Displaying publications 1 - 20 of 27 in total

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  1. A new genus and two new species of trypanorhynch cestodes (Tentaculariidae) from the sharksCarcharhinus sorrah(Müller & Henle) andSphyrna lewini(Griffith & Smith) from off the coasts of Malaysia and Mexico
    Palm HW, Morales-Ávila JR, Galván-Magaña F, Haseli M
    Syst Parasitol, 2020 04;97(2):133-142.
    PMID: 32065375 DOI: 10.1007/s11230-020-09904-w
    Two new tentaculariid species were found infecting carcharhiniform sharks from off the coasts of Malaysian Borneo and the southwestern coast of the Baja California Sur, Mexico. Both new species exhibit a homeoacanthous heteromorphous basal and a homeoacanthous homeomorphous metabasal armature. Since this hook arrangement is unique within the tentaculariids and the taxonomy in this group deeply depends on the tentacular armature, Reimeriella n. g. is erected to accommodate R. varioacantha n. sp. ex Carcharhinus sorrah (Müller & Henle) and R. mexicoensis n. sp. ex Sphyrna lewini (Griffith & Smith). Unlike R. mexicoensis n. sp., R. varioacantha n. sp. has a pars bothrialis not overlapping the pars bulbosa and the number of testes is higher. Reimeriella mexicoensis n. sp. possesses very large uncinate to falcate hooks in the basal armature, while in R. varioacantha n. sp. these hooks are almost the same in size as the remaining hooks in both the basal and metabasal armature. The latter species is the first tentaculariid species where the metabasal armature very closely resembles an eutetrarhynchid with a heteroacanthous typical homeomorphous metabasal armature and a high number of spiniform hooks per half spiral row (10-11 vs 6-7 in R. mexicoensis n. sp.) in the metabasal and apical armature. This pattern provides further morphological evidence for the close relationship of the Eutetrarhynchoidea and the Tentacularioidea. Reimeriella varioacantha n. sp. enriches the trypanorhynch fauna from off the coast of Malaysian Borneo while R. mexicoensis n. sp. is a novel record of a tentaculariid trypanorhynch from the Mexican Pacific.
    Matched MeSH terms: Sharks/parasitology*
  2. Ancipirhynchus afossalis n. g., n. sp. (Trypanorhyncha: Otobothriidae), from two species of sharks off Indonesian and Malaysian Borneo
    Schaeffner BC, Gasser RB, Beveridge I
    Syst Parasitol, 2011 Sep;80(1):1-15.
    PMID: 21805386 DOI: 10.1007/s11230-011-9309-8
    A new genus of trypanorhynch cestode is described from two species of sharks, the sliteye shark Loxodon macrorhinus Müller & Henle and the straight-tooth weasel shark Paragaleus tengi (Chen) collected in the Makassar Strait (off Indonesian Borneo) and Sulu Sea (off Malaysian Borneo). Ancipirhynchus afossalis n. g., n. sp. possesses two bothria and a heteroacanthous, heteromorphous tentacular armature with three distinctive files of hooks on the external tentacle surface but lacks prebulbar organs and gland cells within the tentacular bulbs. The hook arrangement of alternating files on the external surface of the tentacle resembles that seen in the superfamily Otobothrioidea Dollfus, 1942 in the genus Fossobothrium Beveridge & Campbell, 2005. However, the new species lacks the defining characteristic of this group, i.e. the paired bothrial pits. A Bayesian inference (BI) analysis of 37 LSU sequences of trypanorhynchs from three superfamilies provided evidence supporting the taxonomic placement of Ancipirhynchus afossalis n. g., n. sp. within the Otobothrioidea.
    Matched MeSH terms: Sharks/parasitology*
  3. Assessment of metallic trace elements in the muscles and fins of four landed elasmobranchs from Kuala Terengganu Waters, Malaysia
    Ong MC, Gan SL
    Mar Pollut Bull, 2017 Nov 30;124(2):1001-1005.
    PMID: 28807418 DOI: 10.1016/j.marpolbul.2017.08.019
    A study had been carried out to determine Cu, Zn, Cd, Hg and Pb concentrations in the muscle and fins of four elasmobranchs species namely spot-tail sharks, milk sharks, whitespotted bamboo sharks and whitespotted guitarfish from Pulau Kambing LKIM Fishery Complex, Kuala Terengganu, Malaysia. Zinc level was found to have the highest concentration whereas Cd had the lowest concentration in both organs. By comparing both organs, metals concentrations in fins of all elasmobranchs species were higher than muscle. Result obtained was compared with the guidelines set by Malaysian Food Regulation and the provisional tolerable weekly intake was also determined. Current study recommends that the muscle of whitespotted bamboo shark from Kuala Terengganu Waters is likely not to be consumed due to it exceeded the allowable consumption guideline. Finding of this paper is very useful as it provides the baseline data on the pollution status of elasmobranchs in Kuala Terengganu Waters.
    Matched MeSH terms: Sharks
  4. Fulltext Brown banded bamboo shark (Chiloscyllium punctatum) shows high genetic diversity and differentiation in Malaysian waters
    Lim KC, Then AY, Wee AKS, Sade A, Rumpet R, Loh KH
    Sci Rep, 2021 Jul 21;11(1):14874.
    PMID: 34290296 DOI: 10.1038/s41598-021-94257-7
    The demersal brown banded bamboo shark Chiloscyllium punctatum is a major component of sharks landed in Malaysia. However, little is known about their population structure and the effect of high fishing pressure on these weak swimming sharks. Both mitochondrial DNA control region (1072 bp) and NADH dehydrogenase subunit 2 (1044 bp) were used to elucidate the genetic structure and connectivity of C. punctatum among five major areas within the Sundaland region. Our findings revealed (i) strong genetic structure with little present day mixing between the major areas, (ii) high intra-population genetic diversity with unique haplotypes, (iii) significant correlation between genetic differentiation and geographical distance coupled with detectable presence of fine scale geographical barriers (i.e. the South China Sea), (iv) historical directional gene flow from the east coast of Peninsular Malaysia towards the west coast and Borneo, and (v) no detectable genetic differentiation along the coastline of east Peninsular Malaysia. Genetic patterns inferred from the mitochondrial DNA loci were consistent with the strong coastal shelf association in this species, the presence of contemporary barriers shaped by benthic features, and limited current-driven egg dispersal. Fine scale population structure of C. punctatum highlights the need to improve genetic understanding for fishery management and conservation of other small-sized sharks.
    Matched MeSH terms: Sharks/genetics*
  5. Fulltext Checklist of the coral fish fauna of Xisha Islands, China
    Qiu S, Chen B, Du J, Loh KH, Liao J, Liu X, et al.
    Biodivers Data J, 2021;9:e63945.
    PMID: 33732033 DOI: 10.3897/BDJ.9.e63945
    Background: The Xisha Islands are composed of the Yongle Islands and the Xuande Islands in Hainan Province, China. It has one of the highest species diversity in the world and is also a typical oceanic distribution area of coral reefs globally. The ichthyofauna of the Xisha Islands were recorded by underwater visual census in May 2019 and July 2020. The survey data were combined with previous records of species into the checklist of the Xisha Islands presented herein. A total of 691 species, belonging to 24 orders and 97 families, was recorded. The major families were Labridae, Pomacentridae, Serranidae, Chaetodontidae, Hexanchidae, Lutjanidae, Scaridae, Gobiidae, Scorpaenidae and Carangidae. In this study, the Coral Fish iversity Index (CFDI) of six families (Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae and Acanthuridae) was 229, indicating 756 coral fishes. In terms of the IUCN Red List, one species is Critically Endangered (Glyphis gangeticus), six species are Endangered (Stegostoma fasciatum, Aetomylaeus maculatus, Aetomylaeus vespertilio, Epinephelus akaara, Cheilinusundulatus sp. and Xiphias gladius), 16 species are Vulnerable, and 13 species are Near Threatened in the Xisha Archipelago, so conservation should be strengthened in this area in the future.

    New information: One species is a new record for China (Dischistodus pseudochrysopoecilus) and 23 species are newly found in the Xisha Islands.

    Matched MeSH terms: Sharks
  6. Comparison of DNA profiling between fishes and pork meat using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) analysis
    Safiyyah Shahimi, Wan Sakeenah Wan Nazri, Aminah Abdullah, Norrakiah Abdullah Sani, Sahilah Abd. Mutalib
    Sains Malaysiana, 2018;47:1535-1540.
    Genomic DNA of 13 fish (n=13) species consist of four freshwater which were catfish (Clarias gariepinus), shark catfish (Pangasius larnaudii), tilapia (Oreochromis mossambicus), perch (Lates calcarifer) and nine marine species which were black pomfret (Parastromateus niger), anchovy (Stolephorus commersonii), mabong (Rastrelliger kanagurta), red snapper (Lutjanus erythropterus), herring (Chirocentrus dorab), ray fish (Himantura gerrardii), sardine (Decapterus macrosoma), mackerel (Euthynnus affinis) and tuna (Thunnus tuna) were differentiated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Seven endonucleases of AluI, BsaJI, HaeIII, HindIII, HinfI, MboI and MboII were examined for the ability to digest cyt b amplicon from each species. Genomic DNA of pork (Sus scrofa domestica) were differentiated from fishes by comparing the digestion patterns produced by similar amplified region and enzymes used. In the present study, it was demonstrated that fishes and pork DNA genome were successfully differentiated using all endonucleases except for HindIII. Thus, PCR-RFLP analysis was found useful for future pork DNA detection in fish products.
    Matched MeSH terms: Sharks
  7. Fulltext Cross-Cultural Validation of Mood Profile Clusters in a Sport and Exercise Context
    Quartiroli A, Parsons-Smith RL, Fogarty GJ, Kuan G, Terry PC
    Front Psychol, 2018;9:1949.
    PMID: 30356841 DOI: 10.3389/fpsyg.2018.01949
    Mood profiling has a long history in the field of sport and exercise. Several novel mood profile clusters were identified and described in the literature recently (Parsons-Smith et al., 2017). In the present study, we investigated whether the same clusters were evident in an Italian-language, sport and exercise context. The Italian Mood Scale (ITAMS; Quartiroli et al., 2017) was administered to 950 Italian-speaking sport participants (659 females, 284 males, 7 unspecified; age range = 16-63 year, M = 25.03, SD = 7.62) and seeded k-means clustering methodology applied to the responses. Six distinct mood profiles were identified, termed the iceberg, inverse iceberg, inverse Everest, shark fin, surface, and submerged profiles, which closely resembled those reported among English-speaking participants (Parsons-Smith et al., 2017). Significant differences were found in the distribution of specific mood profiles across gender and age groups. Findings supported the cross-cultural generalizability of the six mood profiles and offer new research avenues into their antecedents, correlates and behavioral consequences in Italian-language contexts.
    Matched MeSH terms: Sharks
  8. Fulltext Diagnostic and therapeutic potential of shark variable new antigen receptor (VNAR) single domain antibody
    Cheong WS, Leow CY, Abdul Majeed AB, Leow CH
    Int J Biol Macromol, 2020 Mar 15;147:369-375.
    PMID: 31926922 DOI: 10.1016/j.ijbiomac.2020.01.039
    Conventional monoclonal antibodies (mAbs) have been widely used in research and diagnostic applications due to their high affinity and specificity. However, multiple limitations, such as large size, complex structure and sensitivity to extreme ambient temperature potentially weaken the performance of mAbs in certain applications. To address this problem, the exploration of new antigen binders is extensively required in relation to improve the quality of current diagnostic platforms. In recent years, a new immunoglobulin-based protein, namely variable domain of new antigen receptor (VNAR) was discovered in sharks. Unlike conventional mAbs, several advantages of VNARs, include small size, better thermostability and peculiar paratope structure have attracted interest of researchers to further explore on it. This article aims to first present an overview of the shark VNARs and outline the characteristics as an outstanding new reagent for diagnostic and therapeutic applications.
    Matched MeSH terms: Sharks/immunology*
  9. Fulltext Discovery of a new mode of oviparous reproduction in sharks and its evolutionary implications
    Nakaya K, White WT, Ho HC
    Sci Rep, 2020 07 23;10(1):12280.
    PMID: 32703969 DOI: 10.1038/s41598-020-68923-1
    Two modes of oviparity are known in cartilaginous fishes, (1) single oviparity where one egg case is retained in an oviduct for a short period and then deposited, quickly followed by another egg case, and (2) multiple oviparity where multiple egg cases are retained in an oviduct for a substantial period and deposited later when the embryo has developed to a large size in each case. Sarawak swellshark Cephaloscyllium sarawakensis of the family Scyliorhinidae from the South China Sea performs a new mode of oviparity, which is named "sustained single oviparity", characterized by a lengthy retention of a single egg case in an oviduct until the embryo attains a sizable length. The resulting fecundity of the Sarawak swellshark within a season is quite low, but this disadvantage is balanced by smaller body, larger neonates and quicker maturation. The Sarawak swellshark is further uniquely characterized by having glassy transparent egg cases, and this is correlated with a vivid polka-dot pattern of the embryos. Five modes of lecithotrophic (yolk-dependent) reproduction, i.e. short single oviparity, sustained single oviparity, multiple oviparity, yolk-sac viviparity of single pregnancy and yolk-sac viviparity of multiple pregnancy were discussed from an evolutionary point of view.
    Matched MeSH terms: Sharks/anatomy & histology; Sharks/classification; Sharks/physiology*
  10. Exclusive predation of sea turtle hatchlings by juvenile blacktip reef sharks Carcharhinus melanopterus at a turtle nesting site in Malaysia
    Bashir Z, Abdullah MM, Ghaffar MA, Rusli MU
    J Fish Biol, 2020 Dec;97(6):1876-1879.
    PMID: 32951197 DOI: 10.1111/jfb.14550
    This study reports the discovery of the exclusive predation of sea turtle hatchlings by several juvenile blacktip reef sharks (Carcharhinus melanopterus) in Chagar Hutang bay on Redang Island, Malaysia, in the South China Sea. Three dead specimens of C. melanopterus were retrieved from ghost nets, and the entire digestive tracts of these sharks solely contained the partially digested bodies of sea turtle hatchlings, with no evidence of the remains of any other prey. Thus, juvenile C. melanopterus may opportunistically feed primarily on turtle hatchlings during times when hatchling abundance is high.
    Matched MeSH terms: Sharks
  11. Exploring shark VNAR antibody against infectious diseases using phage display technology
    Lim HT, Kok BH, Leow CY, Leow CH
    Fish Shellfish Immunol, 2023 Sep;140:108986.
    PMID: 37541634 DOI: 10.1016/j.fsi.2023.108986
    Antibody with high affinity and specificity to antigen has widely used as a tool to combat various diseases. The variable domain of immunoglobulin new antigen receptor (VNAR) naturally found in shark contains autonomous function as single-domain antibody. Due to its excellent characteristics, the small, non-complex, and highly stable have made shark VNAR can acquires the antigen-binding capability that might not be reached by conventional antibody. Phage display technology enables shark VNAR to be presented on the surface of phage, allowing the exploration of shark VNAR as an alternative antibody format to target antigens from various infectious diseases. The application of phage-displayed shark VNAR in antibody library and biopanning eventually leads to the discovery and isolation of antigen-specific VNARs with diagnostic and therapeutic potential towards infectious diseases. This review provides an overview of the shark VNAR antibody, the types of phage display technology with comparison to the other types of display system, as well as the application and case studies of phage-displayed shark VNAR antibodies against infectious diseases.
    Matched MeSH terms: Sharks*
  12. First report of echthrogaleus denticulatus (smith 1874) on the pelagic thresher shark (alopias pelagicus nakamura 1935) from indian EEZ of andaman sea
    Arun Kumar M, Swapnil S, Pradeep H
    Sains Malaysiana, 2017;46:1675-1678.
    The present study reports the occurrence of the pandarid parasite, Echthrogaleus denticulatus as an ectoparasite on the pelagic thresher shark (Alopias pelagicus) from the Indian EEZ of Andaman Sea. A total of 36 parasite specimens were found aggregated near the cloacal aperture of eight pelagic thresher sharks caught as bycatch by multifilament tuna longliner MFV Blue Marlin during July 2015 and February 2016 voyages in Andaman and Nicobar waters. This is the first report of ectoparasite from the Indian EEZ of the Andaman Sea.
    Matched MeSH terms: Sharks
  13. Global status and conservation potential of reef sharks
    MacNeil MA, Chapman DD, Heupel M, Simpfendorfer CA, Heithaus M, Meekan M, et al.
    Nature, 2020 07;583(7818):801-806.
    PMID: 32699418 DOI: 10.1038/s41586-020-2519-y
    Decades of overexploitation have devastated shark populations, leaving considerable doubt as to their ecological status1,2. Yet much of what is known about sharks has been inferred from catch records in industrial fisheries, whereas far less information is available about sharks that live in coastal habitats3. Here we address this knowledge gap using data from more than 15,000 standardized baited remote underwater video stations that were deployed on 371 reefs in 58 nations to estimate the conservation status of reef sharks globally. Our results reveal the profound impact that fishing has had on reef shark populations: we observed no sharks on almost 20% of the surveyed reefs. Reef sharks were almost completely absent from reefs in several nations, and shark depletion was strongly related to socio-economic conditions such as the size and proximity of the nearest market, poor governance and the density of the human population. However, opportunities for the conservation of reef sharks remain: shark sanctuaries, closed areas, catch limits and an absence of gillnets and longlines were associated with a substantially higher relative abundance of reef sharks. These results reveal several policy pathways for the restoration and management of reef shark populations, from direct top-down management of fishing to indirect improvement of governance conditions. Reef shark populations will only have a high chance of recovery by engaging key socio-economic aspects of tropical fisheries.
    Matched MeSH terms: Sharks/physiology*
  14. Half a century of rising extinction risk of coral reef sharks and rays
    Sherman CS, Simpfendorfer CA, Pacoureau N, Matsushiba JH, Yan HF, Walls RHL, et al.
    Nat Commun, 2023 Jan 17;14(1):15.
    PMID: 36650137 DOI: 10.1038/s41467-022-35091-x
    Sharks and rays are key functional components of coral reef ecosystems, yet many populations of a few species exhibit signs of depletion and local extinctions. The question is whether these declines forewarn of a global extinction crisis. We use IUCN Red List to quantify the status, trajectory, and threats to all coral reef sharks and rays worldwide. Here, we show that nearly two-thirds (59%) of the 134 coral-reef associated shark and ray species are threatened with extinction. Alongside marine mammals, sharks and rays are among the most threatened groups found on coral reefs. Overfishing is the main cause of elevated extinction risk, compounded by climate change and habitat degradation. Risk is greatest for species that are larger-bodied (less resilient and higher trophic level), widely distributed across several national jurisdictions (subject to a patchwork of management), and in nations with greater fishing pressure and weaker governance. Population declines have occurred over more than half a century, with greatest declines prior to 2005. Immediate action through local protections, combined with broad-scale fisheries management and Marine Protected Areas, is required to avoid extinctions and the loss of critical ecosystem function condemning reefs to a loss of shark and ray biodiversity and ecosystem services, limiting livelihoods and food security.
    Matched MeSH terms: Sharks*
  15. Labuan, Borneo, a new locality for the whale shark
    Herre AWCT
    Science, 1935 Mar 8;81(2097):253-4.
    PMID: 17829102 DOI: 10.1126/science.81.2097.253
    On March 29, 1934, while working at the office of Dr W. Birtwistle, director of fisheries for the Straits Settleents and Federated Malay States, at Singapore, the captain of a coasting vessel came in for information. He had with him the picture and dimensions of a very large fish which he had seen at Labuan a few days before. No one there knew the fish, but I recognized it at once as a fine typical example of Rhineodon typus, the whale shark. The specimen was 25 feet long. [First paragraph: http://science.sciencemag.org/content/81/2097/253]
    Matched MeSH terms: Sharks*
  16. Mode of attachment and lesions associated with trypanorhynch cestodes in the gastrointestinal tracts of two species of sharks collected from coastal waters of Borneo
    Borucinska JD, Caira JN
    J Fish Dis, 2006 Jul;29(7):395-407.
    PMID: 16866923
    Lesions associated with two species of tapeworms within the digestive tract of wild-caught specimens of the bull shark, Carcharhinus leucas, and the sicklefin weasel shark, Hemigaleus microstoma, from Malaysian Borneo are described. Portions of the glandular stomach and pyloric gut with parasites were removed and fixed in 10% formalin buffered in sea water. Whole mounts, histological sections of tissues with and without worms in situ, and scanning electron microscopy images of detached worms were examined. Both species of cestodes belonged to the trypanorhynch family Tentaculariidae. Heteronybelinia estigmena was found in large numbers parasitizing the pyloric gut of C. leucas; an unidentified tentaculariid was found in relatively small numbers in both the glandular stomach and pyloric gut of H. microstoma. Both species burrowed their scoleces deeply in the mucosa and attached via hooked tentacles and unciniform microtriches of the scolex. The lesions induced by the parasites were marked in both sharks and ranged from acute necrotizing to chronic granulomatous gastroenteritis. Regenerative hyperplasia and intestinal metaplasia of gastric epithelium were also present. The severity and character of pathology was causally linked to the intensity of infection, the attachment mode of the parasites, and to the anatomophysiological relationships within the gut of the host shark.
    Matched MeSH terms: Sharks/parasitology*
  17. Fulltext Molecular phylogeny of the bamboo sharks (Chiloscyllium spp.)
    Masstor NH, Samat A, Nor SM, Md-Zain BM
    Biomed Res Int, 2014;2014:213896.
    PMID: 25013766 DOI: 10.1155/2014/213896
    Chiloscyllium, commonly called bamboo shark, can be found inhabiting the waters of the Indo-West Pacific around East Asian countries such as Malaysia, Myanmar, Thailand, Singapore, and Indonesia. The International Union for Conservation of Nature (IUCN) Red List has categorized them as nearly threatened sharks out of their declining population status due to overexploitation. A molecular study was carried out to portray the systematic relationships within Chiloscyllium species using 12S rRNA and cytochrome b gene sequences. Maximum parsimony and Bayesian were used to reconstruct their phylogeny trees. A total of 381 bp sequences' lengths were successfully aligned in the 12S rRNA region, with 41 bp sites being parsimony-informative. In the cytochrome b region, a total of 1120 bp sites were aligned, with 352 parsimony-informative characters. All analyses yield phylogeny trees on which C. indicum has close relationships with C. plagiosum. C. punctatum is sister taxon to both C. indicum and C. plagiosum while C. griseum and C. hasseltii formed their own clade as sister taxa. These Chiloscyllium classifications can be supported by some morphological characters (lateral dermal ridges on the body, coloring patterns, and appearance of hypobranchials and basibranchial plate) that can clearly be used to differentiate each species.
    Matched MeSH terms: Sharks/classification; Sharks/genetics*
  18. Morfologi struktur halus organ deria-elektro (ampullae of lorenzini) ikan yu carcharhinus melanopterus, c. Limbatus dan chiloscyllium griseum
    M. Nor-Fazilla, A. Samat, A.G. Mazlan
    Sains Malaysiana, 2013;42:737-742.
    Satu penyelidikan telah dijalankan untuk mengesan struktur halus organ deria-elektro (Ampullae of Lorenzini) pada Carcharhinus melanopterus, C. limbatus dan Chiloscyllium griseum. Organ ini amat peka terhadap beberapa bentuk rangsangan terutamanya untuk mengesan kedudukan mangsa, penentuan arah dan mengawan. Di dalam makmal, suatu bahagian organ deria ini dipisahkan daripada lapisan dermis kepala ikan yu. Pemerhatian dan pengambilan imej struktur organ deria telah dibuat menggunakan mikroskop elektron imbasan (SEM). Imej-imej yang diperoleh jelas menunjukkan organ deria pada Carcharhinus melanopterus, C. limbatus dan Chiloscyllium griseum berbentuk ampulari terkumpul di dalam kluster. Saluran-saluran deria yang menghubungkan ampula dengan pori didapati mempunyai orientasi panjang dan susunan yang berbeza-beza pada spesies yang berlainan.
    Matched MeSH terms: Sharks
  19. Ocean warming and hypoxia affect embryonic growth, fitness and survival of small-spotted catsharks, Scyliorhinus canicula
    Musa SM, Ripley DM, Moritz T, Shiels HA
    J Fish Biol, 2020 Jul;97(1):257-264.
    PMID: 32383486 DOI: 10.1111/jfb.14370
    Elasmobranchs are key to a healthy marine ecosystem but are under threat from human activities, such as destructive fisheries and shark finning. Embryos of oviparous elasmobranchs may be further challenged during development by rising temperatures and falling dissolved oxygen concentrations in their intertidal environment. However, the impact of climate change on survival and growth of oviparous elasmobranchs is still poorly understood. Here, we investigate the effects of temperature and hypoxia on the growth and survival of small-spotted catshark (Scyliorhinus canicula) embryos by incubating eggs in normoxia 15°C, normoxia 20°C, hypoxia 15°C, or hypoxia 20°C. Incubation under the elevated temperature increased the embryonic growth rate, yolk consumption rate and Fulton's condition factor at hatching, whilst decreasing the total length and body mass of newly hatched sharks. Under low oxygen conditions (50% air saturation) the survival rate of S. canicula embryos dropped significantly and the temperature-induced increase in Fulton's condition factor was reversed. Together, these data demonstrate both the individual and compound effects of elevated temperature and hypoxia on the survival and growth during early ontogeny of a ubiquitous, coastal elasmobranch, S. canicula.
    Matched MeSH terms: Sharks/embryology*; Sharks/physiology*
  20. Fulltext Oviparous elasmobranch development inside the egg case in 7 key stages
    Musa SM, Czachur MV, Shiels HA
    PLoS One, 2018;13(11):e0206984.
    PMID: 30399186 DOI: 10.1371/journal.pone.0206984
    Embryological stages of oviparous elasmobranch during development can be difficult to identify, requiring magnification and/or fixation of an anaesthetized embryo. These restrictions are poorly suited for monitoring the development of living elasmobranchs inside their egg cases. There are two major aims of this study. The first was to observe elasmobranch embryonic development non-invasively and produce a non-invasive developmental key for identifying the life stages for an elasmobranch inside the egg case. To this end, 7 key developmental stages were identified for the greater spotted catshark, Scyliorhinus stellaris, and are provided here with diagrams from multiple perspectives to demonstrate the key features of each stage. The physiological and ecological relevance of each stage are discussed in terms of structure and function for embryonic survival in the harsh intertidal zone. Also discussed is the importance of the egg case membrane and the protective embryonic jelly. The second aim of the study was to understand the applicability of the 7 developmental stages from S. stellaris to other oviparous elasmobranchs. Thus, changes in embryonic body size and egg yolk volume at each stage were measured and compared with those of the closely related, lesser spotted catshark, Scyliorhinus canicula. We find nearly identical growth patterns and yolk consumption patterns in both species across the 7 developmental stages. Thus, although the 7 developmental stages have been constructed in reference to the greater spotted catshark, we suggest that it can be applied to other oviparous elasmobranch species with only minor modification.
    Matched MeSH terms: Sharks/embryology*
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