Protocotyle euzetmaillardi n. sp. is described from the gills of the sixgill shark Hexanchus nakamurai Teng caught in deep-sea off New Caledonia, South Pacific. The new species is compared with the ...two other species of the genus (both from the only other species in this shark genus, H. griseus (Bonn.)), namely P. grisea (Cerfontaine, 1899) Euzet & Maillard, 1974, redescribed from vouchers, and P. taschenbergi (Maillard & Oliver, 1966) Euzet & Maillard, 1974, redescribed from its type-specimens. The anatomy of the reproductive system is detailed; all three species have a characteristic oötype with longitudinal cells (‘ootype côtelé' of Euzet & Maillard). The following unique combination of characters differentiates the new species from its two congeners: posterior lobe of seminal vesicle absent, diverticulum of oviduct present and small body size. Furthermore, its tubular ovary does not include a region with sperm, which is present in both of the other species, and its eggs have only one filament, whereas eggs in the uterus have one or two filaments in P. grisea and one filament in P. taschenbergi. The latter features differ from existing diagnoses of Protocotyle, in which eggs with two filaments and the presence of a tubular ovary dilated with sperm are key characteristics.
A search through field surveys and literature revealed that 39 bluntnose sixgill sharks, Hexanchus griseus, were captured in the Black, Marmara, and Aegean Seas between 1974 and 2003. One of the ...specimens was captured in the prebosphoric waters of the southwestern Black Sea, 27 in the Sea of Marmara, and 11 in the Aegean Sea. H. griseus is hereby recorded for the first time in the southwestern Black Sea. Available information suggests that H. griseus gives birth from October to the end of February in the northern Aegean and Sea of Marmara. The main preys of the listed sixgill sharks were teleosteans.
The paper is based on a literature review and observations conducted off the Maghrebin shore (Algerian and Tunisian coasts) on bluntnose sixgill shark (Hexanchus griseus). The review comprises 167 ...records. Adult bluntnose sixgill shark males and females from the Mediterranean were over 3000 mm TL. Size at birth was 556-680 mm TL. Ripe oocytes ranged 68 and 75 mm TL (mean 71.71~c2.6) in diameter and 127-147 g (mean 134~c8.4) in weight. The reproductive cycle lasted at least one year, but probably more. The chemical balance of development (dry weight of newborn pup/dry weight of ripe oocyte) was 3. One adult female contained 57 ripe oocytes; a second contained 100. H. griseus is probably able to live and reproduce in the Mediterranean Sea, however, further observations are needed to confirm that a sustainable bluntnose sixgill shark population has been established here, especially off the Maghrebin coast.
Bluntnose sixgill shark, Hexanchus griseus (Bonnaterre, 1788), occurrs in Turkish waters from the eastern Black Sea to the eastern Mediterranean. Impacts of environmental deteriorations on bluntnose ...sixgill shark's distribution in the Black Sea (GSA 29), where the deep zone of the sea is permanently anoxic due to hydrogene sulphide contamination, and in the Sea of Marmara (GSA 28), where the hypoxia has been a raising concern for the last 40 years, is another issue in question. A decreasing trend in mean lengths of bluntnose sixgill sharks over the entire period (1967-2022) was found, which supposed "growth overfishing" of H. griseus in Turkish waters. Available information suggests possible breeding grounds of H. griseus in the Sea of Marmara, in the northern Aegean Sea (GSA 22) and in the northeastern Mediterranean Sea (GSA 24). The overlap of major fishing grounds of Turkish commercial bottom-trawling fleet with those suggested breeding grounds in the northern Aegean Sea and in the northeastern Mediterranean Sea, may cause further threat on the survival of the new generations of H. griseus in Turkish waters. Therefore, it is clearly seen that a management and conservation plan of H. griseus in Turkish waters should not solely rely on banning to capture and retain of bluntnose sixgill sharks on board, but should also provide a methodology to the fishermen of how to keep them alive to decrease or even prevent the at-vessel or post-release mortality. Such a plan should also implement an integrated ecosystem management approach for the conservation of those proposed breeding grounds.
AMP-deaminase activity was measured in white muscle from a wide range of fish, including one cyclostome, 13 chondrosteans, and one teleost to elucidate the pattern of the AMP-deaminase activity in ...white muscle of fish. Compared to a mammalian (rat) muscle extract, low enzyme activities are found in the cyclostome and two elasmobranchs from two families (Scyliorhinidae, Hexanchidae). In contrast, higher AMP-deaminase activities, similar to mammals, are expressed in Squalidae, all families of skates, Chimaeridae and in the teleostean fish. We then compared AMP-deaminase activities in red and white muscles from two representative elasmobranch fish, the dogfish (
Scyliorhinus canicula) and the thornback ray (
Raja clavata). The fibre type composition and distribution of the locomotory musculature were determined in these two elasmobranchs to establish a relationship between the morphology, the type of fibres of the locomotion-implicated muscles and the AMP-deaminase activity. Experimental data are discussed with respect to the layout of fibres in the myotome. In both species, three fibre types were identified. In the two fish myotomes, most of the axial muscles are white fibres while red fibres constitute a thin sheet. Some differences were observed between the two species in the distribution of intermediate fibres: in dogfish, these are located between the red and white fibres; in thornback ray, some are dispersed within the white fibre region, while others form an intermediary layer like in dogfish. These results suggest that in the course of evolution, an amplification of the AMP-deaminase activity in muscle was coupled with increase of complexity of the muscular structure.
The third record of the sharpnose seven-gill shark Heptranchias perlo (Selachii: Hexanchidae) north of the Bay of Biscay is reported. The 101 cm total length specimen, which was taken incidentally on ...a commercial bottom-set longline at a depth of 166 m, was an immature female. Beaks belonging to the short-finned squid Illex coindetii (Cephalopoda: Ommastrephidae) were recovered from the stomach, and an unidentified species of nematode was found parasitizing the stomach mucosa.
Chemical preparation of previously illustrated selachian teeth together with recently collected material from the upper part (early-middle NP3) of the Danian sequence in the Limhamn quarry, Skåne, ...southern Sweden, have revealed a rich and diverse selachian fauna. The three families dealt with here, i.e., Hexanchidae, Odontaspididae, and Mitsukurinidae, are represented by at least eight species, including two new ones, assigned to seven genera; Hexanchus spp., Heptranchias sp., Notorynchus sp., Notidanodon brotzeni sp. nov., Carcharias gracilis, C. aff. C. tenuis, Odontaspis speyeri, and Striatolamia cederstroemi sp. nov. At the genus level, the hexanchid fauna is the most diverse fossil assemblage yet reported. Striatolamia cederstroemi sp. nov. is the oldest known species of the genus and its tooth morphology indicates that Striatolamia may be more closely related to Anomotodon than to the odontaspidids.
Vertebrate fossils have been known from South India's Cauvery Basin since the 1840s, but records of marine vertebrates from the late Albian to Turonian Karai Formation have been limited to a single ...set of ichthyosaur remains. Recent surface collecting and sieving of lower Cenomanian glauconitic mudstones has yielded the first ichthyosaur material reported in India over the last 140 years, as well as a diverse and previously unrecorded shark assemblage. The ichthyosaur material, including several teeth and vertebrae, is assigned to the sole described Cretaceous genus Platypterygius and to the species P. indicus (Lydekker, 1879). Eight species of shark (one squaliformes, two hexanchiformes, and five lamniformes) are recorded. A new hexanchiform genus Gladioserratus is erected, and two new species (Gladioserratus magnus, gen. et sp. nov., and Dwardius sudindicus, sp. nov.) are named. Many of the shark genera within this largely species-level endemic fauna are known from high paleolatitudes elsewhere, with many showing an antitropical distribution, but are absent in Tethyan areas. This first description of the Karai Formation marine fauna documents the previously unappreciated diversity and unique character of India's Cretaceous marine vertebrates, and indicates a cool-water paleoenvironment for the marine vertebrate assemblage.
Hexanchid sharks (Family Hexanchidae) are extremely rare in Lower Cretaceous deposits and are known only from isolated teeth. Two species are recorded from the British Lower Cretaceous:
Notidanodon ...lanceolatus (Woodward. 1886), two teeth being known, and
Notorynchus aptiensis (Pictet, 1865), represented by three British teeth.
Until recently only nine isolated teeth of this latter species,
Notorynchus aptiensis, were known including the holotype from Apt, France, and other specimens from France and Germany. This paper describes an assemblage of fifteen additional teeth of
N. aptiensis discovered as isolated specimens from three localities in the Albian sediments of the Leighton Buzzard area.
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