Narkidae
Encyclopedia
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.
s 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.
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 fin
s, 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.
s, such as polychaete worms. They can generate a strong electric shock
as a defense mechanism. Reproduction is ovoviviparous, with eggs
hatching inside the mother.
Indo-West Pacific
The Indo-West Pacific, or IWP, is a zoogeographical region spanning the entire Indian Ocean including the Red Sea and the Pacific Ocean as far as the Caroline Islands but short of the Marshall Islands...
from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
to Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, and are exclusively marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
and are absent from freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
habitats. They occur from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
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 rostal 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 nostrilNostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s 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.
There are a pair of large kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
-shaped electric organs at the base of the pectoral fins, visible through the skin. The genera Heteronarce and Electrolux have two large dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s, 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.
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 invertebrateInvertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, such as polychaete worms. They can generate a strong electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
as a defense mechanism. Reproduction is ovoviviparous, with eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
hatching inside the mother.
Species
- Genus Crassinarke Takagi, 1951
- Crassinarke dormitor Takagi, 1951 (Sleeper torpedo)
- Genus Electrolux CompagnoLeonard CompagnoLeonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...
& Heemstra, 2007- Electrolux addisoniElectrolux addisoniElectrolux addisoni is a species of electric ray and the only member of the genus Electrolux. It lives on reefs feeding on polychaete worms and small crustaceans, it has only been seen by divers to feed during the daytime. It is endemic to the coast of South Africa. It was first recorded in 1984...
CompagnoLeonard CompagnoLeonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...
& Heemstra, 2007 (Ornate sleeper ray)
- Electrolux addisoni
- Genus HeteronarceHeteronarceThe genus Heteronarce is a genus of sleeper rays in the family Narkidae. This genus is found only in the western Indian Ocean along the coasts of Africa, the Arabian Peninsula and India...
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 NarkeNarke (genus)Narke is a genus of electric rays, classified in the family Narkidae.-Species:* Narke capensis * Narke dipterygia...
KaupJohann Jakob KaupJohann Jakob Kaup was a German naturalist.-Biography:He was born at Darmstadt. After studying at Göttingen and Heidelberg he spent two years at Leiden, where his attention was specially devoted to the amphibians and fishes. He then returned to Darmstadt as an assistant in the grand ducal museum,...
, 1826- Narke capensis (GmelinJohann Friedrich GmelinJohann Friedrich Gmelin was a German naturalist, botanist, entomologist, herpetologist and malacologist.- Education :Johann Friedrich Gmelin was born as the eldest son of Philipp Friedrich Gmelin in 1748 in Tübingen...
, 1789) (Onefin electric ray) - Narke dipterygia (BlochMarcus Elieser BlochMarcus Elieser Bloch was a German medical doctor and naturalist. He is generally considered one of the most important ichthyologists of the 18th century.- Life :...
& SchneiderJohann Gottlob SchneiderJohann Gottlob Theaenus Schneider was a German classicist and naturalist.-Biography:Schneider was born at Collm in Saxony...
, 1801) (Numbray) - Narke japonica (TemminckCoenraad Jacob TemminckCoenraad Jacob Temminck was a Dutch aristocrat and zoologist.Temminck was the first director of the National Natural History Museum at Leiden from 1820 until his death. His Manuel d'ornithologie, ou Tableau systematique des oiseaux qui se trouvent en Europe was the standard work on European birds...
& SchlegelHermann SchlegelHermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...
, 1850) (Japanese sleeper ray)
- Narke capensis (Gmelin
- Genus Temera J. E. GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1831- Temera hardwickii J. E. GrayJohn Edward GrayJohn Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....
, 1831 (Finless sleeper ray)
- Temera hardwickii J. E. Gray
- Genus Typhlonarke WaiteEdgar Ravenswood WaiteEdgar Ravenswood Waite was a British/Australian ichthyologist, ornithologist and zoologist.Waite was born in Leeds, Yorkshire, England, the second son of John Waite, a bank clerk,...
, 1909- Typhlonarke aysoni (A. Hamilton, 1902) (Blind electric ray)
- Typhlonarke tarakea Phillipps, 1929 (Oval electric ray)