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This study addresses the effect of various cooking approaches on total Hg (HgT) and total Se (SeT) contents in three predatory fish species. For this purpose, samples of swordfish, dogfish, and tuna from regular French (fish) markets were cooked by boiling, steaming, grilling, and frying, respectively. The levels of HgT and SeT in raw and cooked samples were determined by inductively coupled plasma-mass spectrometry. The data showed a significant increase in HgT and SeT levels between raw and cooked samples (33% of the samples for SeT and 67% for HgT) due to the water loss during the cooking. High intra-species variation related to HgT and SeT levels was found. Considering the level of exposure to HgT through fish consumption and taking also into account the possible protective effect of Se (expressed here via the Se/Hg molar ratio), the safest cooking approach corresponds to grilled swordfish, fried tuna, and steamed dogfish, which show Se/Hg molar ratios of (1.0 ± 0.5), (4.3 ± 4.2), and (1.0 ± 0.6), respectively. [ABSTRACT FROM AUTHOR]

Neurotrophins (NTFs) are structurally related neurotrophic factors essential for differentiation, survival, neurite outgrowth, and the plasticity of neurons. Abnormalities associated with neurotrophin-signaling (NTF-signaling) were associated with neuropathies, neurodegenerative disorders, and age-associated cognitive decline. Among the neurotrophins, brain-derived neurotrophic factor (BDNF) has the highest expression and is expressed in mammals by specific cells throughout the brain, with particularly high expression in the hippocampus and cerebral cortex. Whole genome sequencing efforts showed that NTF signaling evolved before the evolution of Vertebrates; thus, the shared ancestor of Protostomes, Cyclostomes, and Deuterostomes must have possessed a single ortholog of neurotrophins. After the first round of whole genome duplication that occurred in the last common ancestor of Vertebrates, the presence of two neurotrophins in Agnatha was hypothesized, while the monophyletic group of cartilaginous fishes, or Chondrichthyans, was situated immediately after the second whole genome duplication round that occurred in the last common ancestor of Gnathostomes. Chondrichthyans represent the outgroup of all other living jawed vertebrates (Gnathostomes) and the sister group of Osteichthyans (comprehensive of Actinopterygians and Sarcopterygians). We were able to first identify the second neurotrophin in Agnatha. Secondly, we expanded our analysis to include the Chondrichthyans, with their strategic phylogenetic position as the most basal extant Gnathostome taxon. Results from the phylogenetic analysis confirmed the presence of four neurotrophins in the Chondrichthyans, namely the orthologs of the four mammalian neurotrophins BDNF, NGF, NT-3, and NT-4. We then proceeded to study the expression of BDNF in the adult brain of the Chondrichthyan Scyliorhinus canicula. Our results showed that BDNF is highly expressed in the S. canicula brain and that its expression is highest in the Telencephalon, while the Mesencephalic and Diencephalic areas showed expression of BDNF in isolated and well-defined cell groups. NGF was expressed at much lower levels that could be detected by PCR but not by in situ hybridization. Our results warrant further investigations in Chondrichthyans to characterize the putative ancestral function of neurotrophins in Vertebrates. [ABSTRACT FROM AUTHOR]

This study addresses the effect of various cooking approaches on total Hg (HgT) and total Se (SeT) contents in three predatory fish species. For this purpose, samples of swordfish, dogfish, and tuna from regular French (fish) markets were cooked by boiling, steaming, grilling, and frying, respectively. The levels of HgT and SeT in raw and cooked samples were determined by inductively coupled plasma-mass spectrometry. The data showed a significant increase in HgT and SeT levels between raw and cooked samples (33% of the samples for SeT and 67% for HgT) due to the water loss during the cooking. High intra-species variation related to HgT and SeT levels was found. Considering the level of exposure to HgT through fish consumption and taking also into account the possible protective effect of Se (expressed here via the Se/Hg molar ratio), the safest cooking approach corresponds to grilled swordfish, fried tuna, and steamed dogfish, which show Se/Hg molar ratios of (1.0 ± 0.5), (4.3 ± 4.2), and (1.0 ± 0.6), respectively.

Adult neurogenesis is defined as the ability of specialized cells in the postnatal brain to produce new functional neurons and to integrate them into the already-established neuronal network. This phenomenon is common in all vertebrates and has been found to be extremely relevant for numerous processes, such as long-term memory, learning, and anxiety responses, and it has been also found to be involved in neurodegenerative and psychiatric disorders. Adult neurogenesis has been studied extensively in many vertebrate models, from fish to human, and observed also in the more basal cartilaginous fish, such as the lesser-spotted dogfish, Scyliorhinus canicula, but a detailed description of neurogenic niches in this animal is, to date, limited to the telencephalic areas. With this article, we aim to extend the characterization of the neurogenic niches of S. canicula in other main areas of the brain: we analyzed via double immunofluorescence sections of telencephalon, optic tectum, and cerebellum with markers of proliferation (PCNA) and mitosis (pH3) in conjunction with glial cell (S100β) and stem cell (Msi1) markers, to identify the actively proliferating cells inside the neurogenic niches. We also labeled adult postmitotic neurons (NeuN) to exclude double labeling with actively proliferating cells (PCNA). Lastly, we observed the presence of the autofluorescent aging marker, lipofuscin, contained inside lysosomes in neurogenic areas. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Biologia Marina y Oceanografía (RBMO) is the property of Universidad de Valparaiso, Facultad de Ciencias del Mar and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new flow batch (FB) system for chemical vapor generation (CVG) is proposed for mercury (Hg) determination in fish. An inductively coupled plasma mass spectrometer was used as a detector. Low-cost peristaltic mini pumps were used to propel the solutions and different configurations of FB systems (reactor/gas/liquid separator) were studied. The proposed configuration of the FB-CVG system allows good sensitivity, low limit of detection (LOD) and low consumption of reagents and sample solutions. In summary, only 1 mL of reductant, 1 mL of acid and 0.16 mL of sample are needed. The proposed method has good linearity, precision (better than 5 %), LOD of 0.008 μg g -1 and LOQ of 0.012 μg g -1 , and high sample throughput, allowing 90 measurements/h. The accuracy of the method was evaluated through the analysis of a certified reference material (DOLT-4 Dogfish Liver), whose result is in good agreement with certified value (t-test with 95 % confidence level) and the quantification limit meets current legislations, of 1.0 μg g -1 (Brazil) and 0.3 μg g -1  (EU). In addition, analyte recovery test was done, where Hg recovery was better than 95 %, demonstrating the good analytical performance of the method. To demonstrate the applicability of the method, five samples of fish tissue (muscle) were analyzed. The proposed FB-CVG system, in addition to being low cost, is robust and requires only the volume of reagents necessary for Hg vapor generation, producing a very low amount of waste. It can be concluded that the proposed system can be used for routine analysis for Hg determination in fish tissue. It is worth noting that with the appropriate adjustments, the system can be coupled to different Hg detectors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Deep-water dogfish (sharks) are caught on Australia's continental shelf as by-products to other deep-water species with revenue derived from fillets for human consumption and from the livers which are sold for their oil content. Deep-water dogfish utilise a large oil-rich liver for buoyancy, which may account for 20–25% of their body weight. An important constituent of certain dogfish liver oil is squalene, a highly unsaturated triterpenoid (C30H50) hydrocarbon which in some species can be up to 90% of the oil, though in the Australian commercial species it is typically around 50%. Squalene (and deep-water dogfish liver oil in general) has a long-standing high value in products, such as cosmetics and nutraceuticals. Manufacturers are increasingly required to demonstrate the sustainability of products, and this is integral to the importance of demonstrating product provenance. Australia's mid-slope deep-water dogfish fishery is recognised globally as well managed and sustainable; therefore, it is important to be able to distinguish products derived from these regions from other unregulated, unsustainable and cheaper sources in order to protect Australia's competitive advantages and ensure sustainability. In this study, we have sourced deep-water dogfish liver oil samples originating from Southeast Australia, New Zealand, India, Northeast Africa and the Arabian Sea. The squalene was isolated by commercial or laboratory processing. A compound-specific carbon stable isotope analysis of the derived squalene was then used to determine isotopic resolution and assign the likely origins of a variety of commonly available off-the-shelf nutraceuticals in Australian outlets. Squalene sourced and produced from Southeast Australian and New Zealand dogfish liver oils showed δ13C values in the range of −22.1 to −24.2‰, with all other squalene samples distinguishable at −19.9 to −20.7‰. Many of the off-the-shelf squalene products claiming to be of Australian origin showed δ13C values very distinct from the range of the genuine Southeast Australian- and New Zealand-produced squalene. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The release of water from the reservoir hypolimnion, lower concentration of oxygen and the anthropogenic regulation of the river flow, could affect the reproduction of fish, especially migratory species. However, little is known about the effects of these changes in water on non-migratory species. In this sense, the reproduction of Acestrohynchus lacustris was evaluated in two sections of São Francisco River, Minas Gerais, Brazil. Section 1, located immediately downstream from Três Marias Dam (18°09’31.65”S and 45°13’36.00”W) and section 2, located at the confluence of the São Francisco and the Abaeté Rivers (18°02’47.78”S and 45°10’57.95”W). For this, we obtained the physico-chemical parameters of water of each study section. Additionally, biometric data and biological indices of all specimens were measured. Fecundity and follicles diameters were measured in females. Temperature, dissolved oxygen and flow showed lower values in section 1. Fish captured in this section, had lower values of GSI in both sexes, and females presented decreased values of fecundity and follicles diameter. This species showed reproductive activity in the two sections analyzed, however, in section 1 where the temperature and dissolved oxygen presented significant lower values, the reproductive capacity of A. lacustris, was negatively affected.

Environmental pollution with heavy metals and other toxic elements can serve as a predisposing factor for a various type of human diseases. Their accumulation in aquatic organisms used for human consumption increases the risk for daily intake of low doses of heavy metals. The Black Sea spiny dog (Squalus acanthias, Linnaeus 1758) is a cartilaginous fish predator belonging to the spiny shark family. This demersal fish belongs to the common monitoring species in Bulgaria and Romania in terms of pollution of the Black Sea. In this regard, the aim of the present study was to determine the concentrations of As, Pb, Cd, Hg, Mn, Zn and Al in shark meat samples, caught from our northern Black Sea coast (Varna region). The element with the highest concentration was arsenic. Mercury levels have been found to be above the permissible levels set out in European and national legislation, which poses a potential health hazard risk for the consumers. [ABSTRACT FROM AUTHOR]

The few works on audition in sharks and rays concern only adult specimens. We report the hearing abilities in the dogfish Scyliorhinus canicula at different stages, from embryos that still have their yolk sac inside their egg, to juveniles. Hearing development corresponds to an increase in the frequency range from 100−300 Hz in early pre‐hatching stages to 100–600 Hz in juveniles. Modifications in hearing abilities correspond to the development of the brain, the increase of the volume of the membranous labyrinth, the growth of the sensory epithelium, and the development of stereocilia in addition to kinocilium before hatching. This work offers solid insights into the development of hearing abilities that usually can only be inferred from the anatomy of vertebrates or after birth/hatching. It shows also that shark can be sensitive to background noise during development. [ABSTRACT FROM AUTHOR]

Development of artificial production of glass eels still presents many problems to be solved. What and how to feed larvae is one of the most crucial problems for commercial mass production of glass eels. We evaluated a new liquid-type diet and feeding method against the conventional slurry-type diet by comparing the growth and survival of larvae in triplicate for 27 days after hatching. Larvae were fed by immersion in a liquid-type diet that was a 1.5 times dilution of the conventional slurry-type diet based on dogfish yolk spread over the bottom of the rearing tank. Larvae took more and denser liquid-type food in the intestine than the conventional slurry-type diet. Survival rates at 3 weeks after first feeding were about 90% in most experimental groups (5 groups) except one of three slurry-type diet groups (about 70%). Growth rates were 1.35 times higher in liquid-type diet groups (0.27 mm/day at 27 dph) than in conventional slurry-type diet groups (0.20 mm/day). These results suggest that the immersion feeding method in conjunction with the liquid-type diet has the potential to enable large scale production of glass eels by ensuring high growth and survival. [ABSTRACT FROM AUTHOR]

The last-decade changes in the Black Sea ecosystem have contributed to the deterioration of the structural and functional components of the marine ecosystem (Maximov V. et al., 2014, 2018). For most fish species on the Romanian seaside, the formation of fish aggregations and the availability of fish forfishing are strongly influenced by the variation in environmental conditions. Fisheries resource management is an integrated process of gathering information, analyzing, planning, consulting, decisionmaking, allocating resources, and formulating and implementing regulations or rules governing fisheries to ensure the continuity of resource productivity and revenue and other objectives. This paper presents the results obtained in the pelagic expeditions (spring and autumn season) realized in 2018. Data and information regarding the biomass and abundance for the species sprat, picked dogfish and jellyfish are presented. [ABSTRACT FROM AUTHOR]

Technological advances have enabled the expansion of ocean exploration to include the deep ocean, providing new species observations. Here, the authors present two new observations, captured by deep-sea cameras, of the sleeper shark Somniosus cf. pacificus from the Solomon Islands and Palau. This presents the first observation of S. cf. pacificus in the western Pacific tropics and extends its range about 2000 nautical miles south. The observations presented here provide much-needed information on the range of this species which can help guide future management and conservation actions., (© 2023 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Dogfish sharks of the genus Squalus are small, deep-water sharks with a slow rate of molecular evolution that has led to their designation as a series of species complexes, with low between-species diversity relative to other taxa. The largest of these complexes is named for the Shortspine spurdog (Squalus mitsukurii Jordan & Snyder), a medium-sized dogfish shark common to warm upper slope and seamount habitats, with a putative circumglobal distribution that has come under investigation recently due to geographic variation in morphology and genetic diversity. The Hawaiian population of Squalus mitsukurii was examined using both morphological and molecular analyses, putting this group in an evolutionary context with animals from the type population in Japan and closely-related congeners. External morphology differs significantly between the Hawaiian and Japanese S. mitsukurii, especially in dorsal fin size and relative interdorsal length, and molecular analysis of 1,311 base pairs of the mitochondrial genes ND2 and COI show significant, species-level divergence on par with other taxonomic studies of this genus. The dogfish shark in Hawaii represents a new species in the genus, and the name Squalus hawaiiensis, the Hawaiian spurdog, is designated after the type location. [ABSTRACT FROM AUTHOR]

This study examines the diet of lesser spotted dogfish Scyliorhinus canicula, one of the most ubiquitous predators of European coastal waters. This species is of increasing ecological significance as other large predatory fish decline as it has known interactions with fisheries. Scyliorhinus canicula diet was investigated in Irish coastal waters during June and July 2014 using both stomach‐content analysis and δ13C and δ15N stable‐isotope ratios. Prey contribution to the diet from dual stable‐isotope data was estimated using Bayesian mixing models. It was found that only stable‐isotope analysis provided a time‐integrated picture of the diet of S. canicula and allowed for a new estimation of their trophic position. Trophic positions from stomach‐content analysis within the present study and previous studies were found to be higher than revealed by isotopes. Stomach‐content analysis could not reveal the importance of soft‐bodied animals in the diet of these fish, however this approach remains a valuable tool to understand the potential prey spectrum in advance of isotope analysis and allows for a better resolution down to species level. The results highlight a greater variety in the diet of this important predator and the benefit of taking a multidisciplinary approach in dietary studies. [ABSTRACT FROM AUTHOR]

Ethyl acetate extracts of seaweeds were chromatographically fractionated to yield 14-methyl pentyl tetrahydro-8-hydroxy-10-methylnaphthalene–8-carboxylate ( 1 ) and tetrahydro-4-isopropyl-9-(9, 14-dimethyldec-9-enyl)-pyran-1-one ( 2 ) from Sargassum ilicifolium , whereas Padina gymnospora afforded dihydro-2-(10-(hydroxymethyl)-7,15-dimethyl-9-oxoundec-11-enyl)-2-methyl-2 H -pyran-1(4 H )-one ( 3 ) and 1-(decahydro-1-hydroxy-7-methyl-8-vinylnaphthalen-2-yl)ethanone ( 4 ) as major constituents. Compound 1 displayed significantly higher antioxidant activity (IC 50  < 1 mg/mL, p < 0.05) comparable to other analogues (IC 50  > 1 mg/mL). The C 20-22 polyunsaturated fatty acid (C 20-22 PUFA) concentrate (CFA) prepared from the deep-sea dogfish liver oil was added with the studied compounds and physiochemical properties and fatty acid composition during an accelerated storage were evaluated. No significant reduction in C 20-22 PUFAs (∼6%) in the CFA treated with 1 as compared to that with the control (∼35%) was recorded. A greater induction time was observed for the CFA supplemented with 1 (6.8 h) than other compounds (≤6 h) and control (∼1.6 h), maintaining the oxidation indices of the CFA within desirable limits. [ABSTRACT FROM AUTHOR]

Comparative Anatomy deals with the study of the ontogenetic and phylogenetic changes of the vertebrates, requiring complementing the theoretical aspects with the observation of structures in specimens belonging to different taxonomic groups. The aim of the present study was to test the injection of silicone at room temperature in organs and trunk sections of Mustelus schmitti as an alternative to the plastination technique. Samples consisted in brain, eyes, heart, proximal end of the ventral aorta, digestive tract, spleen, pancreas, kidneys, testis and cross body section at a pre-caudal level. Material was fixed with formalin (10-5%), dehydrated with growing concentrations of isopropyl (30% - 50% - 70% - 90% - 100% - 100%), impregnated with diluted commercial silicone and cured at room temperature. The whole process took 66 days. The brain was the unique organ that could not undergo the complete procedure because it did not resist the injection of silicone. The other pieces resulted in materials that characterised by being off-colour, dry, semi-flexible, lightweight, odourless, and non-toxic. They showed no signs of fungal colonization or bacterial degradation after two years of being obtained. Shrinkage was observed, which ranged among 2-25% for total length, and from 5-26% for maximum width (mean values: 14 and 15%, respectively), being testicle the organ that suffered greater shrinkage in both dimensions. The degree of contraction in length and width for each of the samples was generally similar (difference £ 3%), indicating that not striking deformation occurred. Deformation was observed only for the trunk section, eye, stomach, pancreas and valvular intestine. The technique did not affect the morphology of the structures, allowing the correct visualization of all the basic features required to recognise them. We conclude that this simple and economic method is an adequate alternative to be implemented for the conservation of small-size materials with educational purposes in Comparative Anatomy courses. [ABSTRACT FROM AUTHOR]

Abstract: The liver oil of deep‐sea dogfish, Centrophorus squamosus, was extracted by different physical methods and refined by sequential processes of degumming, neutralization, decolorization, and deodorization. Phosphoric acid effectively eliminated the mucilaginous substances in crude oil to result in triglycerides with permissible contents of peroxides, unesterified fatty acids, volatile compounds, thiobarbituric acid reactive species, and total oxidation values. A synergistic combination of activated charcoal and Fuller's earth could effectively bleach the crude deep‐sea dogfish liver oil (CDLO) for greater clarity and acceptable color characteristics. The adverse odors in the crude oil were eliminated by acetic acid treatment and vacuum deodorization. This study shows that the multistep refining process of CDLO significantly enhances the composition of C20–22 n‐3 polyunsaturated fatty acids, with the removal of the components responsible for the undesirable physicochemical characteristics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

1. Conservation and management of shark populations is increasingly becoming important in many marine regions, since there is a growing body of evidence showing that several species are threatened and continuing to decline because of unregulated fishing. Quantifying the extent of sharks' decline, the risk of species extinction, and the consequences for marine ecosystems have been challenging and controversial, mostly due to data limitations. 2. In this study, more than one century of multiple-sources of bibliographic records on presence and frequency of occurrence of three species of commercial sharks, the smooth-hounds Mustelus spp., in the Mediterranean Sea were compiled and analysed. Generalized additive models for location, scale and shape (GAMLSS) were used to estimate the rate of change of two of these species, Mustelus mustelus and Mustelus punctulatus, in four Mediterranean regions. 3. Model results showed that smooth-hounds have declined by 80-90% since the beginning of last century to almost disappear in a large part of their original distributional range during the 1980s and 1990s. 4. Based on modelling results, a revision of the current International Union for Conservation of Nature classification of Mediterranean smooth-hounds would be advisable along with the application of urgent conservation measures. [ABSTRACT FROM AUTHOR]

The present study elucidated the length structure and habitat segregation of North Pacific spiny dogfish (SPD) Squalus suckleyi in the Tsugaru Strait of northern Japan. Length-frequency distributions using kernel density estimation were determined for SPD captured by the bottom longline fishery landed at Minmaya from 1999 to 2011 and at Ohma from 2007 to 2011. Length-frequency distributions significantly differed between landings at the two ports; SPD at Minmaya were on average larger (65-85 cm precaudal length: PCL) than at Ohma (55-75 cm PCL). This difference is evidence of the length-based spatial segregation of the SPD. The seasonal landing pattern of the SPD was also different between the two ports. The SPD landed at Minmaya were largest during February-June and SPD < 75 cm PCL were caught at Ohma throughout the year. This different landing pattern was related to seasonal differences in bottom-layer water temperatures between the two fishing grounds. Females were thought to be dominant at Minmaya, whereas males dominated in most of the catches at Ohma. These results suggest spatial patterns of sexual segregation for this species in the Tsugaru Strait and require elucidation of the SPD stock condition at Minmaya and Ohma. [ABSTRACT FROM AUTHOR]

The North Pacific spiny dogfish (SPD), Squalus suckleyi, is a commercially exploited shark species that plays an important role in the ecosystem. To elucidate the distribution of the SPD in the North Pacific and to evaluate the effects of sea surface temperature (SST) and prey availability on its distribution, we estimated the probability of SPD presence using a generalized additive model with a binomial error distribution from SPD presence/absence data on 14,824 operations in fisheryindependent gillnet surveys between 1972 and 2011. The habitat model was structured in the east and west to reflect differences in the North Pacific oceanic environments. In the east, a higher probability of SPD presence was identified along the coast from the eastern Gulf of Alaska to Queen Charlotte Sound. In the west, it was identified around northern Japan. The estimated distribution was continuous between the two areas, whereas the probability of SPD presence was relatively low. Although the probability of SPD presence was higher at SSTs between 6°C and 12°C, the SST at the peak probability of SPD presence differed between the west and east. The prey species, Japanese sardine, Sardinops melanostictus, and walleye pollock, Gadus chalcogrammus, in the west and boreal clubhook squid, Onychoteuthis borealijaponica, in the east significantly affected the probability of SPD presence, which was higher if the prey species co-existed with SPD. Therefore, SPD might adapt their distribution to that of available prey species. SPD stock assessment and management in these two important areas are required for its sustainable utilization. [ABSTRACT FROM AUTHOR]

The Smallfin Gulper Shark Centrophorus moluccensis is reported for the first time from the Andaman & Nicobar waters of the Indian EEZ. A male specimen of 785mm total length and weighing 2.34kg was landed by a motorized longliner at Burmanallah, South Andaman District. The specimen was caught off Chidiyatapu, South Andaman at a depth of 250m. A detailed morphological description of the specimen and comparison with previous literature is provided. [ABSTRACT FROM AUTHOR]

The long-snouted African spurdog Squalus bassi sp. nov. is described based on material collected from the outer shelf and upper continental slope off South Africa and Mozambique. Squalus bassi shares with S. mitsukurii, S. montalbani, S. chloroculus, S. grahami, S. griffini, S. edmundsi, S. quasimodo and S. lobularis a large snout with prenarial length greater than distance between nostrils and upper labial furrows, dermal denticles tricuspidate and rhomboid and elevated number of vertebrae. Squalus bassi can be distinguished from all its congeners by a combination of body and fin colouration, external morphometrics, vertebral counts and shape of dermal denticles. Similar long-snouted congeners from the Indo-Pacific region, including S. montalbani, S. edmundsi and S. lalannei are compared in detail with the new species. This new species has been misidentified as the Japanese S. mitsukurii and the Mediterranean S. blainvillei due to the lack of comparative morphological analyses. The validity of the nominal species S. mitsukurii in the south-eastern Atlantic Ocean and western Indian Ocean is also clarified herein, indicating it has a more restricted geographical distribution in the North Pacific Ocean. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The alpha taxonomy of the globally distributed shark genus Squalus has been under intense investigation recently, and many new species have been described over the last decade. However, taxonomic uncertainty remains about several taxa. Without consistent nomenclature and the ability to reliably distinguish between the different Squalus species, basic data collection, downstream conservation and management efforts are seriously compromised. To aid in clarifying the taxonomic status of Squalus species in the eastern Atlantic and Mediterranean, we assessed species diversity at the molecular level and evaluated the consistency in species identification in the region. Samples from all nominal Squalus species recognized in the above regions were collected in an international effort and sequenced for regions of the mitochondrial COI and ND2 genes. These data were further analysed alongside publicly available sequences, including 19 of the 26 Squalus species globally recognized, to compare the regional genus-level diversity with that found elsewhere. Our results confirm inconsistent species identification in the eastern Atlantic and Mediterranean Squalus, particularly concerning S. blainville and S. megalops, and reinforce the need to revise the status of S. megalops and S. mitsukurii as they may include several distinct species distributed around the world. The status of S. blainville is also discussed in the light of the current findings and its problematic taxonomic history. [ABSTRACT FROM AUTHOR]

Elasmobranchs (sharks, skates, and rays) are a primarily carnivorous group of fish, consuming few carbohydrates. Further, they tend to exhibit delayed responses to glucose and insulin administration in vivo relative to mammals, leading to a presumption of glucose-intolerance. To investigate the glucoregulatory capabilities of the spiny dogfish ( Squalus suckleyi ), plasma glucose concentration, muscle and liver glycogen content, and glucose transporter ( glut1 and 4 ) mRNA levels were measured following intra-arterial administration of bovine insulin (10 ng kg −1 ) or an approximate doubling of fasting plasma glucose concentration. Within 6 h, following glucose administration, approximately half of the introduced glucose load had been cleared, with control levels being restored by 24 h post-injection. It was determined that plasma clearance was due in part to increased uptake by the tissues as muscle and liver glycogen content increased significantly, correlating with an upregulation of glut mRNA levels. Following administration of bovine insulin, plasma glucose steadily decreased through 18 h before returning toward control levels. Observed decreases in plasma glucose following insulin injection were, however, relatively minor, and no increases in tissue glycogen content were observed. glut4 and glycogen synthase mRNA levels did significantly increase in the muscle in response to insulin, but no changes occurred in the liver. The responses observed mimic what occurs in mammals and teleosts, thus suggesting a conserved mechanism for glucose homeostasis in vertebrates and a high degree of glucose tolerance in these predominantly carnivorous fish. [ABSTRACT FROM AUTHOR]

Proleptus obtusus Dujardin, 1845 is the most common parasite infecting the gut of the lesser spotted dogfish (Scyliorhinus canicula, Linnaeus). This nematode is trophically transmitted from an intermediate crustacean host to the definitive elasmobranch host. Sexual and age-related differences in habitat occupancy and feeding behaviour of the lesser spotted dogfish make this parasite-host dyad ideal for testing which aspects of host biology influence parasite transmission. Here, the relationship between P. obtusus burden and host condition, sex and age were investigated in lesser spotted dogfish captured in the Northeast Atlantic. Prevalence of P. obtusus was of 94.8% with a mean abundance of 23.3 worms per host. Our results indicate that parasite burden is best explained by the interaction between ontogenetic differences in foraging behaviour of the lesser spotted dogfish and seasonal differences in prey availability. [ABSTRACT FROM AUTHOR]

There is a need to better understand the survivorship of discarded fishes, both for commercial stocks and species of conservation concern. Within European waters, the landing obligations that are currently being phased in as part of the European Union's reformed common fisheries policy means that an increasing number of fish stocks, with certain exceptions, should not be discarded unless it can be demonstrated that there is a high probability of survival. This study reviews the various approaches that have been used to examine the discard survival of elasmobranchs, both in terms of at-vessel mortality ( AVM) and post-release mortality ( PRM), with relevant findings summarized for both the main types of fishing gear used and by taxonomic group. Discard survival varies with a range of biological attributes (species, size, sex and mode of gill ventilation) as well as the range of factors associated with capture ( e.g. gear type, soak time, catch mass and composition, handling practices and the degree of exposure to air and any associated change in ambient temperature). In general, demersal species with buccal-pump ventilation have a higher survival than obligate ram ventilators. Several studies have indicated that females may have a higher survival than males. Certain taxa (including hammerhead sharks Sphyrna spp. and thresher sharks Alopias spp.) may be particularly prone to higher rates of mortality when caught. [ABSTRACT FROM AUTHOR]

Objective: To determine the pharmacokinetics of robenacoxib after a single intramuscular dose (4.0 mg/kg) in smooth dogfish (Mustelus canis)., Animals: 8 healthy adult male smooth dogfish in human care within the same habitat., Methods: All sharks received a single intramuscular dose of robenacoxib (4.0 mg/kg) in the right caudolateral epaxial musculature. Blood samples were collected under manual restraint from the ventral tail vessel at 30 minutes, 1 hour, 2 hours, 4 hours, 8 hours, and 24 hours after drug administration. Plasma drug concentrations were determined by HPLC followed by noncompartmental pharmacokinetic analysis of the data., Results: A maximum plasma concentration of 1.24 µg/mL was reached at a mean time of 30 minutes following robenacoxib administration with a plasma elimination half-life of 3.79 hours. Plasma concentrations did not fall below the lower limit of quantification (0.1 µg/mL) at the time points sampled in this study., Clinical Relevance: Intramuscular administration of a single dose (4.0 mg/kg) of robenacoxib in smooth dogfish resulted in rapid absorption to a maximum concentration at approximately 30 minutes after administration and persisted above levels considered to be therapeutic in domestic species for at least 8 hours.

This study's objective was to investigate obtaining high-resolution micro-computed tomography (CT) imaging of the injected arterial circulation of the brains of the dogfish (Squalus acanthias), American bullfrog (Rana catesbeiana), and green iguana (Iguana iguana). No micro-CT images of the arterial morphology of the brains of these vertebrates were previously published. Micro-CT imaging was performed on brains that had the cerebral arterial and ventricular systems injected with a radiopaque barium-gelatin compound in the early 1970s. These specimens were dissected and placed in a preservative fluid for 35 years, until imaged with micro-CT. The obtained micro-CT images were processed with a software program that provided 3D rotational motion rendering, and sequential display of 2D renderings of the micro-CT data. The anatomic information provided by the high-resolution micro-CT is not reproducible by any other radiopaque contrast currently available, without tissue removal corrosion, and enhanced the dissection information. The digital videos of the micro-CT 3D rotational motion rendering and sequential display of 2D renderings of the dogfish, bullfrog, and green iguana, demonstrate the extent of the arterial network within the brain, the arterial segments obscured by overlying structures such as nerves, and identified in the bullfrog the venous cerebral circulation resulting from the centrifugal leptomeningeal arterial capillaries. The rotational 3D images separated superimposed arterial structures, and the sequential display of the 2D renderings clarifies the relationship of cut or overlapped arterial branches. Comparing the brain and arterial morphology of the dogfish, bullfrog, and green iguana demonstrates some of the evolutionary modifications in these vertebrates., (© 2022 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

A solitary Anelasma squalicola specimen was collected from the cloaca of a Greenland shark (Somniosus microcephalus), the first time this association has been recorded. The specimen's identity was confirmed through morphological and genetic assessment (mitochondrial markers: COI and control region). A. squalicola is a species typically associated with deep-sea lantern sharks (Etmopteridae) and, until the present observation, had never been observed at a sexually mature size in the absence of a mating partner. Given the reported negative effects of this parasite on its hosts, monitoring Greenland sharks for additional cases is recommended., (© 2023 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)