Dalatias Research Articles

A new Western North Atlantic Ocean kitefin shark (Squaliformes: Dalatiidae) from the Gulf of Mexico.

A new species of kitefin shark (Squaliformes; Dalatiidae) is described from the Gulf of Mexico (Western North Atlantic Ocean) based on five diagnostic features not seen on the only other known Mollisquama specimen, the holotype of Mollisquama parini Dolganov which was captured in the Eastern South Pacific Ocean. The new species, Mollisquama mississippiensis sp. nov., is distinguished from its congener by a putative pit organ located ventrally just posterior of the lower jaw margin center, photophores irregularly distributed along many areas of the body, 16 distinct ventral-abdominal photophore aggregations, and two differences associated with the dentition. Other potential distinguishing features are 10 fewer vertebrae than Mollisquama parini and six morphometric proportional differences that exceeded +/- 20% from the holotype.

Feeding habits of four sympatric sharks in two deep-water fishery areas of the western Mediterranean Sea

The study of the feeding ecology of marine predators is crucial to understanding their ecological roles and advancing our knowledge of marine ecosystem functioning, especially in highly human-impacted areas. Here, we examined the trophic ecology of three abundant demersal sharks, the velvet belly lantern shark Etmopterus spinax, the blackmouth catshark Galeus melastomus and the small-spotted catshark Scyliorhinus canicula, and the rare kitefin shark Dalatias licha of the western Mediterranean Sea. Data were obtained from two deep-water areas with different degrees of human impact: a fishery restricted area (FRA) in the Gulf of Lions and a highly human-impacted area in the Catalan Sea (non-FRA). We combined analyses of individual stomach contents and stable isotope values from different individuals of each shark species. Our results revealed that D. licha is a predator located higher up on the food web, while G. melastomus, E. spinax and S. canicula are located in lower trophic positions. These results confirm that shark species play important and, most likely, complementary roles as predators in the western Mediterranean Sea. Results also revealed that despite some differences in the diet of the shark species, as revealed by the stomach contents, in the long term (isotopic results) the four species showed similar diet habits and similar trophic relationships in both FRA and non-FRA. This may be due to the fact that despite the fishing regulations in the FRA area, the population of the prey species probably do not vary between the two areas.Overall, this study provides new insights into the trophic ecology of these sharks and contributes to an understanding of their ecological roles within the community.

On the occurrence of the digenean Otodistomum veliporum in the spiracle of the kitefin shark Dalatias licha

The presence of the digenean Otodistomum veliporum is reported here for the first time as a parasite in the spiracle of a Mediterranean specimen of the kitefin shark Dalatias licha.

Hexabothriid monogeneans from the gills of deep-sea sharks off Algeria, with the description of Squalonchocotyle euzeti n. sp. (Hexabothriidae) from the kitefin shark Dalatias licha (Euselachii, Dalatiidae)

Summary Sharks (765 specimens from ten species) from the Mediterranean Sea off Algiers, Algeria, were examined for the presence of gill monogeneans. The following deep-sea sharks were investigated from 2009 to 2015: Centrophorus granulosus (27 specimens); Centrophorus uyato (39); Etmopterus spinax (67); Somniosus rostratus (19); Galeus melanostomus (189); Scyliorhinus canicula (261), Hexanchus griseus 3), and Dalatias licha (100). In addition, two pelagic shark species were examined: Alopias vulpinus (7), and Prionace glauca (53). Only two species of gill monogeneans were found. Protocotyle grisea (Cerfontaine, 1899) Euzet et Maillard, 1974 was found on its type-host Hexanchus griseus; comparative measurements are provided, and Algeria is a new geographic record. Squalonchocotyle euzeti n. sp. from Dalatias licha is described here. We found that the species of Squalonchocotyle Cerfontaine, 1899 can be separated into two groups, according to body size. Small-bodied species include 7 species. Large-bodied species (body > 20mm) include S. borealis (Van Beneden, 1853), S. laymani Yamaguti, 1958 and S. euzeti n. sp; the latter is distinguished from the two other species by a characteristically slender body. A sequence of Cytochrome Oxidase Type I (COI) gene, potentially useful for barcoding, was obtained for S. euzeti n. sp. and is the first for the family Hexabothriidae.

Composition of glycosaminoglycans in elasmobranchs including several deep-sea sharks: identification of chondroitin/dermatan sulfate from the dried fins of Isurus oxyrinchus and Prionace glauca.

Shark fin, used as a food, is a rich source of glycosaminoglyans (GAGs), acidic polysaccharides having important biological activities, suggesting their nutraceutical and pharmaceutical application. A comprehensive survey of GAGs derived from the fin was performed on 11 elasmobranchs, including several deep sea sharks. Chondroitin sulfate (CS) and hyaluronic acid (HA) were found in Isurus oxyrinchus, Prionace glauca, Scyliorhinus torazame, Deania calcea, Chlamydoselachus anguineus, Mitsukurina owatoni, Mustelus griseus and Dasyatis akajei, respectively. CS was only found from Chimaera phantasma, Dalatias licha, and Odontaspis ferox, respectively. Characteristic disaccharide units of most of the CS were comprised of C- and D-type units. Interestingly, substantial amount of CS/dermatan sulfate (DS) was found in the dried fin (without skin and cartilage) of Isurus oxyrinchus and Prionace glauca. 1H-NMR analysis showed that the composition of glucuronic acid (GlcA) and iduronic acid (IdoA) in shark CS/DS was 41.2% and 58.8% (Isurus oxyrinchus), 36.1% and 63.9% (Prionace glauca), respectively. Furthermore, a substantial proportion of this CS/DS consisted of E-, B- and D-type units. Shark CS/DS stimulated neurite outgrowth of hippocampal neurons at a similar level as DS derived from invertebrate species. Midkine and pleiotrophin interact strongly with CS/DS from Isurus oxyrinchus and Prionace glauca, affording Kd values of 1.07 nM, 6.25 nM and 1.70 nM, 1.88 nM, respectively. These results strongly suggest that the IdoA-rich domain of CS/DS is required for neurite outgrowth activity. A detailed examination of oligosaccharide residues, produced by chondroitinase ACII digestion, suggested that the IdoA and B-type units as well as A- and C-type units were found in clusters in shark CS/DS. In addition, it was discovered that the contents of B-type units in these IdoA-rich domain increased in a length dependent manner, while C- and D-type units were located particularly in the immediate vicinity of the IdoA-rich domain.

Short- and long-term importance of small sharks in the diet of the rare deep-sea shark Dalatias licha

Knowing the trophic ecology of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on deep-sea and threatened shark species is limited. Here, by combining analyses of individual stomach contents and stable isotope values, we examined the trophic ecology (dietary composition and trophic position) of the kitefin shark Dalatias licha, a deep-sea shark considered as near threatened globally and as data deficient in the Mediterranean Sea. Results revealed the importance of small sharks in the diet of the kitefin shark at short- and long-term scales, although fin-fish, crustaceans and cephalopods were also found. Predation on sharks reveals the high trophic position of the kitefin shark within the food web of the western Mediterranean Sea. Stable isotope values from liver and muscle tissues confirmed our results from stomach content analysis and the high trophic position.

Cestodes from deep-water squaliform sharks in the Azores

The majority of our knowledge on marine tapeworms (cestodes) is limited to taxa that are relatively easy to obtain (i.e., those that parasitize shallower-water species). The invitation to participate in a deep-water research survey off the Condor seamount in the Azores offered the opportunity to gain information regarding parasites of the less often studied sharks of the mesopelagic and bathypelagic zone. All tapeworms (Platyhelminthes: Cestoda) found parasitizing the spiral intestine of squaliform shark species (Elasmobranchii: Squaliformes) encountered as part of this survey, as well as some additional Azorean sampling from previous years obtained from local fishermen are reported. In total, 112 shark specimens of 12 species of squaliform sharks representing 4 different families from depths ranging between 400 and 1290m were examined. Cestodes were found in the spiral intestines from 11 of the 12 squaliform species examined: Deania calcea, D. cf. profundorum, D. profundorum, Etmopterus princeps, E. pusillus, E. spinax, Centroscyllium fabricii, Centroscymnus coelolepis, C. cryptacanthus, C. crepidater, and Dalatias licha. No cestodes were found in the spiral intestines of Centrophorus squamosus. Light microscopy and scanning electron microscopy revealed several potentially novel trypanorhynch and biloculated tetraphyllidean species. Aporhynchid and gilquiniid trypanorhynchs dominated the adult cestode fauna of Etmopterus and Deania host species, respectively, while larval phyllobothriids were found across several host genera, including, Deania, Centroscyllium, and Centroscymnus. These results corroborate previous findings that deep-water cestode faunas are relatively depauperate and consist primarily of trypanorhynchs of the families Gilquiniidae and Aporhynchidae and larval tetraphyllideans. A subset of specimens of most cestode species was preserved in ethanol for future molecular analysis to allow more definitive determinations of the identification of the larval tetraphyllideans and trypanorhynchs lacking evaginated tentacles and other key diagnostic features.

ON DEEP-WATER SHARKS CAUGHT OFF THE MEDITERRANEAN COAST OF ISRAEL

ABSTRACT Four species of sharks were recently collected at depths of 1330–1440 m off the eastern Mediterranean coast of Israel. The occurrence of Somniosus rostratus is a first record, while Centrophorus granulosus and Dalatias licha are the first substantiated records in this region. The record of Galeus melastomus at the depth of 1440 m increases its bathymetrie range.

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

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

The diet of deepwater sharks and the benefits of using DNA identification of prey

Stomachs from the sharks Dalatias licha, Centrophorus squamosus, Centroscymnus owstoni, Centroselachus crepidater, Proscymnodon plunketi, and Galeorhinus galeus were sampled from three research trawl surveys on Chatham Rise, east of New Zealand. Between 14 and 50 stomachs were examined for each species, of which 8–62% were empty. Prey were visually identified in 80 stomachs, and by DNA barcoding in a further 28 stomachs. The use of DNA methods allowed the identification of chunks of flesh found in the stomachs of D. licha and P. plunketi, and nearly doubled the rate of data accumulation for D. licha, C. squamosus, and C. owstoni. Between 84 and 223 stomachs were estimated to be needed to measure 90% of the extrapolated total prey richness. The prey of D. licha, C. squamosus, and P. plunketi were predominantly benthic or demersal fishes and cephalopods. The prey of C. owstoni and C. crepidater were predominantly mesopelagic fishes and squids. G. galeus foraged throughout the water column. Scavenging of discards from commercial fishing vessels was likely in C. squamosus, P. plunketi, and G. galeus. The diet of all species except C. crepidater was dominated by the commercially important benthopelagic species hoki Macruronus novaezelandiae.

First record of albinism in the deep-water shark Dalatias licha

The first case of albinism in the kitefin shark, Dalatias licha, is reported here through the study of one specimen caught by professional bottom trawl in the Gulf of Genoa, Ligurian Sea. The albino surface was quantified and morphometric and meristic characteristics were compared with those of normal specimens of the same sex and equivalent length, caught within the same area. The shark body presented a partial reduction in pigmentation and no morphometric differences between the albino specimen and the normal individuals were observed.

Concentrations and hazard assessment of polychlorinated biphenyls and organochlorine pesticides in shark liver from the Mediterranean Sea

Concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (DDTs), were determined in the liver of two different shark species Prionace glauca (blue shark) and Dalatias licha (kitefin shark) from the Mediterranean Sea. In blue shark liver, the concentrations of PCBs (2482 ng g −1) and DDTs (2392 ng g −1) were comparable, while in kitefin shark the hepatic concentrations of DDTs (4554 ng g −1) were significantly higher than those of PCBs (1827 ng g −1). Contamination levels differed between species, with kitefin shark showing consistently higher concentrations of DDTs, and blue shark higher levels of PCBs. Congener-specific PCB profiles, similar between the two species were dominated by the higher chlorinated congeners (hexachlorobiphenyls: 62.8–63.9%, penta-: 15.2–21.3%, hepta-: 13.4–14.5%) with most of the lower chlorinated congeners being absent or present at very low levels. In both species, the total 2,3,7,8-tetrachlorodibenz- p-dioxin toxic equivalent (TEQs) concentrations (blue shark: 2.51 pg/g; kitefin shark: 1.46 pg/g) seem to be relatively modest. Regards to DDT component pattern, p, p′-DDE was dominant in the liver of both species (blue shark: 81.5%; kitefin shark: 38.0%), while the percentage composition of the other metabolites was differently characterized. The composition pattern of DDTs and the low value of p, p′-DDE/DDTs ratio in the specimens from Ionian Sea suggest that organochlorine pesticide contamination is still continuing in this marine environment.

On the fossil teeth of kitefin shark from the Middle Miocene Iseyama Formation, Sanada-machi, Nagano Prefecture, central Japan

On the fossil teeth of kitefin shark from the Middle Miocene Iseyama Formation, Sanada-machi, Nagano Prefecture, central Japan

Biological Observations on Shark Species Taken in Commercial Fisheries to the West of Ireland

During an investigation into the biology of three shark species commonly taken in Irish fisheries, biological information was also collected from an additional six less-common species: Galeorhinus galeus, Lamna nasus, Mustelus asterias, Galeus melastomus, Hexanchus griseus and Dalatias licha. Data on age, reproduction, feeding and parasites were collected from a total of 137 sharks. Age data from G. galeus and M. asterias suggest possible differences in growth-rate relative to other areas. The state-of-maturity of all specimens agreed with earlier studies, although data regarding the reproductive cycle of M. asterias and G. melastomus were inconsistent with data commonly reported for these species. Stomach contents were unremarkable, with the exception of 1.3kg of cetacean material recovered from a specimen of H. griseus. Results from the parasite component of the investigation extend the known range of two monogenean species, while a further three parasites were recorded from new hosts.

Sharks from the La Meseta Formation (Eocene), Seymour Island, Antarctic Peninsula

ABSTRACT The marine waters of present-day Antarctica contain an exceedingly depauperate elasmobranch fauna. Recent investigations into the Eocene marine sediments of the La Meseta Formation of Seymour Island, Antarctic Peninsula yielded 13 fossil sharks new to the Antarctic region. Two, Stegostoma cf. S. fasciatum and Pseudoginglymostoma cf. P. brevicaudatum, were unknown as fossils. Squalus woodburnei, S. weltoni, and Anomotodon multidenticulata are new species. Heptranchias howelli, Centrophorus sp., Deania sp., Dalatias licha, Odontaspis rutoti, O. winkleri, Lamna cf. L. nasus, and Scoliodon sp. are reported in Antarctica for the first time. In addition, the new fossil shark material increases the representation of the four previously known fossil sharks from Seymour Island: Squatina sp., Pristiophorus lanceolatus, Carcharias macrota, and Carcharocles auriculatus.

Squalene content and neutral lipis composition of Livers from Deep-sea sharks caught in Tasmanian waters

Deep-sea sharks (mainly dogfish) are a significant by-catch of trawls for the deep-water fish orange roughy (Hoplostethus atlanticus). To test whether the livers of these sharks might be a source of commerically valuable squalene and other lipids, 16 sharks of 8 species were collected from Tasmanian waters at depths of 700-1200 m during research cruise S02/88 of FRV Soela. The sharks were Centroscyrnnus crepidater (longnose velvet dogfish), Centroscyrnnus owstoni (Owston's dogfish), Centroscyrnnus coelolepis (Portuguese dogfish), Deania calcea (shovelnose dogfish), Etmopterus baxteri (Baxter's dogfish), Etmopterus sp. nov. (unnamed dwarf dogfish), Dalatias licha (kitefin or seal shark) and Centrophorus squarnosus (leafscale gulper shark). Squalene content, triacylglycerols, diacylglyceryl ethers, total fatty acids, pristane and other lipids were analysed by capillary gas chromatography and thin-layer chromatography-flame ionization detection. The livers contained high levels of squalene (15-69% by weight), except for the liver of C. squarnosus (I%), which had an unusually high amount of diacylglyceryl ethers (79%). Triacylglycerol and diacylglyceryl ether contents in the livers ranged from 1 to 26% and from 7 to 79% by weight respectively. The C19 isoprenoid alkane pristane was a minor constituent in all samples (0.01-0.56% by weight of liver). The three major esterified fatty acids in all samples were palmitic (16:0), oleic [18: 1 (n - 9)] and eicosa-11-enoic [20: 1 (n - 9)] fatty acids. Polyunsaturated fatty acids were minor constituents. These data indicate that shark livers could provide a profitable by-catch from deep-water trawls, but it is unlikely that shark could form the basis for a target fishery due to their susceptibility to overfishing.

The enzyme cytochemistry and composition of elasmobranch granulocytes

Peroxidase, alkaline phosphatase, acid phosphatase, β‐glucuronidase, α‐naphthyl acetate esterase (ANAE), α‐naphthyl butyrate esterase, naphthol AS‐D chloroacetate esterase, acetyl‐L‐tyrosine‐α‐naphthyl esterase (ATNE), tosyl‐L‐lysine‐α‐naphthyl esterase (TLNE) and periodic acid‐Schiff (PAS) were studied in 17 species of elasmobranchs in which granulocytes had previously been identified at the ultrastructural level.Eosinophils, eosinophilic and neutrophilic granulocytes contained variable acid phosphatase, esterases and PAS, but they were strongest in neutrophilic granulocytes; particularly ANAE. Esterases were released into surrounding plasma and therefore probably function as ectoenzymes. In eosinophils and some neutrophilic granulocytes there were indications of weak peroxidase, but this could not be conclusively demonstrated. Alkaline phosphatase was diffuse between granules in some eosinophils of Pavoraja, and (β‐glucuronidase was diffuse in neutrophilic granulocytes of Etmopterus baxteri, otherwise granulocytes lacked these enzymes. Neutrophilic granulocytes stained moderately to strongly for ATNE and weakly and inconsistently for TLNE in Squalus acanthias and Dalatias licha. with a similar reaction in granular lymphocytoid and thrombocytoid cells of Galeorhinus ausiralis and Raja nasuta. The enzyme composition of these granulocytes is discussed.

New records of fossil elasmobranch generaMegascyliorhinus, Centrophorus, andDalatias(Order Selachii) in New Zealand

Abstract Three elasmobranch genera and species, Megascyliorhinus cooperi (Cappetta & Ward), Centrophorus squamosus (Bonnaterre), and Dalatias licha (Bonnaterre) are recorded from the New Zealand fossil record for the first time. M. cooperi is also identified for the first time from the Australian Miocene. All 3 taxa have long Stratigraphic ranges in New Zealand. M. cooperi extends from the Oligocene to late Pleistocene; C. squamosus is known from either a Late Cretaceous or an Early Paleocene record and extends to the Late Pliocene, and D. licha ranges from Late Eocene to Late Pliocene.

Comparative studies on the ether-linked lipids of ratfish and shark-III. Distribution of squalene and diacyl glyceryl ethers in the different tissues of deep-sea shark, Dalatias licha.

The lipid compositions of the different tissues and gut content of deep-sea shark, Dalatias licha, were determined. In this species, the liver contained 83.4% lipids, which was much larger than that of muscle, ovary and gut content, ranging from 17.3% to 0.8%. The liver and ovary lipids were characterized by high percentages of squalene (40.1%, 20.3%) and diacyl glyceryl ethers (27.8%, 35.7%). On the contrary, the lipids of muscle and gut content contained small amounts of the above types of lipids. Glyceryl ethers of diacyl glyceryl ethers of liver and ovary were very similar in composition: the predominant constituents were 18:1 (52.7%-50.8%) and 20:1 (27.1%-24.7%). In both liver and ovary, the component fatty acids of diacyl glyceryl ethers and triglycerides were also similar in composition, predominantly consisting of monoenes (74.8%-81.3%). Based on the characteristic lipid composition and/or the component glyceryl ethers or fatty acids of diacyl glyceryl ethers and triglycerides, it is suggested that the ovary tissue has directly accumulated the liver lipids for egg development.

Studies on the stomach oils of marine animals—I. Oils of the black shark Dalatias licha (Bonnaterre)

1. 1. Eight specimens of Dalatias licha contained between 12 ml and 550 ml of oil in their stomachs. 2. 2. Squalene, wax esters, diacyl glycerol ethers and triglycerides were major components of the stomach oils. 3. 3. The stomach oils are believed to be dietary residues resulting from inadequate gastric peristalsis. 4. 4. The large quantities of squalene in the liver oils appear to be of dietary origin.