Common torpedo

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Common torpedo
Torpedo torpedo corsica3.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Torpediniformes
Family: Torpedinidae
Genus: Torpedo
Species:
T. torpedo
Binomial name
Torpedo torpedo
Torpedo torpedo rangemap.png
Range of the common torpedo [1]
Synonyms

Raja torpedo Linnaeus, 1758
Torpedo narkeDelaroche, 1809
Torpedo ocellataRafinesque, 1810
Torpedo oculataDavy, 1834
Torpedo unimaculata Risso, 1810

Contents

The common torpedo (Torpedo torpedo), also known as ocellate torpedo or eyed electric ray, is a species of electric ray in the family Torpedinidae. It is found in the Mediterranean Sea and the eastern Atlantic Ocean from the Bay of Biscay to Angola, and is a benthic fish typically encountered over soft substrates in fairly shallow, coastal waters. Growing to 60 cm (24 in) long, this species has a nearly circular pectoral fin disc and a short, thick tail with two dorsal fins of nearly equal size and a large caudal fin. It can be identified by the prominent blue spots on its back, which usually number five but may vary from zero to nine, as well as by the small knobs on the rims of its spiracles.

For attack and defense, the common torpedo can deliver a strong electric shock of up to 200 volts. It is a solitary, nocturnal ambush predator that feeds mainly on bony fishes and crustaceans. This species is aplacental viviparous, with the developing embryos nourished by yolk and histotroph ("uterine milk") produced by the mother. Females produce litters of up to 28 young every year in late summer or autumn, after a gestation period of 4–8 months; the specifics vary between geographical regions. The common torpedo's shock is painful but otherwise of little danger to humans. Its electrogenic properties led it to be used in medicine by the ancient Greeks and Romans. In modern times, it has no economic value and is mostly discarded when caught as bycatch in fisheries. The impact of fishing on its population is uncertain, and the International Union for Conservation of Nature (IUCN) has listed it as Vulnerable.

Taxonomy

The common torpedo and other electric rays were familiar to the peoples of classical antiquity. Torpedo was the Roman name for electric rays, derived from Latin torpere meaning 'to be numb'. [2] [3] Carl Linnaeus, known as the "father of taxonomy", scientifically described the common torpedo as Raja torpedo in the 1758 tenth edition of his Systema Naturae . However, the common torpedo also appeared in at least 52 pre-Linnaean sources under various names such as Torpedo, Raja tota lævis, Torpedo maculosa, and Torpedo Sinûs Persici. These early accounts, including Linnaeus's, confounded the common torpedo with other electric ray species. As Linnaeus did not indicate any type specimens, the designation of a lectotype or neotype is warranted in the interest of taxonomic stability. This measure has yet to be taken. [4]

Peter Forsskål validly published the genus name Torpedo in 1775, predating the use of the genus name Torpedo by Duméril in 1806, meaning that Torpedo Duméril, 1806 (often cited in catalogs) is a junior homonym of Forsskål's name and cannot be used. [5] Forsskål included only a single species, Raja torpedo Linnaeus, 1758, thereby making it the type species of the genus. While Forsskål's description indicated that he had misinterpreted Linnaeus' name and ascribed it to another electric fish (currently known as Malapterurus electricus ), this potential source of confusion was rectified in 2008, when Raja torpedo Linnaeus was officially made the type species under ICZN Article 70.3.1. [5] Within the genus Torpedo, the common torpedo is placed within the subgenus Torpedo, which differs from the other subgenus Tetronarce in having spiracles with papillate rims and ornate dorsal coloration. [6] This species may also be referred colloquially to as crampfish, cramp ray, or torpedo ray. [7] [8]

Distribution and habitat

Native to the eastern Atlantic Ocean, the common torpedo occurs from the Bay of Biscay to Angola. [7] It is present in the Mediterranean Sea as well, with higher densities in the western part of the Basin. [9] A single record from Belgian waters was most likely erroneous. In European waters, it is encountered less frequently than other electric ray species. This species prefers warmer temperatures. [10] It is rare north of the Mediterranean, and within the Mediterranean it is more common off North Africa than off southern Europe. [1] [10] The common torpedo is a bottom-dweller usually found close to shore at depths of 2–70 m (6.6–229.7 ft), though it has occasionally been reported from as deep as 400 m (1,300 ft). It inhabits soft-bottomed habitats such as sandy flats and seagrass beds. [7] [11]

Description

The common torpedo usually has five blue spots on its back, which distinguishes it from other electric rays. Torpedo torpedo corsica4.jpg
The common torpedo usually has five blue spots on its back, which distinguishes it from other electric rays.

The pectoral fin disc of the common torpedo is almost circular in shape and about 1.3–1.4 times wider than long. The front margin of the disc is nearly straight. The two large, kidney-shaped electric organs are visible beneath the skin on either side of the head. The eyes are small and followed by spiracles of comparable size. The lateral and posterior rims of the spiracles bear small, low knobs, which diminish in size with age and may be indiscernible in larger individuals. On the "nape" behind the spiracles, there is a pair of prominent mucous pores. There is a wide, quadrangular flap of skin between the nostrils that almost reaches the mouth. The teeth are small and arranged in a dense quincunx pattern; each tooth has a single sharp cusp. There are around 22–24 and 20–22 tooth rows in the upper and lower jaws respectively. The five pairs of gill slits are placed on the underside of the disc. [10] [12] [13]

The pelvic fins are distinct from the disc and have rounded outer margins. The short and thick tail bears skin folds along either side and two dorsal fins on top. The first dorsal fin is slightly larger than the second. The well-developed caudal fin is triangular with blunt corners, and is approximately as long as the space between it and first dorsal fin. The skin is smooth and soft, entirely lacking dermal denticles. The dorsal coloration of the common torpedo is rusty orange to reddish brown, with distinctive large spots ("ocellae") on the disc; each ocellus is blue and encircled by darker and lighter rings. Typically there are five ocellae arranged symmetrically in a row of three and another of two; rays with 0–4 ocellae are less common, and those with more than five are rarer still. An unusual male with eight ocellae was caught off Tunisia, and another with nine off southern France. When present, the sixth ocellus is similarly sized to the first five and positioned at their center; any additional ocellae tend to be smaller than the first six and placed asymmetrically towards the snout. The underside is cream-colored, with dark disc margins. [12] [13] An adult albino female was captured off Tunisia. [14] Males and females typically measure 30 and 39 cm (12 and 15 in) long respectively; the largest individual on record was 60 cm (24 in) long. [7] Rays from off West Africa grow larger than those from the Mediterranean. [15]

Biology and ecology

The common torpedo is almost invisible when silted up. Sanded ocellate torpedo.png
The common torpedo is almost invisible when silted up.
The common torpedo is an ambush predator that lies in wait for prey on the sea bottom. Torpedo torpedo corsica.jpg
The common torpedo is an ambush predator that lies in wait for prey on the sea bottom.

As with other members of its family, the common torpedo can subdue prey and deter threats with strong electric shocks generated from a pair of large electric organs. Derived from muscle tissue, each organ is made up of 400–500 columns, each column constituting a stack of around 400 jelly-filled disks ("electroplaques"). The columns together essentially act as batteries connected in parallel. [16] The discharge of the electric organs can reach 200 volts, and may occur singly or in bursts ("trains"). [7] [17] Experiments in vitro have found that the nerves innervating the electric organ essentially stop functioning at temperatures below 15 °C (59 °F). Winter water temperatures regularly drop below this threshold in the wild, suggesting the ray may not use its electric organs for part of the year, or has a yet-unknown physiological mechanism to adapt electric organ function to colder conditions. [18]

Solitary and nocturnal, the common torpedo spends much time resting on the sea floor, often buried in sediment. [11] It is an ambush predator that pounces onto prey and stuns them with electricity, the process taking only a fraction of a second. Once the prey is immobilized, it is manipulated to the mouth with motions of the disc, and swallowed whole. [17] Adults feed almost entirely on small benthic bony fishes, including soles, herring, mullet, gobies, goatfishes, porgies, dragonets, and jack mackerels. Large decapod crustaceans are a minor secondary food source, while very rarely skates may be consumed. Juveniles are less exclusively piscivorous than the adults and feed on a variety of invertebrates as well. The most significant prey species differ between seasons and geographic regions. For example, in the Tyrrhenian Sea, juvenile common sole (Solea solea) are by far the most important prey item in autumn and winter, but in spring and summer they become less available and other fishes figure more prominently in the ray's diet. [19] [20] Known parasites of this species include the tapeworm Phyllobothrium lactuca , [21] and the monogeneans Amphibdella paronaperugiae [22] and Amphibdelloides benhassinae . [23]

Life history

Drawing collected by Felix Platter, anonymous, 1546-1558 Animal drawings collected by Felix Platter, p1 - (138).jpg
Drawing collected by Felix Platter, anonymous, 1546–1558

The common torpedo is aplacental viviparous, in which the embryos are sustained by yolk, supplemented by histotroph ("uterine milk") secreted by the mother. However, the organic content of the histotroph in this species is only 1.2%, much lower than in stingrays, and the embryo loses mass over the course of development as its initial yolk supply is expended for metabolic processes. [15] [24] Adult females have two functional ovaries and two functional uteruses, though the reproductive tract on the right side is more developed and consequently tends to carry more embryos. It has an annual reproductive cycle with well-defined seasonality, though the details differ between geographic regions. In the Mediterranean, mating occurs from December to February and birthing from late August to early September after a gestation period of 4–6 months; litter sizes range up to 19 and the newborns measure 8.0–9.7 cm (3.1–3.8 in) long. By contrast, off West Africa the gestation period lasts 6–8 months and birthing occurs from September to October; litter sizes range up to 28 and the newborns measure 10.2–12.5 cm (4.0–4.9 in) long. The litter size increases with female size. [15] [19] [25]

Sexual segregation occurs during the breeding season as pregnant females move into shallow coastal waters. The common torpedo is unusual among sharks and rays in that birthing has been documented both at higher and at lower salinities than seawater, in estuaries and lagoons. [15] Immediately after birth, this species is capable of producing electric shocks of up to four volts. Newborns grow rapidly, with a commensurate increase in electrogenic capacity: after four months, they almost double in weight and can generate 26 volts. [17] Males and females mature sexually at similar lengths: 25 and 26 cm (9.8 and 10.2 in) respectively in the Tyrrhenian Sea, [25] 18 and 22 cm (7.1 and 8.7 in) respectively off Egypt, [19] 19 cm (7.5 in) for both off Tunisia, and 30 and 31 cm (12 and 12 in) respectively off Senegal. [15]

Human interactions

The electric shock of the common torpedo can be severe, but is not life-threatening. [26] In classical antiquity, the electrogenic properties of this species led it (and other strongly electric fishes) to be used in medicine for the treatment of pain and diseases such as gout. [27] For example, the Roman physician Scribonius Largus, in his Compositiones medicae (c. 50 AD), recommended that chronic headaches be treated by the application of a live torpedo to the affected area. [28] The common torpedo is edible, but is little-valued by commercial or artisanal fisheries and is mostly discarded when caught. Because of its shallow-water habits, it may survive being captured and discarded relatively well. It is susceptible to several types of demersal fishing gear, including bottom trawls and trammel nets; fishing activity is heavy within its range but no specific data regarding this species are available. The International Union for Conservation of Nature (IUCN) has listed it as Vulnerable. [1] The common torpedo has been kept in aquariums, but requires live fish for food. [8]

Related Research Articles

<span class="mw-page-title-main">Torpedinidae</span> Family of cartilaginous fishes

The family Torpedinidae contains 22 species of electric rays or torpedoes, flat cartilaginous fishes that produce electricity as a defense and feeding mechanism. They are slow-moving bottom-dwellers.

<span class="mw-page-title-main">Pacific electric ray</span> Species of cartilaginous fish

Tetronarce californica also known as the Pacific electric ray is a species of electric ray in the family Torpedinidae, endemic to the coastal waters of the northeastern Pacific Ocean from Baja California to British Columbia. It generally inhabits sandy flats, rocky reefs, and kelp forests from the surface to a depth of 200 m (660 ft), but has also been known to make forays into the open ocean. Measuring up to 1.4 m (4.6 ft) long, this species has smooth-rimmed spiracles and a dark gray, slate, or brown dorsal coloration, sometimes with dark spots. Its body form is typical of the genus, with a rounded pectoral fin disc wider than long and a thick tail bearing two dorsal fins of unequal size and a well-developed caudal fin.

<i>Torpedo</i> (genus) Genus of cartilaginous fishes

Torpedo is a genus of rays, commonly known as electric rays, torpedo rays, or torpedoes. They are slow-moving bottom-dwellers capable of generating electricity as a defense and feeding mechanism.

<i>Mullus barbatus</i> Species of fish

Mullus barbatus is a species of goatfish found in the Mediterranean Sea, Sea of Marmara, the Black Sea and the eastern North Atlantic Ocean, where its range extends from Scandinavia to Senegal. They are fished, mostly by trawling, with the flesh being well regarded. The International Union for Conservation of Nature has assessed their conservation status as being of "least concern".

<span class="mw-page-title-main">Coffin ray</span> Species of cartilaginous fish

Hypnos monopterygius, also known as the coffin ray or Australian numbfish, is a species of electric ray endemic to Australia, where it is common in inshore waters shallower than 80 m (260 ft). It is the sole member of its genus Hypnos, and family Hypnidae. This small species typically reaches 40 cm (16 in) in length. Greatly enlarged pectoral fins and an extremely short tail, coupled with diminutive dorsal and caudal fins all concentrated towards the rear, give the coffin ray a distinctive pear-like shape. It is a varying shade of brown in colour above, and has tiny eyes and a large, highly distensible mouth.

<span class="mw-page-title-main">Thornback ray</span> Species of cartilaginous fish

The thornback ray, or thornback skate, is a species of ray fish in the family Rajidae.

The Aden Gulf torpedo or Aden torpedo is a poorly known species of electric ray in the family Torpedinidae, seemingly endemic to the eastern Gulf of Aden, near the coast of Yemen. Growing to 41 cm (16 in) long, this species has a nearly circular pectoral fin disc and a short, thick tail with two dorsal fins and a well-developed caudal fin. It is characterized by its reddish dorsal coloration, which in contrast to related species lacks any additional markings. The International Union for Conservation of Nature (IUCN) has assessed the Aden Gulf torpedo as Endangered, citing its extremely small range and the intensive shrimp trawling that occurs in the region.

<span class="mw-page-title-main">Florida torpedo</span> Species of cartilaginous fish

The Florida torpedo is a rare and little-known species of electric ray in the family Torpedinidae. It is known only from two specimens and a some wild sightings. Torpedoes have been recorded from three scattered locations in the Florida Straits and the western Caribbean Sea, and appear to inhabit coral habitats.

<span class="mw-page-title-main">Blackspotted torpedo</span> Species of cartilaginous fish

The black-spotted torpedo is a poorly known, uncommon species of electric ray in the family Torpedinidae, known for being capable of generating an electric shock. It is endemic to southern Africa and possibly several small Indian Ocean islands, although the latter reports may represent undescribed new species. Its appearance is similar to the Gulf torpedo, but it is duller in coloration.

<span class="mw-page-title-main">Gulf torpedo</span> Species of cartilaginous fish

The Gulf torpedo or variable electric ray, is a species of electric ray in the family Torpedinidae. It is found in the Indian Ocean, but may represent a species flock of several local endemic species. It is distinguishable from other Torpedo species in its range by its ornate dorsal coloration. Another common name, marbled electric ray, is not to be confused with Torpedo marmorata.

<span class="mw-page-title-main">Marbled electric ray</span> Species of cartilaginous fish

The marbled electric ray is a species of electric ray in the family Torpedinidae found in the coastal waters of the eastern Atlantic Ocean from the North Sea to South Africa. This benthic fish inhabits rocky reefs, seagrass beds, and sandy and muddy flats in shallow to moderately deep waters. It can survive in environments with very little dissolved oxygen, such as tidal pools. The marbled electric ray has a nearly circular pectoral fin disc and a muscular tail that bears two dorsal fins of nearly equal size and a large caudal fin. It can be identified by the long, finger-like projections on the rims of its spiracles, as well as by its dark brown mottled color pattern, though some individuals are plain-colored. Males and females typically reach 36–38 cm (14–15 in) and 55–61 cm (22–24 in) long respectively.

The lobed stingaree is a common species of stingray in the family Urolophidae, endemic to southern Western Australia in shallow, inshore sand and seagrass habitats. This species is plain sandy in colour above and has a broad, rounded pectoral fin disc. It is characterized by an enlarged, semicircular skin lobe of unknown function on the inner rim of each nostril. Its tail is slender, with lateral skin folds and a lance-like caudal fin but no dorsal fin. The maximum recorded width is 27 cm (11 in).

<span class="mw-page-title-main">Finless sleeper ray</span> Species of cartilaginous fish

The finless sleeper ray is a species of electric ray in the family Narkidae, and the sole member of its genus. It is found over the continental shelf of Southeast Asia from the eastern Andaman Sea to Vietnam and Borneo. Typically growing no more than 15 cm (5.9 in) long, it may be the smallest cartilaginous fish. The finless sleeper ray is the only electric ray that lacks dorsal fins. It has an oval pectoral fin disc that varies from longer than wide to wider than long, depending on age, and a short, robust tail that terminates in a short, deep caudal fin. The trailing margins of its pelvic fins are sexually dimorphic, being more concave in males.

<span class="mw-page-title-main">Reticulate whipray</span> Species of fish

The reticulate whipray or honeycomb stingray is a species of stingray in the family Dasyatidae. It inhabits coastal waters in the western Indian Ocean including the Red Sea, Natal and the Arabian Sea; also a Lessepsian transmigrant in the eastern Mediterranean. A large species reaching 2 m (6.6 ft) in width, the reticulate whipray has a diamond-shaped pectoral fin disc and an extremely long tail without fin folds. Both its common and scientific names refer to its ornate dorsal color pattern of many small, close-set dark spots or reticulations on a lighter background. However, the reticulate whipray is only one of several large spotted stingrays in the Indo-Pacific which, coupled with the variability of its coloration with age and locality, has resulted in a great deal of taxonomic confusion.

<span class="mw-page-title-main">Atlantic torpedo</span> Species of cartilaginous fish

The Atlantic torpedo 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), and in the Mediterranean Sea. 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, and two dorsal fins of unequal size.

<span class="mw-page-title-main">Japanese sleeper ray</span> Species of cartilaginous fish

The Japanese sleeper ray is a species of electric ray in the family Narkidae. It is common in the inshore and offshore waters of the northwestern Pacific Ocean from southern Japan to southern China. Growing up to 40 cm (16 in) long, the Japanese sleeper ray has a nearly circular pectoral fin disc colored reddish to chocolate brown above, sometimes with darker or lighter spots, and lighter brown below. The spiracles behind its small eyes have raised, smooth rims. Its short and muscular tail bears a single dorsal fin positioned aft of the rounded pelvic fins, and terminates in a large caudal fin.

<span class="mw-page-title-main">Onefin electric ray</span> Species of cartilaginous fish

The onefin electric ray or Cape numbfish is a common but little-known species of electric ray in the family Narkidae, native to South Africa and Namibia. It is a benthic fish found in shallow coastal bays over sandy or muddy bottoms. This small species reaches 38 cm (15 in) in length, and has a nearly circular pectoral fin disc and a short, muscular tail that supports a large caudal fin. It can be identified by its single dorsal fin, which is located over the large pelvic fins. Its dorsal coloration is yellowish to dusky brown.

<i>Pontobdella muricata</i> Species of annelid (marine leech)

Pontobdella muricata is a species of marine leech in the family Piscicolidae. It is a parasite of fishes and is native to the northeastern Atlantic Ocean, the Baltic Sea, the North Sea, and the Mediterranean Sea.

<i>Raja radula</i> Ray in the genus Raja

The rough ray is a Mediterranean ray species of the Rajidae family described by Delaroche in 1809.

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