''Narcine entemedor'', the giant electric ray or Cortez electric ray, is a species of

numbfish Narcinidae, or numbfishes, are a family of electric rays (order Torpediniformes). They are bottom-dwelling cartilaginous fishes with large, rounded pectoral fin discs and long tails. They can produce an electric discharge for defense, from whic ...

, family

Narcinidae Narcinidae, or numbfishes, are a family of electric rays (order Torpediniformes). They are bottom-dwelling cartilaginous fishes with large, rounded pectoral fin discs and long tails. They can produce an electric discharge for defense, from whic ...

, native to the eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

from the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

. It is found in shallow water on sandy bottoms and sometimes adjacent to

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...

s. This species is closely related to the

lesser electric ray The lesser electric ray (''Narcine bancroftii''), also known as the Brazilian electric ray, small electric ray, spotted torpedo ray, torpedofish or trembler, is a species of numbfish in the family Narcinidae found on the western coastal fringes o ...

(''Narcine bancroftii'') from the western

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

, and may represent the same species. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''entemedor'' seems to be the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Cana ...

equivalent of "intimidator". This species attains a maximum length of 76 cm (30 in). The flattened

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

disk is round, as long as it is wide, and overlapping the origin of the large

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s. The

eyes Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...

are much smaller than the

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s, which are edged with small tubercles. The

nostril A nostril (or naris , plural ''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 turbi ...

on each side is not divided into two separate apertures. The

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

are mostly exposed when the mouth is closed. The tail is equal in length to the disk, with loose lateral folds of skin and two

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s of equal size. The tips of the dorsal and

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

s are angular. The skin is soft and loose, without

denticle A denticle is any small tooth-like or bristle-like structure. "Denticle" may refer to: * Denticle (tooth feature), serrations on the teeth of dinosaurs, lizards, sharks, and mammals * Dermal denticles or placoid scales, in cartilaginous fishes * ...

s or thorns. The coloration is generally grayish tan to brown above; some individuals have several pairs of faint

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

. The dorsal and caudal fins often darken towards the tips but have fine white margins.Murch, A
CORTEZ ELECTRIC RAY
''Elasmodiver.com''. Retrieved on February 15, 2009. There is a record of a partially

albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...

adult female, measuring 69 cm (27 in) long. Like other numbfishes, the giant electric ray can deliver a painful

electric shock Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce ...

. This species is

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

and spends the day half-buried under sand. At night, it moves into shallow bays to feed, mostly on

polychaete worm Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are mad ...

s but perhaps also on

sea squirt Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class (biology), class in the subphylum Tunicate, Tunicata of sac-like marine (ocean), marine invertebrate filter feeders. Ascidians ar ...

s. It moves along the bottom by "hopping" on its flexible ribbed pelvic fins. If threatened by a

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

, it exhibits a characteristic defense behavior in which it erupts from the bottom, arches its back, and performs a "somersault" in the water column. In one case, a diver was shocked when the ray landed on his back after such a maneuver. Reproduction is

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

, in which the developing

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s are nourished by uterine "milk" produced by the mother. The females give birth to 4-15 young, measuring 11–12 cm (4.3-4.7 in) long. The reproductive cycle is annual, with

ovulation Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized ...

and

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

taking place in July and August.Downton-Hoffmann, C.A. and Villavicencio-Garayzar, C.J. (2000). "El Niño"/Southern Oscillation effects on the shovelnose guitarfish, ''Rinobatos productus'', and Pacific electric ray, ''Narcine entemedor'', in Bahía Almejas, B.C.S., México. American Elasmobranch Society 16th Annual Meeting abstracts. Retrieved on February 15, 2009. Males may exceed 11 years of age, and females 15 years. Known

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s of the giant electric ray include the

tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodar ...

s '' Acanthobothrium franus'' and '' A. inbiorium'', and the

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

'' Taeniacanthodes dojirii''. According to

PhD PHD or PhD may refer to: * Doctor of Philosophy (PhD), an academic qualification Entertainment * '' PhD: Phantasy Degree'', a Korean comic series * ''Piled Higher and Deeper'', a web comic * Ph.D. (band), a 1980s British group ** Ph.D. (Ph.D. albu ...

J. Fernando Marquez-Farias, this species is harvested by an artisanal ray fishery in the

, specifically in the coastal waters of the Mexican states of

Sinaloa Sinaloa (), officially the Estado Libre y Soberano de Sinaloa ( en, Free and Sovereign State of Sinaloa), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. It is d ...

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...

and Sonora, being in this last one part of a multispecies fishery.

References

External links

* {{Taxonbar, from=Q2032915 entemedor Fish of the Gulf of California Fish of Mexican Pacific coast Western Central American coastal fauna Fish described in 1895