Pacific electric ray

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Pacific electric ray
Torpedo californica2.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Superorder: Batoidea
Order: Torpediniformes
Family: Torpedinidae
Genus: Tetronarce
Species:
T. californica
Binomial name
Tetronarce californica
Ayres, 1855
Torpedo californica rangemap.png
Range of the Pacific electric ray
Synonyms

Torpedo californicaAyres, 1855

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 (paired respiratory openings behind the eyes) 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.

Contents

Solitary and nocturnal, the Pacific electric ray can generate up to 45 volts of electricity for the purposes of subduing prey or self-defense. It feeds mainly on bony fishes, ambushing them from the substrate during the day and actively hunting for them at night. Reproduction is aplacental viviparous, meaning that the embryos are initially nourished by yolk, later supplemented by histotroph ("uterine milk") produced by the mother. Females bear litters of 17–20 pups, probably once every other year. Care should be exercised around the Pacific electric ray, as it has been known to act aggressively if provoked and its electric shock can potentially incapacitate a diver. It and other electric rays are used as model organisms for biomedical research. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern, as it is not fished in any significant numbers.

Taxonomy

The Pacific electric ray was described by American ichthyologist William Orville Ayres, the first Curator of Ichthyology at the California Academy of Sciences, who named it after the U.S. state where it was first discovered by science. [2] [3] Ayers published his account in 1855, in the inaugural volume of the Academy's Proceedings; no type specimens were designated. [4] In 1861, Theodore Gill placed this species in his newly created genus Tetronarce, on the basis of its smooth-rimmed spiracles. [5] Later authors have generally regarded Tetronarce as a subgenus of Torpedo. [6] Closely similar electric rays found off Peru, Chile, and Japan may be the same as this species. [7] Other common names used for this ray include California torpedo ray, Pacific torpedo, or simply electric ray or torpedo ray. [3] [8] This species is placed in the genus Tetronarce . [9]

Distribution and habitat

The only electric ray found off western North America, the Pacific electric ray occurs as far south as Sebastian Vizcaino Bay in Baja California, and as far north as the Dixon Entrance in northern British Columbia. It is most common south of Point Conception, California, with the rays north of the Point perhaps representing one or more separate populations. [1] [3]

Off California, the Pacific electric ray is generally encountered at a depth of 3–30 m (10–100 ft), while off Baja California it is typically observed at a depth of 100–200 m (330–660 ft). [3] It has been reported from as deep as 425 m (1,394 ft). [8] This species prefers temperatures of 10–13 °C (50–55 °F). It frequents sandy flats, rocky reefs, and kelp forests. However, one individual has been videotaped 17 km (11 mi) west of Point Pinos, Monterey County, California, swimming 10 m (33 ft) below the surface in water 3 km (1.9 mi) deep; this and other observations suggest that this species makes periodic excursions away from shallow coastal habitats into the epipelagic zone. [3]

Description

Some Pacific electric rays have dark spots on the upper surface. Torpedoray 300.jpg
Some Pacific electric rays have dark spots on the upper surface.

The Pacific electric ray has a soft, flabby body devoid of dermal denticles. It has an oval pectoral fin disc about 1.2 times as wide as long, with a nearly straight front margin and a pair of kidney-shaped electric organs visible beneath the skin. [3] [6] The eyes are small and followed by smooth-rimmed spiracles; the space from the spiracles to the snout tip is about 1.8 times the distance between the spiracles. There is a curtain of skin between the nostrils that almost reaches the mouth, which is arched with deep furrows at the corners. The distance between the mouth and the snout tip is about equal to the mouth width, and three times that of the distance between the nostrils. [6] [10] There are 25–28 upper tooth rows and 19–26 lower tooth rows; each tooth is tiny and smooth, with a single sharp cusp. [3] Pacific electric rays are founded in Japan, south Kuril Islands, and Kinmei Seamount; Wiah Point, Graham Island, northern British Columbia to Todos Santos, southern Baja California, including Isla Guadalupe, central Baja California, and Peru. Although there was one record from the Gulf of California. Common from about San Francisco Bay southward into southern Baja California. Pacific electric rays can grow up to a length more than 140 cm (55.1 in), and 18–23 cm (7.1-9.1 in) at birth. Pacific electric rays are able to swim to a depth from the surf zone to 1,079 m (3,539 ft), usually shallower than 300 m (984 ft).

Two dorsal fins are present, with the first more than twice the size of the second and positioned opposite the large pelvic fins. The tail is short and stocky, terminating in a large, triangular caudal fin with a nearly straight trailing margin. [11] This ray is dark gray, slate, or brown above, sometimes with small darker spots that increase in number with age; the underside is white. Males attain a maximum known length of 0.9 m (3.0 ft), and females 1.4 m (4.6 ft). [12] The maximum recorded weight is 41 kg (90 lb). [8]

Biology and ecology

With a sizable oily liver and low-density tissues, the Pacific electric ray is almost neutrally buoyant and can hover in the water column with very little effort. [13] Propulsive power is provided by the muscular tail, while the disc is held rigid. [14] Telemetry studies have shown that this species swims primarily at night, when it enters reefs and other habitats with high terrain relief, and spends most of the day in nearby open areas buried in sediment. [14] [15] It is nomadic and solitary, though several individuals may rest within the same area. [13]

Like other members of its family, the Pacific electric ray produces powerful electric shocks for attack and defense. Its paired electric organs are derived from muscle and comprise approximately 15% of its total weight, [16] consisting of many thousands of jelly-filled "electric plates" stacked hundreds-high into vertical hexagonal columns. These columns function essentially like batteries connected in parallel; a large adult ray can generate some 45 volts of electricity with a power output of one kilowatt, due to low internal resistance. [6] [15] The electric organs discharge direct current in pulses, each lasting 4–5  ms. When attacking prey, in the first few moments the ray normally produces pulses at a rate of 150–200 per second, slowing down over time. Over a thousand pulses may be produced in all, depending on how long it takes for the prey to be subdued. The pulse rate increases with water temperature. [15]

Because of its large size and formidable defenses, The Pacific electric ray seldom falls prey to other animals. [7] There is a record of one being fed upon by a killer whale (Orcinus orca) off Santa Catalina Island. [17] The Cooper's nutmeg (Cancellaria cooperi) is a specialized parasite of this ray, and possibly other bottom-dwelling fishes such as the Pacific angelshark (Squatina californica). The snail is attracted to the chemicals contained in the ray's surface mucus; it makes a small cut on the ventral surface of the ray and uses its proboscis to suck blood. [18] Other known parasites of this species include the copepod Trebius latifurcatus, [19] the fluke Amphibdelloides maccallumi, [20] and the tapeworm Acanthobothrium hispidum. [21]

Feeding

At night, the Pacific electric ray actively hunts for food over the sea floor. Torpedo californica mt pinos.jpg
At night, the Pacific electric ray actively hunts for food over the sea floor.

The Pacific electric ray feeds mainly on bony fishes, including anchovies, herring, hake, mackerel, croakers, rockfishes, surfperches, kelp bass, and flatfishes, but will also take cephalopods and invertebrates given the opportunity. [3] [12] Its jaws are highly distensible, allowing it to swallow surprisingly large prey: one female 1.2 m (3.9 ft) long has been observed ingesting a silver salmon (Oncorhynchus kisutch) nearly half her length. [14] During the day, the Pacific electric ray is an ambush predator: when a fish approaches its head, the ray "jumps" forward from its resting place and folds down its disc to envelop it, while delivering strong shocks. Once the fish is subdued, the ray repositions itself to swallow it head-first. The entire process takes about two minutes. [15]

At night, when many diurnal fishes descend from the water column and become inactive a short distance above the bottom, the Pacific electric ray switches to an active hunting strategy. It stalks fish by slowly swimming or simply drifting through the water; when it closes to 5 cm (2.0 in) of the prey, it lunges forward and again envelops the prey within its disc while delivering shocks. To better secure the fish within its disc, the ray will make short kicks with its tail that sometimes send it into barrel rolls or somersaults. Finally, the stunned prey is maneuvered to the mouth with ripples of the disc. In one recorded case, a 75 cm (30 in) long female captured and consumed a 20 cm (7.9 in) long jack mackerel (Trachurus symmetricus) in under ten seconds. [14] Nighttime seine net sampling at the surface of Monterey Bay has captured Pacific electric rays in surprising numbers, suggesting that they rise upward from the bottom to feed on small fishes. [22]

Though the Pacific electric ray will feed at any hour, it responds to prey much more quickly at night than during the day. Most prey captures occur in darkness or turbid conditions, when its eyes are largely useless. Instead, it relies on electroreception via its ampullae of Lorenzini to locate food. Experiments in the field have shown that it will attack artificially generated electric fields and conductive metal electrodes. Mechanical sensory cues, detected via the lateral line, also play an important role: this species has been observed preferentially attacking faster-moving prey even if a closer food item was available. [15]

Life history

The Pacific electric ray exhibits aplacental viviparity, with the developing embryos at first receiving nourishment from yolk, and later from histotroph ("uterine milk", enriched with proteins, fat, and mucus) produced by the mother and delivered through specialized outgrowths of the uterine lining. [7] Mature females have two functional ovaries and uteruses. Reproduction occurs year-round, with males apparently capable of mating every year and females every other year. The gestation period is unknown. Reported litter sizes range from 17 to 20; at least the number of ova, and perhaps also the number of young, increases with the size of the female. [3] [23]

The newborns measure 18–23 cm (7.1–9.1 in) long and double their size in the first year of life, adding around 25 cm (9.8 in) to their length. [3] Male grow faster than females but reach a smaller ultimate size. Sexual maturity is attained at a length of 65 cm (26 in) and age of seven years for males, and a length of 73 cm (29 in) and age of nine years for females. The oldest documented individuals are 16 years of age, and extrapolating from growth curves the maximum lifespan of this species may be upwards of 24 years. [23]

Human interactions

Pacific Electric Ray with diver, offshore Anacapa Island Pacific Electric Ray (torpedo californica).jpg
Pacific Electric Ray with diver, offshore Anacapa Island

The shock generated by the Pacific electric ray can be enough to knock down an adult human. It should be treated with caution, especially at night when it is active, and has been known to charge at divers with its mouth agape if harassed. It is not known to be responsible for any fatalities, but may have been involved in several unexplained, fatal diving accidents. [3] This species fares poorly in captivity, as it usually refuses to feed when first introduced into an aquarium. Since 2000, the Aquarium of the Bay and the Monterey Bay Aquarium have had some success keeping Pacific electric rays by offering them moving food. [24]

The Pacific electric ray and its relatives are used as model organisms for biomedical research, because their electric organs contain an abundance of important nervous system proteins such as nicotinic acetylcholine receptor and acetylcholinesterase. [25] In the 1970s and 1980s, acetylcholine receptors from this species and the marbled electric ray (T. marmorata) became the first neurotransmitter receptors to be isolated and sequenced, in what is considered to be a landmark success in the field of neurobiology. [26] This led to a number of further advances, one of the most significant being the elucidation of the pathophysiology underlying the disease myasthenia gravis. [25] A small commercial fishery in southern California supplies Pacific electric rays for research purposes; as of 2005 this fishery may have employed as few as two fishers. [12] Otherwise, this ray has no economic value. It is caught incidentally by commercial trawl and gillnet fisheries, and on hook-and-line by sport anglers. [7] [13] These activities appear to have little impact on its population, leading it to be listed under Least Concern by the International Union for Conservation of Nature (IUCN). Fishing for this ray is not managed by the Pacific Fishery Management Council. [1]

Related Research Articles

<span class="mw-page-title-main">Electric ray</span> Order of cartilaginous fishes

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 on species, used to stun prey and for defense. There are 69 species in four families.

<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">Leopard shark</span> Species of shark

The leopard shark is a species of houndshark, in the family Triakidae. It is found along the Pacific coast of North America, from the U.S. state of Oregon to Mazatlán in Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name. Large schools of leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs. They are most common near the coast, in water less than 4 m (13 ft) deep.

<span class="mw-page-title-main">Horn shark</span> Species of shark

The horn shark is a species of bullhead shark, in the family Heterodontidae. It is endemic to the coastal waters off the western coast of North America, from California to the Gulf of California. Young sharks are segregated spatially from the adults, with the former preferring deeper sandy flats and the latter preferring shallower rocky reefs or algal beds. A small species typically measuring 1 m (3.3 ft) in length, the horn shark can be recognized by a short, blunt head with ridges over its eyes, two high dorsal fins with large spines, and a brown or gray coloration with many small dark spots.

<span class="mw-page-title-main">Japanese bullhead shark</span> Species of shark

The Japanese bullhead shark is a species of bullhead shark in the family Heterodontidae found in the northwestern Pacific Ocean off the coasts of Japan, Korea, and China. This benthic shark occurs at depths of 6–37 m (20–121 ft) over rocky bottoms or kelp beds. Measuring up to 1.2 m (3.9 ft) long, it can be identified by its short, blunt head, two high dorsal fins with anterior spines, and pattern of irregularly shaped, vertical brown bands and stripes. The Japanese bullhead shark is a docile, slow-swimming species that feeds mainly on shelled invertebrates and small bony fishes. Reproduction is oviparous, with females laying spiral-flanged eggs in communal "nests". This species is of little interest to fisheries.

<span class="mw-page-title-main">Pacific angelshark</span> Species of shark

The Pacific angelshark is a species of angelshark, family Squatinidae, found in the eastern Pacific Ocean from Alaska to the Gulf of California, and from Ecuador to Chile, although those in the Gulf of California and southeastern Pacific may in fact be separate species. The Pacific angelshark inhabits shallow, coastal waters on sandy flats, usually near rocky reefs, kelp forests, or other underwater features. This species resembles other angel sharks in appearance, with a flattened body and greatly enlarged pectoral and pelvic fins. Characteristic features of this shark include a pair of cone-shaped barbels on its snout, angular pectoral fins, and a brown or gray dorsal coloration with many small dark markings. It attains a maximum length of 1.5 m (4.9 ft).

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

The diamond stingray is a species of stingray in the family Dasyatidae. It is found in the coastal waters of the eastern Pacific Ocean from southern California to northern Chile, and around the Galápagos and Hawaiian Islands. This bottom-dweller generally inhabits sandy or muddy flats near rocky reefs and kelp forests, to a depth of 30 m (98 ft), though off Hawaii it may range considerably deeper. As its common name suggests, this species has an angular, diamond-shaped pectoral fin disc that is plain brown or gray above, with rows of tubercles along the midline and on the "shoulders". The long, whip-like tail has both dorsal and ventral fin folds, which distinguish this ray from the closely similar longtail stingray. It typically grows to 1 m (3.3 ft) across.

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

The ocellated electric ray or bullseye electric ray is a species of electric ray in the family Narcinidae, native to the shallow inshore waters of the eastern central Pacific from the Gulf of California to Ecuador. Reaching 25 cm (9.8 in) in length, this species has a rounded pectoral fin disc and pelvic fins with convex margins. Its short and thick tail bears two dorsal fins and terminates in a triangular caudal fin. The ocellated electric ray is named for the distinctive large eyespot on the middle of its disc, consisting of a black or yellow center surrounded by concentric rings. Its dorsal coloration is otherwise highly variable, ranging from plain to ornately patterned on a light to dark brown background. The front part of its disc is darker brown.

<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 color above, and has tiny eyes and a large, highly distensible mouth.

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

The thornback guitarfish is a species of ray in the family Platyrhinidae, and the only member of its genus. Despite its name and appearance, it is more closely related to electric rays than to true guitarfishes of the family Rhinobatidae. This species ranges from Tomales Bay to the Gulf of California, generally in inshore waters no deeper than 6 m (20 ft). It can be found on or buried in sand or mud, or in and near kelp beds. Reaching 91 cm (36 in) in length, the thornback guitarfish has a heart-shaped pectoral fin disc and a long, robust tail bearing two posteriorly positioned dorsal fins and a well-developed caudal fin. The most distinctive traits of this plain-colored ray are the three parallel rows of large, hooked thorns that start from the middle of the back and run onto the tail.

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">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.

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

The common 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.

<i>Narcine entemedor</i> Species of cartilaginous fish

Narcine entemedor, the giant electric ray or Cortez electric ray, is a species of numbfish, family Narcinidae, native to the eastern Pacific Ocean from the Gulf of California to Panama. It is found in shallow water on sandy bottoms and sometimes adjacent to reefs. This species is closely related to the lesser electric ray from the western Atlantic, and may represent the same species. The specific epithet entemedor seems to be the Spanish equivalent of "intimidator".

<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.

<i>Oxyjulis</i> Species of fish

Oxyjulis californica is a species of wrasse native to the eastern Pacific Ocean along the coasts of California and Baja California. Its distribution extends from Salt Point in Sonoma County, California, to southern central Baja California, near Cedros Island. It is a very common species; its common name in Spanish is señorita.

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

The Tasmanian numbfish is a species of electric ray in the family Narcinidae. Endemic to southeastern Australia, this common ray inhabits shallow continental shelf waters in the southern portion of its range and deeper continental slope waters in the northern portion of its range. It prefers sand and mud habitats. This species can be identified by its spade-shaped pectoral fin disc with concave anterior margins, long tail with well-developed skin folds along either side, and plain dark brown dorsal colouration. Its maximum known length is 47 cm (19 in).

<i>Sebastes elongatus</i> Species of fish

Sebastes elongatus, the greenstriped rockfish, striped rockfish, strawberry rockfish, poinsettas, reina or serena, is a species of marine ray-finned fish belonging to the subfamily Sebastinae, the rockfishes, part of the family Scorpaenidae. It is found in the northeastern Pacific Ocean.

Torpedo mackayana, commonly known as the ringed torpedo, Western African torpedo, West African torpedo ray, McKay electric ray, or McKay's torpedo ray, is an electric ray species in the family Torpedinidae, which lives in shallow waters on the western coast of Africa. Characterized by rounded spiracles and white and brown spots, females grow to 35–50 centimetres (14–20 in) and males to 31.5–38.2 centimetres (12.4–15.0 in).

References

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  15. 1 2 3 4 5 Lowe, C.G.; Bray, R.N. & Nelson, D.R. (1994). "Feeding and associated electrical behavior of the Pacific electric ray Torpedo californica in the field". Marine Biology. 120 (1): 161–169. doi:10.1007/BF00381951. S2CID   3890498.
  16. ↑ Colowick, S.P.; Kaplan, N.O.; Abelson, J. & Simon, M.I. (1998). Methods in Enzymology. Gulf Professional Publishing. p. 108. ISBN   0-12-182197-8.
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  18. ↑ O'Sullivan, J.B.; McConnaughey, R.R. & Huber, M.E. (1987). "A blood-sucking snail: the Cooper's nutmeg, Cancellaria cooperi Gabb, parasitizes the California electric ray, Torpedo californica Ayres". The Biological Bulletin. Biological Bulletin, Vol. 172, No. 3. 172 (3): 362–366. doi:10.2307/1541716. JSTOR   1541716.
  19. ↑ Deets, G.B. & Dojiri, M. (1989). "Three species of Trebius Krøyer, 1838 (Copepoda: Siphonostomatoida) parasitic on Pacific elasmobranchs". Systematic Parasitology. 13 (2): 81–101. doi:10.1007/bf00015217. S2CID   45745111.
  20. ↑ Alexander, C.G. (1954). "Microcotyle macracantha n. sp., a Monogenetic Trematode from the Gulf of California, with a Redescription of Amphibdelloides maccallumi (Johnston and Tiegs, 1922) Price, 1937". The Journal of Parasitology. 40 (3): 279–283. doi:10.2307/3273739. JSTOR   3273739. PMID   13184373.
  21. ↑ Goldstein, R.J. (1967). "The Genus Acanthobothrium Van Beneden, 1849 (Cestoda: Tetraphyllidea)". The Journal of Parasitology. 53 (3): 455–483. doi:10.2307/3276705. JSTOR   3276705. PMID   6026837.
  22. ↑ Allen, J.G.; Pondella, D.J. & Horn, M.H. (2006). The Ecology of Marine Fishes: California and Adjacent Waters. University of California Press. p. 335. ISBN   0-520-24653-5.
  23. 1 2 Neer, J.A. & Cailliet, G.M. (2001). McEachran, J. D. (ed.). "Aspects of the Life History of the Pacific Electric Ray, Torpedo californica (Ayres)". Copeia. 2001 (3): 842–847. doi:10.1643/0045-8511(2001)001[0842:aotlho]2.0.co;2. S2CID   86134689.
  24. ↑ Lewand, K. & Slager, C.J. (2003). "Feeding Techniques for the Pacific Torpedo Ray, Torpedo californica". Drum and Croaker. 34: 19–21.
  25. 1 2 Scandalios, J.G. & Wright, T.R.F. (1991). Advances in Genetics . Academic Press. p.  178. ISBN   0-12-017629-7.
  26. ↑ Bullock, T.H. (2005). Electroreception. Birkhäuser. p. 41. ISBN   0-387-23192-7.

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