Hypoplectrus unicolor

Lore & Background

Hypoplectrus unicolor was first formally described in 1792 as Perca unicolor by the German physician, naturalist and taxonomist Johann Julius Walbaum, with no type locality given. It has a deep, laterally compressed body and head, a straight forehead, a short snout, and a protrusible upper jaw. The preoperculum is angular with serrations and small forward-pointing spines on its lower margin. The continuous dorsal fin has ten spines and 14-17 soft rays, and the pelvic fins are long, extending to or beyond the anus. The caudal fin is slightly forked. The body is greyish white to yellow, darker on the back, with a large black saddle-like marking on the base of the caudal fin that extends over the lateral line. Horizontal iridescent blue lines run along the head, sometimes extending to the front edge of the pelvic fins, and there is a blue line around the eye. Some individuals may show two black spots on the snout. The pelvic fins are yellowish, and the pectoral fins are transparent.

It has been suggested that H. unicolor is a mimic of the foureye butterflyfish (Chaetodon capistratus), based on resemblances in color patterns and shape, shared shallow-water habitats, and the comparative scarcity of H. unicolor. However, H. unicolor varies in color and pattern geographically whereas C. capistratus does not, and their juveniles do not resemble each other. There is a relationship between the two: individuals that follow feeding pairs of the butterflyfish have a higher success rate in capturing prey than hamlets that do not associate with butterflyfish.

Reader's Guide

Hypoplectrus unicolor is notable for its potential mimicry of the foureye butterflyfish, a relationship that may enhance its feeding success. The species is a synchronous hermaphrodite, able to move between male and female roles when spawning. It is carnivorous, feeding largely on crustaceans and smaller fishes, and is found on shallow fringing reef faces, front slopes of reefs, and under piers at depths between 3 and 25 metres. Juveniles are frequently observed in mangroves. In the aquarium trade, it is one of the most highly desired hamlet species and has been reared in captivity. Its distribution extends from Cape Canaveral in Florida south to the Bahamas, into the Gulf of Mexico as far west as Cedar Key, along the mainland coast of Mexico from Tuxpan to the northern Yucatan Peninsula, and from northwestern Cuba south through the Caribbean Sea.

Did You Know?

• Hypoplectrus unicolor was first described in 1792 as Perca unicolor by Johann Julius Walbaum.
• It attains a maximum total length of 12.7 centimetres (5.0 in).
• It is a synchronous hermaphrodite, able to switch between male and female roles when spawning.
• Individuals that follow feeding pairs of foureye butterflyfish have a higher success rate in capturing prey.