Trophic Interactions and Distribution of Some Squaliforme Sharks, Including New Diet Descriptions for Deania calcea and Squalus acanthias

PubMed Central

Dunn, Matthew R.; Stevens, Darren W.; Forman, Jeffrey S.; Connell, Amelia

2013-01-01

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey. PMID:23536896

Trophic interactions and distribution of some Squaliforme sharks, including new diet descriptions for Deania calcea and Squalus acanthias.

PubMed

Dunn, Matthew R; Stevens, Darren W; Forman, Jeffrey S; Connell, Amelia

2013-01-01

Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200-1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18-4.24, 4.20-4.23, 4.24-4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.

Distribution of radioactivity in the chondrichthyes Squalus acanthias and the osteichthyes salmo gairdneri following intragastric administration of (9-/sup 14/C)phenanthrene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solbakken, J.E.; Palmork, K.H.

1980-12-01

The fate of polycyclic hydrocarbons (PAH) in marine animals has received increasing attention in the last decade. The present studies dealing with spiny dogfish (Squalus acanthias) and rainbow trout (Salmo gairdneri) are part of a series of experiments with different marine organisms. All the experiments were performed under the same laboratory conditions using intragastric administration of the PAH-component, /sup 14/C-labelled phenanthrene. Thus it is possible to compare species differences of disposition of PAH in various marine organisms. The most pronounced differences in the disposition of phenanthrene between bony fish and cartilaginous fish in our studies are that the maximum valuemore » of radioactivity in the liver of cartilaginous fish occurred several days later than the corresponding value in bony fish. Furthermore, the radioactivity in cartilaginous fish was retained at a high level beyond 672 h (28 days), a time at which the radioactivity in bony fish is near the background values.« less

Abundances of Demersal Sharks and Chimaera from 1994-2009 Scientific Surveys in the Central Mediterranean Sea

PubMed Central

Ragonese, Sergio; Vitale, Sergio; Dimech, Mark; Mazzola, Salvatore

2013-01-01

Bibliographic and data gathered in scientific bottom trawl surveys carried out off the Southern Coasts of Sicily (Mediterranean Sea), from 1994 to 2009 and between a depth of 10 and 800 m, were analysed in order to prepare a checklist of demersal sharks and chimaera, which are species sensitive to fisheries exploitation. Out of the 27 previously reported demersal shark and chimaera taxa in the Mediterranean, only 23 were found in literature and 20 sampled during the surveys in the investigated area. Among the species sampled in the surveys, only 2 ubiquitous ( Squalus blainville and Scyliorhinus canicula ) and 3 deep-water ( Chimaera monstrosa , Centrophorus granulosus and Galeus melastomus ) species showed a wide geographical distribution with a consistent abundance. Excluding the rare (such as Oxynotus centrina ) or uncommon shark (e.g. Squalus acanthias ), the estimated frequencies of occurrence and abundance indexes show a possible risk of local extinction for the almost exclusively (e.g. angelshark, Squatina spp.) or preferential (e.g. Scyliorhinus stellaris ) neritic species. PMID:24086386

Vasoactive receptors in abdominal blood vessels of the dogfish shark, Squalus acanthias.

PubMed

Evans, D H

2001-01-01

Previous studies have demonstrated that the ventral aorta of the dogfish shark, Squalus acanthias, responds to a variety of cell-signaling agents. To investigate the generality of vasoactive receptors in the shark vasculature, in particular a conductance artery (anterior mesenteric) and vein (posterior intestinal), I measured the effect of acetylcholine, endothelin, nitric oxide, natriuretic peptides, and prostaglandins on tension in isolated rings from these vessels. Both vessels responded to these agents, and responses to receptor-specific ligands for endothelin and natriuretic peptide receptors suggest that B-type endothelin receptors are expressed in both vessels and that the artery expresses both A- and B-type natriuretic peptide receptors; however, the vein (like the ventral aorta) expresses only the B-type natriuretic peptide receptor. My data suggest that a suite of signaling systems is ubiquitous in both arteries and veins in at least this elasmobranch species. Their role in hemodynamics and osmoregulation (perfusion of gill and rectal gland) remains to be determined.

Three neuropeptide Y receptor genes in the spiny dogfish, Squalus acanthias, support en bloc duplications in early vertebrate evolution.

PubMed

Salaneck, Erik; Ardell, David H; Larson, Earl T; Larhammar, Dan

2003-08-01

It has been debated whether the increase in gene number during early vertebrate evolution was due to multiple independent gene duplications or synchronous duplications of many genes. We describe here the cloning of three neuropeptide Y (NPY) receptor genes belonging to the Y1 subfamily in the spiny dogfish, Squalus acanthias, a cartilaginous fish. The three genes are orthologs of the mammalian subtypes Y1, Y4, and Y6, which are located in paralogous gene regions on different chromosomes in mammals. Thus, these genes arose by duplications of a chromosome region before the radiation of gnathostomes (jawed vertebrates). Estimates of duplication times from linearized trees together with evidence from other gene families supports two rounds of chromosome duplications or tetraploidizations early in vertebrate evolution. The anatomical distribution of mRNA was determined by reverse-transcriptase PCR and was found to differ from mammals, suggesting differential functional diversification of the new gene copies during the radiation of the vertebrate classes.

Fetal bovine serum simultaneously stimulates apoptosis and DNA synthesis in premeiotic stages of spermatogenesis in spiny dogfish (Squalus acanthias) in vitro: modulation by androgen and spermatogenic activity status.

PubMed

McClusky, Leon Mendel

2008-05-01

Using the simple cystic spermatogenesis in the shark testis as a model, we previously reported the relative resistance of immature spermatogonia (stem cell and early-stage spermatogonia) to apoptosis in the normal testis and after spermatoxicant exposure in vivo. Apoptosis was monitored by fluorescence image analysis of living cysts, using the validated acridine orange (AO) vital staining technique. Findings show that FBS simultaneously stimulates both apoptosis and [(3)H]thymidine incorporation in immature spermatogonial clones in a concentration-dependent manner in vitro. Furthermore, androgen inhibits apoptosis and increases cyst viability, more so with 10% FBS than with 1% FBS. All the effects were as a function of spermatogenic activity status but were distinct in early-stage spermatogonial cysts isolated from testes awakening from the previous winter spermatogenic arrest period. Results are discussed in the context of the alternating germ-Sertoli cell population kinetics of early-stage spermatogonial cysts in Squalus acanthias's protracted testicular cycle.

Characterization of the immunoglobulin repertoire of the spiny dogfish (Squalus acanthias).

PubMed

Smith, Lauren E; Crouch, Kathryn; Cao, Wei; Müller, Mischa R; Wu, Leeying; Steven, John; Lee, Michael; Liang, Musen; Flajnik, Martin F; Shih, Heather H; Barelle, Caroline J; Paulsen, Janet; Gill, Davinder S; Dooley, Helen

2012-04-01

The cartilaginous fish (chimeras, sharks, skates and rays) are the oldest group relative to mammals in which an adaptive immune system founded upon immunoglobulins has been found. In this manuscript we characterize the immunoglobulins of the spiny dogfish (Squalus acanthias) at both the molecular and expressed protein levels. Despite the presence of hundreds of IgM clusters in this species the serum levels of this isotype are comparatively low. However, analysis of cDNA sequences and serum protein suggests microheterogeneity in the IgM heavy chains and supports the proposal that different clusters are preferentially used in the two forms (monomer or pentamer) of this isotype. We also found that the IgNAR isotype in this species exists in a previously unknown multimeric format in serum. Finally, we identified a new form of the IgW isotype (the shark IgD orthologue), in which the leader is spliced directly to the first constant domain, resulting in a molecule lacking an antigen-binding domain. Copyright © 2011 Elsevier Ltd. All rights reserved.

Non-dioxin like polychlorinated biphenyl indicator congeners in Northwest Atlantic spiny dogfish (Squalus acanthias).

PubMed

St-Gelais, Adam T; Aeppli, Christoph; Burnell, Craig A; Costa-Pierce, Barry A

2017-07-15

In the Northwest Atlantic Ocean (NWAO), spiny dogfish (Squalus acanthias) is a promising commercial species following of collapse of traditional groundfish stocks. There are little available data assessing polychlorinated biphenyls (PCBs) in NWAO spiny dogfish. Here, six non-dioxin like PCB indicator congeners used in European Union regulations (EU NDL-PCB) were quantified via gas chromatography/mass spectrometry in 50 mature male spiny dogfish landed in southern New England. The average total concentration of EU NDL-PCBs was 58±43ng/g (mean±1 standard deviation). PCB values (corrected for co-elution) were below the 200ng/g EU regulatory limit. Results provide first recent regional insight into the PCB content of spiny dogfish in the NWAO. However, our study offers only a snapshot of one particular dogfish population, and might not be representative for the whole NWAO. This study underscores the need for further testing in this species. Copyright © 2017. Published by Elsevier Ltd.

MOLECULAR CLONING AND STAGE-DEPENDENT EXPRESSION OF A CYTOCHROME P450 AROMATASE DURING SPERMATOGENESIS IN SHARK (SQUALUS ACANTHIAS) TESTIS. (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

MOLECULAR CLONING OF AN ANDROGEN RECEPTOR FROM THE TESTIS OF THE SHARK (SQUALUS ACANTHIAS) AND ITS STAGE-DEPENDENT DISTRIBUTION. (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

STAGE-DEPENDENT ACCUMULATION OF CADMIUM AND INDUCTION OF METALLOTHIONEIN-LIKE BINDING ACTIVITY IN THE TESTIS OF THE DOGFISH SHARK, SQUALUS ACANTHIAS. (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

North Pacific Spiny Dogfish (Squalus suckleyi) presence in Eelgrass habitat in the Salish Sea, Washington

Treesearch

Brooke E. Penaluna; Leo R. Bodensteiner

2015-01-01

Eelgrass (Zostera marina) is the dominant seagrass along the Pacific North American Coast, providing complex physical structure, high trophic productivity, and protection from predators (Phillips 1984; Simenstad 1994). Because of these multiple functions, many fish species and life stages use Eelgrass beds more than other nearshore habitat types (...

Mercury concentrations in Northwest Atlantic winter-caught, male spiny dogfish (Squalus acanthias): A geographic mercury comparison and risk-reward framework for human consumption.

PubMed

St Gelais, Adam T; Costa-Pierce, Barry A

2016-01-15

Mercury (Hg) contamination testing was conducted on winter-caught male spiny dogfish (Squalus acanthias) in southern New England and results compared to available data on Hg concentrations for this species. A limited risk-reward assessment for EPA (eicosapentanoic acid) and DHA (docosahexanoic acid) lipid concentrations of spiny dogfish was completed in comparison with other commonly consumed marine fish. Mean Hg concentrations were 0.19 ppm (±0.30) wet weight. In comparison, mean Hg concentrations in S. acanthias varied geographically ranging from 0.05 ppm (Celtic Sea) to 2.07 ppm (Crete, Mediterranean Sea). A risk-reward assessment for Hg and DHA+EPA placed S. acanthias in both "low-risk, high-reward" and "high-risk, high-reward" categories for consumption dependent on locations of the catch. Our results are limited and are not intended as consumption advisories but serve to illustrate the need for making more nuanced, geo-specific, consumption guidance for spiny dogfish that is inclusive of seafood traceability and nutritional benefits. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Characterisation and expression analysis of B-cell activating factor (BAFF) in spiny dogfish (Squalus acanthias): cartilaginous fish BAFF has a unique extra exon that may impact receptor binding.

PubMed

Li, Ronggai; Dooley, Helen; Wang, Tiehui; Secombes, Christopher J; Bird, Steve

2012-04-01

B-cell activating factor (BAFF), also known as tumour necrosis factor (TNF) ligand superfamily member 13B, is an important immune regulator with critical roles in B-cell survival, proliferation, differentiation and immunoglobulin secretion. A BAFF gene has been cloned from spiny dogfish (Squalus acanthias) and its expression studied. The dogfish BAFF encodes for an anchored type-II transmembrane protein of 288 aa with a putative furin protease cleavage site and TNF family signature as seen in BAFFs from other species. The identity of dogfish BAFF has also been confirmed by conserved cysteine residues, and phylogenetic tree analysis. The dogfish BAFF gene has an extra exon not seen in teleost fish, birds and mammals that encodes for 29 aa and may impact on receptor binding. The dogfish BAFF is highly expressed in immune tissues, such as spleen, and is up-regulated by PWM in peripheral blood leucocytes, suggesting a potentially important role in the immune system. Copyright © 2011 Elsevier Ltd. All rights reserved.

MOLECULAR CLONING, STAGE-RELATED DIFFERENCES, AND EFFECTS OF ESTROGEN ON EXPRESSION OF AN ESTROGEN RECEPTOR BETA-SUBTYPE IN THE TESTIS OF THE DOGFISH SHARK (SQUALUS ACANTHIAS). (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

IN VITRO EFFECTS OF SERUM AND STEROIDS ON CELL PROLIFERATION AND DEATH DURING SPERMATOGONIAL STAGES OF SPERMATOGENESIS IN THE DOGFISH SHARK (SQUALUS ACANTHIAS). (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

STAGE-DEPENDENCE, SEASONAL CHANGES AND EFFECTS OF CADMIUM ON CELL CYCLE AND APOPTOTIC ACTIVITIES DURING THE SPERMATOGENIC PROGRESSION IN THE DOGFISH SHARK (SQUALUS ACANTHIAS). (R825434)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Muscle enzyme activities in a deep-sea squaloid shark, Centroscyllium fabricii, compared with its shallow-living relative, Squalus acanthias.

PubMed

Treberg, Jason R; Martin, R Aidan; Driedzic, William R

2003-12-01

The activities of several enzymes of energy metabolism were measured in the heart, red muscle, and white muscle of a deep and a shallow living squaloid shark, Centroscyllium fabricii and Squalus acanthias, respectively. The phylogenetic closeness of these species, combined with their active predatory nature, similar body form, and size makes them well matched for comparison. This is the first time such a comparison has been made involving a deep-sea elasmobranch. Enzyme activities were similar in the heart, but generally lower in the red muscle of C. fabricii. Paralleling the trend seen in deep-sea teleosts, the white muscle of C. fabricii had substantially lower activities of key glycolytic enzymes, pyruvate kinase and lactate dehydrogenase, relative to S. acanthias or other shallow living elasmobranchs. Unexpectedly, between the squaloid sharks examined, creatine phosphokinase activity was higher in all tissues of the deep living C. fabricii. Low white muscle glycolytic enzyme activities in the deep-sea species coupled with high creatine phosphokinase activity suggests that the capacity for short burst swimming is likely limited once creatine phosphate supplies have been exhausted. Copyright 2003 Wiley-Liss, Inc.

Volume-activated trimethylamine oxide efflux in red blood cells of spiny dogfish (Squalus acanthias).

PubMed

Koomoa, D L; Musch, M W; MacLean, A V; Goldstein, L

2001-09-01

The aims of this study were to determine the pathway of swelling-activated trimethylamine oxide (TMAO) efflux and its regulation in spiny dogfish (Squalus acanthias) red blood cells and compare the characteristics of this efflux pathway with the volume-activated osmolyte (taurine) channel present in erythrocytes of fishes. The characteristics of the TMAO efflux pathway were similar to those of the taurine efflux pathway. The swelling-activated effluxes of both TMAO and taurine were significantly inhibited by known anion transport inhibitors (DIDS and niflumic acid) and by the general channel inhibitor quinine. Volume expansion by hypotonicity, ethylene glycol, and diethyl urea activated both TMAO and taurine effluxes similarly. Volume expansion by hypotonicity, ethylene glycol, and diethyl urea also stimulated the activity of tyrosine kinases p72syk and p56lyn, although the stimulations by the latter two treatments were less than by hypotonicity. The volume activations of both TMAO and taurine effluxes were inhibited by tyrosine kinase inhibitors, suggesting that activation of tyrosine kinases may play a role in activating the osmolyte effluxes. These results indicate that the volume-activated TMAO efflux occurs via the organic osmolyte (taurine) channel and may be regulated by the volume activation of tyrosine kinases.

Structural studies of α-melanocyte-stimulating hormone and a novel β-melanocyte-stimulating hormone from the neurointermediate lobe of the pituitary of the dogfish Squalus acanthias

PubMed Central

Bennett, Hugh P. J.; Lowry, Philip J.; McMartin, Colin; Scott, Alexander P.

1974-01-01

A melanocyte-stimulating hormone (MSH) has been isolated from extracts of the neurointermediate lobe of the pituitary of the dogfish Squalus acanthias by gel-filtration and ion-exchange chromatography. It had approximately 1% of the potency of mammalian α-MSH on bioassays in vitro on frog skin and dogfish skin. Sequence analysis revealed it to be a hexadecapeptide with the following primary structure: Asp-Gly-Asp-Asp-Tyr-Lys-Phe-Gly-His-Phe-Arg-Trp-Ser-Val-Pro-Leu. It appears to be related to the β-MSH species of mammalian species but has only the sequence -His-Phe-Arg-Trp- in common with the heptapeptide core -Met-Glu-His-Phe-Arg-Trp-Gly- which is characteristic not only of the MSH peptides but also of the adrenocorticotrophins and lipotrophins studied so far. An α-MSH was also isolated, 50% of which was amidated at the C-terminus group. Sequence data from this study taken in conjunction with those from a previous study (Lowry & Chadwick, 1970b) revealed it to be a tridecapeptide which is identical with the N-terminal sequence of dogfish adrenocorticotrophin. PMID:4375978

Seasonal dynamics of the cestode fauna in spiny dogfish, Squalus acanthias (Squaliformes: Squalidae).

PubMed

Pickering, Maria; Caira, Janine N

2014-06-01

This study furthers understanding of cestode infections in a marine environment through time and space by following seasonal fluctuations in infection parameters of three cestode species (Gilquinia squali, Trilocularia gracilis and Phyllobothrium squali) parasitizing spiny dogfish (Squalus acanthias) in the northwest Atlantic and comparing them to work previously published from the northeast Atlantic on T. gracilis. For each cestode species, host size, season and presence of the other cestode species were analysed using generalized linear models to determine if they were good predictors of prevalence and intensity. Infection parameters differed across season for the three cestode species. However, within T. gracilis seasonal trends were found to be remarkably similar on both sides of the Atlantic, differing only in a somewhat delayed decline in prevalence in the northwest Atlantic. The differences seen in infection measures across cestode species likely reflect the unique life history strategies of different parasite species. While general trends appear to be maintained across disparate localities, variation seen is likely due to differences in accessibility to intermediate hosts and host diet across sites. The knowledge gained from understanding cestode infections in the vast ocean environment allows us to speculate about the factors driving fluctuations in parasite infections in elasmobranchs.

GFAP-immunopositive structures in spiny dogfish, Squalus acanthias, and little skate, Raia erinacea, brains: differences have evolutionary implications.

PubMed

Kálmán, M; Gould, R M

2001-07-01

GFAP expression patterns were compared between the brains of a spiny dogfish (Squalus acanthias) and a little skate (Raia erinacea). After anesthesia, the animals were perfused with paraformaldehyde. Serial vibratome sections were immunostained against GFAP using the avidin-biotin method. Spiny dogfish brain contained mainly uniformly-distributed, radially arranged ependymoglia. From GFAP distribution, the layered organization in both the telencephalon and the tectum were visible. In the cerebellum, the molecular and granular layers displayed conspicuously different glial structures; in the former a Bergmann glia-like population was found. No true astrocytes (i.e., stellate-shaped cells) were found. Radial glial endfeet lined all meningeal surfaces. Radial fibers also seemed to form endfeet and en passant contacts on the vessels. Plexuses of fine perivascular glial fibers also contributed to the perivascular glia. Compared with spiny dogfish brain, GFAP expression in the little skate brain was confined. Radial glia were limited to a few areas, e.g., segments of the ventricular surface of the telencephalon, and the midline of the diencephalon and mesencephalon. Scarce astrocytes occurred in every brain part, but only the optic chiasm, and the junction of the tegmentum and optic tectum contained large numbers of astrocytes. Astrocytes formed the meningeal glia limitans and the perivascular glia. No GFAP-immunopositive Bergmann glia-like structure was found. Astrocytes seen in the little skate were clearly different from the mammalian and avian ones; they had a different process system - extra large forms were frequently seen, and the meningeal and perivascular cells were spread along the surface instead of forming endfeet by processes. The differences between Squalus and Raia astroglia were much like those found between reptiles versus mammals and birds. It suggests independent and parallel glial evolutionary processes in amniotes and chondrichthyans, seemingly correlated with the thickening of the brain wall, and the growing complexity of the brain. There is no strict correlation, however, between the replacement of radial ependymoglia with astrocytes, and the local thickness of the brain wall.

Carbonic anhydrase I in a cartilaginous fish, the shortspine spurdog ( Squalus mitsukurii)

NASA Astrophysics Data System (ADS)

Kim, Soo Cheol; Sumi, Kanij Rukshana; Kim, Jung Woo; Choi, Myeong Rak; Min, Byung Hwa; Kho, Kang Hee

2016-09-01

Carbonic anhydrase (CA), a ubiquitous enzyme found in many species, including fishes, is involved in physiological functions such as pH homeostasis, calcification, photosynthesis, and ionic regulation. CA I, a member of the α-CA family, is a cytoplasmic isozyme involved in carbon dioxide transport, ion exchange, and acid-base balance. Approximately half of the extant shark species occur only in deep waters; however, few published studies on sharks include these taxa. As fisheries worldwide enter deeper waters, the provision of biological data for these little-known taxa is critical to their management and conservation. To address this limitation, we aimed to detect CA I in various tissues of the shortspine spurdog ( Squalus mitsukurii) and characterize its physicochemical properties by using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and isoelectric focusing, together with immunohistochemistry. CA I was detected on SDS-PAGE and western blot analysis as a specific band at 29 kDa in various tissues of the shortspine spurdog, and as a specific band at pI 6.5 in various tissues of the shortspine spurdog by IEF and western blot analysis. CA I immunoreactivity in various tissues of the shortspine spurdog was detected in intracellular locations. To our knowledge, this is the first report of the localization of CA isozymes in various tissues of S. mitsukurii.

Comparative analysis of methods for determining bite force in the spiny dogfish Squalus acanthias.

PubMed

Huber, Daniel Robert; Motta, Philip Jay

2004-01-01

Many studies have identified relationships between the forces generated by the cranial musculature during feeding and cranial design. Particularly important to understanding the diversity of cranial form amongst vertebrates is knowledge of the generated magnitudes of bite force because of its use as a measure of ecological performance. In order to determine an accurate morphological proxy for bite force in elasmobranchs, theoretical force generation by the quadratomandibularis muscle of the spiny dogfish Squalus acanthias was modeled using a variety of morphological techniques, and lever-ratio analyses were used to determine resultant bite forces. These measures were compared to in vivo bite force measurements obtained with a pressure transducer during tetanic stimulation experiments of the quadratomandibularis. Although no differences were found between the theoretical and in vivo bite forces measured, modeling analyses indicate that the quadratomandibularis muscle should be divided into its constituent divisions and digital images of the cross-sections of these divisions should be used to estimate cross-sectional area when calculating theoretical force production. From all analyses the maximum bite force measured was 19.57 N. This relatively low magnitude of bite force is discussed with respect to the ecomorphology of the feeding mechanism of S. acanthias to demonstrate the interdependence of morphology, ecology, and behavior in organismal design. Copyright 2004 Wiley-Liss, Inc.

Branchial mitochondria-rich cells in the dogfish Squalus acanthias.

PubMed

Wilson, Jonathan M; Morgan, John D; Vogl, A Wayne; Randall, David J

2002-06-01

In marine teleost fishes, the gill mitochondria-rich cells (MRCs) are responsible for NaCl elimination; however, in elasmobranch fishes, the specialized rectal gland is considered to be the most important site for salt secretion. The role of the gills in elasmobranch ion regulation, although clearly shown to be secondary, is not well characterized. In the present study, we investigated some morphological properties of the branchial MRCs and the localization, and activity of the important ionoregulatory enzyme Na(+)/K(+)-ATPase, under control conditions and following rectal gland removal (1 month) in the spiny dogfish, Squalus acanthias. A clear correlation can be made between MRC numbers and the levels of Na(+)/K(+)-ATPase activity in crude gill homogenates (r(2)=-0.69). Strong Na(+)/K(+)-ATPase immunoreactivity is also clearly associated with the basolateral membrane of these MRCs. In addition, the dogfish were able to maintain ionic balance after rectal gland removal. These results all suggest a possible role of the dogfish gill in salt secretion. MRCs were, however, unresponsive to rectal gland removal in terms of changes in number, fine structure and Na(+)/K(+)-ATPase activity, as might be expected if they were compensating for the loss of salt secretion by the rectal gland. Thus, the specific role that these MRCs play in ion regulation in the dogfish remains to be determined

Functional analysis of the musculo-skeletal system of the gill apparatus in Heptranchias perlo (Chondrichthyes: Hexanchidae).

PubMed

Kryukova, Nadezhda V

2017-08-01

Musculo-skeletal morphology is an indispensable source for understanding functional adaptations. Analysis of morphology of the branchial apparatus of Hexanchiform sharks can provide insight into aspects of their respiration that are difficult to observe directly. In this study, I compare the structure of the musculo-skeletal system of the gill apparatus of Heptranchias perlo and Squalus acanthias in respect to their adaptation for one of two respiratory mechanisms known in sharks, namely, the active two-pump (oropharyngeal and parabranchial) ventilation and the ram-jet ventilation. In both species, the oropharyngeal pump possesses two sets of muscles, one for compression and the other for expansion. The parabranchial pump only has constrictors. Expansion of this pump occurs only due to passive elastic recoil of the extrabranchial cartilages. In Squalus acanthias the parabranchial chambers are large and equipped by powerful superficial constrictors. These muscles and the outer walls of the parabranchial chambers are much reduced in Heptranchias perlo, and thus it likely cannot use this pump. However, this reduction allows for vertical elongation of outer gill slits which, along with greater number of gill pouches, likely decreases branchial resistance and, at the same time, increases the gill surface area, and can be regarded as an adaptation for ram ventilation at lower speeds. © 2017 Wiley Periodicals, Inc.

The effect of organotin compounds on chloride secretion by the in vitro perfused rectal gland of Squalus acanthias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomon, R.; Lear, S.; Cohen, R.

1989-09-01

The effects of various organotins on membrane function and electrolyte transport were studied in the marine elasmobranch, Squalus acanthias. The isolated perfused rectal gland was used as a model of electrolyte transport. This gland can be stimulated to secrete chloride by atrial natriuretic peptide, veratrine, and vasoactive intestinal polypeptide although the mechanism of action of each secretagogue is different. By analysis of the inhibitory effect of an organotin in the presence of each secretagogue, the mechanism of inhibition can be inferred. Tributyltin (TBT) produced a reversible inhibition of epithelial transport at 10(-8) to 10(-7) M which resulted from inhibition ofmore » stimulus-secretion coupling in VIP-containing neurons within the gland. The transporting epithelial cells were unaffected at these concentrations. Trimethytin (TMT) produced inhibition at 10(-7) M which was not reversible and which affected primarily the transporting epithelial cells. Triethyltin and triphenyltin were without effect. The inhibitory effect of TBT and TMT was not affected by simultaneous administration of dithiothreitol. TBT also produced inhibition of oxygen consumption, Na+,K-ATPase, and proton ATPase in dispersed rectal gland cells. These results indicate that organotins are toxic to cell membrane functions which are intimately involved in the movement of electrolytes. This is the first evidence of toxicity to membrane transport functions in a marine species which is at risk from environmental exposure.« less

Time course of the acute response of the North Pacific spiny dogfish shark (Squalus suckleyi) to low salinity.

PubMed

Guffey, Samuel C; Goss, Greg G

2014-05-01

Dogfish are considered stenohaline sharks but are known to briefly enter estuaries. The acute response of North Pacific spiny dogfish (Squalus suckleyi) to lowered salinity was tested by exposing sharks to 21‰ salinity for 48 h. Temporal trends in blood pH, plasma osmolality, CO2, HCO3(-), Na(+), Cl(-), K(+), and urea concentrations, and in the rates of urea efflux and O2 consumption, were quantified. The rate of O2 consumption exhibited cyclic variation and was significantly depressed by lowered salinity. After 9 h, plasma [Cl(-)] stabilized at 9% below initial levels, while plasma [Na(+)] decreased by more than 20% within the first 12 h. Plasma [urea] dropped by 15% between 4 and 6 h, and continued to decrease. The rate of urea efflux increased over time, peaking after 36 h at 72% above the initial rate. Free-swimming sharks subjected to the same salinity challenge survived over 96 h and differed from cannulated sharks with respect to patterns of Na(+) and urea homeostasis. This high-resolution study reveals that dogfish exposed to 21‰ salinity can maintain homeostasis of Cl(-) and pH, but Na(+) and urea continue to be lost, likely accounting for the inability of the dogfish to fully acclimate to reduced salinity. Copyright © 2014 Elsevier Inc. All rights reserved.

Embryonic development of fin spines in Callorhinchus milii (Holocephali); implications for chondrichthyan fin spine evolution.

PubMed

Jerve, Anna; Johanson, Zerina; Ahlberg, Per; Boisvert, Catherine

2014-01-01

Fin spines are commonly known from fossil gnathostomes (jawed vertebrates) and are usually associated with paired and unpaired fins. They are less common among extant gnathostomes, being restricted to the median fins of certain chondrichthyans (cartilaginous fish), including chimaerids (elephant sharks) and neoselachians (sharks, skates, and rays). Fin spine growth is of great interest and relevance but few studies have considered their evolution and development. We investigated the development of the fin spine of the chimaerid Callorhinchus milii using stained histological sections from a series of larval, hatchling, and adult individuals. The lamellar trunk dentine of the Callorhinchus spine first condenses within the mesenchyme, rather than at the contact surface between mesenchyme and epithelium, in a manner more comparable to dermal bone formation than to normal odontode development. Trabecular dentine forms a small component of the spine under the keel; it is covered externally with a thin layer of lamellar trunk dentine, which is difficult to distinguish in sectioned adult spines. We suggest that the distinctive characteristics of the trunk dentine may reflect an origin through co-option of developmental processes involved in dermal bone formation. Comparison with extant Squalus and a range of fossil chondrichthyans shows that Callorhinchus is more representative than Squalus of generalized chondrichthyan fin-spine architecture, highlighting its value as a developmental model organism. © 2014 Wiley Periodicals, Inc.

AMP-activated protein kinase and adenosine are both metabolic modulators that regulate chloride secretion in the shark rectal gland ( Squalus acanthias).

PubMed

Neuman, Rugina I; van Kalmthout, Juliette A M; Pfau, Daniel J; Menendez, Dhariyat M; Young, Lawrence H; Forrest, John N

2018-04-01

The production of endogenous adenosine during secretagogue stimulation of CFTR leads to feedback inhibition limiting further chloride secretion in the rectal gland of the dogfish shark (Squalus acanthias). In the present study, we examined the role of AMP-kinase (AMPK) as an energy sensor also modulating chloride secretion through CFTR. We found that glands perfused with forskolin and isobutylmethylxanthine (F + I), potent stimulators of chloride secretion in this ancient model, caused significant phosphorylation of the catalytic subunit Thr 172 of AMPK. These findings indicate that AMPK is activated during energy-requiring stimulated chloride secretion. In molecular studies, we confirmed that the activating Thr 172 site is indeed present in the α-catalytic subunit of AMPK in this ancient gland, which reveals striking homology to AMPKα subunits sequenced in other vertebrates. When perfused rectal glands stimulated with F + I were subjected to severe hypoxic stress or perfused with pharmacologic inhibitors of metabolism (FCCP or oligomycin), phosphorylation of AMPK Thr 172 was further increased and chloride secretion was dramatically diminished. The pharmacologic activation of AMPK with AICAR-inhibited chloride secretion, as measured by short-circuit current, when applied to the apical side of shark rectal gland monolayers in primary culture. These results indicate that that activated AMPK, similar to adenosine, transmits an inhibitory signal from metabolism, that limits chloride secretion in the shark rectal gland.

Extracellular carbonic anhydrase in the dogfish, Squalus acanthias: a role in CO2 excretion.

PubMed

Gilmour, K M; Perry, S F; Bernier, N J; Henry, R P; Wood, C M

2001-01-01

In Pacific spiny dogfish (Squalus acanthias), plasma CO(2) reactions have access to plasma carbonic anhydrase (CA) and gill membrane-associated CA. The objectives of this study were to characterise the gill membrane-bound CA and investigate whether extracellular CA contributes significantly to CO(2) excretion in dogfish. A subcellular fraction containing membrane-associated CA activity was isolated from dogfish gills and incubated with phosphatidylinositol-specific phospholipase C. This treatment caused significant release of CA activity from its membrane association, a result consistent with identification of the dogfish gill membrane-bound CA as a type IV isozyme. Inhibition constants (K(i)) against acetazolamide and benzolamide were 4.2 and 3.5 nmol L(-1), respectively. Use of a low dose (1.3 mg kg(-1) or 13 micromol L(-1)) of benzolamide to selectively inhibit extracellular CA in vivo caused a significant 30%-60% reduction in the arterial-venous total CO(2) concentration difference, a significant increase in Pco(2) and an acidosis, without affecting blood flow or ventilation. No effect of benzolamide on any measure of CO(2) excretion was detected in rainbow trout (Oncorhynchus mykiss). These results indicate that extracellular CA contributes substantially to CO(2) excretion in the dogfish, an elasmobranch, and confirm that CA is not available to plasma CO(2) reactions in rainbow trout, a teleost.

The isolation and amino acid sequence of an adrenocorticotrophin from the pars distalis and a corticotrophin-like intermediate-lobe peptide from the neurointermediate lobe of the pituitary of the dogfish Squalus acanthias

PubMed Central

Lowry, Philip J.; Bennett, Hugh P. J.; McMartin, Colin; Scott, Alexander P.

1974-01-01

An adrenocorticotrophic hormone (ACTH) was isolated from extracts of the pars distalis of the pituitary of the dogfish Squalus acanthias by gel filtration and ion-exchange chromatography. It had 15% of the potency of human ACTH in promoting cortico-steroidogenesis in isolated rat adrenal cells. Sequence analysis revealed it to be a nonatria-contapeptide with the following primary structure: Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Met-Gly-Arg-Lys-Arg-Arg-Pro-Ile-Lys-Val-Tyr-Pro-Asn-Ser-Phe-Glu-Asp-Glu-Ser-Val-Glu-Asn-Met-Gly-Pro-Glu-Leu. The N-terminal tridecapeptide sequence was identical with the proposed structure of dogfish α-melanocyte-stimulating hormone (α-MSH). On comparison with human ACTH eleven amino acid differences were seen, nine of which are in the 20–39 region of the molecule which is not essential for the steroidogenic activity of ACTH. A peptide identical with the 18–39 portion of this new ACTH was similarly isolated from the neurointermediate lobe of the pituitary where considerable amounts of dogfish α-MSH were found. This supported our view that ACTH as well as having a distinct biological role of its own is also the precursor of α-MSH. PMID:4375977

Proteomic identification of processes and pathways characteristic of osmoregulatory tissues in spiny dogfish shark (Squalus acanthias).

PubMed

Lee, Jinoo; Valkova, Nelly; White, Mark P; Kültz, Dietmar

2006-09-01

We used dogfish shark (Squalus acanthias) as a model for proteome analysis of six different tissues to evaluate tissue-specific protein expression on a global scale and to deduce specific functions and the relatedness of multiple tissues from their proteomes. Proteomes of heart, brain, kidney, intestine, gill, and rectal gland were separated by two-dimensional gel electrophoresis (2DGE), gel images were matched using Delta 2D software and then evaluated for tissue-specific proteins. Sixty-one proteins (4%) were found to be in only a single type of tissue and 535 proteins (36%) were equally abundant in all six tissues. Relatedness between tissues was assessed based on tissue-specific expression patterns of all 1465 consistently resolved protein spots. This analysis revealed that tissues with osmoregulatory function (kidney, intestine, gill, rectal gland) were more similar in their overall proteomes than non-osmoregulatory tissues (heart, brain). Sixty-one proteins were identified by MALDI-TOF/TOF mass spectrometry and biological functions characteristic of osmoregulatory tissues were derived from gene ontology and molecular pathway analysis. Our data demonstrate that the molecular machinery for energy and urea metabolism and the Rho-GTPase/cytoskeleton pathway are enriched in osmoregulatory tissues of sharks. Our work provides a strong rationale for further study of the contribution of these mechanisms to the osmoregulation of marine sharks.

Reproductive and population parameters of spiny dogfish Squalus acanthias in the south-western Atlantic Ocean.

PubMed

Colonello, J H; Cortés, F; Belleggia, M; Massa, A M

2016-05-01

The objective of this study was to estimate reproductive and population parameters of the spiny dogfish Squalus acanthias for the south-western Atlantic Ocean. In total, 2714 specimens (1616 males and 1098 females) were collected from surveys carried out using research vessels. Males ranged from 225 to 861 mm total length (LT ) and females from 235 to 925 mm LT . The size at maturity of females (651 mm) was significantly greater than that of males (565 mm). The maximum proportion of mature individuals (Pmax ) of the gestation ogive was <1, which indicates that a proportion of mature females was not in gestation. This inactivity may be explained by the occurrence of resting periods between cycles or by the asynchrony of the reproductive cycle. The estimated Pmax for the maternity ogive suggested that about one third of mature females were in the maternity stage (i.e. with embryos >156 mm). The temporal and spatial co-occurrence of non-gravid adult females at different stages of ovarian development, as well as gravid females at all embryonic development stages would indicate that the female reproductive cycle in the south-western Atlantic Ocean is asynchronous. The results indicate that S. acanthias is susceptible to fishing pressure on account of its length at maturity, extended reproductive cycles and low fecundity. © 2016 The Fisheries Society of the British Isles.

Functional expression of Squalus acanthias melanocortin-5 receptor in CHO cells: ligand selectivity and interaction with MRAP.

PubMed

Reinick, Christina L; Liang, Liang; Angleson, Josepha K; Dores, Robert M

2012-04-05

The melanocortin-5 receptor (MC(5)) of the dogfish Squalus acanthias (SacMC(5) receptor) can be functionally expressed in CHO cells in the absence of the co-expression of an exogenous MRAP cDNA. Both human ACTH(1-24) and dogfish ACTH(1-25) were much better stimulators of the SacMC(5) receptor than any of the mammalian or dogfish MSH ligands that were tested. The order of ligand selectivity for the dogfish melanocortins was ACTH(1-25)>αMSH>γ-MSH=δ-MSH>β-MSH. Unlike mammalian MC(5) receptors, the functional expression of the SacMC(5) receptor was not negatively impacted when the receptor was co-expressed with a cartilaginous fish (Callorhinchus milii) MRAP2 cDNA. However, co-expression with either mouse mMRAP1 or zebrafish zfMRAP1 increased the sensitivity of SacMC(5) receptor for hACTH(1-24) by at least one order of magnitude. Hence, SacMC(5) receptor has the potential to interact with MRAP1 orthologs and in this regard behaved more like a melanocortin MC(2) receptor ortholog than a melanocortin MC(5) receptor ortholog. These observations are discussed in light of the evolution of the melanocortin receptor gene family in cartilaginous fish, and the physiological implications of these observations are considered. Copyright © 2012 Elsevier B.V. All rights reserved.

Gene structure and functional characterization of growth hormone in dogfish, Squalus acanthias.

PubMed

Moriyama, Shunsuke; Oda, Mayumi; Yamazaki, Tomohide; Yamaguchi, Kiyoko; Amiya, Noriko; Takahashi, Akiyoshi; Amano, Masafumi; Goto, Tomoaki; Nozaki, Masumi; Meguro, Hiroshi; Kawauchi, Hiroshi

2008-06-01

Dogfish (Squalus acanthias) growth hormone (GH) was identified by cDNA cloning and protein purification from the pituitary gland. Dogfish GH cDNA encoded a prehormone of 210 amino acids (aa). Sequence analysis of purified GH revealed that the prehormone is composed of a signal peptide of 27 aa and a mature protein of 183 aa. Dogfish GH showed 94% sequence identity with blue shark GH, and also showed 37-66%, 26%, and 48-67% sequence identity with GH from osteichtyes, an agnathan, and tetrapods. The site of production was identified through immunocytochemistry to be cells of the proximal pars distalis of the pituitary gland. Dogfish GH stimulates both insulin-like growth factor-I and II mRNA levels in dogfish liver in vitro. The dogfish GH gene consisted of five exons and four introns, the same as in lamprey, teleosts such as cypriniforms and siluriforms, and tetrapods. The 5'-flanking region within 1082 bp of the transcription start site contained consensus sequences for the TATA box, Pit-1/GHF-1, CRE, TRE, and ERE. These results show that the endocrine mechanism for growth stimulation by the GH-IGF axis was established at an early stage of vertebrate evolution, and that the 5-exon-type gene organization might reflect the structure of the ancestral gene for the GH gene family.

Activation of liver carnitine palmitoyltransferase-1 and mitochondrial acetoacetyl-CoA thiolase is associated with elevated ketone body levels in the elasmobranch Squalus acanthias.

PubMed

Treberg, Jason R; Crockett, Elizabeth L; Driedzic, William R

2006-01-01

Elasmobranch fishes are an ancient group of vertebrates that have unusual lipid metabolism whereby storage lipids are mobilized from the liver for peripheral oxidation largely as ketone bodies rather than as nonesterified fatty acids under normal conditions. This reliance on ketones, even when feeding, implies that elasmobranchs are chronically ketogenic. Compared to specimens sampled within 2 d of capture (recently captured), spiny dogfish Squalus acanthias that were held for 16-33 d without apparent feeding displayed a 4.5-fold increase in plasma concentration of d- beta -hydroxybutyrate (from 0.71 to 3.2 mM) and were considered ketotic. Overt activity of carnitine palmitoyltransferase-1 in liver mitochondria from ketotic dogfish was characterized by an increased apparent maximal activity, a trend of increasing affinity (reduced apparent K(m); P=0.09) for l-carnitine, and desensitization to the inhibitor malonyl-CoA relative to recently captured animals. Acetoacetyl-CoA thiolase (ACoAT) activity in isolated liver mitochondria was also markedly increased in the ketotic dogfish compared to recently captured fish, whereas no difference in 3-hydroxy-3-methylglutaryl-CoA synthase activity was found between these groups, suggesting that ACoAT plays a more important role in the activation of ketogenesis in spiny dogfish than in mammals and birds.

The putative mechanism of Na(+) absorption in euryhaline elasmobranchs exists in the gills of a stenohaline marine elasmobranch, Squalus acanthias.

PubMed

Choe, Keith P; Edwards, Susan L; Claiborne, James B; Evans, David H

2007-02-01

We recently cloned an NHE3 orthologue from the gills of the euryhaline Atlantic stingray (Dasyatis sabina), and generated a stingray NHE3 antibody to unequivocally localize the exchanger to the apical side of epithelial cells that are rich with Na(+)/K(+)-ATPase (A MRC). We also demonstrated an increase in NHE3 expression when stingrays are in fresh water, suggesting that NHE3 is responsible for active Na(+) absorption. However, the vast majority of elasmobranchs are only found in marine environments. In the current study, immunohistochemistry with the stingray NHE3 antibody was used to localize the exchanger in the gills of the stenohaline marine spiny dogfish shark (Squalus acanthias). NHE3 immunoreactivity was confined to the apical side of cells with basolateral Na(+)/K(+)-ATPase and was excluded from cells with high levels of vacuolar H(+)-ATPase. Western blots detected a single protein of 88 kDa in dogfish gills, the same size as NHE3 in stingrays and mammals. These immunological data demonstrate that the putative cell type responsible for active Na(+) absorption in euryhaline elasmobranchs is also present in stenohaline marine elasmobranchs, and suggest that the inability of most elasmobranchs to survive in fresh water is not due to a lack of the gill ion transporters for Na(+) absorption.

Exposure to acute severe hypoxia leads to increased urea loss and disruptions in acid-base and ionoregulatory balance in dogfish sharks (Squalus acanthias).

PubMed

Zimmer, Alex M; Wood, Chris M

2014-01-01

The effects of acute moderate (20% air O2 saturation; 6-h exposure) and severe (5% air O2 saturation; 4-h exposure) hypoxia on N-waste, acid-base, and ion balance in dogfish sharks (Squalus acanthias suckleyi) were evaluated. We predicted that the synthesis and/or retention of urea, which are active processes, would be inhibited by hypoxia. Exposure to moderate hypoxia had negligible effects on N-waste fluxes or systemic physiology, except for a modest rise in plasma lactate. Exposure to severe hypoxia led to a significant increase in urea excretion (Jurea), while plasma, liver, and muscle urea concentrations were unchanged, suggesting a loss of urea retention. Ammonia excretion (Jamm) was elevated during normoxic recovery. Moreover, severe hypoxia led to disruptions in acid-base balance, indicated by a large increase in plasma [lactate] and substantial decreases in arterial pHa and plasma [Formula: see text], as well as loss of ionic homeostasis, indicated by increases in plasma [Mg(2+)], [Ca(2+)], and [Na(+)]. We suggest that severe hypoxia in dogfish sharks leads to a reduction in active gill homeostatic processes, such as urea retention, acid-base regulation and ionoregulation, and/or an osmoregulatory compromise due to increased functional gill surface area. Overall, the results provide a comprehensive picture of the physiological responses to a severe degree of hypoxia in an ancient fish species.

The use of satellite tags to redefine movement patterns of spiny dogfish (Squalus acanthias) along the U.S. east coast: implications for fisheries management.

PubMed

Carlson, Amy E; Hoffmayer, Eric R; Tribuzio, Cindy A; Sulikowski, James A

2014-01-01

Spiny dogfish (Squalus acanthias) are assumed to be a highly migratory species, making habitual north-south migrations throughout their northwestern Atlantic United States (U.S.) range. Also assumed to be a benthic species, spiny dogfish stock structure is estimated through Northeast Fisheries Science Center (NEFSC) bottom-trawl surveys. Recent anomalies in population trends, including a recent four-fold increase in estimated spawning stock biomass, suggest alternative movement patterns could exist for this shark species. To obtain a better understanding of the horizontal and vertical movement dynamics of this species, Microwave Telemetry pop-up satellite archival X-Tags were attached to forty adult spiny dogfish at the northern (Gulf of Maine) and southern (North Carolina) extents of their core U.S. geographic range. Reconstructed geolocation tracks ranging in lengths from two to 12 months suggest that the seasonal migration patterns appear to be local in nature to each respective northern and southern deployment site, differing from previously published migration paradigms. Differences in distance and direction traveled between seasonal geolocations possibly indicate separate migratory patterns between groups. Kernel utilization distribution models also suggest strong separate core home ranges. Significant differences in seasonal temperature and depths between the two regions further substantiate the possibility of separate regional movement patterns between the two groups. Vertical utilization also suggests distinct diel patterns and that this species may not utilize the benthos as previously thought, potentially decreasing availability to benthic gear.

Localization of Mg2+-sensing shark kidney calcium receptor SKCaR in kidney of spiny dogfish, Squalus acanthias.

PubMed

Hentschel, Hartmut; Nearing, Jacqueline; Harris, H William; Betka, Marlies; Baum, Michelle; Hebert, Steven C; Elger, Marlies

2003-09-01

We recently cloned a homologue of the bovine parathyroid calcium receptor from the kidney of a spiny dogfish (Squalus acanthias) and termed this new protein SKCaR. SKCaR senses alterations in extracellular Mg2+ after its expression in human embryonic kidney cells (Nearing J, Betka M, Quinn S, Hentschel H, Elger M, Baum M, Bai M, Chattopadyhay N, Brown E, Hebert S, and Harris HW. Proc Natl Acad. Sci USA 99: 9231-9236, 2002). In this report, we used light and electron microscopic immunocytochemical techniques to study the distribution of SKCaR in dogfish kidney. SKCaR antiserum bound to the apical membranes of shark kidney epithelial cells in the following tubular segments: proximal tubules (PIa and PIIb), late distal tubule, and collecting tubule/collecting duct as well as diffusely labeled cells of early distal tubule. The highly specific distribution of SKCaR in mesial tissue as well as lateral countercurrent bundles of dogfish kidney is compatible with a role for SKCaR to sense local tubular Mg2+ concentrations. This highly specific distribution of SKCaR protein in dogfish kidney could possibly work in concert with the powerful Mg2+ secretory system present in the PIIa segment of elasmobranch fish kidney to affect recycling of Mg2+ from putative Mg2+-sensing/Mg2+-reabsorbing segments. These data provide support for the possible existence of Mg2+ cycling in elasmobranch kidney in a manner analogous to that described for mammals.

Cell and molecular biology of marine elasmobranchs: Squalus acanthias and Raja erinacea.

PubMed

Mattingly, Carolyn; Parton, Angela; Dowell, Lori; Rafferty, Jason; Barnes, David

2004-01-01

Elasmobranchs are among the most primitive existing species exhibiting fundamental vertebrate characteristics, such as neural crest, jaws, teeth, and an adaptive immune system. They are also among the earliest-evolved vertebrates with a closed, pressurized circulatory system and related signaling molecules. Although many species are used experimentally, the spiny dogfish shark (Squalus acanthias) and little skate (Raja erinacea) have particular advantages and are the most commonly used elasmobranch biomedical models. These animals display powerful molecular systems for dealing with salt and water homeostasis, cell volume regulation, and environmental and internal osmotic sensing. They have become important unique models in studies of transport-related diseases such as cystic fibrosis and anion or xenobiotic transport. Much of this work has relied on physiological experiments combined with molecular approaches and the advantages of comparative genomic analyses to identify conserved regions representing functional protein domains. Recent work has seen the development of cell cultures and the beginning of expressed sequence tags (EST) and genomic libraries. Other areas in which elasmobranches have played critical roles include immunology and neurobiology. It also appears that sharks have tissue regenerative capability beyond what is commonly seen in mammals. For example, sharks and skates possess a region of renal regeneration, with new tubules being formed continually through adulthood. As comparative functional genomics comes of age, these comparative vertebrate models may play an increasing role in the larger picture of human biomedical research. There is plenty of ocean to share.

Age, Growth, Reproduction and Feeding of the Spurdog ( Squalus acanthias Linnaeus, 1758) in the South-eastern Black Sea

NASA Astrophysics Data System (ADS)

Avsar, D.

2001-02-01

Life-history parameters and diet of spurdog ( Squalus acanthias) sampled from the SE Black Sea were studied. Spurdog from age classes I to XIV were identified, with a dominance of age class VIII for both sexes. The length-weight relationship was W=0·0040*L 2·95and the mean annual growth rates in length and weight were 7·2 cm and 540·1 g, respectively. The estimated von Bertalanffy growth parameters were: W ∞=12021 (g), L ∞=157 (cm), K=0·12 (year -1) and t 0=-1·30 (year). The size at first maturity was 82 cm for males and 88 cm for females. Mean biennial fecundity was also found to be 8 pups/female. The relationships between fecundity-length, fecundity-weight and fecundity-age were found to be: F=-17·0842+0·2369*L (R=0·93), F=0·3780+0·0018*W (R=0·89) and F =-0·7859+1·1609*A (R=0·94) respectively. The spurdog can be considered an opportunistic feeder. Their natural diet was composed mainly of teleost fishes, followed by Crustaceans, Nematodes and Actinarians (=sea anemones). Whiting ( Merlangius merlangus euxinus) was the predominant prey item among their fish prey. Demersal teleosts formed the majority of the diet, and there was no difference ( P>0·05) among the food items of immature, maturing and mature individuals of both sexes.

Baseline health parameters and species comparisons among free-ranging Atlantic sharpnose (Rhizoprionodon terraenovae), bonnethead (Sphyrna tiburo), and spiny dogfish (Squalus acanthias) sharks in Georgia, Florida, and Washington, USA.

PubMed

Haman, Katherine H; Norton, Terry M; Thomas, Austen C; Dove, Alistair D M; Tseng, Florina

2012-04-01

Sharks are of commercial, research, conservation, and exhibition importance but we know little regarding health parameters and population status for many species. Here we present health indicators and species comparisons for adults of three common wild-caught species: 30 Atlantic sharpnose sharks (Rhizoprionodon terraenovae) and 31 bonnethead sharks (Sphyrna tiburo) from the western Atlantic, and 30 spiny dogfish sharks (Squalus acanthias) from the eastern Pacific. All animals were captured during June-July 2009 and 2010. Median values and preliminary reference intervals were calculated for hematology, plasma biochemistry, trace nutrients, and vitamin A, E, and D concentrations. Significant differences, attributable to physiologic differences among the species, were found in the basic hematologic and plasma biochemistry variables. Significant species differences in arsenic and selenium plasma concentrations were found and appear to coincide with diet and habitat variability among these three species. Vitamin E was significantly higher in the bonnethead shark, again related to the foraging ecology and ingestion of plant material by this species. The Atlantic sharpnose had significantly higher vitamin A concentrations, supported by the higher proportion of teleosts in the diet. Vitamin D was below the limit of quantification in all three species. These preliminary reference intervals for health variables can be used to assess and monitor the population health and serve as indicators of nutritional status in these populations of wild elasmobranchs.

The alkaline tide goes out and the nitrogen stays in after feeding in the dogfish shark, Squalus acanthias.

PubMed

Wood, Chris M; Bucking, Carol; Fitzpatrick, John; Nadella, Sunita

2007-11-15

In light of previous work showing a marked metabolic alkalosis ("alkaline tide") in the bloodstream after feeding in the dogfish shark (Squalus acanthias), we evaluated whether there was a corresponding net base excretion to the water at this time. In the 48 h after a natural voluntary meal (teleost tissue, averaging 5.5% of body weight), dogfish excreted 10,470 micromol kg(-1) more base (i.e. HCO3- equivalents) than the fasted control animals (which exhibited a negative base excretion of -2160 micromol kg(-1)). This large activation of branchial base excretion after feeding thereby prevented a potentially fatal alkalinization of the body fluids by the alkaline tide. The rate peaked at 330 micromol kg(-1) h(-1) at 12.5-24 h after the meal. Despite a prolonged 1.7-fold elevation in MO2 after feeding ("specific dynamic action"), urea-N excretion decreased by 39% in the same 48 h period relative to fasted controls. In contrast, ammonia-N excretion did not change appreciably. The N/O2 ratio declined from 0.51 in fasted animals to 0.19 in fed sharks, indicating a stimulation of N-anabolic processes at this time. These results, which differ greatly from those in teleost fish, are interpreted in terms of the fundamentally different ureotelic osmoregulatory strategy of elasmobranchs, and recent discoveries on base excretion and urea-retention mechanisms in elasmobranch gills.

Global population structure of the spiny dogfish Squalus acanthias, a temperate shark with an antitropical distribution.

PubMed

Veríssimo, A; McDowell, J R; Graves, J E

2010-04-01

The spiny dogfish (Squalus acanthias) is a temperate, coastal squaloid shark with an antitropical distribution in the Atlantic and Pacific oceans. The global population structure of this species is poorly understood, although individuals are known to undergo extensive migrations within coastal waters and across ocean basins. In this study, an analysis of the global population structure of the spiny dogfish was conducted using eight polymorphic nuclear microsatellite markers and a 566-bp fragment of the mitochondrial ND2 gene region. A low level of genetic divergence was found among collections from the Atlantic and South Pacific basins, whereas a high level of genetic divergence was found among Pacific Ocean collections. Two genetically distinct groups were recovered by both marker classes: one exclusive to North Pacific collections, and one including collections from the South Pacific and Atlantic locations. The strong genetic break across the equatorial Pacific coincides with major regional differences in the life-history characters of spiny dogfish, suggesting that spiny dogfish in areas on either side of the Pacific equator have been evolving independently for a considerable time. Phylogeographic analyses indicate that spiny dogfish populations had a Pacific origin, and that the North Atlantic was colonized as a result of a recent range expansion from the South American coast. Finally, the available data strongly argue for the taxonomic separation of the North Pacific spiny dogfish from S. acanthias and a re-evaluation of the specific status of S. acanthias is warranted.

The Use of Satellite Tags to Redefine Movement Patterns of Spiny Dogfish (Squalus acanthias) along the U.S. East Coast: Implications for Fisheries Management

PubMed Central

Carlson, Amy E.; Hoffmayer, Eric R.; Tribuzio, Cindy A.; Sulikowski, James A.

2014-01-01

Spiny dogfish (Squalus acanthias) are assumed to be a highly migratory species, making habitual north-south migrations throughout their northwestern Atlantic United States (U.S.) range. Also assumed to be a benthic species, spiny dogfish stock structure is estimated through Northeast Fisheries Science Center (NEFSC) bottom-trawl surveys. Recent anomalies in population trends, including a recent four-fold increase in estimated spawning stock biomass, suggest alternative movement patterns could exist for this shark species. To obtain a better understanding of the horizontal and vertical movement dynamics of this species, Microwave Telemetry pop-up satellite archival X-Tags were attached to forty adult spiny dogfish at the northern (Gulf of Maine) and southern (North Carolina) extents of their core U.S. geographic range. Reconstructed geolocation tracks ranging in lengths from two to 12 months suggest that the seasonal migration patterns appear to be local in nature to each respective northern and southern deployment site, differing from previously published migration paradigms. Differences in distance and direction traveled between seasonal geolocations possibly indicate separate migratory patterns between groups. Kernel utilization distribution models also suggest strong separate core home ranges. Significant differences in seasonal temperature and depths between the two regions further substantiate the possibility of separate regional movement patterns between the two groups. Vertical utilization also suggests distinct diel patterns and that this species may not utilize the benthos as previously thought, potentially decreasing availability to benthic gear. PMID:25068584

Nitric oxide (NO) in normal and hypoxic vascular regulation of the spiny dogfish, Squalus acanthias.

PubMed

Swenson, Kai E; Eveland, Randy L; Gladwin, Mark T; Swenson, Erik R

2005-02-01

Nitric oxide (NO) is a potent vasodilator in terrestrial vertebrates, but whether vascular endothelial-derived NO plays a role in vascular regulation in fish remains controversial. To explore this issue, a study was made of spiny dogfish sharks (Squalus acanthias) in normoxia and acute hypoxia (60 min exposure to seawater equilibrated with 3% oxygen) with various agents known to alter NO metabolism or availability. In normoxia, nitroprusside (a NO donor) reduced blood pressure by 20%, establishing that vascular smooth muscle responds to NO. L-arginine, the substrate for NO synthase, had no hemodynamic effect. Acetylcholine, which stimulates endothelial NO and prostaglandin production in mammals, reduced blood pressure, but also caused marked bradycardia. L-NAME, an inhibitor of all NO synthases, caused a small 10% rise in blood pressure, but cell-free hemoglobin (a potent NO scavenger and hypertensive agent in mammals) had no effect. Acute hypoxia caused a 15% fall in blood pressure, which was blocked by L-NAME and cell-free hemoglobin. Serum nitrite, a marker of NO production, rose with hypoxia, but not with L-NAME. Results suggest that NO is not an endothelial-derived vasodilator in the normoxic elasmobranch. The hypertensive effect of L-NAME may represent inhibition of NO production in the CNS and nerves regulating blood pressure. In acute hypoxia, there is a rapid up-regulation of vascular NO production that appears to be responsible for hypoxic vasodilation.

Time course of the establishment of uterine seawater conditions in late-term pregnant spiny dogfish (Squalus acanthias).

PubMed

Kormanik, G A

1988-07-01

The gestation period for embryos of the spiny dogfish, Squalus acanthias (L.) lasts for nearly 2 years. During the latter part of this period the pups remain in the uterus and the fluid surrounding the embryos resembles sea water with respect to the major ions, but is low in pH (approx. 6), high in partial pressure of carbon dioxide (approx. 3 mmHg; 1 mmHg = 133.3 Pa), low in total carbon dioxide content (approx. 0.2 mmol l-1), and may have a total ammonia concentration of up to 22 mmol l-1. Thus the conditions under which the pups complete their development in utero is quite remarkable. The derivation of these conditions was examined in late-term pregnant females, from whose uterine horns the pups had been removed, by monitoring changes that occurred in instilled uterine sea water. The mother is responsible for reducing the pH, reducing the total carbon dioxide content and elevating the partial pressure of carbon dioxide to the levels observed in fresh-caught females, in less than 24 h. The ammonia concentration is also elevated, but this takes rather longer. The decreased pH is responsible for the accumulation of ammonia in the uterine sea water, and it also serves to protect the pups from the toxic effects of NH3, by converting it to the relatively non-toxic ionic form, NH4+. The reasons for the establishment of these uterine seawater conditions are still not evident.

Fluorescein-methotrexate transport in dogfish shark (Squalus acanthias) choroid plexus.

PubMed

Baehr, Carsten H; Fricker, Gert; Miller, David S

2006-08-01

The vertebrate choroid plexus removes potentially toxic metabolites and xenobiotics from cerebrospinal fluid (CSF) to blood for subsequent excretion in urine and bile. We used confocal microscopy and quantitative image analysis to characterize the mechanisms driving transport of the large organic anion, fluorescein-methotrexate (FL-MTX), from bath (CSF-side) to blood vessels in intact lateral choroid plexus from dogfish shark, Squalus acanthias, an evolutionarily ancient vertebrate. With 2 microM FL-MTX in the bath, steady-state fluorescence in the subepithelium/vascular space exceeded bath levels by 5- to 10-fold, and fluorescence in the epithelial cells was slightly below bath levels. FL-MTX accumulation in both tissue compartments was reduced by NaCN, Na removal, and ouabain, but not by a 10-fold increase in medium K. Certain organic anions, e.g., probenecid, MTX, and taurocholate, reduced FL-MTX accumulation in both tissue compartments; p-aminohippurate and estrone sulfate reduced subepithelial/vascular accumulation, but not cellular accumulation. At low concentrations, digoxin, leukotriene C4, and MK-571 reduced fluorescence in the subepithelium/vascular space while increasing cellular fluorescence, indicating preferential inhibition of efflux over uptake. In the presence of 10 microM digoxin (reduced efflux, enhanced cellular accumulation), cellular FL-MTX accumulation was specific, concentrative, and Na dependent. Thus transepithelial FL-MTX transport involved the following two carrier-mediated steps: electroneutral, Na-dependent uptake at the apical membrane and electroneutral efflux at the basolateral membrane. Finally, FL-MTX accumulation in both tissue compartments was reduced by phorbol ester and increased by forskolin, indicating antagonistic modulation by protein kinase C and protein kinase A.

Levels of mercury in muscle and liver of star-spotted dogfish (Mustelus manazo) from the northern region of Japan: a comparison with spiny dogfish (Squalus acanthias).

PubMed

Endo, Tetsuya; Hisamichi, Yohsuke; Kimura, Osamu; Ogasawara, Hideki; Ohta, Chiho; Koga, Nobuyuki; Kato, Yoshihisa; Haraguchi, Koichi

2013-04-01

We analyzed mercury (Hg) concentrations in muscle and liver samples of star-spotted dogfish (Mustelus manazo) caught off the northern region of Japan and compared them with those of spiny dogfish (Squalus acanthias) caught in the same region. The average body length of male star-spotted dogfish specimens was significantly smaller than that of female specimens, reflecting the slower growth rate of male fish. Hg concentrations in liver and muscle increased with increases in body length and estimated age of both male and female star-spotted dogfish specimens. However, the relationships between Hg concentration in liver or muscle and body length or estimated age of male specimens differed markedly from those of female specimens, reflecting differences in growth rate and cessation of growth on reaching maturity. Marked increases in Hg concentration in liver of male and female star-spotted dogfish specimens were observed slightly later than increases in Hg concentration in muscle of those specimens due to growth cessation. These marked increases in Hg in liver may reflect increases in Hg due to the formation of mercury selenide. Similar results were previously reported in spiny dogfish specimens, except spiny dogfish showed only trace levels of Hg in liver (Endo et al., Chemosphere 77:1333-1337, 2009). The greater lipid content in liver and the larger liver size in spiny dogfish may explain the much lower levels of Hg observed in liver of spiny dogfish compared with those in the star-spotted dogfish.

Central venous pressure and mean circulatory filling pressure in the dogfish Squalus acanthias: adrenergic control and role of the pericardium.

PubMed

Sandblom, Erik; Axelsson, Michael; Farrell, Anthony P

2006-11-01

Subambient central venous pressure (Pven) and modulation of venous return through cardiac suction (vis a fronte) characterizes the venous circulation in sharks. Venous capacitance was estimated in the dogfish Squalus acanthias by measuring the mean circulatory filling pressure (MCFP) during transient occlusion of cardiac outflow. We tested the hypothesis that venous return and cardiac preload can be altered additionally through adrenergic changes of venous capacitance. The experiments involved the surgical opening of the pericardium to place a perivascular occluder around the conus arteriosus. Another control group was identically instrumented, but lacked the occluder, and was subjected to the same pharmacological protocol to evaluate how pericardioectomy affected cardiovascular status. Routine Pven was negative (-0.08+/-0.02 kPa) in control fish but positive (0.09+/-0.01 kPa) in the pericardioectomized group. Injections of 5 microg/kg body mass (Mb) of epinephrine and phenylephrine (100 microg/kg Mb) increased Pven and MCFP, whereas isoproterenol (1 microg/kg Mb) decreased both variables. Thus, constriction and relaxation of the venous vasculature were mediated through the respective stimulation of alpha- and beta-adrenergic receptors. Alpha-adrenergic blockade with prazosin (1 mg/kg Mb) attenuated the responses to phenylephrine and decreased resting Pven in pericardioectomized animals. Our results provide convincing evidence for adrenergic control of the venous vasculature in elasmobranchs, although the pericardium is clearly an important component in the modulation of venous function. Thus active changes in venous capacitance have previously been underestimated as an important means of modulating venous return and cardiac performance in this group.

Texas Red transport across rat and dogfish shark (Squalus acanthias) choroid plexus.

PubMed

Reichel, Valeska; Miller, David S; Fricker, Gert

2008-10-01

Confocal microscopy and image analysis were used to compare driving forces, specificity, and regulation of transport of the fluorescent organic anion, Texas Red (sulforhodamine 101 free acid; TR), in lateral choroid plexus (CP) isolated from rat and an evolutionarily ancient vertebrate, dogfish shark (Squalus acanthias). CP from both species exhibited concentrative, specific, and metabolism-dependent TR transport from bath to subepithelial/vascular space; at steady state, TR accumulation in vascular/subepithelial space was substantially higher than in epithelial cells. In rat CP, steady-state TR accumulation in subepithelial/vascular spaces was reduced by Na(+)-replacement, but was not affected by a 10-fold increase in buffer K(+). In shark CP, Na(+)-replacement did not alter TR accumulation in either tissue compartment; subepithelial/vascular space levels of TR were reduced in high-K(+) medium. In both species, steady-state TR accumulation was not affected by p-aminohippurate or leukotriene C4, suggesting that neither organic anion transporters (SLC22A family) nor multidrug resistance-associated proteins (ABCC family) contributed. In rat CP, digoxin was without effect, indicating that organic anion transporting polypeptide isoform 2 was not involved. Several organic anions reduced cellular and subepithelial/vascular space TR accumulation in both tissues, including estrone sulfate, taurocholate, and the Mrp1 inhibitor MK571. In rat CP, TR accumulation in subepithelial/vascular spaces increased with PKA activation (forskolin), but was not affected by PKC activation (phorbol ester). In shark, neither PKA nor PKC activation specifically affected TR transport. Thus, rat and dogfish shark CP transport TR but do so using different basic mechanisms that respond to different regulatory signals.

Ontogenetic scaling of caudal fin shape in Squalus acanthias (Chondrichthyes, Elasmobranchii): a geometric morphometric analysis with implications for caudal fin functional morphology.

PubMed

Reiss, Katie L; Bonnan, Matthew F

2010-07-01

The shark heterocercal caudal fin and its contribution to locomotion are of interest to biologists and paleontologists. Current hydrodynamic data show that the stiff dorsal lobe leads the ventral lobe, both lobes of the tail are synchronized during propulsion, and tail shape reflects its overall locomotor function. Given the difficulties surrounding the analysis of shark caudal fins in vivo, little is known about changes in tail shape related to ontogeny and sex in sharks. A quantifiable analysis of caudal fin shape may provide an acceptable proxy for inferring gross functional morphology where direct testing is difficult or impossible. We examined ontogenetic and sex-related shape changes in the caudal fins of 115 Squalus acanthias museum specimens, to test the hypothesis that significant shape changes in the caudal fin shape occur with increasing size and between the sexes. Using linear and geometric morphometrics, we examined caudal shape changes within the context of current hydrodynamic models. We found no statistically significant linear or shape difference between sexes, and near-isometric scaling trends for caudal dimensions. These results suggest that lift and thrust increase linearly with size and caudal span. Thin-plate splines results showed a significant allometric shape change associated with size and caudal span: the dorsal lobe elongates and narrows, whereas the ventral lobe broadens and expands ventrally. Our data suggest a combination of caudal fin morphology with other body morphology aspects, would refine, and better elucidate the hydrodynamic factors (if any) that underlie the significant shape changes we report here for S. acanthias.

Examining urea flux across the intestine of the spiny dogfish, Squalus acanthias.

PubMed

Gary Anderson, W; McCabe, Chris; Brandt, Catherine; Wood, Chris M

2015-03-01

Recent examination of urea flux in the intestine of the spiny dogfish shark, Squalus acanthias, has shown that feeding significantly enhances urea uptake across the intestine, and this was significantly inhibited following mucosal addition of phloretin. The present study examined potential mechanisms of urea uptake across the dogfish intestine in starved and fed dogfish. Unidirectional flux chambers were used to examine the kinetics of urea uptake, and to determine the influence of sodium, ouabain, competitive urea analogues, and phloretin on urea uptake across the gut of fed dogfish. Intestinal epithelial preparations from starved and fed dogfish were mounted in Ussing chambers to examine the effect of phloretin on bidirectional solute transport across the intestine. In the unidirectional studies, the maximum uptake rate of urea was found to be 35.3±6.9 μmol.cm(-2).h(-1) and Km was found to be 291.8±9.6 mM in fed fish, and there was a mild inhibition of urea uptake following mucosal addition of competitive agonists. Addition of phloretin, Na-free Ringers and ouabain to the mucosal side of intestinal epithelia also led to a significant reduction in urea uptake in fed fish. In the Ussing chamber studies there was a net influx of urea in fed fish and a small insignificant efflux in starved fish. Addition of phloretin blocked urea uptake in fed fish when added to the mucosal side. Furthermore, phloretin had no effect on ion transport across the intestinal epithelia with the exception of the divalent cations, magnesium and calcium. Copyright © 2015 Elsevier Inc. All rights reserved.

Spatial overlap of shark nursery areas and the salmon farming industry influences the trophic ecology of Squalus acanthias on the southern coast of Chile.

PubMed

Gaitán-Espitia, Juan Diego; Gómez, Daniela; Hobday, Alistair J; Daley, Ross; Lamilla, Julio; Cárdenas, Leyla

2017-06-01

Potential interactions between marine predators and humans arise in the southern coast of Chile where predator feeding and reproduction sites overlap with fisheries and aquaculture. Here, we assess the potential effects of intensive salmon aquaculture on food habits, growth, and reproduction of a common predator, the spiny dogfish-identified as Squalus acanthias via genetic barcoding. A total of 102 (89 females and 13 males) individuals were collected during winter and summer of 2013-2014 from the Chiloé Sea where salmon aquaculture activities are concentrated. The low frequency of males in our study suggests spatial segregation of sex, while immature and mature females spatially overlapped in both seasons. Female spiny dogfish showed a functional specialist behavior as indicated by the small number of prey items and the relative high importance of the austral hake and salmon pellets in the diet. Immature sharks fed more on pellets and anchovies than the larger hake-preferring mature females. Our results also indicate that spiny dogfish switch prey (anchovy to hake) to take advantage of seasonal changes in prey availability. Despite differences in the trophic patterns of S. acanthias due to the spatial association with intensive salmon farming, in this region, there appears to be no difference in fecundity or size at maturity compared to other populations. Although no demographic effects were detected, we suggest that a range of additional factors should be considered before concluding that intensive aquaculture does not have any impact on these marine predators.

Diet and trophic level of the longnose spurdog Squalus blainville (Risso, 1826) in the deep waters of the Aegean Sea

NASA Astrophysics Data System (ADS)

Kousteni, Vasiliki; Karachle, Paraskevi K.; Megalofonou, Persefoni

2017-06-01

Knowledge of the diet and trophic level of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on the trophic ecology of the deep-sea sharks is rather limited. The purpose of this study was to examine the diet of the longnose spurdog Squalus blainville, a deep-sea shark categorized as "data deficient" within its distribution range, with respect to sex, maturity, age, season and sampling location. The stomach contents of 211 specimens, captured in the Aegean (off Skyros and the Cyclades Islands) and Cretan Seas, using commercial bottom-trawlers from 2005 to 2012, were analysed. The cumulative prey curve showed that the sample size was adequate to describe the species' diet. The identified prey items belonged to five major groups: Teleostei, Crustacea, Cephalopoda, Annelida and Phanerogams. Higher diet diversity was observed in females compared to males, in immature individuals compared to mature ones, regardless of sex, and in spring and winter compared to other seasons. Age and sampling location seemed to influence both the diet diversity and trophic spectrum of the species. Feeding intensity based on the vacuity index was not significantly influenced by any of the factors examined, while the stomach filling degree was significantly influenced by all factors, except sex, showing significantly higher values in mature females compared to immature ones, in older individuals, in autumn compared to winter, and a significantly lower value in the Cyclades Islands compared to other locations. Females showed a significant larger mouth length compared to males of the same length, while no between-sex differences were found in gut morphometrics. The estimated fractional trophic level (TROPH=4.41) classified the species as carnivore with a preference for Teleostei and Cephalopoda, confirming its high trophic position.

Cell and molecular biology of the spiny dogfish Squalus acanthias and little skate Leucoraja erinacea: insights from in vitro cultured cells.

PubMed

Barnes, D W

2012-04-01

Two of the most commonly used elasmobranch experimental model species are the spiny dogfish Squalus acanthias and the little skate Leucoraja erinacea. Comparative biology and genomics with these species have provided useful information in physiology, pharmacology, toxicology, immunology, evolutionary developmental biology and genetics. A wealth of information has been obtained using in vitro approaches to study isolated cells and tissues from these organisms under circumstances in which the extracellular environment can be controlled. In addition to classical work with primary cell cultures, continuously proliferating cell lines have been derived recently, representing the first cell lines from cartilaginous fishes. These lines have proved to be valuable tools with which to explore functional genomic and biological questions and to test hypotheses at the molecular level. In genomic experiments, complementary (c)DNA libraries have been constructed, and c. 8000 unique transcripts identified, with over 3000 representing previously unknown gene sequences. A sub-set of messenger (m)RNAs has been detected for which the 3' untranslated regions show elements that are remarkably well conserved evolutionarily, representing novel, potentially regulatory gene sequences. The cell culture systems provide physiologically valid tools to study functional roles of these sequences and other aspects of elasmobranch molecular cell biology and physiology. Information derived from the use of in vitro cell cultures is valuable in revealing gene diversity and information for genomic sequence assembly, as well as for identification of new genes and molecular markers, construction of gene-array probes and acquisition of full-length cDNA sequences. © 2012 The Author. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

DNA barcoding Australia's fish species

PubMed Central

Ward, Robert D; Zemlak, Tyler S; Innes, Bronwyn H; Last, Peter R; Hebert, Paul D.N

2005-01-01

Two hundred and seven species of fish, mostly Australian marine fish, were sequenced (barcoded) for a 655 bp region of the mitochondrial cytochrome oxidase subunit I gene (cox1). Most species were represented by multiple specimens, and 754 sequences were generated. The GC content of the 143 species of teleosts was higher than the 61 species of sharks and rays (47.1% versus 42.2%), largely due to a higher GC content of codon position 3 in the former (41.1% versus 29.9%). Rays had higher GC than sharks (44.7% versus 41.0%), again largely due to higher GC in the 3rd codon position in the former (36.3% versus 26.8%). Average within-species, genus, family, order and class Kimura two parameter (K2P) distances were 0.39%, 9.93%, 15.46%, 22.18% and 23.27%, respectively. All species could be differentiated by their cox1 sequence, although single individuals of each of two species had haplotypes characteristic of a congener. Although DNA barcoding aims to develop species identification systems, some phylogenetic signal was apparent in the data. In the neighbour-joining tree for all 754 sequences, four major clusters were apparent: chimaerids, rays, sharks and teleosts. Species within genera invariably clustered, and generally so did genera within families. Three taxonomic groups—dogfishes of the genus Squalus, flatheads of the family Platycephalidae, and tunas of the genus Thunnus—were examined more closely. The clades revealed after bootstrapping generally corresponded well with expectations. Individuals from operational taxonomic units designated as Squalus species B through F formed individual clades, supporting morphological evidence for each of these being separate species. We conclude that cox1 sequencing, or ‘barcoding’, can be used to identify fish species. PMID:16214743

B cell receptor accessory molecule CD79α: Characterisation and expression analysis in a cartilaginous fish, the spiny dogfish (Squalus acanthias)

PubMed Central

Li, Ronggai; Wang, Tiehui; Bird, Steve; Zou, Jun; Dooley, Helen; Secombes, Christopher J.

2013-01-01

CD79α (also known as Igα) is a component of the B cell antigen receptor complex and plays an important role in B cell signalling. The CD79α protein is present on the surface of B cells throughout their life cycle, and is absent on all other healthy cells, making it a highly reliable marker for B cells in mammals. In this study the spiny dogfish (Squalus acanthias) CD79α (SaCD79α) is described and its expression studied under constitutive and stimulated conditions. The spiny dogfish CD79α cDNA contains an open reading frame of 618 bp, encoding a protein of 205 amino acids. Comparison of the SaCD79α gene with that of other species shows that the gross structure (number of exons, exon/intron boundaries, etc.) is highly conserved across phylogeny. Additionally, analysis of the 5′ flanking region shows SaCD79α lacks a TATA box and possesses binding sites for multiple transcription factors implicated in its B cell-specific gene transcription in other species. Spiny dogfish CD79α is most highly expressed in immune tissues, such as spleen, epigonal and Leydig organ, and its transcript level significantly correlates with those of spiny dogfish immunoglobulin heavy chains. Additionally, CD79α transcription is up-regulated, to a small but significant degree, in peripheral blood cells following stimulation with pokeweed mitogen. These results strongly indicate that, as in mammals, spiny dogfish CD79α is expressed by shark B cells where it associates with surface-bound immunoglobulin to form a fully functional BCR, and thus may serve as a pan-B cell marker in future shark immunological studies. PMID:23454429

Multidrug Resistance-Associated Protein 3 (Mrp3/Abcc3/Moat-D) Is Expressed in the SAE Squalus acanthias Shark Embryo–Derived Cell Line

PubMed Central

Kobayashi, Hiroshi; Parton, Angela; Czechanski, Anne; Durkin, Christopher; Kong, Chi-Chon; Barnes, David

2008-01-01

The multidrug resistance-associated protein 3 (MRP3/Mrp3) is a member of the ATP-binding cassette (ABC) protein family of membrane transporters and related proteins that act on a variety of xenobiotic and anionic molecules to transfer these substrates in an ATP-dependent manner. In recent years, useful comparative information regarding evolutionarily conserved structure and transport functions of these proteins has accrued through the use of primitive marine animals such as cartilaginous fish. Until recently, one missing tool in comparative studies with cartilaginous fish was cell culture. We have derived from the embryo of Squalus acanthias, the spiny dogfish shark, the S. acanthias embryo (SAE) mesenchymal stem cell line. This is the first continuously proliferating cell line from a cartilaginous fish. We identified expression of Mrp3 in this cell line, cloned the molecule, and examined molecular and cellular physiological aspects of the protein. Shark Mrp3 is characterized by three membrane-spanning domains and two nucleotide-binding domains. Multiple alignments with other species showed that the shark Mrp3 amino acid sequence was well conserved. The shark sequence was overall 64% identical to human MRP3, 72% identical to chicken Mrp3, and 71% identical to frog and stickleback Mrp3. Highest identity between shark and human amino acid sequence (82%) was seen in the carboxyl-terminal nucleotide-binding domain of the proteins. Cell culture experiments showed that mRNA for the protein was induced as much as 25-fold by peptide growth factors, fetal bovine serum, and lipid nutritional components, with the largest effect mediated by a combination of lipids including unsaturated and saturated fatty acids, cholesterol, and vitamin E. PMID:18284333

Flow through the nasal cavity of the spiny dogfish, Squalus acanthias

NASA Astrophysics Data System (ADS)

Timm-Davis, L. L.; Fish, F. E.

2015-12-01

The nasal cavity of spiny dogfish is a blind capsule with no internal connection to the oral cavity. Water is envisioned to flow through the cavity in a smooth, continuous flow pattern; however, this assumption is based on previous descriptions of the morphology of the olfactory cavity. No experimentation on the flow through the internal nasal cavity has been reported. Morphology of the head of the spiny dogfish ( Squalus acanthias) does not suggest a close external connection between the oral and nasal systems. However, dye visualization showed that there was flow through the nasal apparatus and from the excurrent nostril to the mouth when respiratory flows were simulated. The hydrodynamic flow through the nasal cavity was observed from flow tank experiments. The dorsum of the nasal cavity of shark heads from dead animals was exposed by dissection and a glass plate was glued over of the exposed cavity. When the head was placed in a flow, dye was observed to be drawn passively into the cavity showing a complex, three-dimensional hydrodynamic flow. Dye entered the incurrent nostril, flowed through the nasal lamellae, crossed over and under the nasal valve, and circulated around the nasal valve before exiting the excurrent nostril. When the nasal valve was removed, the dye became stagnant and back flowed out through the incurrent nostril. The single nasal valve has a hydrodynamic function that organizes a coherent flow of water through the cavity without disruption. The results suggest that the morphology of the nasal apparatus in concert with respiratory flow and ambient flows from active swimming can be used to draw water through the olfactory cavity of the shark.

The dogfish shark (Squalus acanthias) increases both hepatic and extrahepatic ornithine urea cycle enzyme activities for nitrogen conservation after feeding.

PubMed

Kajimura, Makiko; Walsh, Patrick J; Mommsen, Thomas P; Wood, Chris M

2006-01-01

Urea not only is utilized as a major osmolyte in marine elasmobranchs but also constitutes their main nitrogenous waste. This study investigated the effect of feeding, and thus elevated nitrogen intake, on nitrogen metabolism in the Pacific spiny dogfish Squalus acanthias. We determined the activities of ornithine urea cycle (O-UC) and related enzymes in liver and nonhepatic tissues. Carbamoyl phosphate synthetase III (the rate-limiting enzyme of the O-UC) activity in muscle is high compared with liver, and the activities in both tissues increased after feeding. The contribution of muscle to urea synthesis in the dogfish body appears to be much larger than that of liver when body mass is considered. Furthermore, enhanced activities of the O-UC and related enzymes (glutamine synthetase, ornithine transcarbamoylase, arginase) were seen after feeding in both liver and muscle and were accompanied by delayed increases in plasma urea, trimethylamine oxide, total free amino acids, alanine, and chloride concentrations, as well as in total osmolality. The O-UC and related enzymes also occurred in the intestine but showed little change after feeding. Feeding did not change the rate of urea excretion, indicating strong N retention after feeding. Ammonia excretion, which constituted only a small percentage of total N excretion, was raised in fed fish, while plasma ammonia did not change, suggesting that excess ammonia in plasma is quickly ushered into synthesis of urea or protein. In conclusion, we suggest that N conservation is a high priority in this elasmobranch and that feeding promotes ureogenesis and growth. Furthermore, exogenous nitrogen from food is converted into urea not only by the liver but also by the muscle and to a small extent by the intestine.

Copper toxicity in the spiny dogfish (Squalus acanthias): urea loss contributes to the osmoregulatory disturbance.

PubMed

De Boeck, G; Hattink, J; Franklin, N M; Bucking, C P; Wood, S; Walsh, P J; Wood, C M

2007-08-30

Previous research showed that the spiny dogfish, Squalus acanthias, is much more sensitive to silver exposure than typical marine teleosts. The aim of the present study was to investigate if spiny dogfish were equally sensitive to copper exposure and whether the toxic mechanisms were the same. We exposed cannulated and non-cannulated spiny dogfish to measured concentrations of Cu (nominally 0, 500, 1000 and 1500 microg L(-1) Cu) for 72-96 h. All Cu exposures induced acidosis and lactate accumulation of either a temporary (500 microg L(-1)) or more persistent nature (1000 and 1500 microg L(-1)). At the two highest Cu concentrations, gill Na(+)/K(+)-ATPase activities were reduced by 45% (1000 microg L(-1)) and 62% (1500 microg L(-1)), and plasma Na(+) and Cl(-) concentrations increased by approximately 50 mM each. At the same time urea excretion doubled and plasma urea dropped by approximately 100 mM. Together with plasma urea, plasma TMAO levels dropped proportionally, indicating that the general impermeability of the gills was compromised. Overall plasma osmolarity did not change. Cu accumulation was limited with significant increases in plasma Cu and elevated gill and kidney Cu burdens at 1000 and 1500 microg L(-1). We conclude that Cu, like Ag, exerts toxic effect on Na(+)/K(+)-ATPase activities in the shark similar to those of teleosts, but there is an additional toxic action on elasmobranch urea retention capacities. With a 96 h LC(50) in the 800-1000 microg L(-1) range, overall sensitivity of spiny dogfish for Cu is, in contrast with its sensitivity to Ag, only slightly lower than in typical marine teleosts.

Multidrug resistance-associated protein 3 (Mrp3/Abcc3/Moat-D) is expressed in the SAE Squalus acanthias shark embryo-derived cell line.

PubMed

Kobayashi, Hiroshi; Parton, Angela; Czechanski, Anne; Durkin, Christopher; Kong, Chi-Chon; Barnes, David

2007-01-01

The multidrug resistance-associated protein 3 (MRP3/Mrp3) is a member of the ATP-binding cassette (ABC) protein family of membrane transporters and related proteins that act on a variety of xenobiotic and anionic molecules to transfer these substrates in an ATP-dependent manner. In recent years, useful comparative information regarding evolutionarily conserved structure and transport functions of these proteins has accrued through the use of primitive marine animals such as cartilaginous fish. Until recently, one missing tool in comparative studies with cartilaginous fish was cell culture. We have derived from the embryo of Squalus acanthias, the spiny dogfish shark, the S. acanthias embryo (SAE) mesenchymal stem cell line. This is the first continuously proliferating cell line from a cartilaginous fish. We identified expression of Mrp3 in this cell line, cloned the molecule, and examined molecular and cellular physiological aspects of the protein. Shark Mrp3 is characterized by three membrane-spanning domains and two nucleotide-binding domains. Multiple alignments with other species showed that the shark Mrp3 amino acid sequence was well conserved. The shark sequence was overall 64% identical to human MRP3, 72% identical to chicken Mrp3, and 71% identical to frog and stickleback Mrp3. Highest identity between shark and human amino acid sequence (82%) was seen in the carboxyl-terminal nucleotide-binding domain of the proteins. Cell culture experiments showed that mRNA for the protein was induced as much as 25-fold by peptide growth factors, fetal bovine serum, and lipid nutritional components, with the largest effect mediated by a combination of lipids including unsaturated and saturated fatty acids, cholesterol, and vitamin E.

Adenosine/nitric oxide crosstalk in the branchial circulation of Squalus acanthias and Anguilla anguilla.

PubMed

Pellegrino, D; Tota, B; Randall, D J

2005-10-01

The potent vasomodulator adenosine (AD), thanks to the interaction with by A(1) and A(2) receptors, dilates systemic, coronary and cerebral vasculatures but exert a constrictor action in several vessels of respiratory organs. Recent investigations suggest that nitric oxide (NO) contributes to AD effects. In fish, both NO and AD induce atypical effects compared to mammals. Since there is very little information on the role of NO and its involvement in mediating the actions of AD in fish, we have analysed this question in the branchial vasculature of the elasmobranch Squalus acanthias and the teleost Anguilla anguilla using an isolated perfused head and a branchial basket preparation, respectively. In both dogfish and eel, AD dose-response curves showed a biphasic effect: vasoconstriction (pico to nanomolar range) and vasodilation (micromolar range). Both effects were abolished by the classic xanthine inhibitor theophylline (Theo) and also by specific antagonists of A(1) and A(2) receptor subtypes. To analyse the involvement of the NO/cGMP system in the AD responses, we tested a NOS inhibitor, l-NIO, and a specific soluble guanylate cyclase (sGC) blocker, ODQ. In both dogfish and eel preparations l-NIO abrogated all vasomotor effects of AD, whereas ODQ blocked the AD-mediated vasoconstriction without affecting the vasorelaxant response. This indicates that only AD-induced vasoconstriction is mediated by a NO-cGMP-dependent mechanism. By using the NO donor SIN-1, we showed a dose-dependent vasoconstrictory effect which was completely blocked by ODQ. These results provide compelling evidence that the vasoactive role of AD in the branchial circulation of S. acanthias and A. anguilla involves a NO signalling.

Physiological effects of waterborne lead exposure in spiny dogfish (Squalus acanthias).

PubMed

Eyckmans, Marleen; Lardon, Isabelle; Wood, Chris M; De Boeck, Gudrun

2013-01-15

To broaden our knowledge about the toxicity of metals in marine elasmobranchs, cannulated spiny dogfish (Squalus acanthias) were exposed to 20 μM and 100 μM lead (Pb). Since we wanted to focus on sub lethal ion-osmoregulatory and respiratory disturbances, arterial blood samples were analysed for pH(a), PaO(2), haematocrit and total CO(2) values at several time points. Plasma was used to determine urea, TMAO, lactate and ion concentrations. After 96 h, Pb concentrations were determined in a number of tissues, such as gill, rectal gland, skin and liver. To further investigate ion and osmoregulation, Na(+)/K(+)-ATPase activities in gill and rectal gland were analysed as well as rates of ammonia and urea excretion. Additionally, we studied the energy reserves in muscle and liver. Pb strongly accumulated in gills and especially in skin. Lower accumulation rates occurred in gut, kidney and rectal gland. A clear disturbance in acid-base status was observed after one day of exposure indicating a transient period of hyperventilation. The increase in pH(a) was temporary at 20 μM, but persisted at 100 μM. After 2 days, plasma Na and Cl concentrations were reduced compared to controls at 100 μM Pb and urea excretion rates were elevated. Pb caused impaired Na(+)/K(+)-ATPase activity in gills, but not in rectal gland. We conclude that spiny dogfish experienced relatively low ion-osmoregulatory and respiratory distress when exposed to lead, particularly when compared to effects of other metals such as silver. These elasmobranchs appear to be able to minimize the disturbance and maintain physiological homeostasis during an acute Pb exposure. Copyright © 2012 Elsevier B.V. All rights reserved.

B cell receptor accessory molecule CD79α: characterisation and expression analysis in a cartilaginous fish, the spiny dogfish (Squalus acanthias).

PubMed

Li, Ronggai; Wang, Tiehui; Bird, Steve; Zou, Jun; Dooley, Helen; Secombes, Christopher J

2013-06-01

CD79α (also known as Igα) is a component of the B cell antigen receptor complex and plays an important role in B cell signalling. The CD79α protein is present on the surface of B cells throughout their life cycle, and is absent on all other healthy cells, making it a highly reliable marker for B cells in mammals. In this study the spiny dogfish (Squalus acanthias) CD79α (SaCD79α) is described and its expression studied under constitutive and stimulated conditions. The spiny dogfish CD79α cDNA contains an open reading frame of 618 bp, encoding a protein of 205 amino acids. Comparison of the SaCD79α gene with that of other species shows that the gross structure (number of exons, exon/intron boundaries, etc.) is highly conserved across phylogeny. Additionally, analysis of the 5' flanking region shows SaCD79α lacks a TATA box and possesses binding sites for multiple transcription factors implicated in its B cell-specific gene transcription in other species. Spiny dogfish CD79α is most highly expressed in immune tissues, such as spleen, epigonal and Leydig organ, and its transcript level significantly correlates with those of spiny dogfish immunoglobulin heavy chains. Additionally, CD79α transcription is up-regulated, to a small but significant degree, in peripheral blood cells following stimulation with pokeweed mitogen. These results strongly indicate that, as in mammals, spiny dogfish CD79α is expressed by shark B cells where it associates with surface-bound immunoglobulin to form a fully functional BCR, and thus may serve as a pan-B cell marker in future shark immunological studies. Copyright © 2013 Elsevier Ltd. All rights reserved.

Analysis and functional annotation of expressed sequence tags from in vitro cell lines of elasmobranchs: spiny dogfish shark (Squalus acanthias) and little skate (Leucoraja erinacea)

PubMed Central

Parton, Angela; Bayne, Christopher J.; Barnes, David W.

2010-01-01

Elasmobranchs are the most commonly used experimental models among the jawed, cartilaginous fish (Chondrichthyes). Previously we developed cell lines from embryos of two elasmobranchs, Squalus acanthias the spiny dogfish shark (SAE line), and Leucoraja erinacea the little skate (LEE-1 line). From these lines cDNA libraries were derived and expressed sequence tags (ESTs) generated. From the SAE cell line 4303 unique transcripts were identified, with 1848 of these representing unknown sequences (showing no BLASTX identification). From the LEE-1 cell line, 3660 unique transcripts were identified, and unknown, unique sequences totaled 1333. Gene Ontology (GO) annotation showed that GO assignments for the two cell lines were in general similar. These results suggest that the procedures used to derive the cell lines led to isolation of cell types of the same general embryonic origin from both species. The LEE-1 transcripts included GO categories “envelope” and “oxidoreductase activity” but the SAE transcripts did not. GO analysis of SAE transcripts identified the category “anatomical structure formation” that was not present in LEE-1 cells. Increased organelle compartments may exist within LEE-1 cells compared to SAE cells, and the higher oxidoreductase activity in LEE-1 cells may indicate a role for these cells in responses associated with innate immunity or in steroidogenesis. These EST libraries from elasmobranch cell lines provide information for assembly of genomic sequences and are useful in revealing gene diversity, new genes and molecular markers, as well as in providing means for elucidation of full-length cDNAs and probes for gene array analyses. This is the first study of this type with members of the Chondrichthyes. PMID:20471924

The modulatory effects of noradrenaline on vagal control of heart rate in the dogfish, Squalus acanthias.

PubMed

Agnisola, Claudio; Randall, David J; Taylor, Edwin W

2003-01-01

The possible interactions between inhibitory vagal control of the heart and circulating levels of catecholamines in dogfish (Squalus acanthias) were studied using an in situ preparation of the heart, which retained intact its innervation from centrally cut vagus nerves. The response to peripheral vagal stimulation typically consisted of an initial cardiac arrest, followed by an escape beat, leading to renewed beating at a mean heart rate lower than the prestimulation rate (partial recovery). Cessation of vagal stimulation led to a transient increase in heart rate, above the prestimulation rate. This whole response was completely abolished by 10(-4) M atropine (a muscarinic cholinergic antagonist). The degree of vagal inhibition was evaluated in terms of both the initial, maximal cardiac interval and the mean heart rate during partial recovery, both expressed as a percentage of the prestimulation heart rate. The mean prestimulation heart rate of this preparation (36+/-4 beats min(-1)) was not affected by noradrenaline but was significantly reduced by 10(-4) M nadolol (a beta-adrenergic receptor antagonist), suggesting the existence of a resting adrenergic tone arising from endogenous catecholamines. The degree of vagal inhibition of heart rate varied with the rate of stimulation and was increased by the presence of 10(-8) M noradrenaline (the normal in vivo level in routinely active fish), while 10(-7) M noradrenaline (the in vivo level measured in disturbed or deeply hypoxic fish) reduced the cardiac response to vagal stimulation. In the presence of 10(-7) M noradrenaline, 10(-4) M nadolol further reduced the vagal response, while 10(-4) M nadolol + 10(-4) M phentolamine had no effect, indicating a complex interaction between adrenoreceptors, possibly involving presynaptic modulation of vagal inhibition.

Texas Red transport across rat and dogfish shark (Squalus acanthias) choroid plexus

PubMed Central

Reichel, Valeska; Miller, David S.; Fricker, Gert

2008-01-01

Confocal microscopy and image analysis were used to compare driving forces, specificity, and regulation of transport of the fluorescent organic anion, Texas Red (sulforhodamine 101 free acid; TR), in lateral choroid plexus (CP) isolated from rat and an evolutionarily ancient vertebrate, dogfish shark (Squalus acanthias). CP from both species exhibited concentrative, specific, and metabolism-dependent TR transport from bath to subepithelial/vascular space; at steady state, TR accumulation in vascular/subepithelial space was substantially higher than in epithelial cells. In rat CP, steady-state TR accumulation in subepithelial/vascular spaces was reduced by Na+-replacement, but was not affected by a 10-fold increase in buffer K+. In shark CP, Na+-replacement did not alter TR accumulation in either tissue compartment; subepithelial/vascular space levels of TR were reduced in high-K+ medium. In both species, steady-state TR accumulation was not affected by p-aminohippurate or leukotriene C4, suggesting that neither organic anion transporters (SLC22A family) nor multidrug resistance-associated proteins (ABCC family) contributed. In rat CP, digoxin was without effect, indicating that organic anion transporting polypeptide isoform 2 was not involved. Several organic anions reduced cellular and subepithelial/vascular space TR accumulation in both tissues, including estrone sulfate, taurocholate, and the Mrp1 inhibitor MK571. In rat CP, TR accumulation in subepithelial/vascular spaces increased with PKA activation (forskolin), but was not affected by PKC activation (phorbol ester). In shark, neither PKA nor PKC activation specifically affected TR transport. Thus, rat and dogfish shark CP transport TR but do so using different basic mechanisms that respond to different regulatory signals. PMID:18650317

Chaperone roles for TMAO and HSP70 during hyposmotic stress in the spiny dogfish shark (Squalus acanthias).

PubMed

MacLellan, Robyn J; Tunnah, Louise; Barnett, David; Wright, Patricia A; MacCormack, Tyson; Currie, Suzanne

2015-10-01

Salinity decreases are experienced by many marine elasmobranchs. To understand how these fishes cope with hyposmotic stress on a cellular level, we used the spiny dogfish shark (Squalus acanthias) as a model to test whether a reciprocal relationship exists between the cell's two primary protein protection mechanisms, the chemical (e.g., trimethylamine oxide, TMAO) and molecular (e.g., heat shock protein 70, HSP70) chaperone systems. This relationship is interesting given that many elasmobranchs are expected to gain water and lose osmolytes, chemical chaperones, and ions as they osmoconform to new, lowered salinity. Dogfish were cannulated for repeated blood sampling and exposed to 70% seawater (SW) for 48 h. These hyposmotic conditions had no effect on red blood cell (RBC) and white muscle TMAO concentrations, and did not result in HSP70 induction or signs of protein damage (i.e., increased ubiquitin), suggesting that TMAO levels were sufficiently protective in these tissues. However, in the gill, we observed a significant decrease in TMAO concentration and a significant induction of HSP70 as well as signs of protein damage. In the face of this cellular stress response, gill Na(+)/K(+)-ATPase (NKA) activity significantly increased during hyposmotic conditions, as expected. We suggest that this functional preservation in the gill is partly the result of HSP70 induction with lowered salinity. We conclude a reciprocal relationship between TMAO and HSP70 in the gills of dogfish as a result of in vivo hyposmotic stress. When osmotically induced protein damage surpasses the protective capacity of remaining TMAO, HSP70 is induced to preserve tissue and organismal function.

Molecular detection and immunological localization of gill Na+/H+ exchanger in the dogfish (Squalus acanthias).

PubMed

Claiborne, James B; Choe, Keith P; Morrison-Shetlar, Alison I; Weakley, Jill C; Havird, Justin; Freiji, Abe; Evans, David H; Edwards, Susan L

2008-03-01

The dogfish (Squalus acanthias) can make rapid adjustments to gill acid-base transfers to compensate for internal acidosis/alkalosis. Branchial Na+/H+ exchange (NHE) has been postulated as one mechanism driving the excretion of H+ following acidosis. We have cloned gill cDNA that includes an open reading frame coding for a 770-residue protein most homologous (approximately 71%) to mammalian NHE2. RT-PCR revealed NHE2 transcripts predominantly in gill, stomach, rectal gland, intestine, and kidney. In situ hybridization with an antisense probe against NHE2 in gill sections revealed a strong mRNA signal from a subset of interlamellar and lamellae cells. We developed dogfish-specific polyclonal antibodies against NHE2 that detected a approximately 70-kDa protein in Western blots and immunologically recognized branchial cells having two patterns of protein expression. Cytoplasmic and apical NHE2 immunoreactivity were observed in cells coexpressing basolateral Na+-K+-ATPase. Other large ovoid cells more generally staining for NHE2 also were strongly positive for basolateral H+-ATPase. Gill mRNA levels for NHE2 and H+-ATPase did not change following systemic acidosis (as measured by quantitative PCR 2 h after a 1- or 2-meq/kg acid infusion). These data indicate that posttranslational adjustments of NHE2 and other transport systems (e.g., NHE3) following acidosis may be of importance in the short-term pH adjustment and net branchial H+ efflux observed in vivo. NHE2 may play multiple roles in the gills, involved with H+ efflux from acid-secreting cells, basolateral H+ reabsorption for pHi regulation, and in parallel with H+-ATPase for the generation of HCO3(-) in base-secreting cells.

Contamination levels of mercury in the muscle of female and male spiny dogfishes (Squalus acanthias) caught off the coast of Japan.

PubMed

Endo, Tetsuya; Hisamichi, Yohsuke; Kimura, Osamu; Kotaki, Yuichi; Kato, Yoshihisa; Ohta, Chiho; Koga, Nobuyuki; Haraguchi, Koichi

2009-11-01

We analyzed the total mercury (T-Hg) and stable isotopes of (13)C and (15)N in the muscle of spiny dogfish (Squalus acanthias) caught off the coast of Japan. The average body length of the female spiny dogfish sampled (94.9+/-20.2 cm, 50.5-131.0 cm, n=40) was significantly larger than that of the males sampled (77.8+/-10.8 cm, 55.5-94.0 cm, n=35), although the ages of the samples were unknown. The T-Hg concentration in the muscle samples rapidly increased after maturity in the females (larger than about 120 cm) and males (larger than about 90 cm), followed by a continued gradual increase. Contamination level of T-Hg in female muscle samples (0.387+/-0.378 microg(wet g)(-1), n=40) was slightly higher than that in male muscle samples (0.316+/-0.202 microg(wet g)(-1), n=35), probably due to the greater longevity of females. In contrast, the contamination level of T-Hg in females smaller than 94.0 cm in length (0.204+/-0.098 microg(wet g)(-1), n=20) was slightly lower than that in the males, probably due to the faster growth rate of females. Although the partial differential(13)C and partial differential(15)N values in the muscle samples increased with an increase in body length, there were no significant differences between the females (-17.2+/-0.4 per thousand and 12.4+/-0.9 per thousand, respectively) and males (-17.3+/-0.4 per thousand and 12.4+/-0.8 per thousand, respectively). A positive correlation was found between partial differential(13)C and partial differential(15)N values, suggesting trophic enrichment due to the growth.

Cell and molecular biology of SAE, a cell line from the spiny dogfish shark, Squalus acanthias.

PubMed

Parton, Angela; Forest, David; Kobayashi, Hiroshi; Dowell, Lori; Bayne, Christopher; Barnes, David

2007-02-01

Cartilaginous fish, primarily sharks, rays and skates (elasmobranchs), appeared 450 million years ago. They are the most primitive vertebrates, exhibiting jaws and teeth, adaptive immunity, a pressurized circulatory system, thymus, spleen, and a liver comparable to that of humans. The most used elasmobranch in biomedical research is the spiny dogfish shark, Squalus acanthias. Comparative genomic analysis of the dogfish shark, the little skate (Leucoraja erincea), and other elasmobranchs have yielded insights into conserved functional domains of genes associated with human liver function, multidrug resistance, cystic fibrosis, and other biomedically relevant processes. While genomic information from these animals is informative in an evolutionary framework, experimental verification of functions of genomic sequences depends heavily on cell culture approaches. We have derived the first multipassage, continuously proliferating cell line of a cartilaginous fish. The line was initiated from embryos of the spiny dogfish shark. The cells were maintained in a medium modified for fish species and supplemented with cell type-specific hormones, other proteins and sera, and plated on a collagen substrate. SAE cells have been cultured continuously for three years. These cells can be transfected by plasmids and have been cryopreserved. Expressed Sequence Tags generated from a normalized SAE cDNA library included a number of markers for cartilage and muscle, as well as proteins influencing tissue differentiation and development, suggesting that SAE cells may be of mesenchymal stem cell origin. Examination of SAE EST sequences also revealed a cartilaginous fish-specific repetitive sequence that may be evidence of an ancient mobile genetic element that most likely was introduced into the cartilaginous fish lineage after divergence from the lineage leading to teleosts.

Type IV carbonic anhydrase is present in the gills of spiny dogfish (Squalus acanthias).

PubMed

Gilmour, K M; Bayaa, M; Kenney, L; McNeill, B; Perry, S F

2007-01-01

Physiological and biochemical studies have provided indirect evidence for a membrane-associated carbonic anhydrase (CA) isoform, similar to mammalian type IV CA, in the gills of dogfish (Squalus acanthias). This CA isoform is linked to the plasma membrane of gill epithelial cells by a glycosylphosphatidylinositol anchor and oriented toward the plasma, such that it can catalyze the dehydration of plasma HCO(3)(-) ions. The present study directly tested the hypothesis that CA IV is present in dogfish gills in a location amenable to catalyzing plasma HCO(3)(-) dehydration. Homology cloning techniques were used to assemble a 1,127 base pair cDNA that coded for a deduced protein of 306 amino acids. Phylogenetic analysis suggested that this protein was a type IV CA. For purposes of comparison, a second cDNA (1,107 base pairs) was cloned from dogfish blood; it encoded a deduced protein of 260 amino acids that was identified as a cytosolic CA through phylogenetic analysis. Using real-time PCR and in situ hybridization, mRNA expression for the dogfish type IV CA was detected in gill tissue and specifically localized to pillar cells and branchial epithelial cells that flanked the pillar cells. Immunohistochemistry using a polyclonal antibody raised against rainbow trout type IV CA revealed a similar pattern of CA IV immunoreactivity and demonstrated a limited degree of colocalization with Na(+)-K(+)-ATPase immunoreactivity. The presence and localization of a type IV CA isoform in the gills of dogfish is consistent with the hypothesis that branchial membrane-bound CA with an extracellular orientation contributes to CO(2) excretion in dogfish by catalyzing the dehydration of plasma HCO(3)(-) ions.

Glutamine-dependent carbamoyl-phosphate synthetase and other enzyme activities related to the pyrimidine pathway in spleen of Squalus acanthias (spiny dogfish).

PubMed Central

Anderson, P M

1989-01-01

The first two steps of urea synthesis in liver of marine elasmobranchs involve formation of glutamine from ammonia and of carbamoyl phosphate from glutamine, catalysed by glutamine synthetase and carbamoyl-phosphate synthetase, respectively [Anderson & Casey (1984) J. Biol. Chem. 259, 456-462]; both of these enzymes are localized exclusively in the mitochondrial matrix. The objective of this study was to establish the enzymology of carbamoyl phosphate formation and utilization for pyrimidine nucleotide biosynthesis in Squalus acanthias (spiny dogfish), a representative elasmobranch. Aspartate carbamoyltransferase could not be detected in liver of dogfish. Spleen extracts, however, had glutamine-dependent carbamoyl-phosphate synthetase, aspartate carbamoyltransferase, dihydro-orotase, and glutamine synthetase activities, all localized in the cytosol; dihydro-orotate dehydrogenase, orotate phosphoribosyltransferase, and orotidine-5'-decarboxylase activities were also present. Except for glutamine synthetase, the levels of all activities were very low. The carbamoyl-phosphate synthetase activity is inhibited by UTP and is activated by 5-phosphoribosyl 1-pyrophosphate. The first three enzyme activities of the pyrimidine pathway were eluted in distinctly different positions during gel filtration chromatography under a number of different conditions; although complete proteolysis of inter-domain regions of a multifunctional complex during extraction cannot be excluded, the evidence suggests that in dogfish, in contrast to mammalian species, these three enzymes of the pyrimidine pathway exist as individual polypeptide chains. These results: (1) establish that dogfish express two different glutamine-dependent carbamoyl-phosphate synthetase activities, (2) confirm the report [Smith, Ritter & Campbell (1987) J. Biol. Chem. 262, 198-202] that dogfish express two different glutamine synthetases, and (3) provide indirect evidence that glutamine may not be available in liver for biosynthetic reactions other than urea formation. Images Fig. 1. PMID:2570570

Transcriptome responses in the rectal gland of fed and fasted spiny dogfish shark (Squalus acanthias) determined by suppression subtractive hybridization.

PubMed

Deck, Courtney A; McKay, Sheldon J; Fiedler, Tristan J; LeMoine, Christophe M R; Kajimura, Makiko; Nawata, C Michele; Wood, Chris M; Walsh, Patrick J

2013-12-01

Prior studies of the elasmobranch rectal gland have demonstrated that feeding induces profound and rapid up regulation of the gland's ability to secrete concentrated NaCl solutions and the metabolic capacity to support this highly ATP consuming process. We undertook the current study to attempt to determine the degree to which up regulation of mRNA transcription was involved in the gland's activation. cDNA libraries were created from mRNA isolated from rectal glands of fasted (7days post-feeding) and fed (6h and 22h post-feeding) spiny dogfish sharks (Squalus acanthias), and the libraries were subjected to suppression subtractive hybridization (SSH) analysis. Quantitative real time PCR (qPCR) was also used to ascertain the mRNA expression of several genes revealed by the SSH analysis. In total the treatments changed the abundance of 170 transcripts, with 103 up regulated by feeding, and 67 up regulated by fasting. While many of the changes took place in 'expected' Gene Ontology (GO) categories (e.g., metabolism, transport, structural proteins, DNA and RNA turnover, etc.), KEGG analysis revealed a number of categories which identify oxidative stress as a topic of interest for the gland. GO analysis also revealed that branched chain essential amino acids (e.g., valine, leucine, isoleucine) are potential metabolic fuels for the rectal gland. In addition, up regulation of transcripts for many genes in the anticipated GO categories did not agree (i.e., fasting down regulated in feeding treatments) with previously observed increases in their respective proteins/enzyme activities. These results suggest an 'anticipatory' storage of selected mRNAs which presumably supports the rapid translation of proteins upon feeding activation of the gland. © 2013 Elsevier Inc. All rights reserved.

Branchial CO(2) receptors and cardiorespiratory adjustments during hypercarbia in Pacific spiny dogfish (Squalus acanthias).

PubMed

McKendry, J E; Milsom, W K; Perry, S F

2001-04-01

Adult Pacific spiny dogfish (Squalus acanthias) were exposed to acute (approximately 20 min) hypercarbia while we monitored arterial blood pressure, systemic vascular resistance (R(S)), cardiac output (V(b)) and frequency (fh) as well as ventilatory amplitude (V(AMP)) and frequency (f(V)). Separate series of experiments were conducted on control, atropinized (100 nmol kg(-1)) and branchially denervated fish to investigate putative CO(2)-chemoreceptive sites on the gills and their link to the autonomic nervous system and cardiorespiratory reflexes.In untreated fish, moderate hypercarbia (water CO(2 )partial pressure; Pw(CO2)=6.4+/-0.1 mmHg) (1 mmHg=0.133 kPa) elicited significant increases in V(AMP) (of approximately 92 %) and f(V) (of approximately 18 %) as well as decreases in fh (of approximately 64 %), V.(b) (approximately 29 %) and arterial blood pressure (of approximately 11 %); R(S) did not change significantly. Denervation of the branchial branches of cranial nerves IX and X to the pseudobranch and each gill arch eliminated all cardiorespiratory responses to hypercarbia. Prior administration of the muscarinic receptor antagonist atropine also abolished the hypercarbia-induced ventilatory responses and virtually eliminated all CO(2)-elicited cardiovascular adjustments. Although the atropinized dogfish displayed a hypercarbic bradycardia, the magnitude of the response was significantly attenuated (36+/-6 % decrease in fh in controls versus 9+/-2 % decrease in atropinized fish; means +/- s.e.m.).Thus, the results of the present study reveal the presence of gill CO(2) chemoreceptors in dogfish that are linked to numerous cardiorespiratory reflexes. In addition, because all cardiorespiratory responses to hypercarbia were abolished or attenuated by atropine, the CO(2) chemoreception process and/or one or more downstream elements probably involve cholinergic (muscarinic) neurotransmission.

Analysis and functional annotation of expressed sequence tags from in vitro cell lines of elasmobranchs: Spiny dogfish shark (Squalus acanthias) and little skate (Leucoraja erinacea).

PubMed

Parton, Angela; Bayne, Christopher J; Barnes, David W

2010-09-01

Elasmobranchs are the most commonly used experimental models among the jawed, cartilaginous fish (Chondrichthyes). Previously we developed cell lines from embryos of two elasmobranchs, Squalus acanthias the spiny dogfish shark (SAE line), and Leucoraja erinacea the little skate (LEE-1 line). From these lines cDNA libraries were derived and expressed sequence tags (ESTs) generated. From the SAE cell line 4303 unique transcripts were identified, with 1848 of these representing unknown sequences (showing no BLASTX identification). From the LEE-1 cell line, 3660 unique transcripts were identified, and unknown, unique sequences totaled 1333. Gene Ontology (GO) annotation showed that GO assignments for the two cell lines were in general similar. These results suggest that the procedures used to derive the cell lines led to isolation of cell types of the same general embryonic origin from both species. The LEE-1 transcripts included GO categories "envelope" and "oxidoreductase activity" but the SAE transcripts did not. GO analysis of SAE transcripts identified the category "anatomical structure formation" that was not present in LEE-1 cells. Increased organelle compartments may exist within LEE-1 cells compared to SAE cells, and the higher oxidoreductase activity in LEE-1 cells may indicate a role for these cells in responses associated with innate immunity or in steroidogenesis. These EST libraries from elasmobranch cell lines provide information for assembly of genomic sequences and are useful in revealing gene diversity, new genes and molecular markers, as well as in providing means for elucidation of full-length cDNAs and probes for gene array analyses. This is the first study of this type with members of the Chondrichthyes. Copyright 2010 Elsevier Inc. All rights reserved.

Body fluid osmolytes and urea and ammonia flux in the colon of two chondrichthyan fishes, the ratfish, Hydrolagus colliei, and spiny dogfish, Squalus acanthias.

PubMed

Anderson, W Gary; Nawata, C Michele; Wood, Chris M; Piercey-Normore, Michele D; Weihrauch, Dirk

2012-01-01

The present study has examined the role of the colon in regulating ammonia and urea nitrogen balance in two species of chondrichthyans, the ratfish, Hydrolagus colliei (a holocephalan) and the spiny dogfish, Squalus acanthias (an elasmobranch). Stripped colonic tissue from both the dogfish and ratfish was mounted in an Ussing chamber and in both species bi-directional urea flux was found to be negligible. Urea uptake by the mucosa and serosa of the isolated colonic epithelium through accumulation of (14)C-urea was determined to be 2.8 and 6.2 fold greater in the mucosa of the dogfish compared to the serosa of the dogfish and the mucosa of the ratfish respectively. Furthermore, there was no difference between serosal and mucosal accumulation of (14)C-urea in the ratfish. Through the addition of 2mM NH(4)Cl to the mucosal side of each preparation the potential for ammonia flux was also examined. This was again found to be negligible in both species suggesting that the colon is an extremely tight epithelium to the movement of both urea and ammonia. Plasma, chyme and bile fluid samples were also taken from the agastric ratfish and were compared with solute concentrations of equivalent body fluids in the dogfish. Finally molecular analysis revealed expression of 3 isoforms of the urea transport protein (UT) and an ammonia transport protein (Rhbg) in the gill, intestine, kidney and colon of the ratfish. Partial nucleotide sequences of the UT-1, 2 and 3 isoforms in the ratfish had 95, 95 and 92% identity to the equivalent UT isoforms recently identified in another holocephalan, the elephantfish, Callorhinchus milii. Finally, the nucleotide sequence of the Rhbg identified in the ratfish had 73% identity to the Rhbg protein recently identified in the little skate, Leucoraja erinacea. Copyright © 2011 Elsevier Inc. All rights reserved.

Differential Effects of Temperature on Oxygen Consumption and Branchial Fluxes of Urea, Ammonia, and Water in the Dogfish Shark (Squalus acanthias suckleyi).

PubMed

Giacomin, Marina; Schulte, Patricia M; Wood, Chris M

Environmental temperature can greatly influence the homeostasis of ectotherms through its effects on biochemical reactions and whole-animal physiology. Elasmobranchs tend to be N limited and are osmoconformers, retaining ammonia and urea-N at the gills and using the latter as a key osmolyte to maintain high blood osmolality. However, the effects of temperature on these key processes remain largely unknown. We evaluated the effects of acute exposure to different temperatures (7°, 12°, 15°, 18°, 22°C) on oxygen consumption, ammonia, urea-N, and diffusive water fluxes at the gills of Squalus acanthias suckleyi. We hypothesized that as metabolic demand for oxygen increased with temperature, the fluxes of ammonia, urea-N, and 3 H 2 O at the gills would increase in parallel with those of oxygen. Oxygen consumption (overall [Formula: see text] from 7.5° to 22°C) and water fluxes (overall [Formula: see text]) responded to increases in temperature in a similar, almost linear, manner. Ammonia-N efflux rates varied the most, increasing almost 15-fold from 7.5° to 22°C ([Formula: see text]). Urea-N efflux was tightly conserved over the 7.5°-15°C range ([Formula: see text]) but increased greatly at higher temperatures, yielding an overall [Formula: see text]. These differences likely reflect differences in the transport pathways for the four moieties. They also suggest the failure of urea-N- and ammonia-N-conserving mechanisms at the gill above 15°C. Hyperoxia did not alleviate the effects of high temperature. Indeed, urea-N and ammonia-N effluxes were dramatically increased when animals were exposed to high temperatures in the presence of hyperoxia, suggesting that high partial pressure of oxygen may have caused oxidative damage to gill epithelial membranes.

Na(+)-D-glucose cotransporter in the kidney of Squalus acanthias: molecular identification and intrarenal distribution.

PubMed

Althoff, Thorsten; Hentschel, Hartmut; Luig, Jutta; Schütz, Hendrike; Kasch, Myriam; Kinne, Rolf K-H

2006-04-01

Using primers against conserved regions of mammalian Na(+)-d-glucose cotransporters (SGLT), a cDNA was cloned from the kidney of spiny dogfish shark (Squalus acanthias). On the basis of comparison of amino acid sequence, membrane topology, and putative glycosylation and phosphorylation sites, the cDNA could be shown to belong to the family of sglt genes. Indeed, Na(+)-dependent d-glucose uptake could be demonstrated after expression of the gene in Xenopus laevis oocytes. In a dendrogram, the SGLT from shark kidney has a high homology to the mammalian SGLT2. Computer analysis revealed that the elasmobranch protein is most similar to the mammalian proteins in the transmembrane regions and contains already all the amino acids identified to be functionally important, suggesting early conservation during evolution. Extramembraneous loops show larger variations. This holds especially for loop 13, which has been implied as a phlorizin-binding domain. Antibodies were generated and the intrarenal distribution of the SGLT was studied in cryosections. In parallel, the nephron segments were identified by lectins. Positive immunoreactions were found in the proximal tubule in the early parts PIa and PIb and the late segment PIIb. The large PIIa segment of the proximal tubule showed no reaction. In contrast to the mammalian kidney also the late distal tubule, the collecting tubule, and the collecting duct showed immunoreactivity. The molecular information confirms previous vesicle studies in which a low affinity SGLT with a low stoichiometry has been observed and supports the notion of a similarity of the shark kidney SGLT to the mammalian SGLT2. Despite its presence in the late parts of the nephron, the absence of SGLT in the major part of the proximal tubule, the relatively low affinity, and in particular the low stoichiometry might explain the lack of a T(m) for d-glucose in the shark kidney.

Modulation of contraction by intracellular Na+ via Na(+)-Ca2+ exchange in single shark (Squalus acanthias) ventricular myocytes.

PubMed Central

Näbauer, M; Morad, M

1992-01-01

1. The effect of direct alteration of intracellular Na+ concentration on contractile properties of whole-cell clamped shark ventricular myocytes was studied using an array of 256 photodiodes to monitor the length of the isolated myocytes. 2. In myocytes dialysed with Na(+)-free solution, the voltage dependence of Ca2+ current (ICa) and contraction were similar and bell shaped. Contractions activated at all voltages were completely suppressed by nifedipine (5 microM), and failed to show significant tonic components, suggesting dependence of the contraction on Ca2+ influx through the L-type Ca2+ channel. 3. In myocytes dialysed with 60 mM Na+, a ICa-dependent and a ICa-independent component of contraction could be identified. The Ca2+ current-dependent component was prominent in voltages between -30 to +10 mV. The ICa-independent contractions were maintained for the duration of depolarization, increased with increasing depolarization between +10 to +100 mV, and were insensitive to nifedipine. 4. In such myocytes, repolarization produced slowly decaying inward tail currents closely related to the time course of relaxation and the degree of shortening prior to repolarization. 5. With 60 mM Na+ in the pipette solution, positive clamp potentials activated decaying outward currents which correlated to the size of contraction. These outward currents appeared to be generated by the Na(+)-Ca(2+)-exchanger since they depended on the presence of intracellular Na+, and were neither suppressed by nifedipine nor by K+ channel blockers. 6. The results suggest that in shark (Squalus acanthias) ventricular myocytes, which lack functionally relevant Ca2+ release pools, both Ca2+ channel and the Na(+)-Ca2+ exchanger deliver sufficient Ca2+ to activate contraction, though the effectiveness of the latter mechanism was highly dependent on the [Na+]i. PMID:1338467

Physiological and molecular responses of the spiny dogfish shark (Squalus acanthias) to high environmental ammonia: scavenging for nitrogen.

PubMed

Nawata, C Michele; Walsh, Patrick J; Wood, Chris M

2015-01-15

In teleosts, a branchial metabolon links ammonia excretion to Na(+) uptake via Rh glycoproteins and other transporters. Ureotelic elasmobranchs are thought to have low branchial ammonia permeability, and little is known about Rh function in this ancient group. We cloned Rh cDNAs (Rhag, Rhbg and Rhp2) and evaluated gill ammonia handling in Squalus acanthias. Control ammonia excretion was <5% of urea-N excretion. Sharks exposed to high environmental ammonia (HEA; 1 mmol(-1) NH4HCO3) for 48 h exhibited active ammonia uptake against partial pressure and electrochemical gradients for 36 h before net excretion was re-established. Plasma total ammonia rose to seawater levels by 2 h, but dropped significantly below them by 24-48 h. Control ΔP(NH3) (the partial pressure gradient of NH3) across the gills became even more negative (outwardly directed) during HEA. Transepithelial potential increased by 30 mV, negating a parallel rise in the Nernst potential, such that the outwardly directed NH4(+) electrochemical gradient remained unchanged. Urea-N excretion was enhanced by 90% from 12 to 48 h, more than compensating for ammonia-N uptake. Expression of Rhp2 (gills, kidney) and Rhbg (kidney) did not change, but branchial Rhbg and erythrocytic Rhag declined during HEA. mRNA expression of branchial Na(+)/K(+)-ATPase (NKA) increased at 24 h and that of H(+)-ATPase decreased at 48 h, while expression of the potential metabolon components Na(+)/H(+) exchanger2 (NHE2) and carbonic anhydrase IV (CA-IV) remained unchanged. We propose that the gill of this nitrogen-limited predator is poised not only to minimize nitrogen loss by low efflux permeability to urea and ammonia but also to scavenge ammonia-N from the environment during HEA to enhance urea-N synthesis. © 2015. Published by The Company of Biologists Ltd.

Sensitivity of the spiny dogfish (Squalus acanthias) to waterborne silver exposure.

PubMed

De Boeck, G; Grosell, M; Wood, C

2001-10-01

The physiological effects of waterborne silver exposure (added as AgNO(3)) on spiny dogfish, Squalus acanthias, were evaluated at 30, 200 and 685 microg silver per l in 30 per thousand seawater. These concentrations cover the toxic range observed for freshwater teleosts, where silver is extremely toxic, to seawater teleosts which tolerate higher silver concentrations. However, these levels are considerably higher than those that occur in the normal environment. At 685 microg l(-1), dogfish died within 24 h. Causes of death were respiratory as well as osmoregulatory failure. Arterial P(a)O(2) rapidly declined below 20 Torr, and blood acidosis (both respiratory and metabolic) occurred. Urea excretion increased dramatically and plasma urea dropped from 340 to 225 mM. There were pronounced increases in plasma Na(+), Cl(-), and Mg(2+), indicative of ionoregulatory failure due to increased diffusive permeability as well as inhibited NaCl excretion. At 200 microg l(-1), fish died between 24 and 72 h of silver exposure. The same physiological events occurred with a small time delay. At 30 microg l(-1), effects were much less severe, although slight mortality (12.5%) still occurred. Respiratory alkalosis occurred, together with moderate elevations in plasma Na(+) and Cl(-) levels. Silver accumulated to the highest concentrations on gills, with only low levels in the intestine, in accord with the virtual absence of drinking. Na(+)/K(+)-ATP-ase activities of gill and rectal gland tissue were impaired at the highest silver concentration. Normal gill function was impaired due to swelling and fusion of lamellae, lamellar aneurism and lifting of the lamellar epithelium. Our results clearly indicate that this elasmobranch is much more sensitive (about 10-fold) to silver than marine teleosts, with silver's toxic action exerted on the gill rather than on the intestine, in contrast to the latter.

Nervus terminalis in dogfish (Squalus acanthias, Elasmobranchii) carries tonic efferent impulses.

PubMed

Bullock, T H; Northcutt, R G

1984-02-10

Recordings from the intact nervus terminalis with a hook electrode or from a stump of the divided nerve with a suction electrode show a tonic, irregular discharge of broad, low frequency spikes in ca. 4-6 units. These nerve impulses are efferent from the brain. The mean frequency of discharge is not influenced by various chemical, thermal, tactile, acoustic, photic, vibratory and electric field stimuli but is decreased by certain forms of mechanical stimuli, presumably acting on the lateral line organs of the lateral aspect of the head. We have not succeeded in recording from afferents. The nerve consists of greater than 1000 unmyelinated axons, mostly less than 1 micron, a very few greater than 1.5 micron in diameter; presumably the efferents recorded from were these larger fibers.

Metabolic organization and effects of feeding on enzyme activities of the dogfish shark (Squalus acanthias) rectal gland.

PubMed

Walsh, Patrick J; Kajimura, Makiko; Mommsen, Thomas P; Wood, Chris M

2006-08-01

In order to investigate the metabolic poise of the elasmobranch rectal gland, we conducted two lines of experimentation. First, we examined the effects of feeding on plasma metabolites and enzyme activities from several metabolic pathways in several tissues of the dogfish shark, Squalus acanthias, after starvation and at 6, 20, 30 and 48 h post-feeding. We found a rapid and sustained ten-fold decrease in plasma beta-hydroxybutyrate at 6 h and beyond compared with starved dogfish, suggesting an upregulation in the use of this substrate, a decrease in production, or both. Plasma acetoacetate levels remain unchanged, whereas there was a slight and transient decrease in plasma glucose levels at 6 h. Several enzymes showed a large increase in activity post-feeding, including beta-hydroxybutyrate dehydrogenase in rectal gland and liver, and in rectal gland, isocitrate dehydrogenase, citrate synthase, lactate dehydrogenase, aspartate amino transferase, alanine amino transferase, glutamine synthetase and Na(+)/K(+) ATPase. Also notable in these enzyme measurements was the overall high level of activity in the rectal gland in general. For example, activity of the Krebs' TCA cycle enzyme citrate synthase (over 30 U g(-1)) was similar to activities in muscle from other species of highly active fish. Surprisingly, lactate dehydrogenase activity in the gland was also high (over 150 U g(-1)), suggesting either an ability to produce lactate anaerobically or use lactate as an aerobic fuel. Given these interesting observations, in the second aspect of the study we examined the ability of several metabolic substrates (alone and in combination) to support chloride secretion by the rectal gland. Among the substrates tested at physiological concentrations (glucose, beta-hydroxybutyrate, lactate, alanine, acetoacetate, and glutamate), only glucose could consistently maintain a viable preparation. Whereas beta-hydroxybutyrate could enhance gland activity when presented in combination with glucose, surprisingly it could not sustain chloride secretion when used as a lone substrate. Our results are discussed in the context of the in vivo role of the gland and mechanisms of possible upregulation of enzyme activities.

The effects of C-type natriuretic peptide on catecholamine release in the pacific spiny dogfish (Squalus acanthias).

PubMed

Montpetit, C J; McKendry, J; Perry, S F

2001-08-01

The interaction between homologous C-type natriuretic peptide (dfCNP) and catecholamine release in cardiovascular control was assessed in the marine dogfish (Squalus acanthias). This was accomplished by evaluation of the dynamics of the dfCNP-elicited secretion of catecholamines in situ and in vivo. With an in situ saline-perfused postcardinal sinus preparation, it was demonstrated that perfusion with saline containing dfCNP (10(-9) mol x L(-1)) did not affect the secretion of either noradrenaline or adrenaline. However, the presence of dfCNP in the perfusate significantly enhanced carbachol-evoked secretion of noradrenaline. In vivo, intravascular injection of dfCNP (10(-9) mol x kg(-1)) caused a biphasic pressor-depressor response consisting of a brief increase in caudal artery blood pressure (P(CA)) followed by a prolonged reduction in P(CA). Furthermore, although systemic resistance initially increased, it was subsequently maintained at baseline values in the face of persistent decreases in both P(CA) and cardiac output. Bolus injection of dfCNP elicited significant increases in plasma noradrenaline levels that peaked within 10 min; plasma adrenaline levels were unaffected. The release of noradrenaline elicited by dfCNP was unaffected by prior blockade of the renin-angiotensin system (RAS) (with the angiotensin converting enzyme inhibitor lisinopril) or by pretreatment with the nicotinic receptor blocker hexamethonium. The delayed decrease in P(CA) was not observed in the hexamethonium-treated fish. Prior blockade of beta-adrenoreceptors (with sotalol) or alpha-adrenoreceptors (with prazosin) either significantly reduced (sotalol) or abolished (prazosin) the increase in plasma noradrenaline levels after dfCNP injection. The results of this investigation demonstrate that the elevation of plasma noradrenaline levels observed in vivo following dfCNP injection is not caused by a direct effect of dfCNP on catecholamine secretion from axillary body chromaffin cells. Furthermore, the dfCNP-mediated increase of plasma noradrenaline appears to be unrelated to changes in P(CA) and is insensitive to blockade of the RAS or nicotinic receptors. However, stimulation of adrenergic receptors, in particular the alpha-adrenoreceptors, appears to be a key mechanism underlying the dfCNP-elicited secretion of noradrenaline. Copyright 2001 Academic Press.

Multi-tissue RNA-seq and transcriptome characterisation of the spiny dogfish shark (Squalus acanthias) provides a molecular tool for biological research and reveals new genes involved in osmoregulation.

PubMed

Chana-Munoz, Andres; Jendroszek, Agnieszka; Sønnichsen, Malene; Kristiansen, Rune; Jensen, Jan K; Andreasen, Peter A; Bendixen, Christian; Panitz, Frank

2017-01-01

The spiny dogfish shark (Squalus acanthias) is one of the most commonly used cartilaginous fishes in biological research, especially in the fields of nitrogen metabolism, ion transporters and osmoregulation. Nonetheless, transcriptomic data for this organism is scarce. In the present study, a multi-tissue RNA-seq experiment and de novo transcriptome assembly was performed in four different spiny dogfish tissues (brain, liver, kidney and ovary), providing an annotated sequence resource. The characterization of the transcriptome greatly increases the scarce sequence information for shark species. Reads were assembled with the Trinity de novo assembler both within each tissue and across all tissues combined resulting in 362,690 transcripts in the combined assembly which represent 289,515 Trinity genes. BUSCO analysis determined a level of 87% completeness for the combined transcriptome. In total, 123,110 proteins were predicted of which 78,679 and 83,164 had significant hits against the SwissProt and Uniref90 protein databases, respectively. Additionally, 61,215 proteins aligned to known protein domains, 7,208 carried a signal peptide and 15,971 possessed at least one transmembrane region. Based on the annotation, 81,582 transcripts were assigned to gene ontology terms and 42,078 belong to known clusters of orthologous groups (eggNOG). To demonstrate the value of our molecular resource, we show that the improved transcriptome data enhances the current possibilities of osmoregulation research in spiny dogfish by utilizing the novel gene and protein annotations to investigate a set of genes involved in urea synthesis and urea, ammonia and water transport, all of them crucial in osmoregulation. We describe the presence of different gene copies and isoforms of key enzymes involved in this process, including arginases and transporters of urea and ammonia, for which sequence information is currently absent in the databases for this model species. The transcriptome assemblies and the derived annotations generated in this study will support the ongoing research for this particular animal model and provides a new molecular tool to assist biological research in cartilaginous fishes.

Multi-tissue RNA-seq and transcriptome characterisation of the spiny dogfish shark (Squalus acanthias) provides a molecular tool for biological research and reveals new genes involved in osmoregulation

PubMed Central

Chana-Munoz, Andres; Jendroszek, Agnieszka; Sønnichsen, Malene; Kristiansen, Rune; Jensen, Jan K.; Bendixen, Christian

2017-01-01

The spiny dogfish shark (Squalus acanthias) is one of the most commonly used cartilaginous fishes in biological research, especially in the fields of nitrogen metabolism, ion transporters and osmoregulation. Nonetheless, transcriptomic data for this organism is scarce. In the present study, a multi-tissue RNA-seq experiment and de novo transcriptome assembly was performed in four different spiny dogfish tissues (brain, liver, kidney and ovary), providing an annotated sequence resource. The characterization of the transcriptome greatly increases the scarce sequence information for shark species. Reads were assembled with the Trinity de novo assembler both within each tissue and across all tissues combined resulting in 362,690 transcripts in the combined assembly which represent 289,515 Trinity genes. BUSCO analysis determined a level of 87% completeness for the combined transcriptome. In total, 123,110 proteins were predicted of which 78,679 and 83,164 had significant hits against the SwissProt and Uniref90 protein databases, respectively. Additionally, 61,215 proteins aligned to known protein domains, 7,208 carried a signal peptide and 15,971 possessed at least one transmembrane region. Based on the annotation, 81,582 transcripts were assigned to gene ontology terms and 42,078 belong to known clusters of orthologous groups (eggNOG). To demonstrate the value of our molecular resource, we show that the improved transcriptome data enhances the current possibilities of osmoregulation research in spiny dogfish by utilizing the novel gene and protein annotations to investigate a set of genes involved in urea synthesis and urea, ammonia and water transport, all of them crucial in osmoregulation. We describe the presence of different gene copies and isoforms of key enzymes involved in this process, including arginases and transporters of urea and ammonia, for which sequence information is currently absent in the databases for this model species. The transcriptome assemblies and the derived annotations generated in this study will support the ongoing research for this particular animal model and provides a new molecular tool to assist biological research in cartilaginous fishes. PMID:28832628

Observations on spiny dogfish ( Squalus acanthias) captured in late spring in a North Carolina estuary.

PubMed

Bangley, Charles; Rulifson, Roger

2014-01-01

Five spiny dogfish were captured in early-mid May during gillnet and longline sampling targeting juvenile coastal sharks in inshore North Carolina waters.  Dogfish captures were made within Back Sound and Core Sound, North Carolina. All dogfish were females measuring 849-905 mm total length, well over the size at 50% maturity. Dogfish were caught at stations 1.8-2.7 m in depth, with temperatures 22.9-24.2 °C, 32.8-33.4 ppt salinity, and 6.9-8.0 mg/L dissolved oxygen. These observations are among the latest in the spring for spiny dogfish in the southeastern U.S. and occurred at higher temperatures than previously recorded for this species.  It is unclear whether late-occurring spiny dogfish in this area represent a cryptic late-migrating or resident segment of the Northwest Atlantic population.

Observations on spiny dogfish ( Squalus acanthias) captured in late spring in a North Carolina estuary

PubMed Central

Bangley, Charles; Rulifson, Roger

2014-01-01

Five spiny dogfish were captured in early-mid May during gillnet and longline sampling targeting juvenile coastal sharks in inshore North Carolina waters.  Dogfish captures were made within Back Sound and Core Sound, North Carolina. All dogfish were females measuring 849-905 mm total length, well over the size at 50% maturity. Dogfish were caught at stations 1.8-2.7 m in depth, with temperatures 22.9-24.2 °C, 32.8-33.4 ppt salinity, and 6.9-8.0 mg/L dissolved oxygen. These observations are among the latest in the spring for spiny dogfish in the southeastern U.S. and occurred at higher temperatures than previously recorded for this species.  It is unclear whether late-occurring spiny dogfish in this area represent a cryptic late-migrating or resident segment of the Northwest Atlantic population. PMID:25469229

Plastic debris ingested by deep-water fish of the Ionian Sea (Eastern Mediterranean)

NASA Astrophysics Data System (ADS)

Anastasopoulou, Aikaterini; Mytilineou, Chryssi; Smith, Christopher J.; Papadopoulou, Konstantia N.

2013-04-01

Debris has been recognized as a global environmental problem including within deep habitats. From 26 fish species (1504 specimens) caught in the Eastern Ionian Sea during deep-water long-line surveys, plastic debris was found in 24 individuals of Galeus melastomus (3.2%) and single individuals of Pteroplatytrygon violacea, Squalus blainville, Etmopterus spinax, and Pagellus bogaraveo. The occurrence of debris among their food was infrequent. Ingested debris included primarily plastics (86.5%) and to a lesser extent pieces of metal and wood. Among ingested plastics, fragments of hard plastic material constituted the highest proportion (56.0%), followed by plastic bag fragments (22.0%), fragments of fishing gears (19.0%) and textile fibers (3.0%). Among the species with ingested debris, G. melastomus swallowed all debris categories; P. violacea and S. blainville ingested plastic bag fragments, whereas pieces of hard plastics were found in E. spinax and P. bogaraveo.

Does stimulation of NaCl secretion in in vitro perfused rectal gland tubules of Squalus acanthias increase membrane capacitance?

PubMed

Greger, R; Thiele, I; Warth, R; Bleich, M

1998-07-01

NaCl secretion in rectal gland tubules (RGT) of Squalus acanthias requires the activation of Cl– channels in the luminal membrane. The RGT and its mechanism of activation are an early evolutionary paradigm of exocrine secretion. The respective Cl– channels probably resemble the shark equivalent of the cystic fibrosis transmembrane conductance regulator (CFTR). Activation of these Cl– channels occurs via cAMP. It has been hypothesized that the activation of CFTR occurs via exocytosis or inhibited endocytosis. To examine this question directly by electrical measurements we have performed whole-cell patch-clamp analyses of in vitro perfused RGT. NaCl secretion was stimulated by a solution (Stim) containing forskolin (10 µmol/l), dibutyryl-cAMP (0.5 mmol/l) and adenosine (0.5 mmol/l). This led to the expected strong depolarization and an increase in membrane conductance (G m). The membrane capacitance (C m) was measured by a newly devised two-frequency synchronous detector method. It was increased by Stim significantly from 5.00±0.22 to 5.17±0.21 pF (n=50). The increase in C m correlated with the increase in G m with a slope of 51 fF/nS. Next the effect of furosemide (500 µmol/l) was examined in previously stimulated RGT. Furosemide was supposed to inhibit coupled Na+2Cl–K+ uptake and to reduce cell volume but not membrane trafficking of Cl– channels. Furosemide reduced G m slightly (due to the fall in cytosolic Cl– concentration) and C m to the same extent by which Stim had increased it. Both changes were statistically significant, and the slope of ΔC m/ΔG m was similar to that caused by Stim. Inhibitors of microtubules or actin (colchicine, phalloidin and cytochalasin D added at 10 µmol/l to the pipette solution and dialysed for >10 min) did not alter cell voltage, G m or C m, nor did these inhibitors abolish the stimulatory effect of cAMP. These data suggest that the small C m changes observed with Stim reflect a minor cell volume increase and an ”unfolding” of the plasma membrane. The present data do not support the exocytosis/endocytosis hypothesis of cAMP-mediated activation of Cl– channels in these cells.

Characterization of Aquaporin 4 Protein Expression and Localization in Tissues of the Dogfish (Squalus acanthias)

PubMed Central

Cutler, Christopher P.; Harmon, Sheena; Walsh, Jonathon; Burch, Kia

2012-01-01

The role of aquaporin water channels such as aquaporin 4 (Aqp4) in elasmobranchs such as the dogfish Squalus acanthias is completely unknown. This investigation set out to determine the expression and cellular and sub-cellular localization of Aqp4 protein in dogfish tissues. Two polyclonal antibodies were generated (AQP4/1 and AQP4/2) and these showed somewhat different characteristics in Western blotting and immunohistochemistry. Western blots using the AQP4/1 antibody showed two bands (35.5 and 49.5 kDa) in most tissues in a similar fashion to mammals. Liver had an additional band of 57 kDa and rectal gland two further faint bands of 37.5 and 38.5 kDa. However, unlike in mammals, Aqp4 protein was ubiquitously expressed in all tissues including gill and liver. The AQP4/2 antibody appeared much less specific in Western blots. Both antibodies were used in immunohistochemistry and showed similar cellular localizations, although the AQP4/2 antibody had a more restricted sub-cellular distribution compared to AQP4/1 and therefore appeared to be more specific for Aqp4. In kidney a sub-set of tubules were stained which may represent intermediate tubule segments (In-III–In-VI). AQP4/1 and AQP4/2 antibodies localized to the same tubules segments in serial sections although the intensity and sub-cellular distribution were different. AQP4/2 showed a basal or basolateral membrane distribution whereas AQP4/1 was often distributed throughout the whole cell including the nuclear region. In rectal gland and cardiac stomach Aqp4 was localized to secretory tubules but again AQP/1 and AQP/2 exhibited different sub-cellular distributions. In gill, both antibodies stained large cells in the primary filament and secondary lamellae. Again AQP4/1 antibody stained most or all the cell including the nucleus, whereas AQP4/2 had a plasma membrane or plasma membrane and cytoplasmic distribution. Two types of large mitochondrial rich transport cells are known to exist in elasmobranchs, that express either Na, K-ATPase, or V-type ATPase ion transporters. Using Na, K-ATPase, and V-type ATPase antibodies, Aqp4 was colocalized with these proteins using the AQP4/1 antibody. Results show Aqp4 is expressed in both (and all) branchial Na, K-ATPase, and V-type ATPase expressing cells. PMID:22363294

Regulation of the Na+2Cl–K+ cotransporter in in vitro perfused rectal gland tubules of Squalus acanthias.

PubMed

Warth, R; Bleich, M; Thiele, I; Lang, F; Greger, R

1998-07-01

Previously it has been shown that the Na+2Cl–K+ cotransporter accepts NH4 + at its K+ binding site. This property can be used to estimate its transport rates by adding NH4 + to the bath and measuring the initial furosemide-dependent rates of change in BCECF fluorescence. We have utilized this technique to determine the regulation of the furosemide-inhibitable Na+2Cl–K+ cotransporter in in vitroperfused rectal gland tubules (RGT) of Squalus acanthias. Addition of NH4 + to the bath (20 mmol/l) led to an initial alkalinization, corresponding to NH3 uptake. This was followed by an acidification, corresponding to NH4 + uptake. The rate of this uptake was quantified by exponential curve fitting and is given in arbitrary units (Δfluorescence/time). This acidification could be completely inhibited by furosemide. In the absence of any secretagogue preincubation of RGT in a low Cl– solution (6 mmol/l, low Cl–) for 10 min enhanced the uptake rate significantly from 4.04±0.51 to 12.7±1.30 (n=5). The addition of urea (200 mmol/l) was without effect, but the addition of 300 mmol/l mannitol (+300 mannitol) enhanced the rate significantly from 7.24±1.33 to 14.7±4.6 (n=6). Stimulation of NaCl secretion by a solution maximizing the cytosolic cAMP concentration (Stim) led to a significant increase in NH4 + uptake rate from 5.00±1.33 to 13.3±1.54 (n=6). Similar results were obtained in the additional presence of Ba2+ (1 mmol/l): the uptake rate was increased significantly from 4.23±0.34 to 15.1±1.86 (n=16). In the presence of Stim low Cl– had no additional effect on the uptake rate: 15.1±3.1 versus 15.2±2.8 in high Cl– (n=6). The uptake rate in Stim containing additional +300 mannitol (22.3±4.0, n=5) was not significantly different from that obtained with Stim or +300 mannitol alone. By whatever mechanism the NH4 + uptake rate was increased furosemide (500 µmol/l) always reduced this rate to control values. Hence three manoeuvres enhanced furosemide-inhibitable uptake rates of the Na+2Cl–K+ cotransporter probably independently: (1) lowering of cytosolic Cl– concentration; (2) cell shrinkage; and (3) activation by cAMP.

Characterization of Aquaporin 4 Protein Expression and Localization in Tissues of the Dogfish (Squalus acanthias).

PubMed

Cutler, Christopher P; Harmon, Sheena; Walsh, Jonathon; Burch, Kia

2012-01-01

The role of aquaporin water channels such as aquaporin 4 (Aqp4) in elasmobranchs such as the dogfish Squalus acanthias is completely unknown. This investigation set out to determine the expression and cellular and sub-cellular localization of Aqp4 protein in dogfish tissues. Two polyclonal antibodies were generated (AQP4/1 and AQP4/2) and these showed somewhat different characteristics in Western blotting and immunohistochemistry. Western blots using the AQP4/1 antibody showed two bands (35.5 and 49.5 kDa) in most tissues in a similar fashion to mammals. Liver had an additional band of 57 kDa and rectal gland two further faint bands of 37.5 and 38.5 kDa. However, unlike in mammals, Aqp4 protein was ubiquitously expressed in all tissues including gill and liver. The AQP4/2 antibody appeared much less specific in Western blots. Both antibodies were used in immunohistochemistry and showed similar cellular localizations, although the AQP4/2 antibody had a more restricted sub-cellular distribution compared to AQP4/1 and therefore appeared to be more specific for Aqp4. In kidney a sub-set of tubules were stained which may represent intermediate tubule segments (In-III-In-VI). AQP4/1 and AQP4/2 antibodies localized to the same tubules segments in serial sections although the intensity and sub-cellular distribution were different. AQP4/2 showed a basal or basolateral membrane distribution whereas AQP4/1 was often distributed throughout the whole cell including the nuclear region. In rectal gland and cardiac stomach Aqp4 was localized to secretory tubules but again AQP/1 and AQP/2 exhibited different sub-cellular distributions. In gill, both antibodies stained large cells in the primary filament and secondary lamellae. Again AQP4/1 antibody stained most or all the cell including the nucleus, whereas AQP4/2 had a plasma membrane or plasma membrane and cytoplasmic distribution. Two types of large mitochondrial rich transport cells are known to exist in elasmobranchs, that express either Na, K-ATPase, or V-type ATPase ion transporters. Using Na, K-ATPase, and V-type ATPase antibodies, Aqp4 was colocalized with these proteins using the AQP4/1 antibody. Results show Aqp4 is expressed in both (and all) branchial Na, K-ATPase, and V-type ATPase expressing cells.

The effects of endothelin-1 on the cardiorespiratory physiology of the freshwater trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias).

PubMed

Perry, S F; Montpetit, C J; McKendry, J; Desforges, P R; Gilmour, K M; Wood, C M; Olson, K R

2001-11-01

The aim of the present study was to evaluate the effects of endothelin-l-elicited cardiovascular events on respiratory gas transfer in the freshwater rainbow trout (Oncorhynchus mykiss) and the marine dogfish (Squalus acanthias). In both species, endothelin-1 (666 pmol kg(-1)) caused a rapid (within 4 min) reduction (ca. 30-50 mmHg) in arterial blood partial pressure of O2. The effects of endothelin-1 on arterial blood partial pressure of CO2 were not synchronised with the changes in O2 partial pressure and the responses were markedly different in trout and dogfish. In trout, arterial CO2 partial pressure was increased transiently by approximately 1.0 mmHg but the onset of the response was delayed and occurred 12 min after endothelin-1 injection. In contrast, CO2 partial pressure remained more-or-less constant in dogfish after injection of endothelin-1 and was increased only slightly (approximately 0.1 mmHg) after 60 min. Pre-treatment of trout with bovine carbonic anhydrase (5 mg ml(-1)) eliminated the increase in CO2 partial pressure that was normally observed after endothelin-1 injection. In both species, endothelin-1 injection caused a decrease in arterial blood pH that mirrored the changes in CO2 partial pressure. Endothelin-1 injection was associated with transient (trout) or persistent (dogfish) hyperventilation as indicated by pronounced increases in breathing frequency and amplitude. In trout, arterial blood pressure remained constant or was decreased slightly and was accompanied by a transient increase in systemic resistance, and a temporary reduction in cardiac output. The decrease in cardiac output was caused solely by a reduction in cardiac frequency; cardiac stroke volume was unaffected. In dogfish, arterial blood pressure was lowered by approximately 10 mmHg at 6-10 min after endothelin-1 injection but then was rapidly restored to pre-injection levels. The decrease in arterial blood pressure reflected an increase in branchial vascular resistance (as determined using in situ perfused gill preparations) that was accompanied by simultaneous decreases in systemic resistance and cardiac output. Cardiac frequency and stroke volume were reduced by endothelin-1 injection and thus both variables contributed to the changes in cardiac output. We conclude that the net consequences of endothelin-1 on arterial blood gases result from the opposing effects of reduced gill functional surface area (caused by vasoconstriction) and an increase in blood residence time within the gill (caused by decreased cardiac output.

Atrial natriuretic peptide stimulates salt secretion by shark rectal gland by releasing VIP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, P.; Stoff, J.S.; Solomon, R.J.

1987-01-01

Salt secretion by the isolated perfused rectal gland of the spiny dogfish shark, Squalus acanthias, is stimulated by synthetic rat atrial natriuretic peptide (ANP II) as well as extracts of shark heart, but not by 8-bromo-cyclic guanosine 5'-monophosphate. Cardiac peptides have no effect on isolated rectal gland cells or perfused tubules, suggesting that stimulation requires an intact gland. The stimulation of secretion by ANP II is eliminated by maneuvers that block neurotransmitter release. Cardiac peptides stimulate the release of vasoactive intestinal peptide (VIP), known to be present in rectal glands nerves, into the venous effluent of perfused glands in parallelmore » with their stimulation of salt secretion, but the release of VIP induced by ANP II is prevented by perfusion with procaine. VIP was measured by radioimmunoassay. Cardiac peptides thus appear to regulate rectal gland secretion by releasing VIP from neural stores within the gland. It is possible that other physiological effects of these hormones might be explained by an action to enhanced local release of neurotransmitters.« less

Demersal fish assemblages off southern New Zealand in relation to depth and temperature

NASA Astrophysics Data System (ADS)

Jacob, W.; McClatchie, S.; Probert, P. K.; Hurst, R. J.

1998-12-01

We examined the relationship between demersal fish assemblage and depth, temperature, latitude and longitude off southern New Zealand (46-54°S and 165-180°E) in water depths of 80-787 m. Catch weight data were analysed by two-way indicator analysis (TWIA), groupaverage agglomerative clustering (UPGMA) and Detrended Correspondence Analysis (DCA). The spatial pattern of demersal fish off southern New Zealand conforms to the concept of species groups or fish assemblages related to environmental gradients. Shallow-water assemblages were dominated by species from the families Gempylidae, Squalidae, Triakidae and Moridae, mainly represented by Thyrsites atun, Squalus acanthias, Galeorhinus australis, and Pseudophycis bachus. Deep water assemblages were dominated by Chimaeridae, Argentinidae, Merlucciidae and Macrouridae, mainly represented by Hydrolagus novaezelandiae, Argentina elongata, Macruronus novaezelandiae, and Lepidorhynchus denticulatus. Total catch weight was often dominated by Merlucciidae, Macrouridae and Gempylidae. Fish assemblages were related to discrete ranges of depth (< and >300 m) and temperature (< and >9.5°C), but the range of sediment types was too narrow to show any correlation.

Propionate induces cell swelling and K+ accumulation in shark rectal gland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, G.M.; Ziyadeh, F.N.; Mills, J.W.

1989-08-01

Small organic anions have been reported to induce cell solute accumulation and swelling. To investigate the mechanism of swelling, we utilized preparations of rectal gland cells from Squalus acanthias incubated in medium containing propionate. Propionate causes cells to swell by diffusing across membranes in its nonionic form, acidifying cell contents, and activating the Na+-H+ antiporter. The Na+-H+ exchange process tends to correct intracellular pH (pHi), and thus it maintains a favorable gradient for propionic acid diffusion and allows propionate to accumulate. Activation of the Na+-H+ antiport also facilitates Na+ entry into the cell and Nai accumulation. At the same timemore » Na+-K+-ATPase activity, unaffected by propionate, replaces Nai with Ki, whereas the K+ leak rate, decreased by propionate, allows Ki to accumulate. As judged by {sup 86}Rb+ efflux, the reduction in K+ leak was not due to propionate-induced cell acidification or reduction in Cli concentration. Despite inducing cell swelling, propionate did not disrupt cell structural elements and F actin distribution along cell membranes.« less

Assessing reproductive status in elasmobranch fishes using steroid hormones extracted from skeletal muscle tissue

PubMed Central

Prohaska, Bianca K.; Tsang, Paul C. W.; Driggers, William B.; Hoffmayer, Eric R.; Wheeler, Carolyn R.; Brown, A. Christine; Sulikowski, James A.

2013-01-01

Elasmobranch fishes (sharks, skates, and rays) are particularly susceptible to anthropogenic threats, making a thorough understanding of their life history characteristics essential for proper management. Historically, elasmobranch reproductive data have been collected by lethal sampling, an approach that is problematic for threatened and endangered species. However, recent studies have demonstrated that non-lethal approaches can be as effective as lethal ones for assessment of the reproductive status of an animal. For example, plasma has been used to examine concentrations of steroid hormones. Additionally, skeletal muscle tissue, which can be obtained non-lethally and with minimal stress, can also be used to quantify concentrations of steroid hormones. Skeletal muscle progesterone, testosterone, and estradiol concentrations were determined to be statistically significant indicators of reproductive status in the oviparous Leucoraja erinacea, the yolk-dependent viviparous Squalus acanthias, and the yolk-sac placental viviparous Rhizoprionodon terraenovae. The results of the present study demonstrate that steroid hormones present in non-lethally harvested skeletal muscle tissue can be used as reliable indicators of reproductive status in elasmobranchs. PMID:27293612

The relative roles of external and internal CO(2) versus H(+) in eliciting the cardiorespiratory responses of Salmo salar and Squalus acanthias to hypercarbia.

PubMed

Perry, S F; McKendry, J E

2001-11-01

Fish breathing hypercarbic water encounter externally elevated P(CO(2)) and proton levels ([H(+)]) and experience an associated internal respiratory acidosis, an elevation of blood P(CO(2)) and [H(+)]. The objective of the present study was to assess the potential relative contributions of CO(2) versus H(+) in promoting the cardiorespiratory responses of dogfish (Squalus acanthias) and Atlantic salmon (Salmo salar) to hypercarbia and to evaluate the relative contributions of externally versus internally oriented receptors in dogfish. In dogfish, the preferential stimulation of externally oriented branchial chemoreceptors using bolus injections (50 ml kg(-1)) of CO(2)-enriched (4 % CO(2)) sea water into the buccal cavity caused marked cardiorespiratory responses including bradycardia (-4.1+/-0.9 min(-1)), a reduction in cardiac output (-3.2+/-0.6 ml min(-1) kg(-1)), an increase in systemic vascular resistance (+0.3+/-0.2 mmHg ml min(-1) kg(-1)), arterial hypotension (-1.6+/-0.2 mmHg) and an increase in breathing amplitude (+0.3+/-0.09 mmHg) (means +/- S.E.M., N=9-11). Similar injections of CO(2)-free sea water acidified to the corresponding pH of the hypercarbic water (pH 6.3) did not significantly affect any of the measured cardiorespiratory variables (when compared with control injections). To preferentially stimulate putative internal CO(2)/H(+) chemoreceptors, hypercarbic saline (4 % CO(2)) was injected (2 ml kg(-1)) into the caudal vein. Apart from an increase in arterial blood pressure caused by volume loading, internally injected CO(2) was without effect on any measured variable. In salmon, injection of hypercarbic water into the buccal cavity caused a bradycardia (-13.9+/-3.8 min(-1)), a decrease in cardiac output (-5.3+/-1.2 ml min(-1) kg(-1)), an increase in systemic resistance (0.33+/-0.08 mmHg ml min(-1) kg(-1)) and increases in breathing frequency (9.7+/-2.2 min(-1)) and amplitude (1.2+/-0.2 mmHg) (means +/- S.E.M., N=8-12). Apart from a small increase in breathing amplitude (0.4+/-0.1 mmHg), these cardiorespiratory responses were not observed after injection of acidified water. These results demonstrate that, in dogfish and salmon, the external chemoreceptors linked to the initiation of cardiorespiratory responses during hypercarbia are predominantly stimulated by the increase in water P(CO(2)) rather than by the accompanying decrease in water pH. Furthermore, in dogfish, the cardiorespiratory responses to hypercarbia are probably exclusively derived from the stimulation of external CO(2) chemoreceptors, with no apparent contribution from internally oriented receptors.

In vitro steroid secretion by staged spermatocysts (Sertoli/germ cell units) of dogfish (Squalus acanthias) testis.

PubMed

Cuevas, M E; Callard, G

1992-10-01

Using the dogfish shark (Squalus acanthias) testis model in which different germ cell stages are topographically separated, we previously observed that steroidogenic enzyme activities vary qualitatively and quantitatively during spermatogenesis. To determine whether these data, obtained by radiolabeled tracer analysis of testicular microsomes, accurately predict steroid secretion by intact cultured spermatocysts (germ cell/Sertoli cell units), steroids were radioimmunoassayed directly in spent medium. Steroid output in basal medium was low, but after addition of 25-hydroxycholesterol (25-OH chol, 60 microM), large amounts of progestins (P) and testosterone (T) accumulated. Dehydroepiandrosterone (DHEA), androstenedione (A), and estradiol (E2) were low or nondetectable in the presence or absence of 25-OH chol; however, addition of T (1 microM) as substrate elevated E2 above assay limits. T and P contents of media increased progressively over a 24-hr culture period (Day 1). Replacement and analysis of spent media at 24-hr intervals indicated that secretion was continuous up to 6 days after seeding, although secretory rates (T plus P) and T/P ratios changed with time in culture. Spermatocysts in premeiotic (PrM), meiotic (M), and post-meiotic (PoM) stages all secreted T and P; however, absolute values, T/P ratios, and stage-dependent patterns varied from one experiment to another with no obvious seasonal pattern. Also steroid secretion by staged cysts did not consistently agree with predictions based on steroidogenic enzyme activities measured in earlier cell-free assays, whether or not 25-OH chol was present. This discrepancy was not explained by stage-related patterns of steroid secretion vs retention or by addition of putative in vivo regulators. Agents that elevated P and/or T were dibutyryl cyclic AMP, 1-isobutyl-3-methylxanthine (IBMX), and forskolin, whereas ventral lobe extract and Ca2+ ionophore (A23817) were inhibitory. An autoregulatory feedback loop was indicated by a negative relationship between cyst concentration per well and steroid secretion rate. In contrast to T and P, E2 secretion in the presence of substrate (T, 1 microM) was as predicted from previously determined patterns of aromatase activity (M > PrM > PoM) and increased in response to IBMX. Added [3H]P, [3H]T and [3H]E2 all were extensively metabolized to polar products and P metabolism was stage related (PoM > M > PrM). These data indicate that analysis of free P, T, and E2 in static cyst cultures may underestimate true steroidogenic potential. Assuming further characterization of the system, we conclude that cultured spermatocysts from dogfish testis have potential for studying the multifactorial regulation of steroid synthesis and secretion stage-by-stage during spermatogenesis.

Immunohistochemical localization of urotensin I/corticotropin-releasing factor, urotensin II, and serotonin immunoreactivities in the caudal spinal cord of nonteleost fishes.

PubMed

Onstott, D; Elde, R

1986-07-08

Neurosecretory cells in the caudal spinal cord of fishes were first discovered in elasmobranches. However, most of the subsequent work on the caudal neurosecretory system has emphasized its morphology and function in teleosts. Two major peptides, urotensins I and II (UI and UII), have been isolated from this system in teleosts and their amino acid sequences have been determined. We have used immunohistochemical techniques to confirm and expand previous morphological and pharmacological findings regarding the phylogenetic occurrence and the anatomical organization of the caudal neurosecretory system and to localize putative neurohormonal products within its structural elements. UII-immunoreactive neuronal structures were found in the holocephalan, Hydrolagus collei; the elasmobranches, Squalus acanthias, Dasyatis sabina, and Raja binoculata; the dipnoan, Protopterus annectens; the brachiopterygian, Erpetoichthys calabaricus; the chondrostean, Polyodon spathula; and the holosteans Lepisosteus platyrhinchus and Amia calva. UI/corticotropin-releasing-factor immunoreactive elements were detected in the caudal spinal cords of Petromyzon marinus, Raja binoculata, Polydon spathula, Lepisosteus platyrhinchus, L. osseus, L. platostomus, and Amia calva. In addition, in several of these species, immunohistochemical techniques have provided evidence for serotoninergic input to the caudal neurosecretory system.

Automatic control: the vertebral column of dogfish sharks behaves as a continuously variable transmission with smoothly shifting functions.

PubMed

Porter, Marianne E; Ewoldt, Randy H; Long, John H

2016-09-15

During swimming in dogfish sharks, Squalus acanthias, both the intervertebral joints and the vertebral centra undergo significant strain. To investigate this system, unique among vertebrates, we cyclically bent isolated segments of 10 vertebrae and nine joints. For the first time in the biomechanics of fish vertebral columns, we simultaneously characterized non-linear elasticity and viscosity throughout the bending oscillation, extending recently proposed techniques for large-amplitude oscillatory shear (LAOS) characterization to large-amplitude oscillatory bending (LAOB). The vertebral column segments behave as non-linear viscoelastic springs. Elastic properties dominate for all frequencies and curvatures tested, increasing as either variable increases. Non-linearities within a bending cycle are most in evidence at the highest frequency, 2.0 Hz, and curvature, 5 m -1 Viscous bending properties are greatest at low frequencies and high curvatures, with non-linear effects occurring at all frequencies and curvatures. The range of mechanical behaviors includes that of springs and brakes, with smooth transitions between them that allow for continuously variable power transmission by the vertebral column to assist in the mechanics of undulatory propulsion. © 2016. Published by The Company of Biologists Ltd.

Ultimate Eocene (Priabonian) Chondrichthyans (Holocephali, Elasmobranchii) of Antarctica

PubMed Central

Kriwet, Jürgen; Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo; Pfaff, Cathrin

2017-01-01

The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene–Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics. PMID:28298806

Ultimate Eocene (Priabonian) Chondrichthyans (Holocephali, Elasmobranchii) of Antarctica.

PubMed

Kriwet, Jürgen; Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo; Pfaff, Cathrin

2016-01-01

The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus , Squatina , Pristiophorus , Striatolamia , Palaeohypotodus , Carcharocles , and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene-Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics.

Deepwater Chondrichthyan Bycatch of the Eastern King Prawn Fishery in the Southern Great Barrier Reef, Australia

PubMed Central

Rigby, Cassandra L.; White, William T.; Simpfendorfer, Colin A.

2016-01-01

The deepwater chondrichthyan fauna of the Great Barrier Reef is poorly known and life history information is required to enable their effective management as they are inherently vulnerable to exploitation. The chondrichthyan bycatch from the deepwater eastern king prawn fishery at the Swain Reefs in the southern Great Barrier Reef was examined to determine the species present and provide information on their life histories. In all, 1533 individuals were collected from 11 deepwater chondrichthyan species, with the Argus skate Dipturus polyommata, piked spurdog Squalus megalops and pale spotted catshark Asymbolus pallidus the most commonly caught. All but one species is endemic to Australia with five species restricted to waters offshore from Queensland. The extent of life history information available for each species varied but the life history traits across all species were characteristic of deep water chondrichthyans with relatively large length at maturity, small litters and low ovarian fecundity; all indicative of low biological productivity. However, variability among these traits and spatial and bathymetric distributions of the species suggests differing degrees of resilience to fishing pressure. To ensure the sustainability of these bycatch species, monitoring of their catches in the deepwater eastern king prawn fishery is recommended. PMID:27218654

Active potassium transport coupled to active sodium transport in vesicles reconstituted from purified sodium and potassium ion-activated adenosine triphosphatase from the rectal gland of Squalus acanthias.

PubMed

Hilden, S; Hokin, L E

1975-08-25

Vesicles containing a purified shark rectal gland (sodium + potassium)-activated adenosine triphosphatase-(NaK ATPase) were prepared by dialyzing for 2 days egg lecithin, cholate, and the NaK ATPase purified from the rectal gland of Squalus acanthias. These vesicles were capable of both Na+ and K+ transport. Studies of K+ transport were made by measuring the ATP-stimulated transport outward of 42K+ or 86Rb+. Vesicles were preloaded with isotope by equilibration at 4 degrees for 1 to 3 days. Transport of 42K+ or 86Rb+ was initiated by addition of MgATP to the vesicles. The ATP-dependent exit of either isotope was the same. Experiments are presented which show that this loss of isotope was not due to changes in ion binding but rather due to a loss in the amount of ion trapped in the vesicular volume. The transport of K+ was dependent on external Mg2+. CTP was almost as effective as ATP in stimulating K+ transport, while UTP was relatively ineffective. These effects of nucleotides parallel their effects on Na+ accumulation and their effectiveness as substrates for the enzyme. Potassium transport was inhibited by ouabain and required the presence of Na+. The following asymmetries were seen: (a) addition of external Mg2+ supported K+ transport; (b) ouabain inhibited K+ transport only if it was present inside the vesicles; (c) addition of external Na+ to the vesicles stimulated K+ transport. External Li+ was ineffective as a Na+ substitute. The specific requirement of external Na+ for K+ transport indicates that K+ exit is coupled to Na+ entry. Changes in the internal vesicular ion concentrations were studied with vesicles prepared in 20 mM NaCl and 50 mM KCl. After 1 hour of transport at 25 degrees, a typical Na+ concentration in the vesicles in the presence of ATP was 72 mM. A typical K+ concentration in the vesicles was 10 mM as measured with 42K+ or 6 mM as measured with 86Rb+. The following relationships have been calculated for Na+ transport, K+ transport and ATP hydrolysis: Na+/ATP = 1.42, K+/ATP =1.04, and Na+/K+ = 1.43. The ratio of 2.8 Na+ transported in to 2 K+ transported out is very close to the value reported for the red cell membrane. Potassium-potassium exchange similar to that observed in the red cell membrane and attributed to the Na+-K+ pump (stimulated by ATP and orthophosphate and inhibited by ouabain) was observed when vesicles were prepared in the absence of Na+. The results reported in this paper prove that the shark rectal gland NaK ATPase, which is 90 to 95% pure, is the isolated pump for the coupled transports of Na+ and K+.

Variation in wind and piscivorous predator fields affecting the survival of Atlantic salmon, Salmo salar, in the Gulf of Maine

USGS Publications Warehouse

Friedland, K.D.; Manning, J.P.; Link, Jason S.; Gilbert, J.R.; Gilbert, A.T.; O'Connell, A.F.

2012-01-01

Observations relevant to the North American stock complex of Atlantic salmon, Salmo salar L., suggest that marine mortality is influenced by variation in predation pressure affecting post-smolts during the first months at sea. This hypothesis was tested for Gulf of Maine (GOM) stocks by examining wind pseudostress and the distribution of piscivorous predator fields potentially affecting post-smolts. Marine survival has declined over recent decades with a change in the direction of spring winds, which is likely extending the migration of post-smolts by favouring routes using the western GOM. In addition to changes in spring wind patterns, higher spring sea surface temperatures have been associated with shifting distributions of a range of fish species. The abundance of several pelagic piscivores, which based on their feeding habits may predate on salmon post-smolts, has increased in the areas that serve as migration corridors for post-smolts. In particular, populations of silver hake, Merluccius bilinearis (Mitchell), red hake, Urophycis chuss (Walbaum), and spiny dogfish, Squalus acanthias L., increased in size in the portion of the GOM used by post-smolts. Climate variation and shifting predator distributions in the GOM are consistent with the predator hypothesis of recruitment control suggested for the stock complex.

Elasmobranch bycatch in the Italian Adriatic pelagic trawl fishery

PubMed Central

Fortuna, Caterina Maria; Moro, Fabrizio; Sala, Antonello

2018-01-01

Elasmobranchs are among the most threatened long-lived marine species worldwide, and incidental capture is a major source of mortality. The northern central Adriatic Sea, though one of the most overfished basins of the Mediterranean Sea, supports a very valuable marine biodiversity, including elasmobranchs. This study assesses the impact of the northern central Adriatic pelagic trawl fishery on common smooth-hound (Mustelus mustelus), spiny dogfish (Squalus acanthias), common eagle ray (Myliobatis aquila), and pelagic stingray (Pteroplatytrygon violacea) by examining incidental catches recorded between 2006 and 2015. The distribution of bycatch events was evaluated using geo-referenced data. Generalized Linear Models were computed to standardize the catch of the four species and to predict the relative abundance of bycatch events. Data analysis shows that most bycatch events involving all four species occurred in the northern Adriatic Sea. The models predicted significant, distinct temporal patterns of standardized catches in line with previous investigations. Water depth, season, and fishing region were the best predictors to explain bycatch events. The present data suggest that the northern Adriatic may be an important nursery area for several elasmobranchs. They also highlight the urgent need for a better understanding of the interactions between elasmobranchs and fisheries to develop and apply suitable, ad hoc management measures. PMID:29377920

Shark Interactions With Directed and Incidental Fisheries in the Northeast Pacific Ocean: Historic and Current Encounters, and Challenges for Shark Conservation.

PubMed

King, Jackie; McFarlane, Gordon A; Gertseva, Vladlena; Gasper, Jason; Matson, Sean; Tribuzio, Cindy A

For over 100 years, sharks have been encountered, as either directed catch or incidental catch, in commercial fisheries throughout the Northeast Pacific Ocean. A long-standing directed fishery for North Pacific Spiny Dogfish (Squalus suckleyi) has occurred and dominated shark landings and discards. Other fisheries, mainly for shark livers, have historically targeted species including Bluntnose Sixgill Shark (Hexanchus griseus) and Tope Shark (Galeorhinus galeus). While incidental catches of numerous species have occurred historically, only recently have these encounters been reliably enumerated in commercial and recreational fisheries. In this chapter we present shark catch statistics (directed and incidental) for commercial and recreational fisheries from Canadian waters (off British Columbia), southern US waters (off California, Oregon, and Washington), and northern US waters (off Alaska). In total, 17 species of sharks have collectively been encountered in these waters. Fishery encounters present conservation challenges for shark management, namely, the need for accurate catch statistics, stock delineation, life history parameter estimates, and improved assessments methods for population status and trends. Improvements in management and conservation of shark populations will only come with the further development of sound science-based fishery management practices for both targeted and incidental shark fisheries. © 2017 Elsevier Ltd All rights reserved.

Elasmobranch bycatch in the Italian Adriatic pelagic trawl fishery.

PubMed

Bonanomi, Sara; Pulcinella, Jacopo; Fortuna, Caterina Maria; Moro, Fabrizio; Sala, Antonello

2018-01-01

Elasmobranchs are among the most threatened long-lived marine species worldwide, and incidental capture is a major source of mortality. The northern central Adriatic Sea, though one of the most overfished basins of the Mediterranean Sea, supports a very valuable marine biodiversity, including elasmobranchs. This study assesses the impact of the northern central Adriatic pelagic trawl fishery on common smooth-hound (Mustelus mustelus), spiny dogfish (Squalus acanthias), common eagle ray (Myliobatis aquila), and pelagic stingray (Pteroplatytrygon violacea) by examining incidental catches recorded between 2006 and 2015. The distribution of bycatch events was evaluated using geo-referenced data. Generalized Linear Models were computed to standardize the catch of the four species and to predict the relative abundance of bycatch events. Data analysis shows that most bycatch events involving all four species occurred in the northern Adriatic Sea. The models predicted significant, distinct temporal patterns of standardized catches in line with previous investigations. Water depth, season, and fishing region were the best predictors to explain bycatch events. The present data suggest that the northern Adriatic may be an important nursery area for several elasmobranchs. They also highlight the urgent need for a better understanding of the interactions between elasmobranchs and fisheries to develop and apply suitable, ad hoc management measures.

Biological Sampling and Analysis in Sinclair and Dyes Inlets, Washington: Chemical Analyses for 2007 Puget Sound Biota Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandenberger, Jill M.; Suslick, Carolynn R.; Johnston, Robert K.

2008-10-09

Evaluating spatial and temporal trends in contaminant residues in Puget Sound fish and macroinvertebrates are the objectives of the Puget Sound Ambient Monitoring Program (PSAMP). In a cooperative effort between the ENVironmental inVESTment group (ENVVEST) and Washington State Department of Fish and Wildlife, additional biota samples were collected during the 2007 PSAMP biota survey and analyzed for chemical residues and stable isotopes of carbon (δ13C) and nitrogen (δ15N). Approximately three specimens of each species collected from Sinclair Inlet, Georgia Basin, and reference locations in Puget Sound were selected for whole body chemical analysis. The muscle tissue of specimens selected formore » chemical analyses were also analyzed for δ13C and δ15N to provide information on relative trophic level and food sources. This data report summarizes the chemical residues for the 2007 PSAMP fish and macro-invertebrate samples. In addition, six Spiny Dogfish (Squalus acanthias) samples were necropsied to evaluate chemical residue of various parts of the fish (digestive tract, liver, embryo, muscle tissue), as well as, a weight proportional whole body composite (WBWC). Whole organisms were homogenized and analyzed for silver, arsenic, cadmium, chromium, copper, nickel, lead, zinc, mercury, 19 polychlorinated biphenyl (PCB) congeners, PCB homologues, percent moisture, percent lipids, δ13C, and δ15N.« less

From gelatinous to muscle food chain: rock cod Patagonotothen ramsayi recycles coelenterate and tunicate resources on the Patagonian Shelf.

PubMed

Arkhipkin, A; Laptikhovsky, V

2013-11-01

Stomach contents of 4808 fishes of 20 species caught in the eastern part of the Patagonian Shelf between 1999 and 2012 were analysed to assess dietary contributions of gelatinous plankton resources. Gelatinous plankton occurred in diets of seven species with two species, Patagonotothen ramsayi and Squalus acanthias, having >10% ctenophores in their diet. Consumption of gelatinous plankton was important in P. ramsayi and was strikingly seasonal, with maximum occurrence (up to 46% of non-empty stomachs) in late summer to autumn. Ctenophores were most abundant in P. ramsayi of 25-34 cm total length, L(T) whereas salps were more frequent in larger >35 cm L(T) individuals. In winter to spring, occurrence of gelatinous plankton in diets was minimal, reflecting their overall seasonal abundance in the ocean. The recent increase in abundance of P. ramsayi has enabled the species to recycle a significant proportion of the ecosystem production from gelatinous dead end to the main muscular food chain via seasonal reliance on ctenophores, jellyfish and tunicates. This additional influx of production that has been diverted from the gelatinous food chain favours the increase in abundance of several piscivorous top predators and affects the trophic web structure of the Patagonian Shelf ecosystem. © 2013 The Fisheries Society of the British Isles.

Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

PubMed

Seamone, Scott; Blaine, Tristan; Higham, Timothy E

2014-12-01

Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach. Copyright © 2014 Elsevier GmbH. All rights reserved.

Classification of Sharks in the Egyptian Mediterranean Waters Using Morphological and DNA Barcoding Approaches

PubMed Central

Moftah, Marie; Abdel Aziz, Sayeda H.; Elramah, Sara; Favereaux, Alexandre

2011-01-01

The identification of species constitutes the first basic step in phylogenetic studies, biodiversity monitoring and conservation. DNA barcoding, i.e. the sequencing of a short standardized region of DNA, has been proposed as a new tool for animal species identification. The present study provides an update on the composition of shark in the Egyptian Mediterranean waters off Alexandria, since the latest study to date was performed 30 years ago, DNA barcoding was used in addition to classical taxonomical methodologies. Thus, 51 specimen were DNA barcoded for a 667 bp region of the mitochondrial COI gene. Although DNA barcoding aims at developing species identification systems, some phylogenetic signals were apparent in the data. In the neighbor-joining tree, 8 major clusters were apparent, each of them containing individuals belonging to the same species, and most with 100% bootstrap value. This study is the first to our knowledge to use DNA barcoding of the mitochondrial COI gene in order to confirm the presence of species Squalus acanthias, Oxynotus centrina, Squatina squatina, Scyliorhinus canicula, Scyliorhinus stellaris, Mustelus mustelus, Mustelus punctulatus and Carcharhinus altimus in the Egyptian Mediterranean waters. Finally, our study is the starting point of a new barcoding database concerning shark composition in the Egyptian Mediterranean waters (Barcoding of Egyptian Mediterranean Sharks [BEMS], http://www.boldsystems.org/views/projectlist.php?&#Barcoding%20Fish%20%28FishBOL%29). PMID:22087242

Regulation of branchial V-H(+)-ATPase, Na(+)/K(+)-ATPase and NHE2 in response to acid and base infusions in the Pacific spiny dogfish (Squalus acanthias).

PubMed

Tresguerres, Martin; Katoh, Fumi; Fenton, Heather; Jasinska, Edyta; Goss, Greg G

2005-01-01

To study the mechanisms of branchial acid-base regulation, Pacific spiny dogfish were infused intravenously for 24 h with either HCl (495+/- 79 micromol kg(-1) h(-1)) or NaHCO(3) (981+/-235 micromol kg(-1) h(-1)). Infusion of HCl produced a transient reduction in blood pH. Despite continued infusion of acid, pH returned to normal by 12 h. Infusion of NaHCO(3) resulted in a new steady-state acid-base status at approximately 0.3 pH units higher than the controls. Immunostained serial sections of gill revealed the presence of separate vacuolar proton ATPase (V-H(+)-ATPase)-rich or sodium-potassium ATPase (Na(+)/K(+)-ATPase)-rich cells in all fish examined. A minority of the cells also labeled positive for both transporters. Gill cell membranes prepared from NaHCO(3)-infused fish showed significant increases in both V-H(+)-ATPase abundance (300+/-81%) and activity. In addition, we found that V-H(+)-ATPase subcellular localization was mainly cytoplasmic in control and HCl-infused fish, while NaHCO(3)-infused fish demonstrated a distinctly basolateral staining pattern. Western analysis in gill membranes from HCl-infused fish also revealed increased abundance of Na(+)/H(+) exchanger 2 (213+/-5%) and Na(+)/K(+)-ATPase (315+/-88%) compared to the control.

Properties and function of KCNQ1 K+ channels isolated from the rectal gland of Squalus acanthias.

PubMed

Kerst, G; Beschorner, U; Unsöld, B; von Hahn, T; Schreiber, R; Greger, R; Gerlach, U; Lang, H J; Kunzelmann, K; Bleich, M

2001-10-01

KCNQ1 (KVLQT1) K+ channels play an important role during electrolyte secretion in airways and colon. KCNQ1 was cloned recently from NaCl-secreting shark rectal glands. Here we study the properties and regulation of the cloned sKVLQT1 expressed in Xenopus oocytes and Chinese hamster ovary (CHO) cells and compare the results with those obtained from in vitro perfused rectal gland tubules (RGT). The expression of sKCNQ1 induced voltage-dependent, delayed activated K+ currents, which were augmented by an increase in intracellular cAMP and Ca2+. The chromanol derivatives 293B and 526B potently inhibited sKCNQ1 expressed in oocytes and CHO cells, but had little effect on RGT electrolyte transport. Short-circuit currents in RGT were activated by alkalinization and were decreased by acidification. In CHO cells an alkaline pH activated and an acidic pH inhibited 293B-sensitive KCNQ1 currents. Noise analysis of the cell-attached basolateral membrane of RGT indicated the presence of low-conductance (<3 pS) K+ channels, in parallel with other K+ channels. sKCNQ1 generated similar small-conductance K+ channels upon expression in CHO cells and Xenopus oocytes. The results suggest the presence of low-conductance KCNQ1 K+ channels in RGT, which are probably regulated by changes in intracellular cAMP, Ca2+ and pH.

An acid-sensing ion channel from shark (Squalus acanthias) mediates transient and sustained responses to protons.

PubMed

Springauf, Andreas; Gründer, Stefan

2010-03-01

Acid-sensing ion channels (ASICs) are proton-gated Na(+) channels. They are implicated in synaptic transmission, detection of painful acidosis, and possibly sour taste. The typical ASIC current is a transient, completely desensitizing current that can be blocked by the diuretic amiloride. ASICs are present in chordates but are absent in other animals. They have been cloned from urochordates, jawless vertebrates, cartilaginous shark and bony fish, from chicken and different mammals. Strikingly, all ASICs that have so far been characterized from urochordates, jawless vertebrates and shark are not gated by protons, suggesting that proton gating evolved relatively late in bony fish and that primitive ASICs had a different and unknown gating mechanism. Recently, amino acids that are crucial for the proton gating of rat ASIC1a have been identified. These residues are completely conserved in shark ASIC1b (sASIC1b), prompting us to re-evaluate the proton sensitivity of sASIC1b. Here we show that, contrary to previous findings, sASIC1b is indeed gated by protons with half-maximal activation at pH 6.0. sASIC1b desensitizes quickly but incompletely, efficiently encoding transient as well as sustained proton signals. Our results show that the conservation of the amino acids crucial for proton gating can predict proton sensitivity of an ASIC and increase our understanding of the evolution of ASICs.

Validation of a portable, waterproof blood pH analyser for elasmobranchs.

PubMed

Talwar, Brendan; Bouyoucos, Ian A; Shipley, Oliver; Rummer, Jodie L; Mandelman, John W; Brooks, Edward J; Grubbs, R Dean

2017-01-01

Quantifying changes in blood chemistry in elasmobranchs can provide insights into the physiological insults caused by anthropogenic stress, and can ultimately inform conservation and management strategies. Current methods for analysing elasmobranch blood chemistry in the field are often costly and logistically challenging. We compared blood pH values measured using a portable, waterproof pH meter (Hanna Instruments HI 99161) with blood pH values measured by an i-STAT system (CG4+ cartridges), which was previously validated for teleost and elasmobranch fishes, to gauge the accuracy of the pH meter in determining whole blood pH for the Cuban dogfish ( Squalus cubensis ) and lemon shark ( Negaprion brevirostris ). There was a significant linear relationship between values derived via the pH meter and the i-STAT for both species across a wide range of pH values and temperatures (Cuban dogfish: 6.8-7.1 pH 24-30°C; lemon sharks: 7.0-7.45 pH 25-31°C). The relative error in the pH meter's measurements was ~±2.7%. Using this device with appropriate correction factors and consideration of calibration temperatures can result in both a rapid and accurate assessment of whole blood pH, at least for the two elasmobranch species examined here. Additional species should be examined in the future across a wide range of temperatures to determine whether correction factors are universal.

Polyvalent cation receptor proteins (CaRs) are salinity sensors in fish.

PubMed

Nearing, J; Betka, M; Quinn, S; Hentschel, H; Elger, M; Baum, M; Bai, M; Chattopadyhay, N; Brown, E M; Hebert, S C; Harris, H W

2002-07-09

To determine whether calcium polyvalent cation-sensing receptors (CaRs) are salinity sensors in fish, we used a homology-based cloning strategy to isolate a 4.1-kb cDNA encoding a 1,027-aa dogfish shark (Squalus acanthias) kidney CaR. Expression studies in human embryonic kidney cells reveal that shark kidney senses combinations of Ca(2+), Mg(2+), and Na(+) ions at concentrations present in seawater and kidney tubules. Shark kidney is expressed in multiple shark osmoregulatory organs, including specific tubules of the kidney, rectal gland, stomach, intestine, olfactory lamellae, gill, and brain. Reverse transcriptase-PCR amplification using specific primers in two teleost fish, winter flounder (Pleuronectes americanus) and Atlantic salmon (Salmo salar), reveals a similar pattern of CaR tissue expression. Exposure of the lumen of winter flounder urinary bladder to the CaR agonists, Gd(3+) and neomycin, reversibly inhibit volume transport, which is important for euryhaline teleost survival in seawater. Within 24-72 hr after transfer of freshwater-adapted Atlantic salmon to seawater, there are increases in their plasma Ca(2+), Mg(2+), and Na(+) that likely serve as a signal for internal CaRs, i.e., brain, to sense alterations in salinity in the surrounding water. We conclude that CaRs act as salinity sensors in both teleost and elasmobranch fish. Their tissue expression patterns in fish provide insights into CaR functions in terrestrial animals including humans.

Humoral immune response of the small-spotted catshark, Scyliorhinus canicula.

PubMed

Crouch, Kathryn; Smith, Lauren E; Williams, Rebecca; Cao, Wei; Lee, Mike; Jensen, Allan; Dooley, Helen

2013-05-01

Cartilaginous fishes are the oldest group in which an adaptive immune system based on immunoglobulin-superfamily members is found. This manuscript compares humoral immune function in small-spotted catshark (Scyliorhinus canicula) with that described for spiny dogfish (Squalus acanthias), another member of the Squalomorphi superorder, and nurse shark, the model for humoral immunity in elasmobranchs and a member of the Galeomorphi superorder. Although small-spotted catshark and nurse shark are separated by over 200 million years we found that immunoglobulin isoforms are well conserved between the two species. However, the plasma protein profile of small-spotted catshark was most similar to that of spiny dogfish, with low levels of pentameric IgM, and IgNAR present as a multimer in plasma rather than a monomer. We show that an antigen-specific monomeric IgM response, with a profile similar to that described previously for nurse sharks, can be raised in small-spotted catshark. Lacking polyclonal or monoclonal antibody reagents for detecting catshark IgNAR we investigated phage-display and recombinant Fc-fusion protein expression as alternative methods to look for an antigen-specific response for this isotype. However, we could find no evidence of an antigen-specific IgNAR in the animals tested using either of these techniques. Thus, unlike nurse sharks where antigen-specific monomeric IgM and IgNAR appear together, it seems there may be a temporal or complete 'uncoupling' of these isotypes during a humoral response in the small-spotted catshark. Copyright © 2013 Elsevier Ltd. All rights reserved.

A perfusion study of the handling of urea and urea analogues by the gills of the dogfish shark (Squalus acanthias).

PubMed

Wood, Chris M; Liew, Hon Jung; De Boeck, Gudrun; Walsh, Patrick J

2013-01-01

The branchial mechanism of urea retention in elasmobranchs was investigated using an in vitro isolated-perfused head preparation, as well as in vivo samples, in the spiny dogfish shark. Both in vivo and in control saline perfusions containing 350 mmol L(-1) urea, calculated intracellular urea concentrations in gill epithelial cells were close to extracellular concentrations. Urea efflux to the external water fell only non-significantly, and calculated gill intracellular urea concentration did not change when perfusate urea concentration was reduced from 350 to 175 mmol L(-1) with osmotic compensation by 175 mmol L(-1) mannitol. However, when the urea analogues thiourea or acetamide were present in the perfusate at concentrations equimolar (175 mmol L(-1)) to those of urea (175 mmol L(-1)), urea efflux rates were increased 4-fold and 6.5-fold respectively, and calculated gill intracellular urea concentrations were depressed by about 55%. Analogue efflux rates were similar to urea efflux rates. Previous studies have argued that either the basolateral or apical membranes provided the limiting permeability barrier, and/or that a back-transporter on the basolateral membranes of gill cells is responsible for urea retention. The present results provide new evidence that the apical membrane is the limiting factor in maintaining gill urea impermeability, and raise the prospect that a urea back-transporter, which can be competitively inhibited by thiourea and acetamide, operates at the apical membrane.

An acid-sensing ion channel from shark (Squalus acanthias) mediates transient and sustained responses to protons

PubMed Central

Springauf, Andreas; Gründer, Stefan

2010-01-01

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. They are implicated in synaptic transmission, detection of painful acidosis, and possibly sour taste. The typical ASIC current is a transient, completely desensitizing current that can be blocked by the diuretic amiloride. ASICs are present in chordates but are absent in other animals. They have been cloned from urochordates, jawless vertebrates, cartilaginous shark and bony fish, from chicken and different mammals. Strikingly, all ASICs that have so far been characterized from urochordates, jawless vertebrates and shark are not gated by protons, suggesting that proton gating evolved relatively late in bony fish and that primitive ASICs had a different and unknown gating mechanism. Recently, amino acids that are crucial for the proton gating of rat ASIC1a have been identified. These residues are completely conserved in shark ASIC1b (sASIC1b), prompting us to re-evaluate the proton sensitivity of sASIC1b. Here we show that, contrary to previous findings, sASIC1b is indeed gated by protons with half-maximal activation at pH 6.0. sASIC1b desensitizes quickly but incompletely, efficiently encoding transient as well as sustained proton signals. Our results show that the conservation of the amino acids crucial for proton gating can predict proton sensitivity of an ASIC and increase our understanding of the evolution of ASICs. PMID:20064854

Using omeprazole to link the components of the post-prandial alkaline tide in the spiny dogfish, Squalus acanthias.

PubMed

Wood, Chris M; Schultz, Aaron G; Munger, R Stephen; Walsh, Patrick J

2009-03-01

After a meal, dogfish exhibit a metabolic alkalosis in the bloodstream and a marked excretion of basic equivalents across the gills to the external seawater. We used the H(+), K(+)-ATPase pump inhibitor omeprazole to determine whether these post-prandial alkaline tide events were linked to secretion of H(+) (accompanied by Cl(-)) in the stomach. Sharks were fitted with indwelling stomach tubes for pretreatment with omeprazole (five doses of 5 mg omeprazole per kilogram over 48 h) or comparable volumes of vehicle (saline containing 2% DMSO) and for sampling of gastric chyme. Fish were then fed an involuntary meal by means of the stomach tube consisting of minced flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Omeprazole pre-treatment delayed the post-prandial acidification of the gastric chyme, slowed the rise in Cl(-) concentration of the chyme and altered the patterns of other ions, indicating inhibition of H(+) and accompanying Cl(-) secretion. Omeprazole also greatly attenuated the rise in arterial pH and bicarbonate concentrations and reduced the net excretion of basic equivalents to the water by 56% over 48 h. Arterial blood CO(2) pressure (Pa(CO(2))) and plasma ions were not substantially altered. These results indicate that elevated gastric H(+) secretion (as HCl) in the digestive process is the major cause of the systemic metabolic alkalosis and the accompanying rise in base excretion across the gills that constitute the alkaline tide in the dogfish.

Microtubule-dependent relocation of branchial V-H+-ATPase to the basolateral membrane in the Pacific spiny dogfish (Squalus acanthias): a role in base secretion.

PubMed

Tresguerres, Martin; Parks, Scott K; Katoh, Fumi; Goss, Greg G

2006-02-01

We have previously shown that continuous intravenous infusion of NaHCO3 for 24 h ( approximately 1000 micromol kg(-1) h(-1)) results in the relocation of V-H+-ATPase from the cytoplasm to the basolateral membrane in the gills of the Pacific dogfish. To further investigate this putative base-secretive process we performed similar experiments with the addition of colchicine, an inhibitor of cytoskeleton-dependent cellular trafficking processes. Blood pH and plasma total CO2 were significantly higher in the colchicines-treated, HCO3- -infused fish compared with fish infused with HCO3- alone. The effect of colchicine was highest after 24 h of infusion (8.33+/-0.06 vs 8.02+/-0.03 pH units, 15.72+/-3.29 vs 6.74+/-1.34 mmol CO2 l(-1), N=5). Immunohistochemistry and western blotting confirmed that colchicine blocked the transit of V-H+-ATPase to the basolateral membrane. Furthermore, western blotting analyses from whole gill and cell membrane samples suggest that the short-term (6 h) response to alkaline stress consists of relocation of V-H+-ATPases already present in the cell to the basolateral membrane, while in the longer term (24 h) there is both relocation of preexistent enzyme and upregulation in the synthesis of new units. Our results strongly suggest that cellular relocation of V-H+-ATPase is necessary for enhanced HCO3- secretion across the gills of the Pacific dogfish.

Improving the pharmacokinetic properties of biologics by fusion to an anti-HSA shark VNAR domain

PubMed Central

Müller, Mischa R.; Saunders, Kenneth; Grace, Christopher; Jin, Macy; Piche-Nicholas, Nicole; Steven, John; O’Dwyer, Ronan; Wu, Leeying; Khetemenee, Lam; Vugmeyster, Yulia; Hickling, Timothy P.; Tchistiakova, Lioudmila; Olland, Stephane; Gill, Davinder; Jensen, Allan; Barelle, Caroline J.

2012-01-01

Advances in recombinant antibody technology and protein engineering have provided the opportunity to reduce antibodies to their smallest binding domain components and have concomitantly driven the requirement for devising strategies to increase serum half-life to optimise drug exposure, thereby increasing therapeutic efficacy. In this study, we adopted an immunization route to raise picomolar affinity shark immunoglobulin new antigen receptors (IgNARs) to target human serum albumin (HSA). From our model shark species, Squalus acanthias, a phage display library encompassing the variable binding domain of IgNAR (VNAR) was constructed, screened against target, and positive clones were characterized for affinity and specificity. N-terminal and C-terminal molecular fusions of our lead hit in complex with a naïve VNAR domain were expressed, purified and exhibited the retention of high affinity binding to HSA, but also cross-selectivity to mouse, rat and monkey serum albumin both in vitro and in vivo. Furthermore, the naïve VNAR had enhanced pharmacokinetic (PK) characteristics in both N- and C-terminal orientations and when tested as a three domain construct with naïve VNAR flanking the HSA binding domain at both the N and C termini. Molecules derived from this platform technology also demonstrated the potential for clinical utility by being available via the subcutaneous route of delivery. This study thus demonstrates the first in vivo functional efficacy of a VNAR binding domain with the ability to enhance PK properties and support delivery of multifunctional therapies. PMID:23676205

Validation of a portable, waterproof blood pH analyser for elasmobranchs

PubMed Central

Bouyoucos, Ian A.; Shipley, Oliver; Rummer, Jodie L.; Mandelman, John W.; Brooks, Edward J.; Grubbs, R. Dean

2017-01-01

Abstract Quantifying changes in blood chemistry in elasmobranchs can provide insights into the physiological insults caused by anthropogenic stress, and can ultimately inform conservation and management strategies. Current methods for analysing elasmobranch blood chemistry in the field are often costly and logistically challenging. We compared blood pH values measured using a portable, waterproof pH meter (Hanna Instruments HI 99161) with blood pH values measured by an i-STAT system (CG4+ cartridges), which was previously validated for teleost and elasmobranch fishes, to gauge the accuracy of the pH meter in determining whole blood pH for the Cuban dogfish (Squalus cubensis) and lemon shark (Negaprion brevirostris). There was a significant linear relationship between values derived via the pH meter and the i-STAT for both species across a wide range of pH values and temperatures (Cuban dogfish: 6.8–7.1 pH 24–30°C; lemon sharks: 7.0–7.45 pH 25–31°C). The relative error in the pH meter's measurements was ~±2.7%. Using this device with appropriate correction factors and consideration of calibration temperatures can result in both a rapid and accurate assessment of whole blood pH, at least for the two elasmobranch species examined here. Additional species should be examined in the future across a wide range of temperatures to determine whether correction factors are universal. PMID:28616238

Morphological features of coronary arteries and lesions in hearts from five species of sharks collected from the northwestern Atlantic Ocean.

PubMed

Borucinska, J D; Obasa, O A; Haffey, N M; Scott, J P; Williams, L N; Baker, S M; Min, S J; Kaplan, A; Mudimala, R

2012-10-01

Morphological features of coronary arteries and incidental lesions are reported from hearts in five species of sharks, the shortfin mako shark, Isurus oxyrhinchus Rafinesque, thresher shark Alopias vulpinus (Bonaterre), blue shark, Prionace glauca L., the smooth dogfish, Mustelus canis (Mitchill), and spiny dogfish, Squalus acanthias L. Sharks were collected from the northwestern Atlantic between June and August from 1996 to 2010. They were necropsied dockside and the hearts were preserved in buffered formalin. Routine sections including ventricle/conus arteriosus and the atrio-ventricular junctions were embedded in paraffin, stained with common histological and immunohistochemical methods and examined by brightfield microscopy. Myointimal hyperplasia, medial myo-myxomatous hyperplasia and bifurcation pads were observed commonly, and medial muscle reorientation and epicardial myeloid tissues were rare. All the above features differed in severity, prevalence and distribution depending on anatomical site and shark species/size. Morphometric analysis indicated that myomyxomatous hyperplasia is associated with luminal narrowing of blood vessels. As suggested previously, the described morphological features are most likely physiological responses to blood flow characteristics. Vascular and cardiac lesions were uncommon and included, granulomatous proliferative epicarditis with fibroepitheliomas, myxomatous epicardial expansions, medial arterial vacuolation, myocardial fibrosis, acute ventricular emboli and parasitic granulomas. The lesions of embolism, proliferative and granulomatous epicarditis and myocardial fibrosis were in all sharks associated with capture events including retained fishing hooks. The significance and aetiopathogenesis of medial vacuolation and epicardial myxomatous expansions remains unclear. © 2012 Blackwell Publishing Ltd.

Improving the pharmacokinetic properties of biologics by fusion to an anti-HSA shark VNAR domain.

PubMed

Müller, Mischa R; Saunders, Kenneth; Grace, Christopher; Jin, Macy; Piche-Nicholas, Nicole; Steven, John; O'Dwyer, Ronan; Wu, Leeying; Khetemenee, Lam; Vugmeyster, Yulia; Hickling, Timothy P; Tchistiakova, Lioudmila; Olland, Stephane; Gill, Davinder; Jensen, Allan; Barelle, Caroline J

2012-01-01

Advances in recombinant antibody technology and protein engineering have provided the opportunity to reduce antibodies to their smallest binding domain components and have concomitantly driven the requirement for devising strategies to increase serum half-life to optimise drug exposure, thereby increasing therapeutic efficacy. In this study, we adopted an immunization route to raise picomolar affinity shark immunoglobulin new antigen receptors (IgNARs) to target human serum albumin (HSA). From our model shark species, Squalus acanthias, a phage display library encompassing the variable binding domain of IgNAR (VNAR) was constructed, screened against target, and positive clones were characterized for affinity and specificity. N-terminal and C-terminal molecular fusions of our lead hit in complex with a naïve VNAR domain were expressed, purified and exhibited the retention of high affinity binding to HSA, but also cross-selectivity to mouse, rat and monkey serum albumin both in vitro and in vivo. Furthermore, the naïve VNAR had enhanced pharmacokinetic (PK) characteristics in both N- and C-terminal orientations and when tested as a three domain construct with naïve VNAR flanking the HSA binding domain at both the N and C termini. Molecules derived from this platform technology also demonstrated the potential for clinical utility by being available via the subcutaneous route of delivery. This study thus demonstrates the first in vivo functional efficacy of a VNAR binding domain with the ability to enhance PK properties and support delivery of multifunctional therapies.

Selection of cholera toxin specific IgNAR single-domain antibodies from a naïve shark library.

PubMed

Liu, Jinny L; Anderson, George P; Delehanty, James B; Baumann, Richard; Hayhurst, Andrew; Goldman, Ellen R

2007-03-01

Shark immunoglobulin new antigen receptor (IgNAR, also referred to as NAR) variable domains (Vs) are single-domain antibody (sdAb) fragments containing only two hypervariable loop structures forming 3D topologies for a wide range of antigen recognition and binding. Their small size ( approximately 12kDa) and high solubility, thermostability and binding specificity make IgNARs an exceptional alternative source of engineered antibodies for sensor applications. Here, two new shark NAR V display libraries containing >10(7) unique clones from non-immunized (naïve) adult spiny dogfish (Squalus acanthias) and smooth dogfish (Mustelus canis) sharks were constructed. The most conserved consensus sequences derived from random clone sequence were compared with published nurse shark (Ginglymostoma cirratum) sequences. Cholera toxin (CT) was chosen for panning one of the naïve display libraries due to its severe pathogenicity and commercial availability. Three very similar CT binders were selected and purified soluble monomeric anti-CT sdAbs were characterized using Luminex(100) and traditional ELISA assays. These novel anti-CT sdAbs selected from our newly constructed shark NAR V sdAb library specifically bound to soluble antigen, without cross reacting with other irrelevant antigens. They also showed superior heat stability, exhibiting slow loss of activity over the course of one hour at high temperature (95 degrees C), while conventional antibodies lost all activity in the first 5-10min. The successful isolation of target specific sdAbs from one of our non-biased NAR libraries, demonstrate their ability to provide binders against an unacquainted antigen of interest.

Fibrinogen, Riboflavin, and UVA to Immobilize a Corneal Flap—Conditions for Tissue Adhesion

PubMed Central

Littlechild, Stacy L.; Brummer, Gage; Zhang, Yuntao; Conrad, Gary W.

2012-01-01

Purpose. Laser-assisted in situ keratomileus (LASIK) creates a permanent flap that remains non-attached to the underlying laser-modified stroma. This lack of permanent adhesion is a liability. To immobilize a corneal flap, a protocol using fibrinogen (FIB), riboflavin (RF), and ultraviolet (UVA) light (FIB+RF+UVA) was devised to re-adhere the flap to the stroma. Methods. A model flap was created using rabbit (Oryctolagus cuniculus) and shark (Squalus acanthias) corneas. Solutions containing FIB and RF were applied between corneal strips as glue. Experimental corneas were irradiated with long wavelength (365 nm) UVA. To quantify adhesive strength between corneal strips, the glue-tissue interface was subjected to a constant force while a digital force gauge recorded peak tension. Results. In the presence of FIB, substantive non-covalent interactions occurred between rabbit corneal strips. Adhesiveness was augmented if RF and UVA also were applied, suggesting formation of covalent bonds. Additionally, exposing both sides of rabbit corneas to UVA generated more adhesion than exposure from one side, suggesting that RF in the FIB solution catalyzes formation of covalent bonds at only the interface between stromal molecules and FIB closest to the UVA. In contrast, in the presence of FIB, shark corneal strips interacted non-covalently more substantively than those of rabbits, and adhesion was not augmented by applying RF+UVA, from either or both sides. Residual RF could be rinsed away within 1 hour. Conclusions. Glue solution containing FIB and RF, together with UVA treatment, may aid immobilization of a corneal flap, potentially reducing risk of flap dislodgement. PMID:22589434

Embryonic staging and external features of development of the Chimaeroid fish, Callorhinchus milii (Holocephali, Callorhinchidae).

PubMed

Didier, Dominique A; LeClair, Elizabeth E; Vanbuskirk, Dana R

1998-04-01

The development of Callorhinchus milii, a primitive chondrichthyan fish (Subclass Holocephali) is described in detail based on a complete series of embryos from stage 17 to hatching. The external features of these specimens, in comparison with other chondrichthyan embryos, are used to establish the first staging table for any chimaeroid species. Each stage of C. milii is defined by a suite of morphological characters in addition to total length, including the number of somites, extent of external pigmentation, eye size and shape, head flexure, heart morphology, and size and shape of paired and unpaired fins. Particular attention is given to features of the gill arches and associated structures, including external gill filaments and the opercular flap. Embryos of this species also possess a transient rostral bulb, a feature unique to chimaeroids. Embryological development of Callorhinchus milii is similar to that previously described for sharks and batoids (Subclass Elasmobranchii), including the spiny dogfish, Squalus acanthias, the Japanese bullshark, Heterodontus japonicus, the lesser spotted dogfish, Scyliorhinus canicula, the frill shark, Chlamydoselachus anguineus, the guitarfish, Rhinobatus halavi, and the skate, Raja brachyura. Callorhinchus milii is also similar in overall development to another holocephalan, Hydrolagus colliei. A review of previous staging schemes confirms that early morphological development in all three major chondrichthyan lineages (sharks, batoids, and chimaeras) can be correlated using a common set of stages. A uniform staging system is provided that should prove useful in continuing ontogenetic and phylogenetic studies of this entire clade of fishes. J. Morphol. 236:25-47, 1998. © 1998 Wiley-Liss, Inc. Copyright © 1998 Wiley-Liss, Inc.

3D scanning and printing skeletal tissues for anatomy education.

PubMed

Thomas, Daniel B; Hiscox, Jessica D; Dixon, Blair J; Potgieter, Johan

2016-09-01

Detailed anatomical models can be produced with consumer-level 3D scanning and printing systems. 3D replication techniques are significant advances for anatomical education as they allow practitioners to more easily introduce diverse or numerous specimens into classrooms. Here we present a methodology for producing anatomical models in-house, with the chondrocranium cartilage from a spiny dogfish (Squalus acanthias) and the skeleton of a cane toad (Rhinella marina) as case studies. 3D digital replicas were produced using two consumer-level scanners and specimens were 3D-printed with selective laser sintering. The fidelity of the two case study models was determined with respect to key anatomical features. Larger-scale features of the dogfish chondrocranium and frog skeleton were all well-resolved and distinct in the 3D digital models, and many finer-scale features were also well-resolved, but some more subtle features were absent from the digital models (e.g. endolymphatic foramina in chondrocranium). All characters identified in the digital chondrocranium could be identified in the subsequent 3D print; however, three characters in the 3D-printed frog skeleton could not be clearly delimited (palatines, parasphenoid and pubis). Characters that were absent in the digital models or 3D prints had low-relief in the original scanned specimen and represent a minor loss of fidelity. Our method description and case studies show that minimal equipment and training is needed to produce durable skeletal specimens. These technologies support the tailored production of models for specific classes or research aims. © 2016 Anatomical Society.

Visual optics and ecomorphology of the growing shark eye: a comparison between deep and shallow water species.

PubMed

Litherland, Lenore; Collin, Shaun P; Fritsches, Kerstin A

2009-11-01

Elasmobranch fishes utilise their vision as an important source of sensory information, and a range of visual adaptations have been shown to reflect the ecological diversity of this vertebrate group. This study investigates the hypotheses that visual optics can predict differences in habitat and behaviour and that visual optics change with ontogenetic growth of the eye to maintain optical performance. The study examines eye structure, pupillary movement, transmission properties of the ocular media, focal properties of the lens, tapetum structure and variations in optical performance with ontogenetic growth in two elasmobranch species: the carcharhinid sandbar shark, Carcharhinus plumbeus, inhabiting nearshore coastal waters, and the squalid shortspine spurdog, Squalus mitsukurii, inhabiting deeper waters of the continental shelf and slope. The optical properties appear to be well tuned for the visual needs of each species. Eyes continue to grow throughout life, resulting in an ontogenetic shift in the focal ratio of the eye. The eyes of C. plumbeus are optimised for vision under variable light conditions, which change during development as the animal probes new light environments in its search for food and mates. By contrast, the eyes of S. mitsukurii are specifically adapted to enhance retinal illumination within a dim light environment, and the detection of bioluminescent prey may be optimised with the use of lenticular short-wavelength-absorbing filters. Our findings suggest that the light environment strongly influences optical features in this class of vertebrates and that optical properties of the eye may be useful predictors of habitat and behaviour for lesser-known species of this vertebrate group.

RNA expression in a cartilaginous fish cell line reveals ancient 3′ noncoding regions highly conserved in vertebrates

PubMed Central

Forest, David; Nishikawa, Ryuhei; Kobayashi, Hiroshi; Parton, Angela; Bayne, Christopher J.; Barnes, David W.

2007-01-01

We have established a cartilaginous fish cell line [Squalus acanthias embryo cell line (SAE)], a mesenchymal stem cell line derived from the embryo of an elasmobranch, the spiny dogfish shark S. acanthias. Elasmobranchs (sharks and rays) first appeared >400 million years ago, and existing species provide useful models for comparative vertebrate cell biology, physiology, and genomics. Comparative vertebrate genomics among evolutionarily distant organisms can provide sequence conservation information that facilitates identification of critical coding and noncoding regions. Although these genomic analyses are informative, experimental verification of functions of genomic sequences depends heavily on cell culture approaches. Using ESTs defining mRNAs derived from the SAE cell line, we identified lengthy and highly conserved gene-specific nucleotide sequences in the noncoding 3′ UTRs of eight genes involved in the regulation of cell growth and proliferation. Conserved noncoding 3′ mRNA regions detected by using the shark nucleotide sequences as a starting point were found in a range of other vertebrate orders, including bony fish, birds, amphibians, and mammals. Nucleotide identity of shark and human in these regions was remarkably well conserved. Our results indicate that highly conserved gene sequences dating from the appearance of jawed vertebrates and representing potential cis-regulatory elements can be identified through the use of cartilaginous fish as a baseline. Because the expression of genes in the SAE cell line was prerequisite for their identification, this cartilaginous fish culture system also provides a physiologically valid tool to test functional hypotheses on the role of these ancient conserved sequences in comparative cell biology. PMID:17227856

Escape manoeuvres in the spiny dogfish (Squalus acanthias).

PubMed

Domenici, Paolo; Standen, Emily M; Levine, Robert P

2004-06-01

The locomotor performance of dogfish during escape responses was observed by means of high-speed video. Dogfish show C-type escape responses that are comparable with those shown previously in teleosts. Dogfish show high variability of turning rates of the anterior part of the body (head to centre of mass), i.e. with peak values from 434 to 1023 deg. s(-1). We suggest that this variability may be due to the presence of two types of escape manoeuvres, i.e. responses with high and low turning rates, as previously found in a teleost species. Fast responses (i.e. with high maximum turning rates, ranging between 766 and 1023 deg. s(-1)) showed significantly higher locomotor performance than slow responses (i.e. with low maximum turning rates, ranging between 434 and 593 deg. s(-1)) in terms of distance covered, speed and acceleration, although no differences were found in the turning radius of the centre of mass during the escape manoeuvres. The existence of two types of escape responses would have implications in terms of both neural control and muscular activation patterns. When compared with literature data for the locomotor performance of bony fishes, dogfish showed relatively low speed and acceleration, comparable turning rates and a turning radius that is in the low part of the range when compared with teleosts, indicating relatively high manoeuvrability. The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust developed by their relatively small posterior depth of section and (2) relatively high manoeuvrability associated with their high flexibility.

Arachidonic Acid-Induced Expression of the Organic Solute and Steroid Transporter-beta (Ost-beta) in a Cartilaginous Fish Cell Line

PubMed Central

Hwang, Jae-Ho; Parton, Angela; Czechanski, Anne; Ballatori, Nazzareno; Barnes, David

2008-01-01

The organic solute and steroid transporter (OST/Ost) is a unique membrane transport protein heterodimer composed of subunits designated alpha and beta, that transports conjugated steroids and prostaglandin E2 across the plasma membrane. Ost was first identified in the liver of the cartilaginous fish Leucoraja erinacea, the little skate, and subsequently was found in many other species, including humans and rodents. The present study describes the isolation of a new cell line, LEE-1, derived from an early embryo of L. erinacea, and characterizes the expression of Ost in these cells. The mRNA size and amino acid sequence of Ost-beta in LEE-1 was identical to that previously reported for Ost-beta from skate liver, and the primary structure was identical to that of the spiny dogfish shark (Squalus acanthias) with the exception of a single amino acid. Ost-beta was found both on the plasma membrane and intracellularly in LEE-1 cells, consistent with its localization in other cell types. Interestingly, arachidonic acid, the precursor to eiconsanoids, strongly induced Ost-beta expression in LEE-1 cells and a lipid mixture containing arachidonic acid also induced Ost-alpha. Overall, the present study describes the isolation of a novel marine cell line, and shows that this cell line expresses relatively high levels of Ost when cultured in the presence of arachidonic acid. Although the function of this transport protein in embryo-derived cells is unknown, it may play a role in the disposition of eicosanoids or steroid-derived molecules. PMID:18407792

Control of rectal gland secretion by blood acid-base status in the intact dogfish shark (Squalus acanthias).

PubMed

Wood, Chris M; Munger, R Stephen; Thompson, Jill; Shuttleworth, Trevor J

2007-05-14

In order to address the possible role of blood acid-base status in controlling the rectal gland, dogfish were fitted with indwelling arterial catheters for blood sampling and rectal gland catheters for secretion collection. In intact, unanaesthetized animals, isosmotic volume loading with 500 mmol L-1 NaCl at a rate of 15 mL kg-1 h-1 produced a brisk, stable rectal gland secretion flow of about 4 mL kg-1 h-1. Secretion composition (500 mmol L-1 Na+ and Cl-; 5 mmol L-1 K+; <1 mmol L-1 Ca2+, Mg2+, SO(4)2-, or phosphate) was almost identical to that of the infusate with a pH of about 7.2, HCO3- mmol L-1<1 mmol L-1 and a PCO2 (1 Torr) close to PaCO2. Experimental treatments superimposed on the infusion caused the expected disturbances in systemic acid-base status: respiratory acidosis by exposure to high environmental PCO2, metabolic acidosis by infusion of HCl, and metabolic alkalosis by infusion of NaHCO3. Secretion flow decreased markedly with acidosis and increased with alkalosis, in a linear relationship with extracellular pH. Secretion composition did not change, apart from alterations in its acid-base status, and made negligible contribution to overall acid-base balance. An adaptive control of rectal gland secretion by systemic acid-base status is postulated-stimulation by the "alkaline tide" accompanying the volume load of feeding and inhibition by the metabolic acidosis accompanying the volume contraction of exercise.

Does ammonia trigger hyperventilation in the elasmobranch, Squalus acanthias suckleyi?

PubMed

De Boeck, Gudrun; Wood, Chris M

2015-01-15

We examined the ventilatory response of the spiny dogfish, to elevated internal or environmental ammonia. Sharks were injected via arterial catheters with ammonia solutions or their Na salt equivalents sufficient to increase plasma total ammonia concentration [TAmm]a by 3-5 fold from 145±21μM to 447±150μM using NH4HCO3 and a maximum of 766±100μM using (NH4)2SO4. (NH4)2SO4 caused a small increase in ventilation frequency (+14%) and a large increase in amplitude (+69%), while Na2SO4 did not. However, CO2 partial pressure (PaCO2) also increased and arterial pHa and plasma bicarbonate concentration ([HCO3(-)]a) decreased. NH4HCO3 caused a smaller increase in plasma ammonia resulting in a smaller but significant, short lived increases in ventilation frequency (+6%) and amplitude (36%), together with a rise in PaCO2 and [HCO3(-)]a. Injection with NaHCO3 which increased pHa and [HCO3(-)]a did not change ventilation. Plasma ammonia concentration correlated significantly with ventilation amplitude, while ventilation frequency showed a (negative) correlation with pHa. Exposure to high environmental ammonia (1500μM NH4HCO3) did not induce changes in ventilation until plasma [TAmm]a increased and ventilation amplitude (but not frequency) increased in parallel. We conclude that internal ammonia stimulates ventilation in spiny dogfish, especially amplitude or stroke volume, while environmental ammonia only stimulates ventilation after ammonia diffuses into the bloodstream. Copyright © 2014 Elsevier B.V. All rights reserved.

A perfusion study of the handling of urea and urea analogues by the gills of the dogfish shark (Squalus acanthias)

PubMed Central

Liew, Hon Jung; De Boeck, Gudrun; Walsh, Patrick J.

2013-01-01

The branchial mechanism of urea retention in elasmobranchs was investigated using an in vitro isolated-perfused head preparation, as well as in vivo samples, in the spiny dogfish shark. Both in vivo and in control saline perfusions containing 350 mmol L−1 urea, calculated intracellular urea concentrations in gill epithelial cells were close to extracellular concentrations. Urea efflux to the external water fell only non-significantly, and calculated gill intracellular urea concentration did not change when perfusate urea concentration was reduced from 350 to 175 mmol L−1 with osmotic compensation by 175 mmol L−1 mannitol. However, when the urea analogues thiourea or acetamide were present in the perfusate at concentrations equimolar (175 mmol L−1) to those of urea (175 mmol L−1), urea efflux rates were increased 4-fold and 6.5-fold respectively, and calculated gill intracellular urea concentrations were depressed by about 55%. Analogue efflux rates were similar to urea efflux rates. Previous studies have argued that either the basolateral or apical membranes provided the limiting permeability barrier, and/or that a back-transporter on the basolateral membranes of gill cells is responsible for urea retention. The present results provide new evidence that the apical membrane is the limiting factor in maintaining gill urea impermeability, and raise the prospect that a urea back-transporter, which can be competitively inhibited by thiourea and acetamide, operates at the apical membrane. PMID:23638369

Novel techniques and insights into the deployment of pop-up satellite archival tags on a small-bodied deep-water chondrichthyan

NASA Astrophysics Data System (ADS)

Shipley, Oliver N.; Howey, Lucy A.; Tolentino, Emily R.; Jordan, Lance K. B.; Brooks, Edward J.

2017-01-01

Acquiring movement data for small-bodied, deep-water chondrichthyans is challenged by extreme effects of capture and handling stress, and post-release predation, however, it is urgently required to examine important fisheries interactions and assess the ecological role of these species within deep-water food webs. Here we suggest a novel release-cage mechanism to deploy pop-up satellite archival tags, as well as present vertical habitat data for a data-deficient, small-bodied, deep-water bycatch species, the Cuban dogfish (Squalus cubensis). Data were gathered from seven of eight High Rate X-Tags deployed on mature Cuban dogfish in the Exuma Sound, The Bahamas. Recovery periods appeared variable between individuals and are likely driven by capture-and-handling stress and tag burden. Application of the cross-correlation function to time-series depth and temperature data indicated three of the seven individuals suffered mortality through predation, which occurred during daytime, and suggests Cuban dogfish may constitute a proportion of deep-water apex predator diet in the Exuma Sound. Two animals were successfully released via a novel release-cage mechanism and displayed either no, or rapid (<15 mins) vertically stationary recovery periods and were not consumed by predators; data for these individuals were recorded for the entire deployment duration (14 days). Vertical habitat data suggests Cuban dogfish are diel-vertical migrators, similar to other deep-water taxa, and exhibit a relatively broad temperature and depth range, which may be driven by preference for specific bathymetric structures. These techniques provide an important first step into acquiring and presenting vertical habitat data for small-bodied, deep-water chondrichthyans, which can be directly applied to fisheries and ecosystem-based management approaches.

Delineation and mapping of coastal shark habitat within a shallow lagoonal estuary.

PubMed

Bangley, Charles W; Paramore, Lee; Dedman, Simon; Rulifson, Roger A

2018-01-01

Estuaries function as important nursery and foraging habitats for many coastal species, including highly migratory sharks. Pamlico Sound, North Carolina, is one of the largest estuaries in the continental United States and provides a variety of potential habitats for sharks. In order to identify and spatially delineate shark habitats within Pamlico Sound, shark catch and environmental data were analyzed from the 2007-2014 North Carolina Division of Marine Fisheries (NCDMF) gillnet and longline surveys conducted within the estuary. Principal species were identified and environmental data recorded at survey sites (depth, temperature, salinity, dissolved oxygen, submerged aquatic vegetation (SAV) distance, and inlet distance) were interpolated across Pamlico Sound to create seasonal environmental grids with a 90-m2 cell size. Boosted Regression Tree (BRT) analysis was used to identify the most important environmental factors and ranges associated with presence of each principal species, and the resulting models were used to predict shark capture probability based on the environmental values within the grid cells. The Atlantic Sharpnose Shark (Rhizoprionodon terraenovae), Blacktip Shark (Carcharhinus limbatus), Bull Shark (Carcharhinus leucas), Sandbar Shark (Carcharhinus plumbeus), Smooth Dogfish (Mustelus canis), and Spiny Dogfish (Squalus acanthias) were the principal species in Pamlico Sound. Most species were associated with proximity to the inlet and/or high salinity, and warm temperatures, but the Bull Shark preferred greater inlet distances and the Spiny Dogfish preferred lower temperatures than the other species. Extensive Smooth Dogfish habitat overlap with seagrass beds suggests that seagrass may be a critical part of nursery habitat for this species. Spatial delineation of shark habitat within the estuary will allow for better protection of essential habitat and assessment of potential interactions with other species.

The Economy of Shark Conservation in the Northeast Pacific: The Role of Ecotourism and Citizen Science.

PubMed

Mieras, Peter A; Harvey-Clark, Chris; Bear, Michael; Hodgin, Gina; Hodgin, Boone

Historically sharks have been seen either as a source of income through harvesting, or as a nuisance and danger. The economic value of sharks has traditionally been measured as the total value of sharks caught for liver oil, fins, or meat for consumption. Sharks have also been killed to near extinction in cases where they were seen as a threat to fisheries on other species. This is illustrated by the mass extermination of Basking Sharks (Cetorhinus maximus) in British Columbia. They were seen as a nuisance to fishermen as they got entangled in gill nets during the salmon fishing season. However with the development of the SCUBA diving industry, and ecotourism in general, increased awareness of the role sharks play in marine ecosystems has resulted in changes in how they are perceived and utilized. Despite an ongoing harvest of sharks such as the North Pacific Spiny Dogfish (Squalus suckleyi), sharks now generate economic value through SCUBA diving enthusiasts who travel the globe to see, swim with, and photograph them. The use of digital cameras and other digital media has brought sharks into households around the world and increased awareness of the conservation issues facing many species. This renewed appreciation has led to a better understanding of sharks by the public, resulting in advocates calling for better protections and conservation. In particular, a growing part of the SCUBA diving community wants to contribute to conservation and research projects, which has led to participation in citizen science projects. These projects provide scientific data but also gain ground as ecotourism activities, thus adding to both economic value of tourism and conservation efforts. © 2017 Elsevier Ltd All rights reserved.

Built for speed: strain in the cartilaginous vertebral columns of sharks.

PubMed

Porter, M E; Diaz, Candido; Sturm, Joshua J; Grotmol, Sindre; Summers, A P; Long, John H

2014-02-01

In most bony fishes vertebral column strain during locomotion is almost exclusively in the intervertebral joints, and when these joints move there is the potential to store and release strain energy. Since cartilaginous fishes have poorly mineralized vertebral centra, we tested whether the vertebral bodies undergo substantial strain and thus may be sites of energy storage during locomotion. We measured axial strains of the intervertebral joints and vertebrae in vivo and ex vivo to characterize the dynamic behavior of the vertebral column. We used sonomicrometry to directly measure in vivo and in situ strains of intervertebral joints and vertebrae of Squalus acanthias swimming in a flume. For ex vivo measurements, we used a materials testing system to dynamically bend segments of vertebral column at frequencies ranging from 0.25 to 1.00 Hz and a range of physiologically relevant curvatures, which were determined using a kinematic analysis. The vertebral centra of S. acanthias undergo strain during in vivo volitional movements as well as in situ passive movements. Moreover, when isolated segments of vertebral column were tested during mechanical bending, we measured the same magnitudes of strain. These data support our hypothesis that vertebral column strain in lateral bending is not limited to the intervertebral joints. In histological sections, we found that the vertebral column of S. acanthias has an intracentral canal that is open and covered with a velum layer. An open intracentral canal may indicate that the centra are acting as tunics around some sections of a hydrostat, effectively stiffening the vertebral column. These data suggest that the entire vertebral column of sharks, both joints and centra, is mechanically engaged as a dynamic spring during locomotion. Copyright © 2013 Elsevier GmbH. All rights reserved.

A trans-ecosystem fishery: Environmental effects on the small-scale gillnet fishery along the Río de la Plata boundary

NASA Astrophysics Data System (ADS)

Jaureguizar, Andrés Javier; Cortés, Federico; Milessi, Andrés Conrado; Cozzolino, Ezequiel; Allega, Lucrecia

2015-12-01

To improve the understanding of the environmental processes affecting small-scale gillnet fisheries along neighboring waters of estuaries, we analyzed the main climatic forcing and the environmental conditions, the fishery landing spatial and temporal variation, including the relative importance of site, distance to coast, temperature and salinity in the structuring of landed species profile. Data were collected monthly in two sites along the adjacent south coast of the Río de la Plata between October 2009 and September 2010. The gillnet fishery was dominated by four species (Cynoscion guatucupa, Micropogonias furnieri, Mustelus schmitti and Parona signata) from a total of 38 species landed, which accounted for 98.6% of total landings. The fishing effort and landings by the fishery were largely conditioned by the availability of fish species in the fishing grounds resulting from the combination of the species reproductive behavior and the predominant environmental conditions. The highest abundances for some species occurred before (M. furnieri, C. guatucupa, P. signata) or during the reproductive period (M. schmitti, Squatina guggenheim), while in other species it was associated with favorable environmental conditions during cold months (Squalus acanthias, Callorhinchus callorhynchus, Galeorhinus galeus) or warm months (Trichiurus lepturus). The predominant seasonal environmental conditions along the coast were mainly determined by the location of Río de la Plata boundary, whose spatial extent was forced by the wind patterns and freshwater discharge. The strong environmental dependence means that the small-scale fishery is in fact a seasonal trans-ecosystem fishery. This attribute, together that shared the resources with the industrial fishery and the overlap of the fishery ground with essential habitat of sharks, make this kind of small-scale gillnet fishery particularly relevant to be included in the development of a coastal ecosystem-based management approach.

β-Adrenergic regulation of a novel isoform of NCX: sequence and expression of shark heart NCX in human kidney cells

PubMed Central

Janowski, Einsley; Day, Regina; Kraev, Alexander; Roder, John C.; Cleemann, Lars; Morad, Martin

2009-01-01

The function, regulation, and molecular structure of the cardiac Na+/Ca2+ exchangers (NCXs) vary significantly among vertebrates. We previously reported that β-adrenergic suppression of amphibian cardiac NCX1.1 is associated with specific molecular motifs. Here we investigated the bimodal, cAMP-dependent regulation of spiny dogfish shark (Squalus acanthias) cardiac NCX, exploring the effects of molecular structure, host cell environment, and ionic milieu. The shark cardiac NCX sequence (GenBank accession no. DQ 068478) revealed two novel proline/alanine-rich amino acid insertions. Wild-type and mutant shark NCXs were cloned and expressed in mammalian cells (HEK-293 and FlpIn-293), where their activities were measured as Ni2+-sensitive Ca2+ fluxes (fluo 4) and membrane (Na+/Ca2+ exchange) currents evoked by changes in extracellular Na+ concentration and/or membrane potential. Regardless of Ca2+ buffering, β-adrenergic stimulation of cloned wild-type shark NCX consistently produced bimodal regulation (defined as differential regulation of Ca2+-efflux and -influx pathways), with suppression of the Ca2+-influx mode and either no change or enhancement of the Ca2+-efflux mode, closely resembling results from parallel experiments with native shark cardiomyocytes. In contrast, mutant shark NCX, with deletion of the novel region 2 insertion, produced equal suppression of the inward and outward currents and Ca2+ fluxes, thereby abolishing the bimodal nature of the regulation. Control experiments with nontransfected and dog cardiac NCX-expressing cells showed no cAMP regulation. We conclude that bimodal β-adrenergic regulation is retained in cloned shark NCX and is dependent on the shark's unique molecular motifs. PMID:19395557

Alkaline tide and nitrogen conservation after feeding in an elasmobranch (Squalus acanthias).

PubMed

Wood, Chris M; Kajimura, Makiko; Mommsen, Thomas P; Walsh, Patrick J

2005-07-01

We investigated the consequences of feeding for acid-base balance, nitrogen excretion, blood metabolites and osmoregulation in the Pacific spiny dogfish. Sharks that had been starved for 7 days were surgically fitted with indwelling stomach tubes for gastric feeding and blood catheters for repetitive blood sampling and were confined in chambers, allowing measurement of ammonia-N and urea-N fluxes. The experimental meal infused via the stomach tube consisted of flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Control animals received only saline (4% of body mass). Feeding resulted in a marked rise in both arterial and venous pH and HCO3- concentrations at 3-9 h after the meal, with attenuation by 17 h. Venous P(O2) also fell. As there were negligible changes in P(CO2), the response was interpreted as an alkaline tide without respiratory compensation, associated with elevated gastric acid secretion. Urea-N excretion, which comprised >90% of the total, was unaffected, while ammonia-N excretion was very slightly elevated, amounting to <3% of the total-N in the meal over 45 h. Plasma ammonia-N rose slightly. Plasma urea-N, TMAO-N and glucose concentrations remained unchanged, while free amino acid and beta-hydroxybutyrate levels exhibited modest declines. Plasma osmolality was persistently elevated after the meal relative to controls, partially explained by a significant rise in plasma Cl-. This marked post-prandial conservation of nitrogen is interpreted as reflecting the needs for urea synthesis for osmoregulation and protein growth in animals that are severely N-limited due to their sporadic and opportunistic feeding lifestyle in nature.

Mercury toxicity in the shark (Squalus acanthias) rectal gland: apical CFTR chloride channels are inhibited by mercuric chloride.

PubMed

Ratner, Martha A; Decker, Sarah E; Aller, Stephen G; Weber, Gerhard; Forrest, John N

2006-03-01

In the shark rectal gland, basolateral membrane proteins have been suggested as targets for mercury. To examine the membrane polarity of mercury toxicity, we performed experiments in three preparations: isolated perfused rectal glands, primary monolayer cultures of rectal gland epithelial cells, and Xenopus oocytes expressing the shark cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. In perfused rectal glands we observed: (1) a dose-dependent inhibition by mercury of forskolin/3-isobutyl-1-methylxanthine (IBMX)-stimulated chloride secretion; (2) inhibition was maximal when mercury was added before stimulation with forskolin/IBMX; (3) dithiothrietol (DTT) and glutathione (GSH) completely prevented inhibition of chloride secretion. Short-circuit current (Isc) measurements in monolayers of rectal gland epithelial cells were performed to examine the membrane polarity of this effect. Mercuric chloride inhibited Isc more potently when applied to the solution bathing the apical vs. the basolateral membrane (23 +/- 5% and 68 +/- 5% inhibition at 1 and 10 microM HgCl2 in the apical solution vs. 2 +/- 0.9% and 14 +/- 5% in the basolateral solution). This inhibition was prevented by pre-treatment with apical DTT or GSH; however, only the permeant reducing agent DTT reversed mercury inhibition when added after exposure. When the shark rectal gland CFTR channel was expressed in Xenopus oocytes and chloride conductance was measured by two-electrode voltage clamping, we found that 1 microM HgCl2 inhibited forskolin/IBMX conductance by 69.2 +/- 2.0%. We conclude that in the shark rectal gland, mercury inhibits chloride secretion by interacting with the apical membrane and that CFTR is the likely site of this action. Copyright 2006 Wiley-Liss, Inc.

Relationship between oxidizable fatty acid content and level of antioxidant glutathione peroxidases in marine fish

PubMed Central

Grim, Jeffrey M.; Hyndman, Kelly A.; Kriska, Tamas; Girotti, Albert W.; Crockett, Elizabeth L.

2011-01-01

SUMMARY Biological membranes can be protected from lipid peroxidation by antioxidant enzymes including catalase (CAT) and selenium-dependent glutathione peroxidases 1 and 4 (GPx1 and GPx4). Unlike GPx1, GPx4 can directly detoxify lipid hydroperoxides in membranes without prior action of phospholipase A2. We hypothesized that (1) GPx4 is enhanced in species that contain elevated levels of highly oxidizable polyunsaturated fatty acids (PUFA) and (2) activities of antioxidant enzymes are prioritized to meet species-specific oxidative stresses. In this study we examined (i) activities of the oxidative enzyme citrate synthase (CS) and antioxidant (CAT, GPx1 and GPx4) enzymes, (ii) GPx4 protein expression, and (iii) phospholipid composition in livers of five species of marine fish (Myxine glutinosa, Petromyzon marinus, Squalus acanthias, Fundulus heteroclitus and Myoxocephalus octodecemspinosus) that contain a range of PUFA. GPx4 activity was, on average, 5.8 times higher in F. heteroclitus and S. acanthias than in the other three marine fish species sampled. Similarly, activities of CAT and GPx1 were highest in S. acanthias and F. heteroclitus, respectively. GPx4 activity for all species correlates with membrane unsaturation, as well as oxidative activity as indicated by CS. These data support our hypothesis that GPx4 level in marine fish is a function, at least in part, of high PUFA content in these animals. GPx1 activity was also correlated with membrane unsaturation, indicating that marine species partition resources among glutathione-dependent defenses for protection from the initial oxidative insult (e.g. H2O2) and to repair damaged lipids within biological membranes. PMID:22031739

An evolutionary view on tooth development and replacement in wild Atlantic salmon (Salmo salar L.).

PubMed

Huysseune, A; Witten, P E

2008-01-01

To gain an insight into the evolution of tooth replacement mechanisms, we studied the development of first-generation and replacement teeth on the dentary of wild Atlantic salmon (Salmo salar L.), a protacanthopterygian teleost, using serially sectioned heads of early posthatching stages as well as adults. First-generation teeth develop within the oral epithelium. The anlage of the replacement tooth is first seen as a placode-like thickening of the outer dental epithelium of the predecessor, at its lingual and caudal side. Ongoing development of the replacement tooth germ is characterized by the elaboration of a population of epithelial cells, termed here the middle dental epithelium, apposed to the inner dental epithelium on the lingual side of the tooth germ. Before the formation of the new successor, a single-layered outer dental epithelium segregates from the middle dental epithelium. The dental organs of the predecessor and the successor remain broadly interconnected. The absence of a discrete successional dental lamina in salmon stands in sharp contrast to what is observed in other teleosts, even those that share with salmon the extraosseous formation of replacement teeth. The mode of tooth replacement in Atlantic salmon displays several characters similar to those observed in the shark Squalus acanthias. To interpret similarities in tooth replacement between Atlantic salmon and chondrichthyans as a case of convergence, or to see them as a result of a heterochronic shift, requires knowledge on the replacement process in more basal actinopterygian lineages. The possibility that the middle dental epithelium functionally substitutes for a successional lamina, and could be a source of stem cells, whose descendants subsequently contribute to the placode of the new replacement tooth, needs to be explored.

Delineation and mapping of coastal shark habitat within a shallow lagoonal estuary

PubMed Central

Paramore, Lee; Dedman, Simon; Rulifson, Roger A.

2018-01-01

Estuaries function as important nursery and foraging habitats for many coastal species, including highly migratory sharks. Pamlico Sound, North Carolina, is one of the largest estuaries in the continental United States and provides a variety of potential habitats for sharks. In order to identify and spatially delineate shark habitats within Pamlico Sound, shark catch and environmental data were analyzed from the 2007–2014 North Carolina Division of Marine Fisheries (NCDMF) gillnet and longline surveys conducted within the estuary. Principal species were identified and environmental data recorded at survey sites (depth, temperature, salinity, dissolved oxygen, submerged aquatic vegetation (SAV) distance, and inlet distance) were interpolated across Pamlico Sound to create seasonal environmental grids with a 90-m2 cell size. Boosted Regression Tree (BRT) analysis was used to identify the most important environmental factors and ranges associated with presence of each principal species, and the resulting models were used to predict shark capture probability based on the environmental values within the grid cells. The Atlantic Sharpnose Shark (Rhizoprionodon terraenovae), Blacktip Shark (Carcharhinus limbatus), Bull Shark (Carcharhinus leucas), Sandbar Shark (Carcharhinus plumbeus), Smooth Dogfish (Mustelus canis), and Spiny Dogfish (Squalus acanthias) were the principal species in Pamlico Sound. Most species were associated with proximity to the inlet and/or high salinity, and warm temperatures, but the Bull Shark preferred greater inlet distances and the Spiny Dogfish preferred lower temperatures than the other species. Extensive Smooth Dogfish habitat overlap with seagrass beds suggests that seagrass may be a critical part of nursery habitat for this species. Spatial delineation of shark habitat within the estuary will allow for better protection of essential habitat and assessment of potential interactions with other species. PMID:29649261

Trophic interactions of common elasmobranchs in deep-sea communities of the Gulf of Mexico revealed through stable isotope and stomach content analysis

NASA Astrophysics Data System (ADS)

Churchill, Diana A.; Heithaus, Michael R.; Vaudo, Jeremy J.; Grubbs, R. Dean; Gastrich, Kirk; Castro, José I.

2015-05-01

Deep-water sharks are abundant and widely distributed in the northern and eastern Gulf of Mexico. As mid- and upper-level consumers that can range widely, sharks likely are important components of deep-sea communities and their trophic interactions may serve as system-wide baselines that could be used to monitor the overall health of these communities. We investigated the trophic interactions of deep-sea sharks using a combination of stable isotope (δ13C and δ15N) and stomach content analyses. Two hundred thirty-two muscle samples were collected from elasmobranchs captured off the bottom at depths between 200 and 1100 m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Although we detected some spatial, temporal, and interspecific variation in apparent trophic positions based on stable isotopes, there was considerable isotopic overlap among species, between locations, and through time. Overall δ15N values in the NGS region were higher than in the WFS. The δ15N values also increased between April 2011 and 2012 in the NGS, but not the WFS, within Squalus cf. mitsukurii. We found that stable isotope values of S. cf. mitsukurii, the most commonly captured elasmobranch, varied between sample regions, through time, and also with sex and size. Stomach content analysis (n=105) suggested relatively similar diets at the level of broad taxonomic categories of prey among the taxa with sufficient sample sizes. We did not detect a relationship between body size and relative trophic levels inferred from δ15N, but patterns within several species suggest increasing trophic levels with increasing size. Both δ13C and δ15N values suggest a substantial degree of overlap among most deep-water shark species. This study provides the first characterization of the trophic interactions of deep-sea sharks in the Gulf of Mexico and establishes system baselines for future investigations.

cGMP inhibition of type 3 phosphodiesterase is the major mechanism by which C-type natriuretic peptide activates CFTR in the shark rectal gland

PubMed Central

De Jonge, Hugo R.; Tilly, Ben C.; Hogema, Boris M.; Pfau, Daniel J.; Kelley, Catherine A.; Kelley, Megan H.; Melita, August M.; Morris, Montana T.; Viola, Ryan M.

2013-01-01

The in vitro perfused rectal gland of the dogfish shark (Squalus acanthias) and filter-grown monolayers of primary cultures of shark rectal gland (SRG) epithelial cells were used to analyze the signal transduction pathway by which C-type natriuretic peptide (CNP) stimulates chloride secretion. CNP binds to natriuretic receptors in the basolateral membrane, elevates cellular cGMP, and opens cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels in the apical membrane. CNP-provoked chloride secretion was completely inhibitable by the nonspecific protein kinase inhibitor staurosporine and the PKA inhibitor H89 but insensitive to H8, an inhibitor of type I and II isoforms of cGMP-dependent protein kinase (cGKI and cGKII). CNP-induced secretion could not be mimicked by nonhydrolyzable cGMP analogs added alone or in combination with the protein kinase C activator phorbolester, arguing against a role for cGK or for cGMP-induced PKC signaling. We failed to detect a dogfish ortholog of cGKII by molecular cloning and affinity chromatography. However, inhibitors of the cGMP-inhibitable isoform of phosphodiesterase (PDE3) including milrinone, amrinone, and cilostamide but not inhibitors of other PDE isoenzymes mimicked the effect of CNP on chloride secretion in perfused glands and monolayers. CNP raised cGMP and cAMP levels in the SRG epithelial cells. This rise in cAMP as well as the CNP and amrinone-provoked chloride secretion, but not the rise in cGMP, was almost completely blocked by the Gαi-coupled adenylyl cyclase inhibitor somatostatin, arguing against a role for cGMP cross-activation of PKA in CNP action. These data provide molecular, functional, and pharmacological evidence for a CNP/cGMP/PDE3/cAMP/PKA signaling cascade coupled to CFTR in the SRG. PMID:24259420

Nitrogen metabolism, acid-base regulation, and molecular responses to ammonia and acid infusions in the spiny dogfish shark (Squalus acanthias).

PubMed

Nawata, C Michele; Walsh, Patrick J; Wood, Chris M

2015-07-01

Although they are ureotelic, marine elasmobranchs express Rh glycoproteins, putative ammonia channels. To address questions raised by a recent study on high environmental ammonia (HEA) exposure, dogfish were intravascularly infused for 24 h at 3 ml kg(-1) h(-1) with isosmotic NaCl (500 mmol l(-1), control), NH4HCO3 (500 mmol l(-1)), NH4Cl (500 mmol l(-1)), or HCl (as 125 mmol l(-1) HCl + 375 mmol l(-1) NaCl). While NaCl had no effect on arterial acid-base status, NH4HCO3 caused mild alkalosis, NH4Cl caused strong acidosis, and HCl caused lesser acidosis, all predominantly metabolic in nature. Total plasma ammonia (T(Amm)) and excretion rates of ammonia (J(Amm)) and urea-N (J(Urea-N)) were unaffected by NaCl or HCl. However, despite equal loading rates, plasma T(Amm) increased to a greater extent with NH4Cl, while J(Amm) increased to a greater extent with NH4HCO3 due to much greater increases in blood-to-water PNH3 gradients. As with HEA, both treatments caused large (90%) elevations of J(Urea-N), indicating that urea-N synthesis by the ornithine-urea cycle (OUC) is driven primarily by ammonia rather than HCO3(-). Branchial mRNA expressions of Rhbg and Rhp2 were unaffected by NH4HCO3 or NH4Cl, but v-type H(+)-ATPase was down-regulated by both treatments, and Rhbg and Na(+)/H(+) exchanger NHE2 were up-regulated by HCl. In the kidney, Rhbg was unresponsive to all treatments, but Rhp2 was up-regulated by HCl, and the urea transporter UT was up-regulated by HCl and NH4Cl. These responses are discussed in the context of current ideas about branchial, renal, and OUC function in this nitrogen-limited predator.

Phylogenetic Analysis of the MS4A and TMEM176 Gene Families

PubMed Central

Zuccolo, Jonathan; Bau, Jeremy; Childs, Sarah J.; Goss, Greg G.; Sensen, Christoph W.; Deans, Julie P.

2010-01-01

Background The MS4A gene family in humans includes CD20 (MS4A1), FcRβ (MS4A2), Htm4 (MS4A3), and at least 13 other syntenic genes encoding membrane proteins, most having characteristic tetraspanning topology. Expression of MS4A genes is variable in tissues throughout the body; however, several are limited to cells in the hematopoietic system where they have known roles in immune cell functions. Genes in the small TMEM176 group share significant sequence similarity with MS4A genes and there is evidence of immune function of at least one of the encoded proteins. In this study, we examined the evolutionary history of the MS4A/TMEM176 families as well as tissue expression of the phylogenetically earliest members, in order to investigate their possible origins in immune cells. Principal Findings Orthologs of human MS4A genes were found only in mammals; however, MS4A gene homologs were found in most jawed vertebrates. TMEM176 genes were found only in mammals and bony fish. Several unusual MS4A genes having 2 or more tandem MS4A sequences were identified in the chicken (Gallus gallus) and early mammals (opossum, Monodelphis domestica and platypus, Ornithorhyncus anatinus). A large number of highly conserved MS4A and TMEM176 genes was found in zebrafish (Danio rerio). The most primitive organism identified to have MS4A genes was spiny dogfish (Squalus acanthus). Tissue expression of MS4A genes in S. acanthias and D. rerio showed no evidence of expression restricted to the hematopoietic system. Conclusions/Significance Our findings suggest that MS4A genes first appeared in cartilaginous fish with expression outside of the immune system, and have since diversified in many species into their modern forms with expression and function in both immune and nonimmune cells. PMID:20186339

Aquaporin 4 is a Ubiquitously Expressed Isoform in the Dogfish (Squalus acanthias) Shark.

PubMed

Cutler, Christopher P; Maciver, Bryce; Cramb, Gordon; Zeidel, Mark

2011-01-01

The dogfish ortholog of aquaporin 4 (AQP4) was amplified from cDNA using degenerate PCR followed by cloning and sequencing. The complete coding region was then obtained using 5' and 3' RACE techniques. Alignment of the sequence with AQP4 amino acid sequences from other species showed that dogfish AQP4 has high levels (up to 65.3%) of homology with higher vertebrate sequences but lower levels of homology to Agnathan (38.2%) or teleost (57.5%) fish sequences. Northern blotting indicated that the dogfish mRNA was approximately 3.2 kb and was highly expressed in the rectal gland (a shark fluid secretory organ). Semi-quantitative PCR further indicates that AQP4 is ubiquitous, being expressed in all tissues measured but at low levels in certain tissues, where the level in liver > gill >  intestine. Manipulation of the external environmental salinity of groups of dogfish showed that when fish were acclimated in stages to 120% seawater (SW) or 75% SW, there was no change in AQP4 mRNA expression in either rectal gland, kidney, or esophagus/cardiac stomach. Whereas quantitative PCR experiments using the RNA samples from the same experiment, showed a significant 63.1% lower abundance of gill AQP4 mRNA expression in 120% SW-acclimated dogfish. The function of dogfish AQP4 was also determined by measuring the effect of the AQP4 expression in Xenopus laevis oocytes. Dogfish AQP4 expressing-oocytes, exhibited significantly increased osmotic water permeability (P(f)) compared to controls, and this was invariant with pH. Permeability was not significantly reduced by treatment of oocytes with mercury chloride, as is also the case with AQP4 in other species. Similarly AQP4 expressing-oocytes did not exhibit enhanced urea or glycerol permeability, which is also consistent with the water-selective property of AQP4 in other species.

Aquaporin 4 is a Ubiquitously Expressed Isoform in the Dogfish (Squalus acanthias) Shark

PubMed Central

Cutler, Christopher P; MacIver, Bryce; Cramb, Gordon; Zeidel, Mark

2012-01-01

The dogfish ortholog of aquaporin 4 (AQP4) was amplified from cDNA using degenerate PCR followed by cloning and sequencing. The complete coding region was then obtained using 5′ and 3′ RACE techniques. Alignment of the sequence with AQP4 amino acid sequences from other species showed that dogfish AQP4 has high levels (up to 65.3%) of homology with higher vertebrate sequences but lower levels of homology to Agnathan (38.2%) or teleost (57.5%) fish sequences. Northern blotting indicated that the dogfish mRNA was approximately 3.2 kb and was highly expressed in the rectal gland (a shark fluid secretory organ). Semi-quantitative PCR further indicates that AQP4 is ubiquitous, being expressed in all tissues measured but at low levels in certain tissues, where the level in liver > gill >  intestine. Manipulation of the external environmental salinity of groups of dogfish showed that when fish were acclimated in stages to 120% seawater (SW) or 75% SW, there was no change in AQP4 mRNA expression in either rectal gland, kidney, or esophagus/cardiac stomach. Whereas quantitative PCR experiments using the RNA samples from the same experiment, showed a significant 63.1% lower abundance of gill AQP4 mRNA expression in 120% SW-acclimated dogfish. The function of dogfish AQP4 was also determined by measuring the effect of the AQP4 expression in Xenopus laevis oocytes. Dogfish AQP4 expressing-oocytes, exhibited significantly increased osmotic water permeability (Pf) compared to controls, and this was invariant with pH. Permeability was not significantly reduced by treatment of oocytes with mercury chloride, as is also the case with AQP4 in other species. Similarly AQP4 expressing-oocytes did not exhibit enhanced urea or glycerol permeability, which is also consistent with the water-selective property of AQP4 in other species. PMID:22291652

A comparative study of the ocular skeleton of fossil and modern chondrichthyans

PubMed Central

Pilgrim, Brettney L; Franz-Odendaal, Tamara A

2009-01-01

Many vertebrates have an ocular skeleton composed of cartilage and/or bone situated within the sclera of the eye. In this study we investigated whether modern and fossil sharks have an ocular skeleton, and whether it is conserved in morphology. We describe the scleral skeletal elements of three species of modern sharks and compare them to those found in fossil sharks from the Cleveland Shale (360 Mya). We also compare the elements to contemporaneous arthrodires from the same deposit. Surprisingly, the morphology of the skeletal support of the eye was found to differ significantly between modern and fossil sharks. All three modern shark species examined (spiny dogfish shark Squalus acanthias, porbeagle shark Lamna nasus and blue shark Prionace glauca) have a continuous skeletal element that encapsulates much of the eyeball; however, the tissue composition is different in each species. Histological and morphological examination revealed scleral cartilage with distinct tesserae in parts of the sclera of the porbeagle and blue shark, and more diffuse calcification in the dogfish. Strengthening of the scleral cartilage by means of tesserae has not been reported previously in the shark eye. In striking contrast, the ocular skeleton of fossil sharks comprises a series of individual elements that are arranged in a ring, similar to the arrangement in modern and fossil reptiles. Fossil arthrodires also have a multi-unit sclerotic ring but these are composed of fewer elements than in fossil sharks. The morphology of these elements has implications for the behaviour and visual capabilities of sharks that lived during the Devonian Period. This is the first time that such a dramatic variation in the morphology of scleral skeletal elements has been observed in a single lineage (Chondrichthyes), making this lineage important for broadening our understanding of the evolution of these elements within jawed vertebrates. PMID:19538630

Exercise and recovery metabolism in the Pacific spiny dogfish (Squalus acanthias).

PubMed

Richards, J G; Heigenhauser, G J F; Wood, C M

2003-08-01

We examined the effects of exhaustive exercise and post-exercise recovery on white muscle substrate depletion and metabolite distribution between white muscle and blood plasma in the Pacific spiny dogfish, both in vivo and in an electrically stimulated perfused tail-trunk preparation. Measurements of arterial-venous lactate, total ammonia, beta-hydroxybutyrate, glucose, and L-alanine concentrations in the perfused tail-trunk assessed white muscle metabolite fluxes. Exhaustive exercise was fuelled primarily by creatine phosphate hydrolysis and glycolysis as indicated by 62, 71, and 85% decreases in ATP, creatine phosphate, and glycogen, respectively. White muscle lactate production during exercise caused a sustained increase (approximately 12 h post-exercise) in plasma lactate load and a short-lived increase (approximately 4 h post-exercise) in plasma metabolic acid load during recovery. Exhaustive exercise and recovery did not affect arterial PO2, PCO2, or PNH3 but the metabolic acidosis caused a decrease in arterial HCO3- immediately after exercise and during the first 8 h recovery. During recovery, lactate was retained in the white muscle at higher concentrations than in the plasma despite increased lactate efflux from the muscle. Pyruvate dehydrogenase activity was very low in dogfish white muscle at rest and during recovery (0.53 +/- 0.15 nmol g wet tissue(-1) min(-1); n=40) indicating that lactate oxidation is not the major fate of lactate during post-exercise recovery. The lack of change in white muscle free-carnitine and variable changes in short-chain fatty acyl-carnitine suggest that dogfish white muscle does not rely on lipid oxidation to fuel exhaustive exercise or recovery. These findings support the notion that extrahepatic tissues cannot utilize fatty acids as an oxidative fuel. Furthermore, our data strongly suggest that ketone body oxidation is important in fuelling recovery metabolism in dogfish white muscle and at least 20% of the ATP required for recovery could be supplied by uptake and oxidation of beta-hydroxybutyrate from the plasma.

Mercury bioaccumulation in cartilaginous fishes from Southern New England coastal waters: Contamination from a trophic ecology and human health perspective

PubMed Central

Taylor, David L.; Kutil, Nicholas J.; Malek, Anna J.; Collie, Jeremy S.

2014-01-01

This study examined total mercury (Hg) concentrations in cartilaginous fishes from Southern New England coastal waters, including smooth dogfish (Mustelus canis), spiny dogfish (Squalus acanthias), little skate (Leucoraja erinacea), and winter skate (L. ocellata). Total Hg in dogfish and skates were positively related to their respective body size and age, indicating Hg bioaccumulation in muscle tissue. There were also significant inter-species differences in Hg levels (mean ± 1 SD, mg Hg/kg dry weight, ppm): smooth dogfish (3.3 ± 2.1 ppm; n = 54) > spiny dogfish (1.1 ± 0.7 ppm; n = 124) > little skate (0.4 ± 0.3 ppm; n = 173) ~ winter skate (0.3 ± 0.2 ppm; n = 148). The increased Hg content of smooth dogfish was attributed to its upper trophic level status, determined by stable nitrogen (δ15N) isotope analysis (mean δ15N = 13.2 ± 0.7‰), and the consumption of high Hg prey, most notably cancer crabs (0.10 ppm). Spiny dogfish had depleted δ15N signatures (11.6 ± 0.8‰), yet demonstrated a moderate level of contamination by foraging on pelagic prey with a range of Hg concentrations, e.g., in order of dietary importance, butterfish (Hg = 0.06 ppm), longfin squid (0.17 ppm), and scup (0.11 ppm). Skates were low trophic level consumers (δ15N = 11.9-12.0‰) and fed mainly on amphipods, small decapods, and polychaetes with low Hg concentrations (0.05-0.09 ppm). Intra-specific Hg concentrations were directly related to δ15N and carbon (δ13C) isotope signatures, suggesting that Hg biomagnifies across successive trophic levels and foraging in the benthic trophic pathway increases Hg exposure. From a human health perspective, 87% of smooth dogfish, 32% of spiny dogfish, and < 2% of skates had Hg concentrations exceeding the US Environmental Protection Agency threshold level (0.3 ppm wet weight). These results indicate that frequent consumption of smooth dogfish and spiny dogfish may adversely affect human health, whereas skates present minimal risk. PMID:25081850

Hydrodynamic function of dorsal fins in spiny dogfish and bamboo sharks during steady swimming.

PubMed

Maia, Anabela; Lauder, George V; Wilga, Cheryl D

2017-11-01

A key feature of fish functional design is the presence of multiple fins that allow thrust vectoring and redirection of fluid momentum to contribute to both steady swimming and maneuvering. A number of previous studies have analyzed the function of dorsal fins in teleost fishes in this context, but the hydrodynamic function of dorsal fins in freely swimming sharks has not been analyzed, despite the potential for differential functional roles between the anterior and posterior dorsal fins. Previous anatomical research has suggested a primarily stabilizing role for shark dorsal fins. We evaluated the generality of this hypothesis by using time-resolved particle image velocimetry to record water flow patterns in the wake of both the anterior and posterior dorsal fins in two species of freely swimming sharks: bamboo sharks ( Chiloscyllium plagiosum ) and spiny dogfish ( Squalus acanthias ). Cross-correlation analysis of consecutive images was used to calculate stroke-averaged mean longitudinal and lateral velocity components, and vorticity. In spiny dogfish, we observed a velocity deficit in the wake of the first dorsal fin and flow acceleration behind the second dorsal fin, indicating that the first dorsal fin experiences net drag while the second dorsal fin can aid in propulsion. In contrast, the wake of both dorsal fins in bamboo sharks displayed increased net flow velocity in the majority of trials, reflecting a thrust contribution to steady swimming. In bamboo sharks, fluid flow in the wake of the second dorsal fin had higher absolute average velocity than that for first dorsal fin, and this may result from a positive vortex interaction between the first and second dorsal fins. These data suggest that the first dorsal fin in spiny dogfish has primarily a stabilizing function, while the second dorsal fin has a propulsive function. In bamboo sharks, both dorsal fins can contribute thrust and should be considered as propulsive adjuncts to the body during steady swimming. The function of shark dorsal fins can thus differ considerably among fins and species, and is not limited to a stabilizing role. © 2017. Published by The Company of Biologists Ltd.

Cyclooxygenase cloning in dogfish shark, Squalus acanthias, and its role in rectal gland Cl secretion.

PubMed

Yang, T; Forrest, S J; Stine, N; Endo, Y; Pasumarthy, A; Castrop, H; Aller, S; Forrest, J N; Schnermann, J; Briggs, J

2002-09-01

The present studies were carried out with the aims to determine the cDNA sequence for cyclooxygenase (COX) in an elasmobranch species and to study its role in regulation of chloride secretion in the perfused shark rectal gland (SRG). With the use of long primers (43 bp) derived from regions of homology between zebrafish and rainbow trout COX-2 genes, a 600-bp product was amplified from SRG and was found to be almost equally homologous to mammalian COX-1 and COX-2 (65%). The full-length cDNA sequence was obtained by 5'-RACE and by analyzing an EST clone generated by the EST Project of the Mt. Desert Island Biological Laboratory Marine DNA Sequencing Center. The longest open reading frame encodes a 593-amino acid protein that has 68 and 64% homology to mammalian COX-1 and COX-2, respectively. The gene and its protein product is designated as shark COX (sCOX). The key residues in the active site (Try(385), His(388), and Ser(530)) are conserved between the shark and mammalian COX. sCOX contains Val(523) that has been shown to be a key residue determining the sensitivity to COX-2-specific inhibitors including NS-398. The mRNA of sCOX, detected by RT-PCR, was found in all tissues tested, including rectal gland, kidney, spleen, gill, liver, brain, and heart, but not in fin. In the perfused SRG, vasoactive intestinal peptide (VIP) at 5 nM induced rapid and marked Cl(-) secretion (basal: <250 microeq x h(-1) x g(-1); peak response: 3,108 +/- 479 microeq x h(-1) x g(-1)). In the presence of 50 microM NS-398, both the peak response (2,131 +/- 307 microeq x h(-1) x g(-1)) and the sustained response to VIP were significantly reduced. When NS-398 was removed, there was a prompt recovery of chloride secretion to control values. In conclusion, we have cloned the first COX in an elasmobranch species (sCOX) and shown that sCOX inhibition suppresses VIP-stimulated chloride secretion in the perfused SRG.

The influence of feeding and fasting on plasma metabolites in the dogfish shark (Squalus acanthias).

PubMed

Wood, Chris M; Walsh, Patrick J; Kajimura, Makiko; McClelland, Grant B; Chew, Shit F

2010-04-01

Dogfish sharks are opportunistic predators, eating large meals at irregular intervals. Here we present a synthesis of data from several previous studies on responses in plasma metabolites after natural feeding and during prolonged fasting (up to 56days), together with new data on changes in plasma concentrations of amino acids and non-esterified fatty acids. Post-prandial and long-term fasting responses were compared to control sharks fasted for 7days, a typical inter-meal interval. A feeding frenzy was created in which dogfish were allowed to feed naturally on dead teleosts at two consumed ration levels, 2.6% and 5.5% of body weight. Most responses were more pronounced at the higher ration level. These included increases in urea and TMAO concentrations at 20h, followed by stability through to 56days of fasting. Ammonia levels were low and exhibited little short-term response to feeding, but declined to very low values during the extended fast. Glucose and beta-hydroxybutyrate both fell after feeding, the latter to a greater and more prolonged extent (up to 60h), whereas acetoacetate did not change. During prolonged fasting, glucose concentrations were well regulated, but beta-hydroxybutyrate increased to 2-3-fold control levels. Total plasma amino acid concentrations increased in a biphasic fashion, with peaks at 6-20h, and 48-60h after the meal, followed by homeostasis during the extended fast. Essential and non-essential amino acids generally followed this same pattern, though some exhibited different trends after feeding: taurine, beta-alanine, and glycine (decreases or stability), alanine and glutamine (modest prolonged increases), and threonine, serine, asparagine, and valine (much larger short-term increases). Plasma non-esterified fatty acid concentrations declined markedly through 48h after the 2.6% meal. These data are interpreted in light of companion studies showing elevations in aerobic metabolic rate, urea production, rectal gland function, metabolic base excretion, and activation of ornithine-urea cycle and aerobic enzymes after the meal, and muscle N-depletion but maintenance of osmolality and urea production during long-term fasting.

Osmoregulation, ionoregulation and acid-base regulation by the gastrointestinal tract after feeding in the elasmobranch (Squalus acanthias).

PubMed

Wood, Chris M; Kajimura, Makiko; Bucking, Carol; Walsh, Patrick J

2007-04-01

In order to study the physiological consequences of voluntary feeding in the gastrointestinal tract of a ureotelic marine elasmobranch, dogfish (fasted for 96 h) were sampled at various times up to 360 h after consuming a 5-6% ration of teleost fish (hake) under natural feeding conditions. Digestion and absorption were completed between 120 and 360 h post-feeding. The tissue masses of different segments of the gastrointestinal tract increased and decreased markedly as the chyme moved through, mainly because of fluid engorgement rather than hyperplasia. In fasted dogfish, the cardiac and pyloric stomachs contained only small volumes of highly acidic fluid (pH 1.77+/-1.12, 2.05+/-0.08) similar in composition to seawater. Feeding resulted in gastric pHs of 3.20+/-0.31 and 3.95+/-0.40 at 6 h, followed by slow declines through 60 h. An alkaline tide in the blood also occurred at 6 h. In the face of large changing masses of highly acidic chyme in the stomachs, the pH (6.50+/-0.10), ionic composition and volume of chyme in the intestine (spiral valve) were precisely regulated from 6 to 60 h post-feeding at very different values from those in the stomachs, and intestinal HCO3(-) remained low (5.12+/-0.83 mmol l(-1)). The colon was usually empty and its pH constant at 7.20+/-0.16 at all times. Despite the ingestion of strongly hypo-osmotic teleost tissue, the osmolality of the chyme remained in equilibrium with that of the blood plasma in all segments at all times after feeding. Much of the osmotic equilibration was because of the secretion of urea into the chyme, particularly in the intestine. After feeding, gastric fluid concentrations of Na(+) and Mg(2+) declined, K(+) and Ca(2+) increased, whereas Cl(-) exhibited little change, indicating that additional drinking of seawater was minimal. Na(+), K(+), water and especially Cl(-) were absorbed in the intestine, whereas Mg(2+) and Ca(2+) were largely excluded. Our results illustrate the complex integration of digestive and ionoregulatory function in the elasmobranch digestive tract, and marked differences from the teleost pattern.

Is the alkaline tide a signal to activate metabolic or ionoregulatory enzymes in the dogfish shark (Squalus acanthias)?

PubMed

Wood, Chris M; Kajimura, Makiko; Mommsen, Thomas P; Walsh, Patrick J

2008-01-01

Experimental metabolic alkalosis is known to stimulate whole-animal urea production and active ion secretion by the rectal gland in the dogfish shark. Furthermore, recent evidence indicates that a marked alkaline tide (systemic metabolic alkalosis) follows feeding in this species and that the activities of the enzymes of the ornithine-urea cycle (OUC) for urea synthesis in skeletal muscle and liver and of energy metabolism and ion transport in the rectal gland are increased at this time. We therefore evaluated whether alkalosis and/or NaCl/volume loading (which also occurs with feeding) could serve as a signal for activation of these enzymes independent of nutrient loading. Fasted dogfish were infused for 20 h with either 500 mmol L(-1) NaHCO3 (alkalosis + volume expansion) or 500 mmol L(-1) NaCl (volume expansion alone), both isosmotic to dogfish plasma, at a rate of 3 mL kg(-1) h(-1). NaHCO3 infusion progressively raised arterial pH to 8.28 (control = 7.85) and plasma [HCO3-] to 20.8 mmol L(-1) (control = 4.5 mmol L(-1)) at 20 h, with unchanged arterial P(CO2), whereas NaCl/volume loading had no effect on blood acid-base status. Rectal gland Na+,K+-ATPase activity was increased 50% by NaCl loading and more than 100% by NaHCO3 loading, indicating stimulatory effects of both volume expansion and alkalosis. Rectal gland lactate dehydrogenase activity was elevated 25% by both treatments, indicating volume expansion effects only, whereas neither treatment increased the activities of the aerobic enzymes citrate synthase, NADP-isocitrate dehydrogenase, or the ketone body-utilizing enzyme beta-hydroxybutyrate dehydrogenase in the rectal gland or liver. The activity of ornithine-citrulline transcarbamoylase in skeletal muscle was doubled by NaHCO3 infusion, but neither treatment altered the activities of other OUC-related enzymes (glutamine synthetase, carbamoylphosphate synthetase III). We conclude that both the alkaline tide and salt loading/volume expansion act as signals to activate some but not all of the elevated metabolic pathways and ionoregulatory mechanisms needed during processing of a meal.

An in vitro study of urea, water, ion and CO2/HCO3- transport in the gastrointestinal tract of the dogfish shark (Squalus acanthias): the influence of feeding.

PubMed

Liew, Hon Jung; De Boeck, Gudrun; Wood, Chris M

2013-06-01

In vitro gut sac preparations made from the cardiac stomach (stomach 1), pyloric stomach (stomach 2), intestine (spiral valve) and colon were used to examine the impact of feeding on transport processes in the gastrointestinal tract of the dogfish shark. Preparations were made from animals that were euthanized after 1-2 weeks of fasting, or at 24-48 h after voluntary feeding on a 3% ration of teleost fish (hake). Sacs were incubated under initially symmetrical conditions with dogfish saline on both surfaces. In comparison to an earlier in vivo study, the results confirmed that feeding caused increases in H(+) secretion in both stomach sections, but an increase in Cl(-) secretion only in stomach 2. Na(+) absorption, rather than Na(+) secretion, occurred in both stomach sections after feeding. All sections of the tract absorbed water and the intestine strongly absorbed Na(+) and Cl(-), regardless of feeding condition. The results also confirmed that feeding increased water absorption in the intestine (but not in the colon), and had little influence on the handling of Ca(2+) and Mg(2+), which exhibited negligible absorption across the tract. However, K(+) was secreted in the intestine in both fasted and fed preparations. Increased intestinal water absorption occurred despite net osmolyte secretion into the mucosal saline. The largest changes occurred in urea and CO2/HCO3(-) fluxes. In fasted preparations, urea was absorbed at a low rate in all sections except the intestine, where it was secreted. Instead of an increase in intestinal urea secretion predicted from in vivo data, feeding caused a marked switch to net urea absorption. This intestinal urea transport occurred at a rate comparable to urea reabsorption rates reported at gills and kidney, and was apparently active, establishing a large serosal-to-mucosal concentration gradient. Feeding also greatly increased intestinal CO2/HCO3(-) secretion; if interpreted as HCO3(-) transport, the rates were in the upper range of those reported in marine teleosts. Phloretin (0.25 mmol l(-1), applied mucosally) completely blocked the increases in intestinal urea absorption and CO2/HCO3(-) secretion caused by feeding, but had no effect on Na(+), Cl(-) or water absorption.

A critical analysis of carbonic anhydrase function, respiratory gas exchange, and the acid-base control of secretion in the rectal gland of Squalus acanthias.

PubMed

Shuttleworth, Trevor J; Thompson, Jill; Munger, R Stephen; Wood, Chris M

2006-12-01

We compared in vivo responses of rectal gland secretion to carbonic anhydrase (CA) inhibition (10(-4) mol l(-1) acetazolamide) in volume-loaded dogfish with in vitro responses in an isolated-perfused gland stimulated with 5 x 10(-6) mol l(-1) forskolin and removed from systemic influences. We also measured respiratory gas exchange in the perfused gland, described the acid-base status of the secreted fluid, and determined the relative importance of various extracellular and intracellular acid-base parameters in controlling rectal gland secretion in vitro. In vivo, acetazolamide inhibited Cl(-) secretion and decreased pHi in the rectal gland, but interpretation was confounded by an accompanying systemic respiratory acidosis, which would also have contributed to the inhibition. In the perfused gland, M(CO(2)) and M(O(2)) increased in linear relation to increases in Cl(-) secretion rate. CA inhibition (10(-4) mol l(-1) acetazolamide) had no effect on Cl(-) secretion rate or pHi in the perfused gland, in contrast to in vivo, but caused a transitory 30% inhibition of M(CO(2)) (relative to stable M(O(2))) and elevation in secretion P(CO(2)) effects, which peaked at 2 h and attenuated by 3.5-4 h. Secretion was inhibited by acidosis and stimulated by alkalosis; the relationship between relative Cl(-) secretion rate and pHe was almost identical to that seen in vivo. Experimental manipulations of perfusate pH, P(CO(2)) and HCO(3)(-) concentration, together with measurements of pHi, demonstrated that these responses were most strongly correlated with changes in pHe, and were not related to changes in P(CO(2)), extracellular HCO(3)(-), or intracellular HCO(3)(-) levels, though changes in pHi may also have played a role. The acid-base status of the secreted fluid varied with that of the perfusate, secretion pH remaining about 0.3-0.5 units lower, and changing in concert with pHe rather than pHi; secretion HCO(3)(-) concentrations remained low, even in the face of greatly elevated perfusate HCO(3)(-) concentrations. We conclude that pH effects on rectal gland secretion rate are adaptive, that CA functions to catalyze the hydration of CO(2), thereby maintaining a gradient for diffusive efflux of CO(2) from the working cells, and that differences in response to CA inhibition likely reflect the higher perfusion-to-secretion ratio in vitro than in vivo.

Elucidating dynamic responses of North Pacific fish populations to climatic forcing: Influence of life-history strategy

NASA Astrophysics Data System (ADS)

Yatsu, A.; Aydin, K. Y.; King, J. R.; McFarlane, G. A.; Chiba, S.; Tadokoro, K.; Kaeriyama, M.; Watanabe, Y.

2008-05-01

In order to explore mechanistic linkages between low-frequency ocean/climate variability, and fish population responses, we undertook comparative studies of time-series of recruitment-related productivity and the biomass levels of fish stocks representing five life-history strategies in the northern North Pacific between the 1950s and the present. We selected seven species: Japanese sardine ( Sardinopus melanostictus) and California sardine ( Sardinopus sagax) (opportunistic strategists), walleye pollock ( Theragra chalcogramma, intermediate strategist), pink salmon ( Oncorhynchus gorbuscha, salmonic strategist), sablefish ( Anoplopoma fimbria) and Pacific halibut ( Hippoglossus stenolepis) (periodic strategists) and spiny dogfish ( Squalus acanthias, equilibrium strategist). The responses in terms of productivity of sardine, pink salmon, sablefish and halibut to climatic regime shifts were generally immediate, delayed, or no substantial responses depending on the particular regime shift year and fish stock (population). In walleye pollock, there were some periods of high productivity and low productivity, but not coincidental to climatic regime shifts, likely due to indirect climate forcing impacts on both bottom-up and top-down processes. Biomass of zooplankton and all fish stocks examined, except for spiny dogfish whose data were limited, indicated a decadal pattern with the most gradual changes in periodic strategists and most intensive and rapid changes in opportunistic strategists. Responses of sardine productivity to regime shifts were the most intense, probably due to the absence of density-dependent effects and the availability of refuges from predators when sardine biomass was extremely low. Spiny dogfish were least affected by environmental variability. Conversely, spiny dogfish are likely to withstand only modest harvest rates due to their very low intrinsic rate of increase. Thus, each life-history strategy type had a unique response to climatic forcing, owing to their inherent biological traits such as mode, frequency and intensity of reproduction, early life style, age of maturity and longevity. On the other hand, responses of different stocks within a species to climatic regime shifts were unique to each local region, because large-scale climatic forcings are modulated by local physical, chemical and biological processes. The observed response time or absence of response in recruitment-related fish productivity to climatic regime shifts may be influenced by (1) local environmental conditions (immediate, with a delay or no effects), (2) phenological shifts in zooplankton life-history (immediate or with a delay), and (3) stochastic episodic events in both top-down and bottom-up processes (immediate, with a delay or no effects).