About Narcine entemedor Jordan & Starks, 1895
Narcine entemedor, commonly known as the giant electric ray or Cortez electric ray, is a species of numbfish in the family Narcinidae. It is native to the eastern Pacific Ocean, ranging from the Gulf of California to Panama. It inhabits shallow water on sandy bottoms, and is sometimes found adjacent to reefs. This species is closely related to the lesser electric ray (Narcine bancroftii) of the western Atlantic, and may actually be the same species. The specific epithet entemedor is likely the Spanish term for "intimidator". This species reaches a maximum total length of 76 cm (30 in). Its flattened pectoral fin disk is round, as long as it is wide, and overlaps the origin of its large pelvic fins. The eyes are much smaller than the spiracles, which are bordered by small tubercles. Each nostril is not split into two separate openings. When the mouth is closed, most of the teeth remain exposed. The tail is the same length as the disk, has loose lateral folds of skin, and bears two equal-sized dorsal fins. The tips of the dorsal and caudal fins are angular. The skin is soft and loose, and lacks denticles or thorns. The upper side of the body is generally grayish tan to brown; some individuals have several pairs of faint ocelli. The dorsal and caudal fins often darken toward their tips, but have fine white margins. There is one recorded case of a partially albino adult female of this species, measuring 69 cm (27 in) long. Like all other numbfishes, the giant electric ray can produce a painful electric shock. This species is nocturnal: it spends the day half-buried in sand, and moves into shallow bays at night to feed. Its diet mostly consists of polychaete worms, and may also include sea squirts. It travels along the seabed by "hopping" using its flexible, ribbed pelvic fins. When threatened by a predator, it performs a characteristic defensive behavior: it erupts from the seabed, arches its back, and does a "somersault" in the water. In one documented incident, a diver received an electric shock after this ray landed on his back following such a maneuver. This species has ovoviviparous reproduction: developing embryos are nourished by uterine "milk" produced by the mother. Females give birth to litters of 4 to 15 young, which measure 11–12 cm (4.3–4.7 in) long at birth. The reproductive cycle occurs annually, with ovulation and fertilization taking place in July and August. Males can live longer than 11 years, while females can live longer than 15 years. Known parasites of the giant electric ray include the tapeworms Acanthobothrium franus and A. inbiorium, and the copepod Taeniacanthodes dojirii. According to PhD J. Fernando Marquez-Farias, this species is caught by an artisanal ray fishery in the Gulf of California. It is harvested in the coastal waters of the Mexican states of Sinaloa, Baja California, Baja California Sur and Sonora; in Sonora, it is part of a multispecies fishery.
