Ocellated Electric Ray

The **ocellated electric ray** or **bullseye electric ray** (*Diplobatis ommata*) 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.

Solitary and nocturnal in nature, the ocellated electric ray is a bottom-dweller found in sandy and rocky habitats. It moves along the bottom by "hopping" on its pelvic fins, and feeds on small crustaceans and polychaete worms. For defense, it can generate an electrical discharge from its electric organs. This species probably bears live young that are sustained by yolk and later histotroph ("uterine milk") during gestation. The International Union for Conservation of Nature (IUCN) has listed the ocellated electric ray as Vulnerable, as it is susceptible to the heavy trawling activity within its limited range.

## Description

The pectoral fin disc of the ocellated electric ray is heart- or trowel-shaped and slightly wider than long. A pair of large, kidney-shaped electric organs 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 rows in each jaw. The small and pointed teeth become progressively longer and sharper towards the back, and are arranged in a quincunx pattern. Five pairs of small gill slits are present on the underside of the disc.

The large pelvic fins originate beneath the disc and have convex trailing margins. Adult males have very short and thick claspers. The broad and flattened tail is shorter than the disc and bears a fold of skin along either side. There are two small dorsal fins, 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 caudal fin is triangular with rounded corners, and is roughly symmetrical above and below. The skin is soft and entirely devoid of dermal denticles.

The dorsal coloration of the ocellated electric ray is extremely variable, with the only constant being the large ocellus ("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 25 cm (9.8 in) long.

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