Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Classis: Chondrichthyes
Subclassis: Elasmobranchii
Superordo: Rajomorphii
Ordo: Torpediniformes
Familia: Narkidae
Genera: Electrolux – Heteronarce – Narke – Temera – Typhlonarke
References
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 bulletin, (7): 15–49. ISSN 1684-4130
Vernacular names
English: sleeper rays
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. They occur from the intertidal zone to the continental shelf and the upper continental slope to a depth of 350 meters, favoring soft-bottomed habitats.
Description
Adult sleeper rays range in size from 8 to 46 cm in length and have flattened oval, circular, or pear-shaped pectoral fin discs. They have naked skin, without dermal denticles or thorns. The snout is moderately elongate and broadly rounded, with the rostral cartilage reduced to a slender medial rod. This distinguishes the narkids from the family Narcinidae, which have somewhat longer snouts supported by broad rostral cartilages. The mouth is straight, very narrow, and not highly protrusible, with strong labial folds and a weak groove around the periphery. The nostrils are placed just forward of the mouth and are connected to it by a broad nasoral groove; the nasal flaps are long and fused into a central nasal curtain that overlaps the mouth.[1]
There are a pair of large kidney-shaped electric organs at the base of the pectoral fins, visible through the skin. The genera Heteronarce and Electrolux have two large dorsal fins, Narke, Crassinarke, and Typhlonarke have a single dorsal fin, and Temera has none. No other group of electric rays have genera with a variable number of dorsal fins. The tail is moderately long, with a large, rounded, symmetrical caudal fin. The color is usually brown or reddish brown above, white or brownish below. There may be spots, blotches, or bands on the dorsal surface, but most species lack complex color patterns or ocelli.[1]
Biology and ecology
Sleeper rays are bottom-dwelling, slow-moving fishes often found on soft mud or sand. From those species that have been examined, their diet may be restricted to small, soft-bodied, bottom invertebrates, such as polychaete worms. They can generate a strong electric shock as a defense mechanism. Reproduction is ovoviviparous, with eggs hatching inside the mother.[1]
Species
Genus Crassinarke Takagi, 1951
Crassinarke dormitor Takagi, 1951 (Sleeper torpedo)
Genus Electrolux Compagno & Heemstra, 2007
Electrolux addisoni Compagno & Heemstra, 2007 (Ornate sleeper-ray)
Genus Heteronarce Regan, 1921
Heteronarce bentuviai (Baranes & Randall, 1989) (Elat electric ray)
Heteronarce garmani Regan, 1921 (Natal electric ray)
Heteronarce mollis (Lloyd, 1907) (Soft electric ray)
Heteronarce prabhui Talwar, 1981 (Quilon electric ray)
Genus Narke Kaup, 1826
Narke capensis (Gmelin, 1789) (Onefin electric ray)
Narke dipterygia (Bloch & Schneider, 1801) (Numbray)
Narke japonica (Temminck & Schlegel, 1850) (Japanese sleeper ray)
Genus Temera J. E. Gray, 1831
Temera hardwickii J. E. Gray, 1831 (Finless sleeper ray)
Genus Typhlonarke Waite, 1909
Typhlonarke aysoni (A. Hamilton, 1902) (Blind electric ray)
Typhlonarke tarakea Phillipps, 1929 (Oval electric ray)
References
Froese, Rainer; Pauly, Daniel (eds.). "Family Narkidae". FishBase. February 2011 version.
Compagno, L.J.V. and Last, P.R. (1999). Narkidae. Sleeper rays. p. 1443-1446. In: K.E. Carpenter and V.H. Niem (eds.) FAO identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Rome: Food and Agriculture Organization.
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