Atlantic Torpedo

The **Atlantic torpedo** (*Tetronarce nobiliana*) is a species of electric ray in the family Torpedinidae. It is found in the Atlantic Ocean, from Nova Scotia to Brazil in the west and from Scotland to West Africa and off southern Africa in the east, occurring at depths of up to 800 m (2,600 ft). Younger individuals generally inhabit shallower, sandy or muddy habitats, whereas adults are more pelagic in nature and frequent open water. Up to 1.8 m (6 ft) long and weighing 90 kg (200 lb), the Atlantic torpedo is the largest known electric ray. Like other members of its genus, it has an almost circular pectoral fin disk with a nearly straight leading margin, and a robust tail with a large triangular caudal fin. Distinctive characteristics include its uniform dark color, smooth-rimmed spiracles (paired respiratory openings behind the eyes), and two dorsal finsof unequal size.

Solitary and nocturnal, the Atlantic torpedo is capable of generating up to 220 volts of electricity to subdue its prey or defend itself against predators. Its diet consists mainly of bony fishes, though it also feeds on small sharks and crustaceans. It is an aplacental viviparous species, wherein the developing embryos are nourished by yolk and later maternally provided histotroph ("uterine milk"). Females give birth to up to 60 young following a gestation period of one year. The electric shock of this species can be quite severe and painful, though it is not fatal. Because of its electrogenic properties, the Atlantic torpedo was used in medicine by the Ancient Greeksand Romans and became the namesake of the naval weapon. Prior to the 19th century, its liver oil was used as lamp fuel, but it is no longer of any economic value. The International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient; it is caught unintentionally by commercial and recreational fishers, but the impact of these activities on its population is unknown.

## Description

The Atlantic torpedo has a nearly circular pectoral fin disc 1.2 times as wide as it is long, with a thick and nearly straight front margin. The eyes are small and are followed by much larger spiracles, which do not have papillae on their inner rims. The nostrils are close to the mouth; there is a flap of skin between them three times as wide as long, with a sinuous rear margin. The mouth is wide and arched, with prominent furrows at the corners. The teeth are pointed and increase in number with age, ranging from 38 rows in juveniles to 66 rows in adults; the first several series of teeth are functional. The gill slits are small, with the first and fifth pairs shorter than the others.

The pelvic fins are rounded and slightly overlapped by the disc at the front. The first dorsal fin is triangular with a rounded apex, originating in front of the pelvic fin insertions. The second dorsal fin is only one-half to two-thirds as large as the first; the distance between the dorsal fins is less than the length of the first dorsal fin base. The stout tail comprises about one-third of the total length, terminating in a caudal fin shaped like an equilateral triangle with slightly convex margins. The skin is soft and completely devoid of dermal denticles (scales). The dorsal coloration is a plain dark brown to gray, sometimes with a few diffuse spots, and darkening at the fin margins. The underside is white, with dark fin margins. The largest of the electric rays, the Atlantic torpedo can measure 1.8 m (6 ft) long and weigh 90 kg (200 lb). However, a length of 0.6–1.5 m (2.0–4.9 ft) and weight of 30 lb (14 kg) is more typical. Females attain a larger size than males.

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