The ocellated electric ray or bullseye electric ray (''Diplobatis ommata'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

electric ray 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 ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Narcinidae Narcinidae, or numbfishes, are a family of electric rays (order Torpediniformes). They are bottom-dwelling cartilaginous fishes with large, rounded pectoral fin discs and long tails. They can produce an electric discharge for defense, from whi ...

, native to the shallow

inshore A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

waters of the eastern central Pacific from the

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

to Ecuador. Reaching in length, this species has a rounded

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

disc and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s with convex margins. Its short and thick tail bears two

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s and terminates in a triangular

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

. 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. Solitary and

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

in nature, the ocellated electric ray is a bottom-dweller found in sandy and rocky

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s. It moves along the bottom by "hopping" on its pelvic fins, and feeds on small

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s and

polychaete worm Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ma ...

s. For defense, it can generate an electrical discharge from its

electric organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since develop ...

s. This species probably bears live young that are sustained by

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

and later

histotroph Uterine glands or endometrial glands are tubular glands, lined by a simple columnar epithelium, found in the functional layer of the endometrium that lines the uterus. Their appearance varies during the menstrual cycle. During the proliferative pha ...

("uterine milk") during

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

(IUCN) has listed the ocellated electric ray as least concern. It is susceptible to the heavy

trawl Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...

ing activity within its limited range.

Taxonomy

American

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...

David Starr Jordan David Starr Jordan (January 19, 1851 – September 19, 1931) was the founding president of Stanford University, serving from 1891 to 1913. He was an ichthyologist during his research career. Prior to serving as president of Stanford Universi ...

and

Charles Henry Gilbert Charles Henry Gilbert (December 5, 1859 in Rockford, Illinois – April 20, 1928 in Palo Alto, California) was a pioneer ichthyologist and Fisheries science, fishery biologist of particular significance to natural history of the western Unit ...

described the ocellated electric ray in an 1890 article for the

scientific journal In academic publishing, a scientific journal is a periodical publication designed to further the progress of science by disseminating new research findings to the scientific community. These journals serve as a platform for researchers, schola ...

''Proceedings of the United States National Museum''. Their account was based on a female specimen caught by the

United States Fish Commission The United States Fish Commission, formally known as the United States Commission of Fish and Fisheries, was an agency of the United States government created in 1871 to investigate, promote, and preserve the Fishery, fisheries of the United St ...

steamer USS ''Albatross'' in 1888. The female was collected off the Pacific coast of

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

at a depth of . Gilbert had previously obtained a specimen from Panama in 1882, but it had been destroyed in a fire before it could be studied. Jordan and Gilbert named the new species ''ommata'' (

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

for "eyed") in reference to the distinctive spot on its back, and assigned it to the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Discopyge ''Discopyge'' is a small genus of fish, the apron rays, in the family Narcinidae. Species * '' Discopyge castelloi'' Menni, Rincón & M. L. Garcia, 2008 * '' Discopyge tschudii'' Heckel, 1846 (Apron ray) References Narcinidae Ray gen ...

''. In 1948,

Henry Bryant Bigelow Henry Bryant Bigelow (October 3, 1879 – December 11, 1967) was an American oceanographer and marine biologist. He was a professor at Harvard University for 60 years and was the founding director of the Woods Hole Oceanographic Institution. Th ...

and

William Charles Schroeder William Charles Schroeder (1895–1977) was an American ichthyologist. He was born on Staten Island, New York. He, along with his lifelong colleague Henry Bryant Bigelow, made substantial contributions to the knowledge of the fish fauna of the wes ...

created the new genus ''

Diplobatis ''Diplobatis'' is a genus of electric rays in the family (biology), family Narcinidae. Species * ''Diplobatis colombiensis'' Janice D. Fechhelm, Fechhelm & John D. McEachran, McEachran, 1984 (Colombian electric ray) * ''Diplobatis guamachensis'' ...

'' for this species based on then-unique subdivision of its nostrils. Three other species of ''Diplobatis'' have since been described from the Atlantic. The Atlantic species more closely resemble each other in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

than they do the ocellated electric ray, though as a whole all four ''Diplobatis'' species are extremely similar. Another

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

for this species is "target ray".

Description

The

disc of the ocellated electric ray is heart- or trowel-shaped and slightly wider than long. A pair of large, kidney-shaped

s are visible through the skin on either side of the head. The small eyes are followed by smaller spiracles, which have seven to ten small, rounded projections on their rims. The snout is broadly rounded, with each nostril divided into two openings by a strut. Between the nostrils is a curtain of skin with a smooth to gently wavy posterior margin. The small mouth forms a transverse line; the edge of the lower jaw is scalloped, and when closed usually conceals the teeth. There are 14–16

tooth row Sharks continually shed their teeth; some Carcharhiniformes shed approximately 35,000 teeth in a lifetime, replacing those that fall out. There are four basic types of shark teeth: dense flattened, needle-like, pointed lower with triangular upp ...

s in each jaw. The small and pointed teeth become progressively longer and sharper towards the back, and are arranged in a

quincunx A quincunx ( ) is a geometry, geometric pattern consisting of five points arranged in a cross, with four of them forming a Square (geometry), square or rectangle and a fifth at its center. The same pattern has other names, including "in saltire" ...

pattern. Five pairs of small

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In c ...

s are present on the underside of the disc. The large

s originate beneath the disc and have convex trailing margins. Adult males have very short and thick

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...

. The broad and flattened tail is shorter than the disc and bears a fold of skin along either side. There are two small

s, both with rounded to angular apices; the first is slightly smaller than the second, and its position varies from over to behind the pelvic fins. The

is triangular with rounded corners, and is roughly symmetrical above and below. The skin is soft and entirely devoid of

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s. The dorsal coloration of the ocellated electric ray is extremely variable, with the only constant being the large

ocellus A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

("eyespot") in the middle of the back. The center of the ocellus is black or yellow, which is surrounded by concentric, alternating dark and light rings that may be either continuous or broken. The remainder of the upper surface is most commonly a shade of light brown with numerous fine dark dots; there may also be light dots, larger dark spots or blotches, and/or irregular brown marbling. Some individuals are plain light or dark brown with a black ocellus. The portion of the disc in front of the eyes is brown with up to five darker blotches. The dorsal pattern often extends to the ventral fin margins; the underside is otherwise white to cream-colored. This species grows up to long.

Distribution and habitat

The ocellated electric ray is common in the

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

coastal waters of the eastern Pacific. Its range extends as far north as the

and Bahía San Juanico in

Baja California Sur Baja California Sur, officially the Free and Sovereign State of Baja California Sur, is a state in Mexico. It is the 31st and last state to be admitted, in 1974. It is also the second least populated Mexican state and the ninth-largest state by ...

, and as far south as Ecuador. A

bottom-dwelling The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

species, it has been recorded from the

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

to a depth of . The favored

of this ray is sandy

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a ''gulf'', ''sea'', ''sound'', or ''bight''. A ''cove'' is a small, ci ...

s, though it can also be found over rubble bottoms, rocky terrain, and

rhodolith Rhodoliths (from Greek for ''red rocks'') are colorful, unattached calcareous nodules, composed of crustose, benthic marine red algae that resemble coral. Rhodolith beds create biogenic habitat for diverse benthic communities. The rhodolithic gr ...

beds.

Biology and ecology

Like the rest of its family, the ocellated electric ray can defend itself by producing a moderate

electric shock An electrical injury (electric injury) or electrical shock (electric shock) is damage sustained to the skin or internal organs on direct contact with an electric current. The injury depends on the Current density, density of the current, tissu ...

. During the day, this solitary ray spends most of its time lying partially buried in sand, often near rocky reefs. It becomes more active at night, using its pelvic fins to "hop" along the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. It feeds on small

s such as

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

s and

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

, as well as

Parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s documented from this species include the

tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass being Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Ce ...

s '' Acanthobothrium dollyae'', '' A. maryanskii'', and '' A. royi'', and the fluke '' Anaporrhutum euzeti''. Though reproductive details are unknown, the ocellated electric ray is presumably

viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...

, with the developing

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

s sustained first by

and later by maternally produced

("uterine milk"), as in other electric rays. Females

mature sexually Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized as ...

at under long; the maturation size for males is unknown.

Human interactions

The shock from the ocellated electric ray is not dangerous to humans. It occasionally appears in the

home aquarium A home, or domicile, is a space used as a permanent or semi-permanent residence for one or more human occupants, and sometimes various companion animals. Homes provide sheltered spaces, for instance rooms, where domestic activity can be pe ...

trade, but is difficult to keep because it requires live

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s for food. The ocellated electric ray and other electric rays are used as

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

s in biomedical research because their electric organs are rich in

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by Gating (electrophysiol ...

s and

acetylcholine receptor An acetylcholine receptor (abbreviated AChR) or a cholinergic receptor is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter. Classification Like other transmembrane receptors, acetylcholine receptor ...

s, which play important roles in the human

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

. The

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

agrin Agrin is a large proteoglycan whose best-characterised role is in the development of the neuromuscular junction during embryogenesis. Agrin is named based on its involvement in the aggregation of acetylcholine receptors during synaptogenesi ...

, which concentrates acetylcholine receptors during human embryonic development, was first isolated from this species. Though the ocellated electric ray is not utilized economically, it is caught incidentally by shrimp

ers. Its mortality from fishing has not been quantified but is thought to be high, considering that trawling operations in the Atlantic are known to take ''Diplobatis'' species in large numbers. The catch rate is also probably underestimated due to problematic identification. Given the restricted range of this species and the intensity of trawling within its habitat, the

(IUCN) has assessed it as least concern.

References

External links

* {{Good article

ocellated electric ray The ocellated electric ray or bullseye electric ray (''Diplobatis ommata'') is a species of electric ray in the family (biology), family Narcinidae, native to the shallow inshore waters of the eastern central Pacific from the Gulf of California t ...

Fish of the Gulf of California Fish of Colombia Western Central American coastal fauna Strongly electric fish Taxa named by David Starr Jordan Taxa named by Charles Henry Gilbert

Taxonomy articles created by Polbot