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The genus Etmopterus is the most speciose group of small bodied deep-sea sharks found throughout the tropical and subtropical Western Atlantic. Despite exhibiting a global distribution at the genus-level, the blurred lantern shark (Etempoterus bigelowi) is known only from a few records in the Western and Southern Atlantic Ocean. Through in-situ video observations using deep-sea landers, we provide two new locality records of the blurred lantern shark from the deep waters off the Cayman Islands, Caribbean Sea. Three unique individuals were recorded across two separate deployments between 653m – 668m. These observations provide the first records of this species in the Caribbean Sea, adding to the minimal knowledge of the species’ distribution throughout the Western Atlantic Ocean.

Lantern sharks are small shark species that can be seen at depths between 70 and 2000 meters. Due to their luminescent characteristics, they have been called “Lantern shark”. In total eleven specimens of the velvet belly lantern shark, Etmopterus spinax (Linnaeus, 1758), were caught in the deep seas of Northern Cyprus by using a bottom trawl. Sampling was carried out using 13 trawling operations. The collected samples were placed in 4% formalin and stored at the Museum of the Systematic, Faculty of Fisheries, Mersin University, (catalogue number: MEUFC-18-11-082). As a sampling area, the depths between 274 and 641 m were selected. Other cartilaginous fish caught during sampling except E. spinax were Galeus melastomus (1 individual), Squalus acanthias (4 individuals), Scyliorhinus canicula (85 individuals). E. spinax made up 10.89% of all cartilaginous fishes which were caught. Species identification for all fishes caught is made with the help of morphological features.

The lantern shark genus Etmopterus contains approximately 40 species of deep-sea bioluminescent cartilaginous fishes. They emit blue light mainly from the ventral body surface. The biological functions of this bioluminescence have been discussed based on the luminescence patterns, but the bioluminescence mechanism remains uncertain. In this study, we detected both coelenterazine and coelenterazine-dependent luciferase activity in the ventral photophore tissue of Etmopterus molleri. The results suggested that bioluminescence in lantern sharks is produced using coelenterazine as the substrate for the luciferin-luciferase reaction, as some luminous bony fishes. [Display omitted] • Lantern shark Etmopterus contains coelenterazine as a substrate for bioluminescence. • The shark possesses coelenterazine-dependent luciferase for bioluminescence. • Lantern shark Etmopterus use coelenterazine for bioluminescence. • The bioluminescence reaction of lantern shark Etmopterus is luciferin-luciferase reaction. [ABSTRACT FROM AUTHOR]

The article discusses a study that examined the intrinsic photophores of the lantern shark, Etmopterus spinax. Photophore-containing skin patches from the sharks were excised. The study showed that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris. It suggests that the luminescence control of the shark originates from the mechanism for physiological colour change found in shallow water sharks.

Abstract: Many midwater animals emit ventral light to hide their silhouette in the water column. This phenomenon known as counterillumination typically requires fine control over light emission since it needs a luminescence that closely matches the properties of downwelling light (intensity, angular distribution and wavelength). Here we provide evidence that, although lacking complex structures of counterilluminating animals, the deepwater luminescent shark Etmopterus spinax could, in Norwegian fjords, efficiently cloak its silhouette from downwelling ambient light to remain hidden from predator and prey. This represents the first experimentally tested function of luminescence in a shark and illustrates how evolution can take different routes to converge on identical complex behavior. [Copyright &y& Elsevier]

Taxonomic distinction to species level of deep water sharks is complex and often impossible to achieve during fisheries-related studies. The species of the genus Etmopterus are particularly difficult to identify, so they often appear without species assignation as Etmopetrus sp. or spp. in studies, even those focusing on elasmobranchs. During this work, the morphometric traits of two species of Etmopterus, E. spinax and E. pusillus were studied using 27 different morphological measurements, relatively easy to obtain even in the field. These measurements were processed with multivariate analysis in order to find out the most important ones likely to separate the two species. Sexual dimorphism was also assessed using the same techniques, and it was found that it does not occur in these species. The two Etmopterus species presented in this study share the same habitats in the overlapping ranges of distribution and are caught together on the outer shelves and slopes of the north-eastern Atlantic. [ABSTRACT FROM PUBLISHER]

The article discusses a study on Etmopterus species, a lantern shark in Taiwan, which was found to have an Elthusa raynaudii attached in the mouth. The mouths of fishes are commonly seen to have cymothoid isopods with heads facing outward. In this case, the Elthusa raynaudii was facing inward. It was concluded that such incident transpires in the southern and northern hemispheres but there is rarity in its occurrence since it has transpired only once in each of the hemispheres. It was also the first time to happen in Taiwan.