Narcinidae, or numbfishes, are a family of

electric ray The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, composing the order Torpediniformes . They are known for being capable of producing an electric discharge, ranging from 8 to 220 volts, depending ...

s (order

Torpediniformes Fernando de Buen y Lozano was a Spanish ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, ...

). They are

bottom-dwelling The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

cartilaginous fish Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeleto ...

es with large, rounded

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

discs and long tails. They can produce an

electric discharge In electromagnetism, an electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas (i.e., an outgoing flow of electric current through a non-metal medium).American Geophysical U ...

for defense, from which their

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

is derived (

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, meaning 'paralysis'). Members of this family are commonly known as the numbfishes, and are found almost worldwide in warm temperate and tropical continental and continental insular waters. They are strictly marine, so are absent from

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s. They occur in

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from Rock (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological s ...

es, muddy enclosed

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a ''gulf'', ''sea'', ''sound'', or ''bight''. A ''cove'' is a small, ci ...

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

, off

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...

s and river mouths, and on the upper

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

to a depth of 1,071 m.Compagno, L.J.V. and Last, P.R. (1999). Narcinidae. Numbfishes. p. 1433-1437. 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 The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates ...

Description

Small to medium-sized

rays Ray or RAY may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), the bony or horny spine on ray-finned fish Science and mathematics * Half-line (geometry) or ray, half of a line split at an ...

, adult numbfishes range from 15 to 66 cm long, though most are less than 50 cm. They have oval, rounded, or

shovel A shovel is a tool used for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Most shovels are hand tools consisting of a broad blade fixed to a medium-length handle. Shovel blades are usually made ...

-shaped pectoral discs and stout tails of equal or longer length. The snout is moderately elongated, rounded, or rounded-angular, differing from the narkids in being supported by broad rostral

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

s. The mouth is straight, with stout, elongated, and highly protrusible jaws and a prominent groove around its periphery. The

nostril A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates ...

s are just forward of the mouth and connected to it by a broad groove; the nasal flaps are short, but merged into a broad nasal curtain that overlaps the mouth. The small teeth have a single moderate cusp; the teeth and tooth bands are exposed when the mouth is closed (except in ''Diplobatis''). Two prominent

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s of roughly equal size and a large

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

are present. Numbfishes vary in color from whitish or yellowish to brownish, grey-brown, greenish, reddish, or black above, either plain or with small to large spots, blotches, bars or lines, sometimes forming complex eye-shaped spots or

ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

on the pectoral fins. They are usually white underneath, or black in deep-water species. The large,

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

-shaped electric organs at the base of the pectoral fins are visible through the skin.

Biology and ecology

Numbfishes are slow-swimming bottom-dwellers that feed on small

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

es and

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s off the bottom; their protrusible jaws aid in removing prey from the substrate. They can generate a moderate shock if disturbed and contact is made with the electric organs; the electrical discharges of narcinids have been measured at 8-37

volt The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Uni ...

s, much less than the electric rays of the genus ''

Torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such ...

''.Martin, R. Aidan
Electric Rays
''ReefQuest Centre for Shark Research.'' Retrieved on October 12, 2008. All species are

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

, with eggs hatching inside the mother.

Genera

These genera are included in this family: * ''

Benthobatis ''Benthobatis'' is a genus of fish in the family Narcinidae with four currently recognized species. Species * ''Benthobatis kreffti'' Getúlio Rincón, Rincón, Matthias Stehmann, Stehmann & Carolus Maria Vooren, Vooren, 2001 (Brazilian blind e ...

'' * ''

Diplobatis ''Diplobatis'' is a genus of electric rays in the family (biology), family Narcinidae. Species * ''Diplobatis colombiensis'' Janice D. Fechhelm, Fechhelm & John D. McEachran, McEachran, 1984 (Colombian electric ray) * ''Diplobatis guamachensis'' ...

'' * ''

Discopyge ''Discopyge'' is a small genus of fish, the apron rays, in the family Narcinidae. Species * '' Discopyge castelloi'' Menni, Rincón & M. L. Garcia, 2008 * '' Discopyge tschudii'' Heckel, 1846 (Apron ray) References Narcinidae Ray gen ...

'' * ''

Narcine ''Narcine'' is a genus of electric rays in the family (biology), family Narcinidae. These species have a rounded pectoral fin disc and two dorsal fins, the first usually smaller than the second and placed behind the pelvic fin bases. The caudal f ...

'' * '' Narcinops''

References

{{Taxonbar, from=Q2167421 Torpediniformes Marine fish families Ray families Taxa named by Theodore Gill