Typhlonarke

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Typhlonarke
Typhlonarke aysoni by hamilton.png
Blind electric ray (T. aysoni)
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Torpediniformes
Family: Narkidae
Genus: Typhlonarke
Waite, 1909
Type species
Astrape aysoni

Typhlonarke is a genus of sleeper ray in the family Narkidae, containing two poorly known species. The group is known for producing electric shocks for defense. Both species are deep-sea rays endemic to the waters off New Zealand. They are not to be confused with the blind electric rays of the genus Benthobatis .

Contents

Taxonomy

Typhlonarke was created by Edgar R. Waite, in a 1909 issue of the scientific journal Records of the Canterbury Museum. [1]

Species

Distribution and habitat

Both Typhlonarke species are native to New Zealand; the exact distribution of each species is uncertain due to confusion between the two. They have been caught by trawls off the east coast of North Island south of East Cape, South Island, Stewart Island/Rakiura, Chatham Rise (Mernoo Bank and Chatham Islands), and the Snares Shelf. They occur at a depth of 46–800 meters, but most are found between 300 and 400 meters. [2]

Description

The blind electric rays are small, flat cartilaginous fish with the round pectoral fin disc characteristic of electric rays, a short, fleshy tail, and one dorsal fin. The front part of their pelvic fins 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. [3] T. aysoni grows to a maximum length of 38 cm and T. tarakea to 35 cm. [2]

Biology and ecology

The flabby disc and rudimentary tail of the blind electric rays suggest that they are poor swimmers. [4] 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 rays, including species of Raja , Cruriraja and Anacanthobatis , and are believed to be an adaptation for feeding on invertebrates in the substrate. [5] The diet of Typhlonarke includes polychaete worms. [4] Reproduction is likely ovoviviparous, as with the other species in the family, with litters of up to 11 pups. The young measure 9–10 cm at birth. [2]

Human interactions

The IUCN Red List assesses both species as Data Deficient (DD); although they are apparently rare, confusion between the two species has made their distribution and population status uncertain. As they are benthic fishes, blind electric rays are potentially vulnerable to bottom trawling as their range coincides with major commercial trawling fisheries. No current conservation measures are in place for the genus. [2]

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Blind electric ray Species of cartilaginous fish

The blind electric ray 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 300–400 m (980–1,310 ft). Reaching 38 cm (15 in) in length, this species has a thin, nearly circular pectoral fin disc without visible eyes, and a short tail with a single dorsal fin. Its pelvic fins are divided in two, with the anterior portion forming a limb-like appendage; in males the claspers do not extend past the disc margin. A weak swimmer, the blind electric ray likely pushes itself along using its pelvic fins. It is known to feed on polychaete worms, and can defend itself with an electric shock. Reproduction is aplacental viviparous. The International Union for Conservation of Nature (IUCN) does not have enough information to assess the conservation status of this species.

Japanese sleeper ray Species of cartilaginous fish

The Japanese sleeper ray is a species of electric ray in the family Narkidae. It is common in the inshore and offshore waters of the northwestern Pacific Ocean from southern Japan to southern China. Growing up to 40 cm (16 in) long, the Japanese sleeper ray has a nearly circular pectoral fin disc colored reddish to chocolate brown above, sometimes with darker or lighter spots, and lighter brown below. The spiracles behind its small eyes have raised, smooth rims. Its short and muscular tail bears a single dorsal fin positioned aft of the rounded pelvic fins, and terminates in a large caudal fin.

Peppered maskray Species of cartilaginous fish

The peppered maskray or speckled maskray, is a species of stingray in the family Dasyatidae, found in shallow waters off northeastern Australia. This small, thin-bodied ray attains a maximum width of 32 cm (13 in). It has a diamond-shaped pectoral fin disc with a row of tiny thorns along the midline, and a relatively short, whip-like tail with both upper and lower fin folds. Its upper surface has a speckled color pattern consisting of black spots and brownish reticulations on a light yellow to brown background.

Onefin electric ray Species of cartilaginous fish

The onefin electric ray or Cape numbfish is a common but little-known species of electric ray in the family Narkidae, native to South Africa and Namibia. It is a benthic fish found in shallow coastal bays over sandy or muddy bottoms. This small species reaches 38 cm (15 in) in length, and has a nearly circular pectoral fin disc and a short, muscular tail that supports a large caudal fin. It can be identified by its single dorsal fin, which is located over the large pelvic fins. Its dorsal coloration is yellowish to dusky brown.

Tasmanian numbfish Species of cartilaginous fish

The Tasmanian numbfish is a species of electric ray in the family Narcinidae. Endemic to southeastern Australia, this common ray inhabits shallow continental shelf waters in the southern portion of its range and deeper continental slope waters in the northern portion of its range. It prefers sand and mud habitats. This species can be identified by its spade-shaped pectoral fin disc with concave anterior margins, long tail with well-developed skin folds along either side, and plain dark brown dorsal colouration. Its maximum known length is 47 cm (19 in).

References

  1. Waite, E.R. (July 13, 1909). "Pisces. Part I. In: Scientific results of the New Zealand government trawling expedition, 1907". Records of the Canterbury Museum. 1 (2): 131–155.
  2. 1 2 3 4 Cavanagh, R.D.; Kyne, P.M.; Fowler, S.L.; Musick, J.A. & Bennett, M.B. (2003). The conservation status of Australasian chondrichthyans. Brisbane, Australia: The University of Queensland. ISBN   0-9751041-0-1.
  3. Garrick, J.A.F. (1951). "The blind electric rays of the genus Typhlonarke (Torpedinidae)". Zoology Publications from Victoria University College (15).
  4. 1 2 Duffy, C. (2003). "IUCN 2008 Red List - Typhlonarke aysoni".
  5. Holst, R.J. & Bone, Q. (January 29, 1993). "On Bipedalism in Skates and Rays". Philosophical Transactions: Biological Sciences. 339 (1287): 105–108. doi:10.1098/rstb.1993.0007. JSTOR   55736.