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Concern over the use of lethal techniques to collect basic biological data from sharks has necessitated the development of nonlethal methods of data collection. We evaluated the nonlethal method of removing stomach contents using acrylic tubes. Stomach contents of Spiny Dogfish (Squalus acanthias) captured with bottom trawls and longlines were collected using acrylic tubes flushed with seawater. The largest tube used during the trawl survey was 30 mm in diameter, while a larger tube (37 mm in diameter) was used during longline sampling due to catches of larger dogfish. The average efficiency of stomach content removal was 79.5% overall, and improved to 93% with the addition of the larger tube. Selection of a tube with a diameter 10--20 mm less than mouth width can be reasonably expected to recover over 90% of stomach contents. Stomach-tube lavage is a useful and efficient method for nonlethal sampling of stomach contents from Spiny Dogfish, and perhaps other small sharks. [ABSTRACT FROM AUTHOR]

Abstract: 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 &y& Elsevier]

Abstract: Understanding the relationship between abundance of spawners and subsequent recruitment is one of the central issues in fisheries stock assessment. We developed a new, pre-recruit survival based stock–recruitment model that enables explicit modeling of survival between embryos and age 0 recruits, and allows the description of a wide range of pre-recruit survival curves. The model is especially useful for low fecundity species that produce relatively few offspring per litter and exhibit a more direct connection between spawning output and recruitment than species generating millions of eggs. The proposed model provides additional flexibility in the stock–recruitment options that may be explored in any fishery stock assessment, and it is now available within the Stock Synthesis assessment platform. In this paper, we describe the mathematical formulation of the new stock–recruitment model, explain how this model can be specified within Stock Synthesis, and use it to model the stock–recruitment relationship of the spiny dogfish shark in the Northeast Pacific Ocean. We compare the results of the application of our new stock–recruitment model, with those from traditional Beverton–Holt relationship, and illustrate why the new approach is more appropriate for this species. [Copyright &y& Elsevier]

Abstract: It has been recently shown that the somatostatin gene family was likely composed of at least three paralogous genes in the common ancestor of all extant jawed vertebrates. These three genes, namely SS1, SS2 and SS5, are thought to have been generated through the two rounds of whole-genome duplications (2R) that took place early during the vertebrate evolution. In the present study, we report the cloning of three distinct somatostatin cDNAs from the dogfish Scylorhinus canicula, a member of the group of cartilaginous fish. We decided to call these cDNAs, at least provisionally, SSa, SSb and SSc, respectively. Two of them, SSa and SSb, encode proteins that both contain the same tetradecapeptide sequence at their C-terminal extremity (AGCKNFFWKTFTSC). This putative peptide is identical to that generated by the SS1 gene in other vertebrate species. The last cDNA, SSc, encodes a protein that contains at its C-terminal extremity the same peptide sequence as that generated by the SS2 gene in teleosts (APCKNFFWKTFTSC). Phylogenetic analysis showed that the SSa and SSc genes likely correspond to the dogfish counterparts of the SS1 and SS2 genes, respectively. In contrast, the phylogenetic status of the SSb gene is less clear. Several lines of evidence suggest that it could correspond to the SS5 gene, but this view will need to be confirmed, for example by synteny analysis. Finally, RT-PCR analysis revealed that SSa, SSb and SSc genes are differentially expressed in dogfish tissues, suggesting that the corresponding peptides may exert distinct functions. [Copyright &y& Elsevier]

In the past few years, the small spotted dogfish has become the primary model for analyses of early development in chondrichthyans. Its phylogenetic position makes it an ideal outgroup to reconstruct the ancestral gnathostome state by comparisons with established vertebrate model organisms. It is also a suitable model to address the molecular bases of lineage-specific diversifications such as the rise of extraembryonic tissues, as it is endowed with a distinct extraembryonic yolk sac and yolk duct ensuring exchanges between the embryo and a large undivided vitelline mass. Experimental or functional approaches such as cell marking or in ovo pharmacological treatments are emerging in this species, but recent analyses of early development in this species have primarily concentrated on molecular descriptions. These data show the dogfish embryo exhibits early polarities reflecting the dorso-ventral axis of amphibians and teleosts at early blastula stages and an atypical anamniote molecular pattern during gastrulation, independently of the presence of extraembryonic tissues. They also highlight unexpected relationships with amniotes, with a strikingly similar Nodal-dependent regional pattern in the extraembryonic endoderm. In this species, extraembryonic cell fates seem to be determined by differential cell behaviors, which lead to cell allocation in extraembryonic and embryonic tissues, rather than by cell regional identity. We suggest that this may exemplify an early evolutionary step in the rise of extraembryonic tissues, possibly related to quantitative differences in the signaling activities, which shape the early embryo. These results highlight the conservation across gnathostomes of a highly constrained core genetic program controlling early patterning. This conservation may be obscured in some lineages by taxa-specific diversifications such as specializations of extraembryonic nutritive tissues. [ABSTRACT FROM AUTHOR]

This is the first molecular identification of the Arrowhead dogfish Deania profundorum based on the mitochondrial cytochrome oxidase c subunit I (COI) ever made. It is based on four specimens caught in the Cantabrian Sea (north of Spain) during a monitoring survey in the summer of 2009. Three specimens of Deania calcea were also sampled as comparative material. The sequences obtained were in concordance with the identification of the Deania species. The two Deania species shared no COI haplotypes and showed a genetic distance of 3.6% (23 fixed differences out of 652 bp), which is within the range of congeneric species. [ABSTRACT FROM AUTHOR]

The basic anatomy of the elasmobranch brain has been previously established after studying the organization of the different subdivisions in the adult brain. However, despite the relatively abundant immunohistochemical and hodologic studies performed in different species of sharks and skates, the organization of some brain subdivisions remains unclear. The present study focuses on some brain regions in which subdivisions established on the basis of anatomical data in adults remain controversial, such as the subpallium, mainly the striatal subdivision. Taking advantage of the great potential of the lesser spotted dogfish, Scyliorhinus canicula, as a model for developmental studies, we have characterized the subpallium throughout development and postembryonic stages by analyzing the distribution of immuno-markers for GABA, catecholamines, and neuropeptides, such as substance P. Moreover, we have analyzed the expression pattern of regulatory genes involved in the regionalization of the telencephalon, such as D1x2, Nkx2.1, and Shh, and followed their derivatives throughout development in relation to the distribution of such neurochemical markers. For further characterization, we have also analyzed the patterns of innervation of the subpallium after applying tract-tracing techniques. Our observations may shed light on postulate equivalences of regions and nuclei among elasmobranchs and support homologies with other vertebrates. [ABSTRACT FROM AUTHOR]

Using network models consisting of gap-junction-coupled Wang-Buszaki neurons, we demonstrate that it is possible to obtain not only synchronous activity between neurons but also a variety of constant phase shifts between 0 and π. We call these phase shifts intermediate stable phase-locked states. These phase shifts can produce a large variety of wavelike activity patterns in one-dimensional chains and two-dimensional arrays of neurons, which can be studied by reducing the system of equations to a phase model. The 2π periodic coupling functions of these models are characterized by prominent higher order terths intheir Fourier expansion, which can be varied by changing model parameters. We study how the relative contribution of the odd and even terms affects what solutions are possible, the basin of attraction of those solutions, and their stability. These models may be applicable to the spinal central pattern generators of the dogfish and also to the developing neocortex of the neonatal rat. [ABSTRACT FROM AUTHOR]

SUMMARY Vertebrate head segmentation has attracted the attention of comparative and evolutionary morphologists for centuries, given its importance for understanding the developmental body plan of vertebrates and its evolutionary origin. In particular, the segmentation of the mesoderm is central to the problem. The shark embryo has provided a canonical morphological scheme of the head, with its epithelialized coelomic cavities (head cavities), which have often been regarded as head somites. To understand the evolutionary significance of the head cavities, the embryonic development of the mesoderm was investigated at the morphological and histological levels in the shark, Scyliorhinus torazame. Unlike somites and some enterocoelic mesodermal components in other vertebrates, the head cavities in S. torazame appeared as irregular cyst(s) in the originally unsegmented mesenchymal head mesoderm, and not via segmentation of an undivided coelom. The mandibular cavity appeared first in the paraxial part of the mandibular mesoderm, followed by the hyoid cavity, and the premandibular cavity was the last to form. The prechordal plate was recognized as a rhomboid roof of the preoral gut, continuous with the rostral notochord, and was divided anteroposteriorly into two parts by the growth of the hypothalamic primordium. Of those, the posterior part was likely to differentiate into the premandibular cavity, and the anterior part disappeared later. The head cavities and somites in the trunk exhibited significant differences, in terms of histological appearance and timing of differentiation. The mandibular cavity developed a rostral process secondarily; its homology to the anterior cavity reported in some elasmobranch embryos is discussed. [ABSTRACT FROM AUTHOR]

Life-history parameters of Deania calcea and Deania quadrispinosa suggested that their productivity was very low. Maturity ( LT50) occurs at c. 80% of maximum observed total lengths ( LT) for both species and sexes. A large proportion of mature females were neither pre-ovulatory nor pregnant, and the reproductive cycle included a distinct resting phase after pregnancy. For D. calcea, mean ovarian fecundity was 12 and maximum observed litter size was 10 (average of six); D. quadrispinosa averaged 17 pups per litter. Birth LT was 28-33 cm for D. calcea and 23-25 cm for D. quadrispinosa. The male and female reproductive cycles were aseasonal, and consequently, the length of the reproductive cycle could not be determined. Preliminary ageing data from dorsal-spine growth bands suggested that female D. calcea lived to 31-36 years and males to 24-32 years. The LT-at-age data using external bands on the spines showed maturity occurring at 15·5 years (males) and 21·5 years (females), whereas banding on the internal dentine indicated maturity at 10·5 and 17·5 years for males and females. Thus, a female lifetime of 31-36 years allowed for a maximum of 7 litters if a 2 year cycle is assumed or only five litters with a 3 year cycle, resulting in a lifetime fecundity of only 42 pups (2 year cycle) or even lower (3 year cycle). [ABSTRACT FROM AUTHOR]

We used a comprehensive dataset on the diet of Squalus acanthias in the southwestern Atlantic Ocean (35-55°S) to test the hypothesis that fishery has caused a decrease in the trophic level of this species (fishing down process). Of 3,644 stomachs examined between the years 1985 and 2010, 2,214 (60.77%) contained prey items. Generalized linear models were used to evaluate the support in our data for five explanatory variables (sex, predator's total length, season, region and decade) that may explain the consumption of the given prey. The frequency of fish, mainly Merluccius hubbsi, and benthos in the stomachs decreased through time, whereas the squid Illex argentinus and jellyfishes exhibited positive trends. The trophic level of S. acanthias declined from the 1980s to the 1990s due to the high consumption of prey items at lower trophic levels. On the other hand, the consumption of argentine anchovy, Engraulis anchoita, an underexploited species, did not reveal changes through time. [ABSTRACT FROM AUTHOR]

Multiple paternity (MP) has been demonstrated in a variety of sharks, although its prevalence and the number of sires per litter vary considerably among species. To date, such analyses have focused on viviparous species that possess only part of the wide spectrum of reproductive strategies developed in elasmobranchs. We analyzed MP in an oviparous species, the small-spotted catshark (Scyliorhinus canicula). In total, 150 neonates originating from 13 different mothers were genotyped using 12 microsatellite loci. MP was commonplace, with progeny from 92% of females sired by multiple males. This result is consistent with the reproductive biology of the species, particularly its protracted breeding season and potential for long-term sperm storage. The significance of these findings is discussed in light of small-spotted catshark behavior, which suggests that the cost of avoiding mating attempts initiated by males may be high and is therefore supportive of convenience polyandry as an explanation for MP. Eggs were followed from the time they were laid to when they hatched, offering a rare opportunity to investigate juvenile development in more detail. [ABSTRACT FROM PUBLISHER]

Most sharks, rays and chimaeras (chondrichthyans) taken in commercial fisheries are discarded (i.e. returned to the ocean either dead or alive). Quantifying the post-capture survival (PCS) of discarded species is therefore essential for the improved management and conservation of this group. For all chondrichthyans taken in the main shark fishery of Australia, we quantified the immediate PCS of individuals reaching the deck of commercial shark gillnet fishing vessels and applied a riskbased method to semi-quantitatively determine delayed and total PCS. Estimates of immediate, delayed and total PCS were consistent, being very high for the most commonly discarded species (Port Jackson shark, Australian swellshark, and spikey dogfish) and low for the most important commercial species (gummy and school sharks). Increasing gillnet soak time or water temperature significantly decreased PCS. Chondrichthyans with bottom-dwelling habits had the highest PCS whereas those with pelagic habits had the lowest PCS. The risk-based approach can be easily implemented as a standard practice of on-board observing programs, providing a convenient first-step assessment of the PCS of all species taken in commercial fisheries. [ABSTRACT FROM AUTHOR]

In this study, the concentrations of elements in muscle, liver and cartilage tissues of spiny dogfish (Squalus acanthias) were investigated. Spiny dogfish caught from the Marmara Sea at three different times of the year (October 2008, January and April 2009) were purchased from sea products factories (exporter) in Çanakkale (Turkey). The results showed that the element accumulations were higher in liver than the cartilage and muscle tissues in all three months. Al, Fe and Zn. concentrations in all exammed tissues were remarkably higher than the other elements. However, all the elements (especially Al, Cd, Pb) were below the Turkish legislation and European Commission legal limits for fish muscle, cartilage and liver. Therefore, we can conclude that Squalus acanthias from Marmara Sea (Turkey) are safe for human consumption. [ABSTRACT FROM AUTHOR]

Abstract: 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 14C-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 14C-urea in the ratfish. Through the addition of 2mM NH4Cl 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 &y& Elsevier]

Fishing trials with bottom fixed gears (primarily gillnets but also shrimp and crab traps and longlines) were conducted on the continental slope off Nova Scotia in August 1991. Fishing was conducted at several depths between 500 and 2800 m in two areas, one on the open slope south of Emerald Bank and the other at the mouth of The Gully, a large canyon. Catches by gillnets accounted for about 90% of the total and were predominated by deepwater chimaera (Hydrolagus affinis), black dogfish (Centroscyllium fabricii) and Portuguese shark (Centroscymnus coelolepis). The most frequently caught species in traps were snubnose eel (Simenchelys parasitica) and abyssal grenadier (Coryphaenoides armatus). Variations in catches by depth and area are described, and comparisons are made with catches from otter trawl surveys at similar depths with regard to the most prominent species caught and their size compositions. [ABSTRACT FROM AUTHOR]

Previous studies indicate that elasmobranch fishes (sharks, skates and rays) detect the Earth's geomagnetic field by indirect magnetoreception through electromagnetic induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of elasmobranchs overall in comparison with control-and procedural control hooks in the hook-and-line experiment. Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were significantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not. Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish (Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-andline or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations. [ABSTRACT FROM AUTHOR]

scavenging interaction between the arrow tooth eel Synaphobranchus kaupii and the Portuguese dogfish Centroscymnus coelolepis, both ubiquitous components of fish assemblages at bathyal depths, was observed. Using a baited camera between 1297 and 2453 m in the eastern Atlantic Ocean continental slope, it was shown that despite consistently rapid arrival times of S. kaupii (<5 min), their feeding bouts (indicated by acute peak in numbers) did not take place until shortly after C. coelolepis arrived and removed the exterior surface of the bait (skipjack tuna Katsuwonus pelamis carcass). Change in the numbers of S. kaupii was hence dependent on the arrival of a more powerful scavenger throughout the study site, and at the deeper stations where the population of C. coelolepis declined, S. kaupii was observed to be present but waited for >2 h before feeding, thus contradicting conventional scavenging assumptions in the presence of a food fall. [ABSTRACT FROM AUTHOR]

Abstract: Halogenated persistent organic pollutants [polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)] along with total lipid, were measured in the liver and muscle of three species of deep water fish (black scabbard, black dogfish (liver only) and roundnose grenadier) collected from the Rockall fishing area, to the west of Scotland, between 2006 and 2008. Both contaminant groups were detected in the muscle and liver, with concentrations of PCBs being higher than PBDEs. There were no significant differences in the PCB or PBDE concentrations between the three species, or different sampling locations in the Rockall fishing area. PCB concentrations (ΣICES (International Council for the Exploration of the Sea)7 PCBs) greater than 500μgkg−1 lipid weight were found in 26 of the 106 liver samples. PCB concentrations were compared to OSPAR assessment criteria, concentrations were above background but below Environmental Assessment Criteria. Estimated Toxic Equivalent (TEQ) concentrations, calculatedusing published models, in the fish muscle and liver indicated that consumption of deep water fish is unlikely to represent a risk to human health. The high squalene content in some of the black dogfish liver necessitated an additional clean-up step, involving gel permeation chromatography, when analyzing for PBDEs. Concentrations of PBDEs were low with many congeners being below detection limits, particularly in the muscle. There are currently no assessment criteria available for PBDEs. Furthermore, thereis only very limited data on PBDEs in deep water fish. However, the concentrations observed in this study were similar to the concentrationsrecently reported in Mediterranean deep water fish. [Copyright &y& Elsevier]

Abstract: The levels of trace metals of front (F) and rear (R) dorsal ordinary muscles (dom) of wild and farmed bluefin tuna (BFT) were determined by atomic absorption spectrometry. Wilds were obtained from Antalya Bay and farmed were taken from a fish farm in Ildir Bay (Izmir), during spring to early summer. The accuracy of the method was checked standard reference material (NRCC-DORM-2 Dogfish Muscle). Mean trace element content of the wild samples (Fdom and Rdom, respectively) was found as: Cu, 0.790 and 0.591; Mn, 0.084 and 0.096; Ni, 0.101 and 0.124; Zn, 4.788 and 5.577; Fe, 7.670 and 9.222 (μgg−1 wetwt.). Values for farmed were detected as Cu, 0.581 and 0.453; Mn, 0.111 and 0.139; Ni, 0.072 and 0.092; Zn, 4.631 and 3.380; Fe, 4.957 and 7.156 (μgg−1 wetwt.). The results were compared with literature values. [Copyright &y& Elsevier]

Veríssimo, A., McDowell, J. R., and Graves, J. E. 2011. Population structure of a deep-water squaloid shark, the Portuguese dogfish (Centroscymnus coelolepis). – ICES Journal of Marine Science, 68: .The genetic population structure of the deep-water squaloid Centroscymnus coelolepis (the Portuguese dogfish) in the eastern Atlantic was investigated using eight polymorphic nuclear microsatellite markers and a 496-bp fragment of the mitochondrial DNA control region (mtDNA CR). Samples (20–50 individuals per location) were collected off Ireland, Portugal, Madeira, Mauritania, South Africa, and the Azores (Mid-Atlantic Ridge). High levels of genetic diversity were found at the nuclear microsatellite loci (mean A = 17.3; overall Ho = 0.77), although there was low diversity at the mtDNA CR (h = 0.65, π = 0.0018). Genetic diversity for the Portuguese dogfish was homogeneously distributed among sampling locations, resulting in low and non-significant indices of genetic differentiation (e.g. FST = −0.0013 to 0.0096, ΦST = −0.017 to 0.033; p > 0.5), consistent with the absence of population structure within the area sampled. The results indicate that C. coelolepis has a high dispersal potential within the eastern Atlantic, and its apparent spatial segregation by size and maturity stage suggest large-scale migration associated with the reproductive cycle. [ABSTRACT FROM PUBLISHER]

Sperm storage in males and females was studied for the deepwater shark Portuguese dogfish Centroscymnus coelolepis. In males, sperm is stored in the seminal vesicle from early maturity stages until mating. The epithelium of the seminal vesicle secretes an acid mucopolysaccharide that might preserve sperm until it is released. The oviducal gland (OG) presents the four distinct zones described for other elasmobranchs: club, papillary, baffle and terminal. Mature, pregnant, resting and regenerating females are able to store sperm in the terminal zone. Sperm was found within sperm storage tubules (SSTs), involved by a secretory matrix. The localization of SSTs deeper in the OG suggests long-term sperm storage, which is in agreement with the long reproductive cycle described for this species. Sperm storage is an advantage for this deepwater species that presents sexual segregation and lives in a food-constrained environment, increasing the efficiency in reproduction. [ABSTRACT FROM AUTHOR]

The embryonic development and the level of dependency of the embryos from the maternal organism were investigated for Centroscymnus coelolepis. During the development, there is a 22-32% loss of organic matter and gains of 95-122% and 29-46% on moisture and inorganic matter, respectively. Only 28-48% of the initial yolk energy is conserved in embryos, being the remaining used in catabolism. In late pregnancy, the epithelium thickness of uterine villi decreases and vascularity increases. Results suggest that only water and minerals are transferred from the mother to the embryos. Monounsaturated fatty acids are the main type of fatty acids representing 48% of the total yolk fatty acid content, followed by polyunsaturated (30%) and saturated fatty acids (18-21%). [ABSTRACT FROM AUTHOR]

The article focuses on Dlx gene expression in oral teeth and dermal denticles in order to test the hypothesis of serial homology between odontodes. Six Dlx paralogs were identified in the dogfish and found that three showed strong transcription in teeth and dermal denticles whereas a weak expression was detected for Dlx1 in dermal denticles and teeth, and for Dlx2 in dermal denticles.

Hallett, C. S., and Daley, R. K. 2011. Feeding ecology of the southern lanternshark (Etmopterus baxteri) and the brown lanternshark (E. unicolor) off southeastern Australia. – ICES Journal of Marine Science, 68: 157–165. Little is known about the ecological interactions between bycatch species and orange roughy (Hoplostethus atlanticus) within exploited slope and seamount communities off Tasmania. The diet of Etmopterus baxteri and E. unicolor, two important bycatch species of these fisheries, is described using four indices [percentage frequency of occurrence, percentage by number, percentage by weight, and percentage by the index of relative importance (%IRI)] calculated for broad prey categories, individual prey taxa, and functional prey groups. The identifiable diet of E. unicolor was dominated by benthic cephalopods (96%IRI), whereas benthic teleost prey, notably orange roughy (43%IRI), dominated the diet of E. baxteri. Similar trophic mechanisms appear to support aggregations of orange roughy and Etmopterus spp. off Tasmania; they feed on demersal species and mesopelagic or vertically migrating nekton advected laterally onto the mid-slope. The importance of teleost prey in the diet of E. baxteri apparently increases with shark length, whereas crustaceans become less important, which is a similar diet shift to that of orange roughy. Etmopterus baxteri is both a potential competitor and predator of orange roughy in these ecosystems. Fishery managers need to understand and consider the complex trophic interactions between orange roughy, sharks, and other exploited species in managing recently reopened deep-water fisheries off southeastern Australia. [ABSTRACT FROM PUBLISHER]

The article discusses a study on the feeding habits of specimens of the deep-sea sharks hooktooth dogfish (Aculeola nigra) and dusky catshark (Bythalaelurus canescens) from central-northern Chile. Individual shark specimens were gathered as by-catch from the deep-sea crustacean fishery from January 1997 to July 2000. The benthic deep-sea shrimp Heterocarpus reedi was identified as the most important prey by index of relative importance and by frequency of occurrence in A. nigra and H. reedi. The significance of the euphausiid Euphausia mucronata and the common hake Merluccius gayi as prey for A. nigra is also considered.

The article examines the efficacy of a small popup satellite archival transmitting tag called the X-tag in tracking the movements of spiny dogfish Squalus acanthias in the western North Atlantic Ocean. Materials and methods used in the study are detailed. The results indicate the horizontal and vertical movements of each shark as well as the diel depth pattern of the species. In conclusion, a smaller transmitting tag can provide useful data on the movement patterns of a relatively small species of shark.

Most studies of the function of feeding muscles in fish have implanted electromyogram electrodes unilaterally to understand the motor pattern associated with a behavior. The few studies that have implanted bilaterally have found that paired muscles may be activated asynchronously, often resulting in visible kinematic asymmetry. We investigated modulation of pairwise asynchrony (modulation in the activation patterns of left and right members of a muscle) of feeding muscles during capture and processing of two types of prey in spiny dogfish Squalus acanthias and little skates Leucoraja erinacea (Elasmobranchii). Two asynchrony indices quantified the degree to which muscles in a pair were activated out of phase (lag index, AIlag) and the degree to which durations differ (duration index, AIdur). Feeding behaviors for both species were compared according to these indices and total event duration using principal components analysis. Both species modulated pairwise asynchrony according to prey type, exhibiting more asynchronous motor patterns when feeding on more complex prey items (those requiring more processing); however, the motor patterns underlying this asynchrony differed between species. Dogfish process complex prey using head-shaking, which requires alternating activation of contralateral head muscles (i.e. high lag index value). In contrast, little skates process complex prey using a completely unilateral behavior in which prey is moved to one corner of the jaws and jaw muscles are activated on that side only (i.e. high duration index value). Asynchronous behaviors are not detected by unilateral implants; our data demonstrate the importance of bilateral implantation to identify fine details of feeding motor patterns, particularly those involving complex prey. [ABSTRACT FROM AUTHOR]

Abstract: The annual and life-cycle mercury bioaccumulation pattern in selected tissues of the economically relevant Elasmobranchii species Scyliorhinus canicula was studied, and the risks associated with its consumption evaluated. Preferential mercury bioaccumulation occurred in muscle tissue, and followed the order muscle>heart>liver>gills>pancreas. Total mercury in muscle tissue ranged from 0.13mgkg−1 (wwt) in 1+year old males to 0.8mgkg−1 (wwt) in 8+ year old mature females, with no significant differences found between genders, and no clear lifespan bioaccumulation pattern observed, except for mature females. Organic mercury in the muscle ranged from 0.05mgkg−1 (wwt) to 0.52mgkg−1 (wwt), corresponding to an average of 70% of total mercury content. In mature females, a significant correlation (R =0.99, P =0.01) was found between size and organic mercury fraction, suggesting reproduction as an important factor controlling organic mercury bioaccumulation in the spotted dogfish. [ABSTRACT FROM AUTHOR]

Farrell, E. D., Mariani, S., and Clarke, M. W. 2010. Age and growth estimates for the starry smoothhound (Mustelus asterias) in the Northeast Atlantic Ocean. – ICES Journal of Marine Science, 67: 931–939.Age, growth, and longevity were estimated for the starry smoothhound (Mustelus asterias), based on the interpretation of sectioned vertebrae of 106 males (35–104 cm stretch total length, STL) and 114 females (44–112 cm STL). Growth curves were fitted to length-at-age data using von Bertalanffy and Gompertz models. The three-parameter von Bertalanffy growth function (VBGF) provided the best statistical fit to the male data (L∞ = 103.7 cm STL, L0 = 38.1 cm STL, k = 0.195 year−1). The Gompertz growth function provided the best statistical fit to the female data, although the estimated parameters were biologically unreasonable. Therefore, the three-parameter VBGF was also accepted for females (L∞ = 123.5 cm STL, L0 = 34.9 cm STL, k = 0.146 year−1). Longevity was estimated to be 13 and 18.3 years for males and females, respectively. The length–weight relationship is also presented for 304 male and 424 female M. asterias. The von Bertalanffy model was fitted to the weight-at-age data. These estimates can form the basis of future work on the assessment and management of this species. [ABSTRACT FROM PUBLISHER]

Klug, S. & Kriwet, J. (2010). Timing of deep-sea adaptation in dogfish sharks: insights from a supertree of extinct and extant taxa. — Zoologica Scripta, 39, 331–342. Dogfish sharks (Squaliformes) constitute a monophyletic group of predominantly deep-water neoselachians, but the reasons and timing of their adaptation to this hostile environment remain ambiguous. Late Cretaceous dogfish sharks, which generally would be associated with deep-water occur predominantly in shallow water environments. Did the end-Cretaceous mass extinction event that eliminated large numbers of both terrestrial and aquatic taxa and clades including sharks trigger the evolutionary adaptation of present deep-water dogfish sharks? Here, we construct, date, and analyse a genus-level phylogeny of extinct and living dogfish sharks to bring a new perspective to this question. For this, eleven partial source trees of dogfish shark interrelationships were merged to create a comprehensive phylogenetic hypothesis. The resulting supertree is the most inclusive estimate of squaliform interrelationships that has been proposed to date containing 23 fossil and extant members of all major groups. † Eoetmopterus represents the oldest dalatoid. † Microetmopterus, † Paraphorosoides, † Proetmopterus and † Squaliogaleus are stem-group dalatoids in which bioluminescence most likely was not developed. According to our analyses, bioluminescence in dogfish sharks was already developed in the early Late Cretaceous indicating that these sharks adapted to deep-water conditions most likely at about 100 Mya. The advantage of this reconstruction is that the fossil record is used directly for age node estimates rather than employing molecular clock approaches. [ABSTRACT FROM AUTHOR]

The mechanical performance of red and white muscle fibres from dogfish was compared during a long series of contractions with sinusoidal movement or under isometric conditions at 12°C (normal in vivo temperature). Power output was measured during sinusoidal movement at 0.75 Hz and peak-to-peak amplitude about 12% L0. Tetanus duty cycle was 33% (0.44 s) at phase -8% (first stimulus at 0.107 s before shortening started). Initially, the red fibres produced only about one third as much power as the white fibres, 6.57±0.63 W kg-1 wet mass (mean ± s.e.m.) and 18.3±2.3, respectively. Red fibres were better at sustaining power output; it declined rapidly to about 60% of its initial value and then remained relatively steady for up to 450 cycles of movement. Force during shortening declined, but force during stretch did not increase: force always relaxed to a low value before stretch started. By contrast, net power output by white fibres declined rapidly to zero within about 50 cycles. Two changes contributed: decline in force during shortening and an increase in force during stretch because relaxation became progressively less complete during the series of contractions. In isometric series (0.44 s stimulation every 1.33 s, cycle frequency 0.75 Hz), red and white fibres sustained peak isometric force similarly; in the 50th cycle force was 59±3% and 56±4% of initial values. The time required for force to relax to 10% of its maximum value decreased during the series for red fibres and increased for white fibres. [ABSTRACT FROM AUTHOR]

Abstract: Carbonic anhydrase (CA) is a zinc metalloenzyme that catalyzes the reversible hydration–dehydration reactions of CO2. It is present in high abundance in the cytoplasm of vertebrate red blood cells, where it contributes to CO2 excretion. A membrane-bound CA isoform (CA IV) is also present in the lungs of mammals and reptiles, but plays little role in CO2 excretion. The gills of teleost fish appear to lack plasma-accessible CA activity. In elasmobranchs, however, evidence gathered using a variety of physiological, biochemical and molecular approaches suggests that CA IV is present in the gills, and that at least in dogfish, this CA IV makes a significant contribution to CO2 excretion by catalyzing the dehydration of plasma HCO3 −. The contribution of CA IV to CO2 excretion is favoured by unusually high relative plasma buffering that aids in the provision of protons for HCO3 − dehydration. Moreover, reduced emphasis on HCO3 − flux through the red blood cell may reflect the occurrence of a slower turnover cytosolic CA in dogfish. This model of CO2 excretion, in which HCO3 − dehydration in the red blood cell catalyzed by cytosolic CA and HCO3 − dehydration in the plasma catalyzed by membrane-bound CA IV are of comparable importance, has been described for the dogfish. Further work is required to determine whether it applies to elasmobranch fish as a group. [Copyright &y& Elsevier]

The granule cell layer of the cerebellum comprises the largest population of neurons in the vertebrate CNS. In amniotes, its precursors undergo a unique phase of transit amplification, regulated by Sonic hedgehog. They do so within a prominent but transient secondary proliferative epithelium, the external germinal layer, which is formed by tangential migration of precursor cells from the rhombic lip. This behavior is a hallmark of bird and mammal cerebellum development. Despite its significance for both development and disease, it is unclear whether an external germinal layer is a requirement for granule cell production or an expedient of transit amplification. Evidence for its existence in more basal vertebrates is contradictory. We therefore examined cerebellum development in the zebrafish, specifically in relation to the expression of the basic helix-loop- helix gene Atonal 1, which definitively characterizes granule cell precursors. The expression of Atoh1a-Atoh1c, in combination with patterns of proliferation and fate maps, define precursor pools at the rhombic lip and cerebellar midline but demonstrate that an external germinal layer is absent. Sonic hedgehog signaling is correspondingly absent in the zebrafish cerebellum. Sustained roof-plate-derived signals suggest that, in the absence of transit amplification, primary granule cell precursor pools are maintained throughout development. To determine whether this pattern is specific to zebrafish or reflects a more general anamniote organization, we examined the expression of similar genes in the dogfish, Scylliorhinus canicula.We show that these anamniotes share a common ground plan of granule cell production that does not include an external germinal layer. [ABSTRACT FROM AUTHOR]

pH homeostasis is essential for life, yet it remains unclear how animals sense their systemic acid/base (A/B) status. Soluble adenylyl cyclase (SAC) is an evolutionary conserved signaling enzyme that produces the second messenger CAMP in response to bicarbonate ions (HCO-3). We cloned the sAC ortholog from the dogfish, a shark that regulates blood A/B by absorbing and secreting protons (H+) and HCO-3 at its gills. Similar to mammalian sAC, dogfish soluble adenylyl cyclase (dfsAC) is activated by HCO-3 and can be inhibited by two structurally and mechanistically distinct small molecule inhibitors. dfsAC is expressed in the gill epithelium, where the subset of base-secreting cells resides. Injection of inhibitors into animals under alkaline stress confirmed that dfsAC is essential for maintaining systemic pH and HCO-3 levels in the whole organism. One of the downstream effects of dfsAC is to promote the insertion of vacuolar proton pumps into the baso-lateral membrane to absorb H+ into the blood, sAC orthologs are present throughout metazoans, and mammalian sAC is expressed in A/B regulatory organs, suggesting that systemic A/B sensing via sAC is widespread in the animal kingdom. [ABSTRACT FROM AUTHOR]

Deepwater dogsharks (Order Squaliformes) are thought to be particularly vulnerable to overfishing due to life history strategies that place them at the lower end of the shark productivity spectrum. Sharks frequently have relatively low value in multispecies fisheries, where management is usually aimed at maintaining harvest of more valuable and productive teleosts. This results in low priority being given to data collection for sharks and hampers identification of appropriate harvest strategies. Here an age-structured model with maximum sustainable harvest rate (UMSY) as leading productivity parameter is systematically applied to show that for certain growth and reproductive schedules that apply to some sharks, the range of possible values that can be taken by UMSY can become very small. The model was applied to 12 Australian dogshark species and was used to show that UMSY is highly constrained under some selectivity schedules. Results were consistent with estimates of the intrinsic rate of growth obtained using a demographic model, suggesting that there may be more certainty about UMSY than expected for many shark species, given uncertainty in recruitment parameters. The approach could be used to inform policy for some sharks and may be useful in the development of informative Bayesian priors for assessment models. [ABSTRACT FROM AUTHOR]

The feeding habits of birdbeak dogfish Deania calcea, velvet belly lantern shark Etmopterus spinax and blackmouth catshark Galeus melastomus at Le Danois Bank, Cantabrian Sea, south Bay of Biscay were studied in relation to their bathymetric distribution. Deep-sea sharks were collected during two multidisciplinary surveys carried out in October 2003 and April 2004 at the Le Danois Bank. Two different habitats were defined: (1) the top of the bank, ranging from 454 to 642 m depth and covered by fine-sand sediments with a low percentage of organic matter, and (2) the inner basin located between the bank and the Cantabrian Sea's continental shelf, at depths of 810–1048 m, which was characterized by a high proportion of silt and organic matter. Deania calcea was not present at the top of the bank but was abundant below 642 m, while E. spinax was abundant in the shallower top of the bank but was not found in the deeper inner basin. There was almost no bathymetric overlap between these two deep-sea shark species. Galeus melastomus was found over the whole depth range. There seemed to be an ontogenetic segregation with depth for this species, however, since 80% of the specimens collected at the top of the bank were < 600 mm total length ( LT) (mean 510 mm LT), whereas larger individuals (mean 620 mm LT) inhabited deeper zones. Galeus melastomus exhibited a significantly higher feeding intensity than both E. spinax at the top of the bank and D. calcea in the inner basin. Little dietary overlap between D. calcea and G. melastomus in the inner basin was found, with D. calcea being an ichthyophagous predator while the diet of G. melastomus at these depths was composed of a variety of meso-bathypelagic shrimps ( e.g. Acantephyra pelagica, Pasiphaea spp. and Sergia robusta), cephalopods and fishes. The diets of E. spinax and G. melastomus at the top of the bank showed a high dietary overlap of euphausiids, which represented the main prey taxa for both species. Euphausiids declined in abundance with depth which was reflected in the diet of G. melastomus. The cluster analysis of prey affinities among hauls depicted two major groups, corresponding to the two different habitats (top of the bank and inner basin). Redundancy analysis also indicated top–basin segregation, with euphausiids representing the main prey taxa at the top of the bank and bathypelagic shrimps in the inner basin. Euphausiids and Micromesistius poutassou were key prey within the Le Danois Bank ecosystem since they were positively selected by the three deep-sea shark species. These results show that the feeding ecology of these predators in Le Danois Bank ecosystem is highly influenced by depth-related variables, as a result of changes in prey availability. Overall results were analysed in relation to the deep-sea Le Danois ecosystem structure and functioning. [ABSTRACT FROM AUTHOR]

Abstract: A visceral excitatory neuropeptide with a molecular weight of 1563Da was isolated from the brain extracts of cloudy dogfish (Scyliorhinus torazame) discarded as a fishery by-product. Fish hindgut was employed to carry out physiological assay for its visceral excitation. During consecutive purification using C18 cartridge and high-performance liquid chromatography (HPLC), a neuropeptide (DF-2) was isolated from neuronal cell extracts of dogfish brain tissue and clearly exhibited potential to exert visceral excitatory effect on hindgut of dogfish. The primary structure of DF-2 established by ESI-Q-TOF tandem mass was LESLVYEQLWPWamide. The results of database search provided evidence for this peptide sequence to be novel. In visceral excitatory assay using myography, the threshold concentration of DF-2 required for the changes in spontaneous contraction of cloudy dogfish hindgut was found to be 10−6 M. Therefore, this study suggests that DF-2 isolated from brain of elasmobranches could be one of the sequences, which regulates spontaneous visceral contractions in dogfish digestive duct. [Copyright &y& Elsevier]

Hypoxia and increased temperature alter venous blood pressures in teleosts through active changes in venous tone. Elasmobranchs possess a capacious venous system but have limited adrenergic vascular innervation and subambient central venous pressure (Pcv). In this study, we explored venous hemodynamic responses to acute temperature increase and moderate (6.9 kPa) and severe (2.5 kPa) hypoxia in the dogfish (Squalus acanthias). Normoxic dogfish at 10°C had a Pcv between -0.08 and -0.04 kPa and a mean circulatory filling pressure of -0.12 kPa. At 16°C, heart rate (ƒH), cardiac output (Q), and increased but Pmef and plasma epinephrine and norepinephrine levels were unchanged. In contrast, moderate and severe hypoxia increased and decreased Q aid stroke volume (Vs). ƒH decreased in severe hypoxia, whereas Pmef was unaffected despite elevated catecholamine levels. Atropine abolished hypoxic reductions in Q, Vs, and ƒH, but Pcv still increased. In contrast to the response in teleosts, this study on dogfish suggests that venous capacitance changes associated with warming and hypoxia are minimal and likely not mediated by circulating catecholamines. Thus hemodynamic status of the capacious elasmobranch venous circulation is potentially regulated by blood volume shifts from passive flow-mediated events and possibly through myogenie mechanisms. [ABSTRACT FROM AUTHOR]

Monomethylmercury (MeHg+and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules, but the actual identities of these target biomolecules remain unknown. While binding with glutathione acts as a detoxification mechanism for MeHg, binding with L-cysteine is thought to be the main pathway of MeHg transport across the blood–brain barrier. Here we report a HPLC-ICP-MS method that is capable of separating and analyzing MeHg-cysteine complexes (MeHgCys; charges are neglected for simplicity) and MeHg-glutathione complexes (MeHgGlu), as well as MeHgX (X = H2O, OH−, or Cl−) and inorganic HgX, with detection limits at the sub-micromolar levels. The method was successfully applied for the determination of MeHg speciation in a dogfish muscle sample after enzymatic hydrolysis with trypsin, and provided the first analytical evidence for the presence and dominance of MeHgCys in fish muscle. [ABSTRACT FROM AUTHOR]

Tallack, S. M. L., and Mandelman, J. W. 2009. Do rare-earth metals deter spiny dogfish? A feasibility study on the use of electropositive “mischmetal” to reduce the bycatch of Squalus acanthias by hook gear in the Gulf of Maine. – ICES Journal of Marine Science, 66: 315–322.Catches of spiny dogfish (Squalus acanthias) are considered by commercial and recreational fishers to be unacceptably high during summer and autumn in the Gulf of Maine off the northeast coast of the USA. Consequently, there is interest in finding a dogfish deterrent for application in various fishing gears. Field studies tested triangular slices of the rare-earth metal cerium/lanthanide alloy (“mischmetal”) incorporated into longlines and rod-and-reel gear to assess its effectiveness in reducing dogfish catches. Treatment catches (mischmetal present) were compared with control (no mischmetal) catches. Laboratory studies provided video-taped, behavioural observations on the effects of alloys under variable levels of food deprivation and dogfish density. No significant reductions in dogfish catch were recorded for either rod and reel or longline, and in situ video footage verified persistent dogfish feeding behaviour, regardless of mischmetal presence. The laboratory trials found some evidence of avoidance behaviour in dogfish approaching treatment baits, but only with dogfish fed to satiation; no aversion to the material was observed after 2 and 4 d of food deprivation. Dogfish density had no effect on feeding behaviour in the laboratory. Overall, there is little evidence to suggest that mischmetal can significantly reduce catches of dogfish in hook gears in the Gulf of Maine. [ABSTRACT FROM PUBLISHER]

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 Cr) in the stomach. Sharks were fitted with indwelling stomach tubes for pretreatment with omeprazole (five doses of 5 mg omeprazole per kilogram over 48h) 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 CI- concentration of the chyme and altered the patterns of other ions, indicating inhibition of H+ and accompanying CI- 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 48h. Arterial blood CO2 pressure (PaCO2) and plasma ions were not substantially altered. These results indicate that elevated gastric H+ secretion (as HCI) 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. [ABSTRACT FROM AUTHOR]