered with the liverwort Gymnocolea inflata whereas the mosses Polytrichum commune and P. juniperinum inhabit the area adjacent to the water and within the splash zone. Both the liverwort-encrusted sediment and Polytrichum thalli have high concentrations of major and trace metal cations (e.g., Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do not reflect the geochemical signature of the mineral deposit and we postulate they are influenced by the chemistry of eolian sediments derived from outside the deposit area. The willow, Salix pulchra, growing mostly within and adjacent to the larger streams, has much higher concentrations of Al, As, Cd, Cr, Fe, La, Pb, and Zn when compared to the same species collected in non-mineralized areas of Alaska. The Cd levels are especially high and are shown to exceed, by an order of magnitude, levels demonstrated to be toxic to ptarmigan in Colorado. Willow, growing in this naturally occurring metal-rich Red Mountain alteration zone, may adversely affect the health of browsing animals. ?? 2006 Regents of the University of Colorado.

Gough, L.P.; Eppinger, R.G.; Briggs, P.H.; Giles, S.



?-Alkylidene-?-lactones and isobutylpyrrol-2(5H)-ones analogues to rubrolides as inhibitors of biofilm formation by gram-positive and gram-negative bacteria.  


Several molecules have been discovered that interfere with formation of bacterial biofilms, opening a new strategy for the development of more efficient treatments in case of antibiotic resistant bacteria. Amongst the most active compounds are some natural brominated furanones from marine algae Delisea pulchra that have proven to be able to control pathogenic biofilms. We have recently reported that some rubrolide analogues are able to inhibit biofilm formation of Enterococcus faecalis. In the present Letter we describe results of the biological evaluation of a small library of 28 compounds including brominated furanones and the corresponding lactams against biofilm formation of Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus epidermidis and Streptococcus mutans. Our results showed that in general these compounds were more active against biofilms of S. epidermidis and P. aeruginosa, with little or no inhibition of planktonic bacterial growth. In some cases they were able to prevent biofilm formation of P. aeruginosa at concentrations as low as 0.6 ?g/mL (1.3 ?M, compound 3d) and 0.7 ?g/mL (1.3 ?M, 3f). Results also indicate that, in general, lactams are more active against biofilms than their precursors, thus designating this class of molecules as good candidates for the development of a new generation of antimicrobial drugs targeted to biofilm inhibition. PMID:24484899

Pereira, Ulisses A; Barbosa, Luiz C A; Maltha, Célia R A; Demuner, Antônio J; Masood, Mohammed A; Pimenta, Andréa L



Examining vertical patterns in Arctic tundra shrub canopies: Implications for carbon cycling in a changing environment  

NASA Astrophysics Data System (ADS)

Climate change is facilitating the northward encroachment and expansion of woody shrub species into the Arctic tundra, which in turn is altering a number of physical and biogeochemical processes that are likely to affect how carbon is cycled in this region. Greater shrub presence also increases leaf area index and canopy complexity in the tundra, introducing the potential for vertical variation in nitrogen, photosynthesis, and respiration through the canopy. For these reasons, Arctic tundra shrub communities represent an ecologically relevant case study for investigating carbon cycling-nitrogen relationships and testing optimization models. Here, we measured photosynthesis, respiration in the dark and light, the light inhibition of respiration, stomatal conductance, leaf nitrogen, and related leaf traits at different heights representing variation in light availability in multiple Arctic Alaskan shrub communities dominated by Salix pulchra and Betula nana to examine if the relatively low-stature canopies exhibit vertical patterns. Highest rates of photosynthesis and respiration (P < 0.0001) were observed at the top of the canopy, suggesting substrate-limitation of respiration at lower, more shaded canopy levels. Leaves at the top of the canopy also exhibited the lowest inhibition of respiration by light (NS), and the highest nitrogen concentrations. (P < 0.05) implying a relationship between photosynthesis, nitrogen, and a relaxation of light-inhibition to optimize metabolic efficiency. Data from this study was also used to test leaf-level and canopy nitrogen optimization models. These data emphasize the need to include canopy complexity in tundra carbon models, as neglecting physiological differences through a canopy may lead to an underestimation of stored carbon.

Heskel, M.; Atkin, O.; Turnbull, M.; Rastetter, E.; Griffin, K. L.



Long-term deeper snow causes changes in litter quality, soil C and N storage in moist acidic tundra in Northern Alaska  

NASA Astrophysics Data System (ADS)

Tundra ecosystems store over one third of the global terrestrial organic C pool and have the potential to release large amounts of CO2 as organic matter decomposition is expected to increase as climate warms and precipitation changes. However, a warming climate and increased snow pack soil thermal insulation is expected to shift dominant vegetative cover type affecting above and below ground litter quality, soil organic matter storage depth, and decomposition rates in respective soils. These changes can affect the magnitude and even direction of soil C storage in the Arctic tundra.. At a sixteen-year snow fence experiment at Toolik Lake, as part of the International Tundra Experiment (ITEX), increased snow pack resulted in a shift from a Sphagnum moss-dominated mixed graminoid-deciduous ecosystem (moist tussock tundra) to one covered largely by deciduous shrubs and Carex in more water-saturated soil conditions. We investigated relationships between shifting dominance of plant species and impacts to soils using a multiproxy isotope and biomarker approach in plants and soils from the areas with control, deep, intermediate, and low snow pack. A comparison of the same plant species (Betula nana, Carex bigelowii, Eriophorum vaginatum, Salix pulchra, and Sphagnum spp.) along the snow zones showed leaf tissue C-to-N ratio decreasing in the deep snow areas when compared to control and low snow pack areas, driven by an increase in plant N content. Root and stem tissue was impacted similarly across the experimental treatments. Changes in soil ?13C and ?15N values with depth and along the transect demonstrate impacts to C and N cycling. These results demonstrate litter quality and soil carbon storage feedbacks in response to snow pack thermal insulation that could influence litter accumulation, decay rates and the chemical nature of soil carbon under climate conditions with deeper snow in winter.

Miller, O.; Xu, D.; Gonzalez-Meler, M. A.; Welker, J. M.; Filley, T. R.



Stage-dependent border cell and carbon flow from roots to rhizosphere.  


Rising CO(2) levels in the atmosphere have drawn attention to the important role of soil in sequestering carbon. This project goal was to quantify soil carbon deposition associated with border cell release and exudation from root growth zones. Carbon was measured with a Carlo Erba C/N analyzer in soil from the rhizosphere of mature grasses and, in separate experiments, in soil collected around root growth zones. Root border cells in "rhizosphere soil" (silica sand) were counted using a compound microscope after soil sonication and extraction with surfactant. For sand-grown Bromus carinatus, Zea mays, and Cucumis sativus, young seedlings (with roots shorter than 2 cm) released thousands of border cells, while older root tips released only hundreds. For a variety of native annual and perennial grasses and invasive annual grasses (Nassella pulchra, B. carinatus, B. diandrus, B. hordeaceus, Vulpia microstachys, Aegilops triuncialis, Lolium multiflorum, Zea mays), the rhizosphere of mature root systems contained between 18 and 32 ?g C g(-1) sand more than that of the unplanted controls. Spatial analysis of the rhizosphere around the cucumber growth zone confirmed C enrichment there. The root tip provided C to the rhizosphere: 4.6 ?g C in front of the growing tip, with the largest deposition, 20.4 ?g C, to the rhizosphere surrounding the apical 3 mm (root cap/meristem). These numbers from laboratory studies represent the maximum C that might be released during flooding in soils. Scaling up from the organ scale to the field requires a growth analysis to quantify root tip distributions in space and time. PMID:21632368

Odell, Ryan E; Dumlao, Matthew R; Samar, Danial; Silk, Wendy K



Furanone at Subinhibitory Concentrations Enhances Staphylococcal Biofilm Formation by luxS Repression ?  

PubMed Central

Brominated furanones from marine algae inhibit multicellular behaviors of gram-negative bacteria such as biofilm formation and quorum sensing (QS) without affecting their growth. The interaction of furanone with QS in gram-positive bacteria is unknown. Staphylococci have two QS systems, agr and luxS, which lower biofilm formation by two different pathways, RNAIII upregulation and bacterial detachment, and polysaccharide intercellular adhesin (PIA) reduction, respectively. We synthesized natural furanone compound 2 [(5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone] from Delisea pulchra and three analogues to investigate their effect on biofilm formation in gram-positive bacteria. Compound 2, but not the analogues, enhanced the biofilms of Staphylococcus epidermidis 1457 and 047 and of S. aureus Newman at concentrations between 1.25 and 20 ?M. We show the growth inhibition of S. epidermidis and S. aureus by free furanone and demonstrate bactericidal activity. An induction of biofilm occurred at concentrations of 10 to 20% of the MIC and correlated with an increase in PIA. The biofilm effect was agr independent. It was due to interference with luxS, as shown by reduced luxS expression in the presence of compound 2 and independence of the strong biofilm formation in a luxS mutant upon furanone addition. Poly(l-lysine)-grafted/poly(ethylene glycol)-grafted furanone was ineffective on biofilm and not bactericidal, indicating the necessity for free furanone. Free furanone was similarly toxic for murine fibroblasts as for staphylococci, excluding a therapeutic application of this compound. In summary, we observed a biofilm enhancement by furanone in staphylococci at subinhibitory concentrations, which was manifested by an increase in PIA and dependent on luxS. PMID:19620329

Kuehl, Richard; Al-Bataineh, Sameer; Gordon, Oliver; Luginbuehl, Reto; Otto, Michael; Textor, Marcus; Landmann, Regine



The Genera of Fungi: fixing the application of type species of generic names.  


To ensure a stable platform for fungal taxonomy, it is of paramount importance that the genetic application of generic names be based on their DNA sequence data, and wherever possible, not morphology or ecology alone. To facilitate this process, a new database, accessible at (GoF) was established, which will allow deposition of metadata linked to holo-, lecto-, neo- or epitype specimens, cultures and DNA sequence data of the type species of genera. Although there are presently more than 18 000 fungal genera described, we aim to initially focus on the subset of names that have been placed on the "Without-prejudice List of Protected Generic Names of Fungi" (see IMA Fungus 4(2): 381-443, 2013). To enable the global mycological community to keep track of typification events and avoid duplication, special MycoBank Typification identfiers (MBT) will be issued upon deposit of metadata in MycoBank. MycoBank is linked to GoF, thus deposited metadata of generic type species will be displayed in GoF (and vice versa), but will also be linked to Index Fungorum (IF) and the curated RefSeq Targeted Loci (RTL) database in GenBank at the National Center for Biotechnology Information (NCBI). This initial paper focuses on eight genera of appendaged coelomycetes, the type species of which are neo- or epitypified here: Bartalinia (Bartalinia robillardoides; Amphisphaeriaceae, Xylariales), Chaetospermum (Chaetospermum chaetosporum, incertae sedis, Sebacinales), Coniella (Coniella fragariae, Schizoparmaceae, Diaporthales), Crinitospora (Crinitospora pulchra, Melanconidaceae, Diaporthales), Eleutheromyces (Eleutheromyces subulatus, Helotiales), Kellermania (Kellermania yuccigena, Planistromataceae, Botryosphaeriales), Mastigosporium (Mastigosporium album, Helotiales), and Mycotribulus (Mycotribulus mirabilis, Agaricales). Authors interested in contributing accounts of individual genera to larger multi-authored papers to be published in IMA Fungus, should contact the associate editors listed below for the major groups of fungi on the List of Protected Generic Names for Fungi. PMID:25083414

Crous, Pedro W; Giraldo, Alejandra; Hawksworth, David L; Robert, Vincent; Kirk, Paul M; Guarro, Josep; Robbertse, Barbara; Schoch, Conrad L; Damm, Ulrike; Trakunyingcharoen, Thippawan; Groenewald, Johannes Z



Increasing leaf temperature reduces the suppression of isoprene emission by elevated CO? concentration.  


Including algorithms to account for the suppression of isoprene emission by elevated CO2 concentration affects estimates of global isoprene emission for future climate change scenarios. In this study, leaf-level measurements of isoprene emission were made to determine the short-term interactive effect of leaf temperature and CO2 concentration. For both greenhouse plants and plants grown under field conditions, the suppression of isoprene emission was reduced by increasing leaf temperature. For each of the four different tree species investigated, aspen (Populus tremuloides Michx.), cottonwood (Populus deltoides W. Bartram ex Marshall), red oak (Quercus rubra L.), and tundra dwarf willow (Salix pulchra Cham.), the suppression of isoprene by elevated CO2 was eliminated at increased temperature, and the maximum temperature where suppression was observed ranged from 25 to 35°C. Hypotheses proposed to explain the short-term suppression of isoprene emission by increased CO2 concentration were tested against this observation. Hypotheses related to cofactors in the methylerythritol phosphate (MEP) pathway were consistent with reduced suppression at elevated leaf temperature. Also, reduced solubility of CO2 with increased temperature can explain the reduced suppression for the phosphoenolpyruvate (PEP) carboxylase competition hypothesis. Some global models of isoprene emission include the short-term suppression effect, and should be modified to include the observed interaction. If these results are consistent at longer timescales, there are implications for predicting future global isoprene emission budgets and the reduced suppression at increased temperature could explain some of the variable responses observed in long-term CO2 exposure experiments. PMID:24614154

Potosnak, Mark J; Lestourgeon, Lauren; Nunez, Othon



Experimental biological effects assessment associated with on-shore brine discharge from the creation of gas storage caverns  

NASA Astrophysics Data System (ADS)

Most of the studies on biological and ecological effects associated with brine discharge into the marine environment are related to the operation of desalination plants, for the production of freshwater. In this study we analysed the biological effects of a brine effluent from a completely different source, produced from the lixiviation of rock salt caves, for the creation of natural gas storage caverns. Lethal and sub-lethal endpoints following exposure to the brine were studied in a range of macrofauna species characteristic of the soft and hard bottom habitats in the vicinity of the discharge area, namely the isopod Eurydice pulchra, the annelids Sabellaria alveolata and Ophelia radiata, the sea-urchin Paracentrotus lividus and the bivalve Mytilus galloprovincialis. In a first series of experiments, brine, with salinity above 300, was diluted in distilled water to a salinity value close to that of the seawater in the discharge area (salinity 36) and, surprisingly, none of the exposed species was able to survive or develop into viable larvae. A second series of experiments exposed the species to brine diluted with seawater, simulating more realistic discharge circumstances. All the tested species at all the measured endpoints (adult survival, larval abnormal development, sperm fertilization success) showed negative biological effects in brine solutes always at a lower salinity than that of a salinity control obtained with concentrated seawater. The sub-lethal experiments with larval development of P. lividus, S. alveolata and M. galloprovincialis, and the fertilization success of P. lividus gave EC 50 values for the brine solute with salinity in the range of 40.9-43.5, whereas the EC 50 values for the concentrated seawater were in the range of salinity 44.2-49.0. It is hypothesised that differences in the ionic composition of the brine cause the inability of the species to tolerate the exposure to brine.

Quintino, Victor; Rodrigues, Ana Maria; Freitas, Rosa; Ré, Ana



The effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone on the pressure overload-induced progression of cardiac hypertrophy to cardiac failure.  


We investigated the effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC), which was isolated from the roots of Millettia pulchra (Benth.) Kurz var. Laxior (Dunn) Z.Wei (Papilionaceae) (MKL), on the progression of cardiac hypertrophy to failure in a rat model of abdominal aortic banding (AAB)-induced pressure overloading. Endothelial dysfunction is central to pressure overload-induced cardiac hypertrophy and failure. It would be useful to clarify whether MHBFC could prevent this dysfunction. The effects of pressure overload were assessed in male Sprague-Dawley rats 6 weeks after AAB using the progression of cardiac hypertrophy to heart failure as the endpoint. The AAB-treated rats exhibited a greater progression to heart failure and had significantly elevated blood pressure, systolic and diastolic cardiac dysfunction, and evidence of left ventricular hypertrophy (LVH). LVH was characterized by increases in the ratios of heart and left ventricular weights to body weight, increased myocyte cross-sectional areas, myocardial and perivascular fibrosis, and elevated cardiac hydroxyproline. These symptoms could be prevented by treatment with MHBFC at daily oral doses of 6 and 12 mg/kg for 6 weeks. The progression to cardiac failure, which was demonstrated by increases in relative lung and right ventricular weights, cardiac function disorders and overexpression of atrial natriuretic peptide (ANP) mRNA, could also be prevented. Furthermore, MHBFC partialy rescued the downregulated nitric oxide signaling system, whereas inhibited the upregulated endothelin signaling system, normalizing the balance between these two systems. MHBFC protected the endothelium and prevented the pressure overload-induced progression of cardiac hypertrophy to cardiac failure. PMID:24622486

Huang, Jianchun; Tang, XiaoJun; Liang, Xingmei; Wen, Qingwei; Zhang, Shijun; Xuan, Feifei; Jian, Jie; Lin, Xing; Huang, Renbin



Differential Gene Expression To Investigate the Effect of (5Z)-4-Bromo- 5-(Bromomethylene)-3-Butyl-2(5H)-Furanone on Bacillus subtilis  

PubMed Central

(5Z)-4-Bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone (furanone) from the red marine alga Delisea pulchra was found previously to inhibit the growth, swarming, and biofilm formation of gram-positive bacteria. Using the gram-positive bacterium Bacillus subtilis as a test organism, we observed cell killing by 20 ?g of furanone per ml, while 5 ?g of furanone per ml inhibited growth approximately twofold without killing the cells. To discover the mechanism of this inhibition on a genetic level and to investigate furanone as a novel antibiotic, full-genome DNA microarrays were used to analyze the gene expression profiles of B. subtilis grown with and without 5 ?g of furanone per ml. This agent induced 92 genes more than fivefold (P < 0.05) and repressed 15 genes more than fivefold (P < 0.05). The induced genes include genes involved in stress responses (such as the class III heat shock genes clpC, clpE, and ctsR and the class I heat shock genes groES, but no class II or IV heat shock genes), fatty acid biosynthesis, lichenan degradation, transport, and metabolism, as well as 59 genes with unknown functions. The microarray results for four genes were confirmed by RNA dot blotting. Mutation of a stress response gene, clpC, caused B. subtilis to be much more sensitive to 5 ?g of furanone per ml (there was no growth in 8 h, while the wild-type strain grew to the stationary phase in 8 h) and confirmed the importance of the induction of this gene as identified by the microarray analysis. PMID:15294834

Ren, Dacheng; Bedzyk, Laura A.; Setlow, Peter; England, Dacre F.; Kjelleberg, Staffan; Thomas, Stuart M.; Ye, Rick W.; Wood, Thomas K.



Inferring extinction of mammals from sighting records, threats, and biological traits.  


For species with five or more sightings, quantitative techniques exist to test whether a species is extinct on the basis of distribution of sightings. However, 70% of purportedly extinct mammals are known from fewer than five sightings, and such models do not include some important indicators of the likelihood of extinction such as threats, biological traits, search effort, and demography. Previously, we developed a quantitative method that we based on species' traits in which we used Cox proportional hazards regression to calculate the probability of rediscovery of species regarded as extinct. Here, we used two versions of the Cox regression model to determine the probability of extinction in purportedly extinct mammals and compared the results of these two models with those of stationary Poisson, nonparametric, and Weibull sighting-distribution models. For mammals with five or more sightings, the stationary Poisson model categorized all but two critically endangered (flagged as possibly extinct) species in our data set as extinct, and results with this model were consistent with current categories of the International Union for the Conservation of Nature. The scores of probability of rediscovery for individual species in one version of our Cox regression model were correlated with scores assigned by the stationary Poisson model. Thus, we used this Cox regression model to determine the probability of extinction of mammals with sparse records. On the basis of the Cox regression model, the most likely mammals to be rediscovered were the Montane monkey-faced bat (Pteralopex pulchra), Armenian myotis (Myotis hajastanicus), Alcorn's pocket gopher (Pappogeomys alcorni), and Wimmer's shrew (Crocidura wimmeri). The Cox model categorized two species that have recently disappeared as extinct: the baiji (Lipotes vexillifer) and the Christmas Island pipistrelle (Pipistrellus murrayi). Our new method can be used to test whether species with few records or recent last-sighting dates are likely to be extinct. PMID:22136403

Fisher, Diana O; Blomberg, Simon P



The Effects of 17-Methoxyl-7-Hydroxy-Benzene-Furanchalcone on the Pressure Overload-Induced Progression of Cardiac Hypertrophy to Cardiac Failure  

PubMed Central

We investigated the effects of 17-methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC), which was isolated from the roots of Millettia pulchra (Benth.) Kurz var. Laxior (Dunn) Z.Wei (Papilionaceae) (MKL), on the progression of cardiac hypertrophy to failure in a rat model of abdominal aortic banding (AAB)-induced pressure overloading. Endothelial dysfunction is central to pressure overload-induced cardiac hypertrophy and failure. It would be useful to clarify whether MHBFC could prevent this dysfunction. The effects of pressure overload were assessed in male Sprague–Dawley rats 6 weeks after AAB using the progression of cardiac hypertrophy to heart failure as the endpoint. The AAB-treated rats exhibited a greater progression to heart failure and had significantly elevated blood pressure, systolic and diastolic cardiac dysfunction, and evidence of left ventricular hypertrophy (LVH). LVH was characterized by increases in the ratios of heart and left ventricular weights to body weight, increased myocyte cross-sectional areas, myocardial and perivascular fibrosis, and elevated cardiac hydroxyproline. These symptoms could be prevented by treatment with MHBFC at daily oral doses of 6 and 12 mg/kg for 6 weeks. The progression to cardiac failure, which was demonstrated by increases in relative lung and right ventricular weights, cardiac function disorders and overexpression of atrial natriuretic peptide (ANP) mRNA, could also be prevented. Furthermore, MHBFC partialy rescued the downregulated nitric oxide signaling system, whereas inhibited the upregulated endothelin signaling system, normalizing the balance between these two systems. MHBFC protected the endothelium and prevented the pressure overload-induced progression of cardiac hypertrophy to cardiac failure. PMID:24622486

Liang, Xingmei; Wen, Qingwei; Zhang, Shijun; Xuan, Feifei; Jian, Jie; Lin, Xing; Huang, Renbin



Effects of increased snow on growth response and allocation patterns of arctic plants  

NASA Astrophysics Data System (ADS)

Warming in the Arctic has led to an increase in shrub cover on the tundra that has been well documented in arctic Alaska. Fall and winter precipitation are also predicted to increase in arctic regions under continued climate change, resulting in greater snow depths and insulating winter soil, thus facilitating overwinter nitrogen mineralization by microbes. We predict that this increased microbial activity will enhance plant growth because more nutrients will be available for plant uptake at spring thaw. We studied the effect of increased snow on plant growth and nutrient allocation patterns using snow fences located across a gradient of shrub height and density at Toolik Field Station on the north slope of Alaska's Brooks Range. We compared growth and nutrient content of deciduous shrubs, evergreen shrubs, and graminoids on either side of the fences. Species behaved individualistically, with some showing increased growth with snow addition, others showing decreased growth, and some showing no effect of snow at all. The biggest increases in growth were seen in deciduous shrubs, particularly Salix pulchra, due to increases in secondary, or radial, growth which allowed plants to support more branches and thus more leaves. This provides a preliminary mechanistic explanation for the widespread increase in shrub cover across the northern latitudes. In addition, species that experienced increases in biomass due to snow also generally displayed increased nitrogen and carbon content in both leaves and stems, indicating that plants which got bigger were also better able to capture available resources. We conclude that faster growing species with the ability to respond rapidly to changes in nutrient availability will likely dominate under continued climate change, and may alter important ecosystem processes such as carbon and nitrogen storage.

Addis, C. E.; Bret-Harte, M. S.



Unusually high food availability in Kaikoura Canyon linked to distinct deep-sea nematode community  

NASA Astrophysics Data System (ADS)

Kaikoura Canyon, on the eastern New Zealand continental margin, is the most productive, non-chemosynthetic deep-sea habitat described to date, with megafaunal biomass 100-fold higher than those of other deep-sea habitats. The present study, which focused on free-living nematodes, provides the first comparison of faunal community structure and diversity between Kaikoura Canyon and nearby open slope habitats. Results show substantially higher food availability in the canyon relative to open slope sediments, which probably reflects greater levels of primary productivity above the canyon, coupled with downwelling and/or topographically-induced channelling, which serves to concentrate surface-derived organic matter along the canyon axis. This high food availability appears to be responsible for the elevated nematode biomass in Kaikoura Canyon, with values exceeding all published nematode biomass data from canyons elsewhere. There was also markedly lower local species diversity of nematodes inside the canyon relative to the open slope habitat, as well as a distinct community structure. The canyon community was dominated by species, such as Sabateria pulchra, which were absent from the open slope and are typically associated with highly eutrophic and/or disturbed environments. The presence of these taxa, as well as the low observed diversity, is likely to reflect the high food availability, and potentially the high levels of physically and biologically induced disturbance within the canyon. Kaikoura Canyon is a relatively small habitat characterised by different environmental conditions that makes a disproportionate contribution to deep-sea diversity in the region, despite its low species richness.

Leduc, D.; Rowden, A. A.; Nodder, S. D.; Berkenbusch, K.; Probert, P. K.; Hadfield, M. G.



High resolution records of upwelling and tropical incursions of the of Gulf of California during the past 1,600 years: diatom and silicoflagellate proxy data  

NASA Astrophysics Data System (ADS)

High-resolution upwelling records of the past 1,600 years are compared in a north-south transect (28 deg. N to 24 deg. N) of three cores from the eastern slopes of the Guaymas, Carmen, and Pescadero Basins of the Gulf of California. Evenly-spaced samples were collected from varved sediments in each core. Resolution ranges from ca.16 yr to ca. 37 yr. Diatoms and silicoflagellates capture the seasonal variation between a late fall to early spring upwelling period of high biosiliceous productivity, that is driven by northwest winds, and a summer period of warmer, more stratified waters during which these winds slacken and/or reverse direction. Northward incursions of tropical waters, which today are strongest during intense El Niño years, are recorded by increased numbers of Azpeitia nodulifera, a tropical diatom. Enhanced northward incursions of tropical waters, alternating with periods of increased late winter to early spring upwelling (indicated by abundant Octactis pulchra, a silicoflagellate), are recorded in regularly-spaced cycles of ca. 100 yr duration (possible solar cycles) between 400 A.D. and ca. 1700 A.D. in the Carmen Basin core, NH01-21 (26.3 deg. N). Disappearance of these cycles during the past ca. 200 yr may be indicative of changing surface water conditions in the modern Gulf of California. Azpeitia nodulifera records in northern core BAM80 E17 (27.9 deg. N), are evidence that the most intense of these tropical incursions appears to have occurred between ca. 940 A.D. and 1000 A.D., during the early part of the Medieval Warm Period and corresponding with the onset of expanded building in Chaco Canyon (New Mexico) by the Anasazi people. In the modern Gulf, a strong relationship exists between warmer SST in the northern Gulf and intensified monsoonal conditions in Arizona and New Mexico. We propose that a period of increased regularity of summer rains between ca. 940 A.D. and 1000 A.D would have benefited the Anasazi. Core NH01-26 (24.3 deg. N) near the mouth of the Gulf is dominated by tropical silicoflagellates and by Cyclotella spp., a diatom that indicates warm, stratified conditions. Between ca. 1280 A.D. and ca. 1820 A.D., however, Roperia tesselata, a diatom associated with enhanced late fall to early winter production in the central Gulf, becomes an important component of the diatom assemblages. Abundance cycles of R. tesselata approximate 60 yr. and may be indicative of Pacific Decadal Oscillation (PDO).

Barron, J. A.; Bukry, D.



Solar forcing of Gulf of California climate during the past 2000??yr suggested by diatoms and silicoflagellates  

USGS Publications Warehouse

High-resolution records of the past 2000??yr are compared in a north-south transect (28?? N to 24?? N) of three cores from the eastern slopes of the Guaymas, Carmen, and Pescadero Basins of the Gulf of California (hereafter referred to as the "Gulf"). Evenly-spaced samples from the varved sediments in each core allow sample resolution ranging from ?????16 to ?????37??yr. Diatoms and silicoflagellates capture the seasonal variation between a late fall to early spring period of high biosiliceous productivity, that is driven by northwest winds, and a summer period of warmer, more stratified waters during which these winds slacken and/or reverse direction (monsoonal flow). As these winds decrease, tropical waters enter the Gulf and spread northward. Individual samples represent a composite of 7 to 23??yr of deposition and are assumed to record the relative dominance of the winter vs. summer floral components. Intervals of enhanced summer incursion of tropical waters, alternating with periods of increased late fall to early spring biosiliceous productivity are recorded in all three cores. Regularly spaced cycles (?????100??yr duration) of Octactis pulchra, a silicoflagellate proxy for lower SST and high productivity, and Azpeitia nodulifera, a tropical diatom, occur between ?????A.D. 400 and ?????1700 in the more nearshore Carmen Basin core, NH01-21 (26.3?? N), suggesting a possible solar influence on coastal upwelling. Cores BAM80 E-17 (27.9?? N) and NH01-26 (24.3?? N) contain longer-duration cycles of diatoms and silicoflagellates. The early part of Medieval Climate Anomaly (?????A.D. 900 to 1200) is characterized by two periods of reduced productivity (warmer SST) with an intervening high productivity (cool) interval centered at ?????A.D. 1050. Reduced productivity and higher SST also characterize the record of the last ?????100 to 200??yr in these cores. Solar variability appears to be driving productivity cycles, as intervals of increased radiocarbon production (sunspot minima) correlate with intervals of enhanced productivity. It is proposed that increased winter cooling of the atmosphere above southwest U.S. during sunspot minima causes intensification of the northwest winds that blow down the Gulf during the late fall to early spring, leading to intensified overturn of surface waters and enhanced productivity. A new silicoflagellate species, Dictyocha franshepardii Bukry, is described and illustrated. ?? 2006 Elsevier B.V. All rights reserved.

Barron, J.A.; Bukry, D.



Assessing seedbank recruitment windows of opportunity in thaw slump thermokarsts  

NASA Astrophysics Data System (ADS)

Tall shrub thickets (>1m) of birch and willow have been observed in stabilized lobes of thaw slump thermokarsts (gullies cause by thawed permafrost) in the Low Arctic near Toolik Lake, Alaska. We tested whether there are differences in seedling recruitment and establishment in thermokarsts vs outside the disturbance by comparing in-situ seedling presence, greenhouse germination of natural seedbanks, and cohort age groups of willow (Salix spp.) and birch in two 50m transects sampled in thermokarst lobes of different age: one young lobe of 7 y.a. at Lake NE-14, and one older lobe of 22 y.a. at Lake I-minus 1 vs. two transects outside the lobes. Young thermokarsts may provide germination windows of opportunity for fast growing species like graminoids and deciduous shrubs. In-situ seedling observations generally agreed with expectations. Fifteen times as many live seedlings were observed in the young lobe vs. outside, composed mainly of graminoids and willows, and five times more seedlings were observed inside the older lobe vs. outside, including 25% birch. Germination trials of seedbanks, as expected, showed a reverse trend. The smaller seedbanks in the young lobe had far fewer germinants than outside: over 49 times more seedlings germinated in the outside seedbank compared to the thermokarst, and were composed mainly of longer-lived evergreen shrubs in the genera Ledum and Rhododendron. The older lobe, by contrast, showed seven times greater germination than outside and was composed mainly of graminoids. Birch made up only 5%, reflecting variation in species composition between sites. ANOVA of seedbank germination across sites showed unit increase in number of germinated seeds was negatively correlated to percent cover of bare soil, positively correlated to the amount of organic matter present in the surface soil as reflected in sample volume, and positively correlated to thaw depth. Reverse trends in germination trials vs. presence of live seedlings may be explained by lower seedbank quality but higher recruitment in younger lobes due to greater viable seed input and turnover, particularly of short-lived seeds such as willow, whereas older lobes and undisturbed tundra may have larger seedbanks whose recruitment of new individuals may be limited under natural conditions. Age cohort comparisons between willow species (Salix pulchra or S. glauca), as expected, found over 80% of individuals sampled at the young lobe between 3-4 y.a., while outside showed more variable distribution across six cohorts spanning five to 35 y.a. For both birch and willow, there was more cohort variability in the older lobe than outside, suggesting recruitment outcomes could have site-species interactions.

Huebner, D. C.; Bret-Harte, M. S.



Rainfall, nitrogen deposition and fire disturbance impacts in a California coastal grassland  

NASA Astrophysics Data System (ADS)

In semi-arid ecosystems, shifts in soil moisture availability may mediate the response of individual species, communities and ecosystems to disturbance or changes in nutrient availability. How these interactive effects scale through different levels of ecological organization is poorly understood but essential for robust predictions of the effects of environmental change. In 2007, a year of record low rainfall, we conducted a prescribed fire in a coastal grassland in Orange County California. Within both burned and unburned portions of the grassland, we increased and decreased rainfall (with water addition and rainout shelters, respectively) and increased nitrogen (with N fertilization) in all possible treatment combinations. We asked the question: can physiological responses of the dominant species predict changes in ecosystem function to these interactive environmental manipulations? The native perennial bunchgrass, Nassella pulchra had higher rates of CO 2 uptake and stomatal conductance than the nonnative annual grass, Bromus diandrus across rainfall treatments in both the burned and unburned areas. Both species maintained relatively constant physiological responses regardless of environmental manipulation. Thus, based on these resilient individual-level responses, we predicted that ecosystem-responses would be relatively resilient to the environmental changes. Consistent with this prediction, burning and nitrogen did not strongly affect ecosystem function. However, we detected relatively large responses at the ecosystem level in response to rainfall manipulations, and these effects were generally consistent across burning and N fertilization treatments. Ecosystem respiration, photosynthesis (GEE) and evapotranspiration (ET) declined in response to rainfall removal but did not respond to increases in rainfall. In contrast, the response of annual net primary productivity (ANPP) and a canopy spectral index (NDVI) was greatest in rainfall addition plots. NDVI was correlated with ANPP, GEE and ET in both experiments. During this extremely dry growing season, many on the ecosystem responses were likely driven by soil microbial and plant population- level changes rather than changes in individual plant physiology. Ongoing research at the site will determine whether these relationships will change with annual climatic variation and as longer-term processes (e.g., species turnover, organic matter) begin to contribute more to individual and ecosystem responses.

Potts, D. L.; Winston, G.; Rocha, A.; Suding, K. N.; Goulden, M. L.