About Hypoplectrus nigricans (Poey, 1852)
Hypoplectrus nigricans is a small fish that reaches a total length between 85 and 150 mm, which equals 3.3 to 5.9 inches. This species shows variation in morphology and colouring across its geographic range. Individuals from Puerto Rico have greyish bodies, translucent pectoral fins, pointed pelvic fins, and a crescent moon-shaped caudal fin. Individuals from Mexico and Belize are slightly smaller, with a darker body colour, dark pectoral fins, blunt pelvic fins, and a short, square-cut caudal fin. This species is native to the central West Atlantic Ocean. Its range extends from southeastern Florida and the Bahamas, through the Caribbean Sea and the Gulf of Mexico, to Santa Marta in Colombia and the islands off the coast of Venezuela. It is a reef fish that lives on reefs containing both stony corals and soft corals. Hypoplectrus nigricans is a simultaneous hermaphrodite, with an unusual reproductive strategy called egg trading. Individuals are usually solitary, but two fish gather together at night during the breeding season. Courtship starts when one fish temporarily takes on a female role. The other fish acts as a male and fertilizes a batch of eggs produced by the first fish. On the following night, their roles are reversed: the second fish lays eggs, and the first fish fertilizes them. The two fish continue alternating roles this way over several nights. The pair usually stays together through this whole sequence of role alternations, but occasionally each fish will find a different partner.
