Finless sleeper ray
| Finless sleeper ray | |
|---|---|
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Superorder: | Batoidea |
| Order: | Torpediniformes |
| Family: | Narkidae |
| Genus: | Temera J. E. Gray, 1831 |
| Species: | T. hardwickii
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| Binomial name | |
| Temera hardwickii J. E. Gray, 1831
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| Range of the finless sleeper ray[1] | |
The finless sleeper ray (Temera hardwickii) is a
sexually dimorphic
, being more concave in males.
Like other members of its family, the finless sleeper ray can generate a defensive
fisheries throughout its range, which likely cause high mortality
regardless of whether it is discarded or utilised.
Taxonomy and phylogeny
The finless sleeper ray was described as a new species and genus by English
phylogenetic study, based on morphology, corroborated the close relationship between Temera and Narke.[3]
Description
The
electric organs are visible beneath the skin on either side of the head. A curtain of skin, reaching the mouth, is present between the small, circular nostrils. The nostrils are connected to the corners of the mouth by a pair of grooves. The small mouth is gently arched and protrusible. The flattened teeth have hexagonal bases and are arranged into narrow bands. There are five pairs of short gill slits.[4][5][6][7]
The
cartilaginous fish, the smallest known adult finless sleeper ray measured only 8.2 cm (3.2 in) long and weighed 13 g (0.46 oz).[4] Few individuals exceed 15 cm (5.9 in) and the maximum length is thought to be 18 cm (7.1 in),[1] though there is a dubious old record of a specimen 46 cm (18 in) long.[6]
Distribution and habitat
The range of the finless sleeper ray extends from the eastern
bottom-dwelling species inhabits fine sediment habitat over the continental shelf in both inshore and offshore waters.[1] In the 19th century, it was reportedly abundant year-round in the Straits of Malacca.[8] It is locally common in some areas.[5]
Biology and ecology
The finless sleeper ray can produce a moderate
Theodore Edward Cantor wrote in an 1850 account that this species was often infested by minute worms under the skin, which he termed "Cysteocercus temerae" and classified as "entozoa" (an obsolete grouping that included acanthocephalans, trematodes, cestodes, and nematodes).[8]
Reproduction in the finless sleeper ray is
foetuses each 2.9 cm (1.1 in) long; the young were similar in form and colouration to the adult, but had thicker discs.[8] Males reach sexual maturity at around 8.2–10.9 cm (3.2–4.3 in) in length, and females at around 10.5–14.8 cm (4.1–5.8 in) in length.[6]
Human interactions
The finless sleeper ray is susceptible to
Phuket in Thailand. Due to heavy fishing pressure within its range and its low reproductive rate, the finless sleeper ray has been assessed as Vulnerable by the International Union for Conservation of Nature (IUCN).[1] Specific population data are lacking, but at least off Thailand electric ray populations overall appear to have declined since 1975.[1][7]
References
- ^ . Retrieved 20 November 2021.
- ^ Gray, J.E. (1831). "Description of twelve new genera of fish, discovered by Gen. Hardwicke, in India, the greater part in the British Museum". Zoological Miscellany. 1831: 7–9.
- ISBN 978-1-4398-3924-9.
- ^ a b Compagno, L.J.V.; Heemstra, P.C. (2007). "Electrolux addisoni, a new genus and species of electric ray from the east coast of South Africa (Rajiformes: Torpedinoidei: Narkidae), with a review of torpedinoid taxonomy". Smithiana, Publications in Aquatic Biodiversity, Bulletin. 7: 15–49.
- ^ ISBN 978-92-5-104302-8.
- ^ ISBN 978-1-921605-59-8.
- ^ a b c Monkolprasit, S. (1990). "The Electric Rays Found In Thailand". Kasetsart Journal: Natural Science. 24: 388–397.
- ^ a b c d Cantor, T. (1850). "Catalogue of Malayan Fishes". Journal of the Asiatic Society of Bengal. 18 (2): 983–1694.
- PMID 21672821.