''Typhlonarke'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

sleeper ray Members of the family Narkidae are commonly known as sleeper rays. They are restricted to the temperate and tropical Indo-West Pacific from South Africa to Japan to Indonesia, and are exclusively marine and are absent from freshwater habitats. Th ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Narkidae Members of the family Narkidae are commonly known as sleeper rays. They are restricted to the temperate and tropical Indo-West Pacific from South Africa to Japan to Indonesia, and are exclusively marine and are absent from freshwater habitats. Th ...

, containing two poorly known

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. The group is known for producing

electric shocks Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce a ...

for defense. Both species are deep-sea rays

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the waters off

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. They are not to be confused with the blind electric rays of the genus ''

Benthobatis ''Benthobatis'' is a genus of fish in the family Narcinidae Narcinidae, or numbfishes, are a family of electric rays (order Torpediniformes). They are bottom-dwelling cartilaginous fishes with large, rounded pectoral fin discs and long tails ...

''.

Taxonomy

''Typhlonarke'' was created by Edgar R. Waite, in a 1909 issue of the

scientific journal In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. Content Articles in scientific journals are mostly written by active scientists such as s ...

''Records of the Canterbury Museum''.

Species

* ''

Typhlonarke aysoni The blind electric ray (''Typhlonarke aysoni'') is a little-known species of sleeper ray in the family Narkidae, endemic to New Zealand. It is found on the bottom, typically at a depth of . Reaching in length, this species has a thin, nearly ci ...

'' A. Hamilton, 1902 (Blind electric ray) * ''

Typhlonarke tarakea The oval electric ray (''Typhlonarke aysoni'') is a little-known species of sleeper ray in the family Narkidae. It is endemic to New Zealand, where it is generally found on the sea floor at a depth of . Seldom exceeding in length, this species ...

Phillipps Phillipps is both a given name and an English surname. Notable people with the name include: "Phillipps" has also been a shortened version of Philippson, a German surname especially prevalent amongst German Jews and Dutch Jews. People with the g ...

, 1929 (Oval electric ray)

Distribution and habitat

Both ''Typhlonarke'' species are native to

; the exact distribution of each species is uncertain due to confusion between the two. They have been caught by

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...

s off the east coast of

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

south of

East Cape East Cape is the easternmost point of the main islands of New Zealand. It is located at the northern end of the Gisborne District of New Zealand's North Island. It can also refer to the broader Gisborne cape. East Cape was originally named "C ...

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

Stewart Island/Rakiura Stewart Island ( mi, Rakiura, ' glowing skies', officially Stewart Island / Rakiura) is New Zealand's third-largest island, located south of the South Island, across the Foveaux Strait. It is a roughly triangular island with a total land ar ...

, Chatham Rise ( Mernoo Bank and

Chatham Islands The Chatham Islands ( ) (Moriori: ''Rēkohu'', 'Misty Sun'; mi, Wharekauri) are an archipelago in the Pacific Ocean about east of New Zealand's South Island. They are administered as part of New Zealand. The archipelago consists of about te ...

), and the Snares Shelf. They occur at a depth of 46–800 meters, but most are found between 300 and 400 meters.

Description

The blind electric rays are small, flat

cartilaginous fish Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

with the round

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

disc characteristic of electric rays, a short, fleshy tail, and one

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

. The front part of their

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are modified for walking, while the back is fused to the disk. Their eyes are not visible externally and are practically useless, hence the name. The coloration is dark brown above and lighter below. ''T. aysoni'' grows to a maximum length of 38 cm and ''T. tarakea'' to 35 cm.

Biology and ecology

The flabby disc and rudimentary tail of the blind electric rays suggest that they are poor swimmers. Instead, examination of their anatomy suggests that they may push themselves along the bottom using the modified forward lobes of their pelvic fins, called "crurae". These structures have also evolved independently in other

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

rays, including species of ''

Raja ''Raja'' (; from , IAST ') is a royal title used for South Asian monarchs. The title is equivalent to king or princely ruler in South Asia and Southeast Asia. The title has a long history in South Asia and Southeast Asia, being attested f ...

'', ''

Cruriraja ''Cruriraja'' is a genus of skates in the family Gurgesiellidae.Weigmann, S., Séret, B., Last, P.R. & McEachran, J.D. 2016. Pygmy Skates, Family Gurgesiellidae. Pp. 473–493 in Last, P.R., White, W.T., Carvalho, M.R., Séret, B., Stehmann, M. ...

'' and ''

Anacanthobatis ''Anacanthobatis'' is a genus of smooth skate The Anacanthobatidae, the smooth skates or leg skates, are a family of skates found at depths below in the Indian, Pacific and Atlantic Oceans. They lack the dorsal denticles (sharp, tooth-lik ...

'', and are believed to be an adaptation for feeding on

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s in the substrate. The diet of ''Typhlonarke'' includes

polychaete worm Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are mad ...

s. Reproduction is likely

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, as with the other species in the family, with litters of up to 11 pups. The young measure 9–10 cm at birth.

Human interactions

The

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

assesses both species as

Data Deficient A data deficient (DD) species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as offering insufficient information for a proper assessment of conservation status to be made. This does not necessaril ...

(DD); although they are apparently rare, confusion between the two species has made their distribution and population status uncertain. As they are

fishes, blind electric rays are potentially vulnerable to bottom trawling as their range coincides with major commercial trawling

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

. No current conservation measures are in place for the genus.

References

{{Taxonbar, from=Q13590170 Endemic marine fish of New Zealand Narkidae Ray genera Taxa named by Edgar Ravenswood Waite