The oval electric ray (''Typhlonarke aysoni'') is a little-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 ...

of sleeper ray 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 ...

. It is

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 ...

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 ...

, where it is generally found on the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

at a depth of . Seldom exceeding in length, this species has a thick, oval

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 and a short, stout tail with a single

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 ...

. It is blind, as its tiny eyes are covered by skin. Its

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 divided in two, with the anterior portion forming a limb-like appendage. These appendages likely allow the ray, which may not be able to swim at all, to "walk" along the bottom. The

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's ...

of adult males extend beyond the disc.

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 are known to be part of its diet, and its reproduction is

aplacental viviparous 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 ...

. It can produce an

electric shock 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 ...

for defense. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

presently lacks the data to assess its conservation status.

Taxonomy

The oval electric ray was described by William John Phillipps of the

Dominion Museum The Museum of New Zealand Te Papa Tongarewa is New Zealand's national museum and is located in Wellington. ''Te Papa Tongarewa'' translates literally to "container of treasures" or in full "container of treasured things and people that spring fr ...

, in a 1929 volume of the ''New Zealand Journal of Science and Technology''. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was collected off

Island Bay, Wellington Island Bay is a coastal suburb of Wellington, the capital of New Zealand, situated south of the city centre. Island Bay lies on the bay which shares its name, one of numerous small bays off Cook Strait and west of Lyall Bay. 500m offshore in ...

. A specimen of this ray had been illustrated earlier by Augustus Hamilton, in his 1909 description of the related ''T. aysoni''. Hamilton obtained the specimen at the fish market at

Dunedin Dunedin ( ; mi, Ōtepoti) is the second-largest city in the South Island of New Zealand (after Christchurch), and the principal city of the Otago region. Its name comes from , the Scottish Gaelic name for Edinburgh, the capital of Scotland. Th ...

and made note of its different shape, but did not recognize it as a distinct species. Along with ''T. aysoni'', this species may also be called the blind electric ray.

Distribution and habitat

Confusion between the two ''Typhlonarke'' species has led to uncertainty regarding the extent of the oval electric ray's distribution. Both species are found off the eastern coast of

, between the

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 ...

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 ...

and the Snares Shelf south of

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 ...

, including the

Cook Cook or The Cook may refer to: Food preparation * Cooking, the preparation of food * Cook (domestic worker), a household staff member who prepares food * Cook (professional), an individual who prepares food for consumption in the food industry * ...

and Foveaux Straits and the Stewart 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 ...

. Bottom-dwelling in nature, this species is generally found at a depth of but has been recorded from as shallow as and as deep as .

Description

The

disc of the oval electric ray is ovoid in shape, tapering smoothly towards the rear, and has a very thick margin. The eyes are minute and located beneath the surface of the skin; though not visible externally, their positions are marked by small white patches. The

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s follow the eyes and are oval with smooth rims. The nostrils are closely together, with their outer rims curled to nearly form tubes and their inner rims expanded and fused together into a fleshy skirt-shaped curtain, that nearly conceals the small, deeply recessed mouth. The teeth number 11 rows in either jaw and are arranged with a

quincunx A quincunx () is a geometric pattern consisting of five points arranged in a cross, with four of them forming a square or rectangle and a fifth at its center. The same pattern has other names, including "in saltire" or "in cross" in heraldry (dep ...

pattern to form narrow plates restricted to the front of the jaws. The teeth in the back have a single sharp cusp, while those at the front are worn down and blunt. There are five pairs of short, curved

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s, with the first and fifth pairs smaller than the others. Each

is divided: the anterior portion is formed into a long appendage resembling a finger, while the posterior portion is merged smoothly with the pectoral fin to form part of the disc. The trailing margins of the pelvic fins join the body evenly, without a notch. Adult males have cylindrical

clasper In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...

s that extend past the disc margin. The single

has a rounded margin and originates just ahead of where the disc margin meets the body. The tail is short and thick, with faint lateral skin folds running along the sides, and ends in a nearly circular

caudal 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 se ...

. The skin is completely smooth. The oval electric ray is dark brown above, lightening towards the disc margins and on the underside. The area around the mouth and nostrils, and the underside of the pelvic appendages, are white. This species can grow to long, but most do not exceed .

Biology and ecology

Thick and flabby with a rudimentary tail, the oval electric ray seems virtually incapable of swimming. Instead, it likely relies on its mobile pelvic fin appendages, which are better developed than those of ''T. aysoni'', to push it along the bottom. Like other electric rays, it can produce a defensive

from a pair of kidney-shaped

electric organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since developed ...

s placed on either side of its head. Each organ consists of 180–200 relatively large, fluid-filled hexagonal columns, which essentially act as

batteries Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

connected in parallel. The oval electric ray is sightless and captures prey via suction; it is known to feed on

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. It is

, with females bearing litters of up to 11 pups. The newborns measure long.

Human interactions

The oval electric ray is susceptible to capture in

bottom trawl Bottom trawling is trawling (towing a trawl, which is a fishing net) along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing ...

s, and the presence of major

commercial fishing Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

activity within its range may merit concern. However, given insufficient data the

(IUCN) has listed it under

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 ...

. In June 2018 the New Zealand

Department of Conservation An environmental ministry is a national or subnational government agency politically responsible for the environment and/or natural resources. Various other names are commonly used to identify such agencies, such as Ministry of the Environment ...

classified the oval electric ray as "Not Threatened" with the qualifier "Data Poor" under the

New Zealand Threat Classification System The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand. The system was developed because the IUCN Red List, a similar conservation status system, had some ...

References

{{Taxonbar, from=Q4668267 Narkidae Endemic marine fish of New Zealand Fish described in 1929 Strongly electric fish Taxobox binomials not recognized by IUCN