Taillight shark
| Taillight shark | |
|---|---|
Scientific classification
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Subdivision: | Selachimorpha |
| Order: | Squaliformes |
| Family: | Dalatiidae |
| Genus: | Euprotomicroides Hulley&M. J. Penrith,1966 |
| Species: | E. zantedeschia
|
| Binomial name | |
| Euprotomicroides zantedeschia Hulley&M. J. Penrith,1966
| |
| |
| Occurrences of the taillight shark | |
Thetaillight shark(Euprotomicroides zantedeschia) is a little-knownspeciesofsharkin thefamilyDalatiidaeand theonly memberof itsgenus.[2]It is known from only fourspecimenscollected from deepoceanic watersin the southernAtlantic OceanandPacific Ocean.[2]A small shark with a laterally compressed body and a bulboussnout,this species has unusualadaptationsthat indicate a specialized lifestyle: itspectoral finsare paddle-like and may be used for propulsion, unlike other sharks and it has a pouch-like gland on its abdomen that emits clouds ofluminescentblue fluid.[2]This shark is likelyaplacental viviparousand a formidablepredatorfor its size.
Taxonomy and phylogeny
[edit]The first specimen of the taillight shark was collected by theCape TowntrawlerArumin 1963 and was initially identified as alongnose pygmy sharkbefore being recognized as a hitherto unknown species. The genus nameEuprotomicroidescomes from this shark's resemblance to thepygmy shark.
Phylogeneticanalysis based ondentitionindicates that the taillight shark is the most basal member of its family and is sister to thecladecontaining all other dalatiid species. Although no definitivefossilremains have been found, the taillight shark may have evolved in the earlyPaleoceneepoch(65.5–55.8 million years ago - Mya), as part of a largeradaptive radiationof dogfish sharks into midwater habitats. The teeth of the extinct sharkParaphorosoides ursulae,found in earlyCampanian(83.5–70.6 Mya) deposits inGermany,closely resemble those of the taillight shark.[3]
Etymology
[edit]Thespecific epithetzantedeschiais derived fromZantedeschia aethiopica,a species ofarum lilyfor which the trawlerArumwas named.[4]
Distribution and habitat
[edit]The four specimens of the taillight shark were caught offSouth Africain a trawl operating at a depth of 458–641 m (1,503–2,103 ft), offUruguayin a trawl operating at a depth of 195–205 m (640–673 ft) and offChile,nearJuan Fernández Islands.[2]These records suggest this shark is an inhabitant of the open ocean. However, whether the known specimens were captured near the sea bottom where the trawls operated or from midwater as the nets were being retrieved is unclear.[1]
Description
[edit]The taillight shark is laterally compressed, with a long rounded snout and large oval eyes. The mouth is large, containing 29 tooth rows in theupper jawand 34 tooth rows in thelower jaw.The upper teeth are small and needle-like, while the lower teeth are large and triangular, with their bases interlocking to form a continuous cutting surface. Thelipsare thick and fringed, though not modified to besuctorial.The five pairs ofgill slitsare large and increase in size from the first to the last.[4][5]
The twodorsal finsare rounded and lackspines;the first is smaller than the second and located about halfway between the pectoral andpelvic fins.Thepectoral finsare enlarged into rounded paddles. The pelvic fins are small and originate at the level of the second dorsal fin; theanal finis absent. Thecaudal finhas a strong lower lobe and a long upper lobe with a prominent notch near the tip. The body is covered by small, non-overlappingdermal denticles;each denticle has radial ridges converging to a round central pit. The body is dark brown above and black below, with light margins on the fins.[4][5]Small, light-emittingphotophoresare scattered over the body.[6]The first specimen was an immature female (originally reported incorrectly as a mature male) 17.6 cm (6.9 in) long, the second was a mature male 41.6 cm (16.4 in) long, the third was also a mature male 45.5 cm (17.9 in) long and the fourth specimen was a mature female 51.5 cm (20.3 in).[1][2]
Biology and ecology
[edit]The muscular, lobe-like pectoral fins of the taillight shark suggest they may be used for propulsion, in a manner more akin to that ofchimaerasthan other sharks or at least for hovering in the water column.[5]Its strongly built jaws and teeth likely allow it to tackle relatively large prey.[7]On the belly in front of thecloacais a pouch-like groove devoid of denticles and lined with a luminescent tissue formed into numerous, tightly packed papillae (nipple-like structures).[2]The entrance to the pouch is a slit lined with folds of skin. In life, the pouch emits a glowing blue fluid of unknown function.[6]Reproduction is presumablyaplacental viviparousas in the other members of its family.[5]
Human interactions
[edit]The taillight shark is not caught significantly by anyfishery,possibly due to its small size and habitat preferences. TheInternational Union for Conservation of Naturehas assessed its conservation status asleast concern.[1]
References
[edit]- ^abcdPollom, R.; Ebert, D.A.; Leslie, R. (2019)."Euprotomicroides zantedeschia".IUCN Red List of Threatened Species.2019:e.T44603A2998283.doi:10.2305/IUCN.UK.2019-2.RLTS.T44603A2998283.en.Retrieved18 November2021.
- ^abcdefStehmann, M.F.W., Van Oijen, M. & Kamminga, P. (2016): Re-description of the rare taillight sharkEuprotomicroides zantedeschia(Squaliformes, Dalatiidae), based on third and fourth record from off Chile.Cybium, 40 (3): 187-197.
- ^Adnet, S. & Cappetta, H. (2001):A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters.Lethaia, 34 (3): 234-248.
- ^abcHulley, P.A. & Penrith, M.J. (1966):Euprotomicroides zantedeschia,a new genus and species of pigmy dalatiid shark from South Africa.Bulletin of Marine Science, 16 (2): 222-229.
- ^abcdCompagno, L.J.V. (1984).Sharks of the World: An annotated and illustrated catalogue of Shark species known to date.FAO. pp. 89–90.ISBN978-9251013847.
- ^abMunk, O. & Jørgensen, J.M. (1988):Putatively luminous tissue in the abdominal pouch of a male dalatiine shark,Euprotomicroides zantedeschiaHulley & Penrith, 1966.Acta Zoologica, 69 (4): 247-251.
- ^Froese, Rainer;Pauly, Daniel (eds.)."Euprotomicroides zantedeschia".FishBase.June 2016 version.