# Viper dogfish > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Viper_dogfish > Markdown URL: https://mediated.wiki/source/Viper_dogfish.md > Source: https://en.wikipedia.org/wiki/Viper_dogfish > Source revision: 1354732815 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Species of shark}} {{good article}} {{speciesbox | image = Trigonognathus kabeyai head 1.jpg | status = LC | status_system = IUCN3.1 | status_ref = {{cite iucn |author=Rigby, C.L. |author2=Ebert, D.A. |author3=Herman, K. |date=2020 |title=''Trigonognathus kabeyai'' |volume=2020 |article-number=e.T44205A80678455 |doi=10.2305/IUCN.UK.2020-3.RLTS.T44205A80678455.en |access-date=19 November 2021}} | genus = Trigonognathus | parent_authority = [Mochizuki](/source/Kenji_Mochizuki) & [Ohe](/source/Fumio_Ohe), 1990 | species = kabeyai | range_map = Trigonognathus kabeyai distmap.png | range_map_caption = Range of the viper dogfish | authority = [Mochizuki](/source/Kenji_Mochizuki) & [Ohe](/source/Fumio_Ohe), 1990 }} The '''viper dogfish''' or '''viper shark''' (''Trigonognathus kabeyai'') is a rare [species](/source/species) of [dogfish shark](/source/Squaliformes) in the [family](/source/Family_(taxonomy)) [Etmopteridae](/source/Etmopteridae), and the only extant member of its [genus](/source/genus). It has been found in the Pacific Ocean off southern Japan, the [Bonin Islands](/source/Bonin_Islands), Pacific Ocean off northern [Taitung County](/source/Taitung_County) and the [Northwestern Hawaiian Islands](/source/Northwestern_Hawaiian_Islands). This species inhabits upper [continental slope](/source/continental_slope)s and [seamount](/source/seamount)s. It may [migrate vertically](/source/diel_vertical_migration), shifting between bottom waters {{convert|270|-|360|m|ft|abbr=on}} deep during the day and upper waters less than {{convert|150|m|ft|abbr=on}} deep at night. A slender, black shark reaching {{convert|54|cm|in|abbr=on}} in length, the viper dogfish can be recognized by its narrow, triangular jaws and well-spaced, fang-like teeth. It also has two spined [dorsal fin](/source/dorsal_fin)s, [dermal denticle](/source/dermal_denticle)s with faceted crowns, and numerous light-emitting [photophore](/source/photophore)s concentrated on its ventral surface. Feeding mainly on [bony fish](/source/bony_fish)es, the viper dogfish captures prey by protruding its jaws and impaling them with its teeth. Its impressive gape allows it to swallow relatively large fish whole. The [skeletal](/source/skeletal) and [muscular](/source/muscular) structure of its head shows unique features that support this feeding mechanism, which is unlike that of other dogfish sharks. This shark [gives birth to live young](/source/viviparous), which are nourished by [yolk](/source/yolk) during [gestation](/source/gestation); the litter size is probably fewer than 26 pups. Small numbers of viper dogfish are [caught incidentally](/source/bycatch) in [purse seine](/source/purse_seine)s and [bottom trawl](/source/bottom_trawl)s. ==Taxonomy== The first specimens of the viper dogfish were two immature males caught off southern Japan by the [bottom trawl](/source/bottom_trawl)er ''Seiryo-Maru'' in 1986. The first, designated as the [holotype](/source/holotype), measured {{convert|22|cm|in|abbr=on}} long and was collected off [Cape Shiono](/source/Cape_Shiono) at a depth of {{convert|330|m|ft|abbr=on}}. The second measured {{convert|37|cm|in|abbr=on}} long and was collected off [Hiwasa, Tokushima](/source/Hiwasa%2C_Tokushima) at a depth of {{convert|360|m|ft|abbr=on}}. The shark was described as a new species and genus by [University of Tokyo](/source/University_of_Tokyo) researchers Kenji Mochizuki and Fumio Ohe in a 1990 article for the ''Japanese Journal of Ichthyology''. They gave it the name ''Trigonognathus kabeyai''; the [generic name](/source/genus) is derived from the [Greek](/source/ancient_Greek) ''trigonon'' ("triangle") and ''gnathus'' ("jaw"),{{Source?|reason=The specific 'Greek' forms are not mentioned by Mochizuki and Ohe. Moreover, ''gnathus'' is not Greek, as γνάθος, ''gnathos'' is the actual form.|date=October 2018}} while the [specific name](/source/specific_name_(zoology)) honors Hiromichi Kabeya, the captain of the ''Seiryo-Maru''. Mochizuki and Ohe originally assigned the viper dogfish to the family [Squalidae](/source/Squalidae), which at the time was used for all members of the [order](/source/order_(biology)) [Squaliformes](/source/Squaliformes) aside from the [bramble](/source/Echinorhinidae) and [rough shark](/source/rough_shark)s. In a 1992 [morphological](/source/morphology_(biology)) study, Shigeru Shirai and Osamu Okamura placed this species in the squalid subfamily Etmopterinae, which most taxonomists now recognize as the separate family Etmopteridae. ==Phylogeny and evolution== The position of ''Trigonognathus'' within the Etmopteridae is uncertain. Morphological and [molecular phylogenetic](/source/molecular_phylogenetic) data generally support the subdivision of the Etmopteridae into two [clade](/source/clade)s, one consisting of ''[Etmopterus](/source/Etmopterus)'' and ''[Miroscyllium](/source/Miroscyllium)'' and the other consisting of ''[Centroscyllium](/source/Centroscyllium)'' and ''[Aculeola](/source/Aculeola)''. [Phylogenetic](/source/Phylogenetic) analyses have variously placed ''Trigonognathus'' as closer to one clade or the other or as [basal](/source/basal_(phylogenetics)) to both, depending on which morphological characters, [nuclear DNA](/source/nuclear_DNA) markers, and/or [mitochondrial DNA](/source/mitochondrial_DNA) markers were used. Based on [molecular clock](/source/molecular_clock) estimation, ''Trigonognathus'' is thought to have originated around 41 million years ago during the [Middle Eocene](/source/Middle_Eocene), as part of a larger [evolutionary radiation](/source/evolutionary_radiation) of etmopterid genera. The genus is represented in this time period by the [extinct](/source/extinct) species ''[T. virginiae](/source/Trigonognathus_virginiae)'', whose [fossil](/source/fossil)ized teeth have been recovered from [Lutetian](/source/Lutetian) age (47.8–41.3 Mya) [strata](/source/strata) in [Landes](/source/Landes_(department)), southwestern France. Fossil teeth virtually identical to those of the modern viper dogfish are known from the Cubagua Formation in northeastern Venezuela, which dates to the [Late Miocene](/source/Late_Miocene) and [Early Pliocene](/source/Early_Pliocene) (11.6–3.6 Mya). ==Description== thumb|left|The narrow jaws and needle-like teeth of the viper dogfish are distinctive. The viper dogfish has a slender, cylindrical body and a moderately flattened head with a very short and blunt snout. Behind the large oval eyes are narrow, elliptical [spiracle](/source/Spiracle_(vertebrates))s. The nostrils are nearly vertical slits. The jaws are long and narrowly triangular, and can be protruded from the head. The teeth are distinctively fang-like and widely spaced; the most anterior teeth are grooved lengthwise. Six to 10 upper and seven to 10 lower [tooth row](/source/tooth_row)s occur on each side, along with a single tooth row at the upper and lower symphyses (jaw midpoints). The teeth are largest at the symphysis and decline in size towards the corners of the mouth. When the mouth is closed, the upper symphysial tooth overlaps the lower, while the lateral teeth interlock. Five [gill slit](/source/gill_slit)s are seen, with the fifth pair longer than the others. The fins are small and very thin. The [pectoral fin](/source/pectoral_fin)s are rounded and lobe-like. The two [dorsal fin](/source/dorsal_fin)s are positioned about between the pectoral and [pelvic fin](/source/pelvic_fin)s. Each dorsal fin bears a slightly grooved spine in front; the second dorsal spine is longer than the first. The [anal fin](/source/anal_fin) is absent, and the [caudal peduncle](/source/caudal_peduncle) lacks keels or notches. The upper lobe of the [caudal fin](/source/caudal_fin) is larger than the lower and has a notch in the trailing margin. The skin, excluding on the fins, is densely covered with irregularly arranged, nonoverlapping [dermal denticle](/source/dermal_denticle)s. Each denticle has a swollen [rhombic](/source/rhombus) shape with 10–40 facets on the crown. The viper dogfish is black with distinct darker markings on the underside. These markings contain large numbers of tiny light-producing [photophore](/source/photophore)s; more photophores are found sparsely scattered over the rest of the body, as well as in a translucent patch on the upper eyelid. The fins are translucent, and the tip of the caudal fin upper lobe is blackish. The largest known male is {{convert|47|cm|in|abbr=on}} long and weighs {{convert|0.43|kg|lb|abbr=on}}, and the largest female is {{convert|54|cm|in|abbr=on}} long and weighs {{convert|0.76|kg|lb|abbr=on}}. ==Distribution and habitat== Most specimens of the viper dogfish have been collected from a relatively small area of the northwestern Pacific Ocean off the [Kii Peninsula](/source/Kii_Peninsula) in Japan. A number of specimens were also recovered from the stomachs of predatory fishes caught in the [Bonin Islands](/source/Bonin_Islands). One specimen was caught from the [Hancock Seamount](/source/Hancock_Seamount), located some {{convert|300|km|mi|abbr=on}} northwest of [Kure Atoll](/source/Kure_Atoll) in the [northwestern Hawaiian Islands](/source/northwestern_Hawaiian_Islands). During the day, this species has been caught close to the bottom on the upper reaches of [continental slope](/source/continental_slope)s and [seamount](/source/seamount)s, at depths of {{convert|270|-|360|m|ft|abbr=on}}. At night, it has been caught between the surface and a depth of {{convert|150|m|ft|abbr=on}} in water over {{convert|1.5|km|mi|abbr=on}} deep. This pattern suggests the viper dogfish performs a [diel vertical migration](/source/diel_vertical_migration), spending the day in deeper water and rising towards the surface at night; such daily movement may relate to feeding. ==Biology and ecology== thumb|The bigeye tuna preys on the viper dogfish. The viper dogfish feeds primarily on [bony fish](/source/bony_fish)es, notably [lanternfish](/source/lanternfish)es in the genera ''[Benthosema](/source/Benthosema)'' and ''[Diaphus](/source/Diaphus)'', and also takes [crustacean](/source/crustacean)s. Its long jaws and slender teeth are [adapted](/source/adaptation) for grasping rather than cutting, in contrast to the short jaws and saw-like lower teeth of other dogfish sharks that are suited for excising chunks of meat. Prey is seized by a rapid extension of the jaws and swallowed whole; the shark can consume fish close to 40% as long as itself. The viper dogfish is the only dogfish species that lacks a suborbital muscle, which is normally responsible for pulling the jaws forward when biting. Jaw protrusion is instead effected by the [hyomandibula](/source/hyomandibula)r bone, which is articulated to the [skull](/source/skull) in a manner that allows it to swing down and forward. This unique arrangement serves to increase the distance the shark can protrude its jaws, as well as the size of its gape both vertically and horizontally. Known [predator](/source/predator)s of the viper dogfish include the [bigeye tuna](/source/bigeye_tuna) (''Thunnus obesus'') and the [sickle pomfret](/source/sickle_pomfret) (''Taractichthys steindachneri''). Like other members of its family, this species is [viviparous](/source/viviparous), giving birth to live offspring, with the developing [embryo](/source/embryo)s sustained to term by [yolk](/source/yolk). Adult females have two functional [ovaries](/source/ovaries) and two functional [uteri](/source/uterus). Two of the recorded female specimens contained 25 and 26 mature [ova](/source/ovum); in the related [black dogfish](/source/black_dogfish) (''Centroscyllium fabricii''), the number of mature ova in a female is slightly greater than the number of resulting embryos, which suggests a litter size under 26 in the viper dogfish. Males and females [mature sexually](/source/mature_sexually) at roughly {{convert|43|and|52|cm|in|abbr=on}} long, respectively. ==Human interactions== The viper dogfish has no economic value. It is very infrequently caught in [commercial](/source/commercial_fishing) [purse seine](/source/purse_seine)s and bottom trawls targeting other species, though what effect, if any, fishing has on its population is unknown. The IUCN has listed it as Least Concern. ==References== {{Reflist|30em|refs= {{cite journal |author1=Adnet, S. |author2=Cappetta, H. |year=2001 |title=A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters |journal=Lethaia |volume=34 |pages=234–248 |doi=10.1111/j.1502-3931.2001.tb00052.x |issue=3|bibcode=2001Letha..34..234A }} {{cite journal |author1=Aguilera, O. |author2=De Aguilera, D.R. |year=2001 |title=An exceptional coastal upwelling fish assemblage in the Caribbean Neogene |journal=Journal of Paleontology |volume=75 |issue=3 |pages=732–742 |doi=10.1666/0022-3360(2001)075<0732:AECUFA>2.0.CO;2|s2cid=73533277 }} {{cite journal |author1=Cappetta, H. |author2=Adnet, S. |year=2001 |title=Découverte du genre actuel ''Trigonognathus'' (Squaliformes: Etmopteridae) dans le Lutétien des Landes (sud-ouest de la France). Remarques sur la denture de l'espèce actuelle ''Trigonognathus kabeyai'' |journal=Paläontologische Zeitschrift |volume=74 |issue=4 |pages=575–581 |doi=10.1007/bf02988163|s2cid=127171343 }} {{cite journal |author1=Mochizuki, K. |author2=Ohe, F. |year=1990 |title=''Trigonognathus kabeyai'', a new genus and species of the squalid sharks from Japan |journal=Japanese Journal of Ichthyology |volume=36 |issue=4 |pages=385–390|doi=10.1007/BF02905456 |s2cid=80791036 }} {{cite book |author1=Naylor, G.J. |author2=Caira, J.N. |author3=Jensen, K. |author4=Rosana, K.A. |author5=Straube, N. |author6=Lakner, C. |year=2012 |chapter=Elasmobranch phylogeny: A mitochondrial estimate based on 595 species |title=The Biology of Sharks and Their Relatives |pages=31–57 |edition=second |editor1=Carrier, J.C. |editor2=Musick, J.A. |editor3=Heithaus, M.R. |publisher=CRC Press |isbn=978-1-4398-3924-9}} {{cite journal |author1=Shirai, S. |author2=Okamura, O. |year=1992 |title=Anatomy of ''Trigonognathus kabeyai'', with comments on feeding mechanism and phylogenetic relationships (Elasmobranchii, Squalidae) |journal=Japanese Journal of Ichthyology |volume=39 |issue=2 |pages=139–150|doi=10.1007/BF02905997 |s2cid=84072512 }} {{cite journal |author1=Straube, N. |author2=Iglésias, S.P. |author3=Sellos, D.Y. |author4=Kriwet, J. |author5=Schliewen, U.K. |year=2010 |title=Molecular phylogeny and node time estimation of bioluminescent lantern sharks (Elasmobranchii: Etmopteridae) |journal=Molecular Phylogenetics and Evolution |volume=56 |issue=3 |pages=905–917 |doi=10.1016/j.ympev.2010.04.042 |pmid=20457263|bibcode=2010MolPE..56..905S }} {{cite journal |author1=Wetherbee, B.M. |author2=Kajiura, S.M. |year=2000 |title=Occurrence of a rare squaloid shark, ''Trigonognathus kabeyai'', from the Hawaiian Islands |journal=Pacific Science |volume=54 |pages=389–394}} {{cite journal |author1=Yano, K. |author2=Mochizuki, K. |author3=Tsukada, O. |author4=Suzuki, K. |year=2003 |title=Further description and notes of natural history of the viper dogfish, ''Trigonognathus kabeyai'' from the Kumano-nada Sea and the Ogasawara Islands, Japan (Chondrichthyes: Etmopteridae) |journal=Ichthyological Research |volume=50 |pages=251–258 |doi=10.1007/s10228-003-0165-7 |issue=3|bibcode=2003IchtR..50..251Y |s2cid=115185 }} }} ==External links== {{Commons category|Trigonognathus kabeyai}} * [http://fishbase.org/summary/Trigonognathus-kabeyai.html "''Trigonognathus kabeyai'', Viper dogfish" at FishBase] * [https://shark-references.com/species/view/Trigonognathus-kabeyai "Species description of ''Trigonognathus kabeyai''" at Shark-References.com] {{Squaliformes}} {{Taxonbar|from=Q1424187}} Category:Etmopteridae Category:Fish of the Pacific Ocean Category:Taxa named by Kenji Mochizuki Category:Taxa named by Fumio Ohe Category:Fish described in 1990 --- Adapted from the Wikipedia article [Viper dogfish](https://en.wikipedia.org/wiki/Viper_dogfish) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Viper_dogfish?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.