Pacific electric ray

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. Ayers published his account in 1855, in the inaugural volume of the academy's Proceedings; no type specimens were designated. In 1861, Theodore Gill placed this species in his newly created genus Tetronarce, on the basis of its smooth-rimmed spiracles. Later authors have generally regarded Tetronarce as a subgenus of Torpedo. Closely similar electric rays found off Peru, Chile, and Japan may be the same as this species. Other common names used for this ray include California torpedo ray, Pacific torpedo, or simply electric ray or torpedo ray. This species is placed in the genus Tetronarce. ==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. The Pacific electric ray is generally common, especially along the California coastline, from Monterey Bay southward to Baja California. It is least abundant in its range's most northernmost and southernmost sections. Its northernmost point, northern British Columbia, has much cooler water temperatures, making the habitat far less adequate than the temperate southern waters it is most commonly found. They have also been sighted in the Gulf of California (the easter side of the Baja California Peninsula), and although the sightings are extremely rare, it infers that they are far less abundant there than on the California and western Baja California coastlines. Although it has fairly stable populations, detailed information on its abundance throughout its entire range is scarce, mainly because the species holds little commercial or charismatic value. Overall, the pacific electric ray's range expands from of coastline. ==Description==

The Pacific electric ray has a soft, flabby, limp depressiform body type lacking placoid scales (dermal denticles) typically found on cartilaginous fish. It has an oval pectoral fin disc that is more complicated than most fishes due to the ray's depressiform body style. The size of their pectoral fin disc, in this case, is the width of their entire body. It is 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. up to 220 volts, from their kidney-shaped organs with modified muscle tissues arranged in columns containing electrolytes that cause ions to move across a cell membrane, thus creating an electric discharge. Following their mouth are two pairs of five vertical gill slits that expel water since they respire through their spiracles on their dorsal side. Tasking in water through their dorsal side enables the ray to breathe while submerging in sediment on the ocean floor. 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 , and at birth. Pacific electric rays are able to swim to a depth from the surf zone to , usually shallower than . Two dorsal fins are present, with the first more than twice the size of the second Their first dorsal fin is long, nearly double the size of their second dorsal fin, ; The Pacific electric ray gets confused with other rays due to its similar body plan, behavior, and ability to produce electricity. These species include the Marbled electric ray (Torpedo marmorata), lesser electric ray (Narcine brasiliensis), and the spotted electric ray (Torpedo macneilli). However, they differ geologically. The marbled electric ray is located in the Atlantic Ocean and the Mediterranean Sea, the lesser electric ray is smaller and located in the western Atlantic Ocean, and the spotted electric ray occurs in regions of the Indo-Pacific. This contrasts with the Pacific electric ray, located predominantly in the northeastern Pacific Ocean. ==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. 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. 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. Female Pacific electric rays undergo fertilization via the male copulatory organs, known as claspers, which are used for internal fertilization. The claspers have a tube-shaped structure with a ventral groove called the hypostyle, where sperm will flow into the female's cloaca. 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. The newborns measure long and double their size in the first year of life, adding around to their length. Male grow faster than females but reach a smaller ultimate size, known as the von Bertalanffy growth model. Sexual maturity is attained at a length of and age of seven years for males, and a length of 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 for females. In contrast, males have a shorter lifespan, usually living up to around 13 years.[23] Estimating the age of Pacific electric rays is difficult because their vertebrae are delicate, thin, and not well-calcified. Despite these issues, techniques like graphite microtopography have been used to estimate their age, though confirming these estimates is still a challenge. ==Human interactions==

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. 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. 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. 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. This led to a number of further advances, one of the most significant being the elucidation of the pathophysiology underlying the disease myasthenia gravis. 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. Otherwise, this ray has no economic value. Although not specifically targeted by fisheries, It is caught incidentally by commercial trawl and gillnet fisheries, and on hook-and-line by sport anglers. 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), showing that its population is also currently facing no major threats that may negatively affect its numbers. However, the threats this species faces are bycatch in fisheries, habitat degradation, climate change, and human disturbance. Their preferred habitats, kelp forests, and rocky reefs, are being degraded, polluted, and destroyed, which presents a potential challenge to this species. Various actions like dredging, coastal construction, and polluting of northwestern coastal waters could reduce the quality of its habitat, especially in shallow waters. The warming of our oceans due to climate change is causing a shift in species ranges, and altercations to our marine ecosystems could affect their distribution. Shifts in water temperature could affect its habitat range or prey availability, though the exact impacts are not yet fully understood. Fishing for this ray is not managed by the Pacific Fishery Management Council. ==References==