Hypoplectrus nigricans (Poey, 1852)

Size

Hypoplectrus nigricans is a small fish that reaches a total length between 85 and 150 mm, which equals 3.3 to 5.9 inches.

Morphology Variation

This species shows variation in morphology and colouring across its geographic range.

Puerto Rico Population Traits

Individuals from Puerto Rico have greyish bodies, translucent pectoral fins, pointed pelvic fins, and a crescent moon-shaped caudal fin.

Mexico and Belize Population Traits

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.

Native Range

This species is native to the central West Atlantic Ocean.

Geographic Distribution

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.

Habitat

It is a reef fish that lives on reefs containing both stony corals and soft corals.

Reproductive Strategy

Hypoplectrus nigricans is a simultaneous hermaphrodite, with an unusual reproductive strategy called egg trading.

Breeding Social Behavior

Individuals are usually solitary, but two fish gather together at night during the breeding season.

Courtship Initiation

Courtship starts when one fish temporarily takes on a female role.

First Fertilization Event

The other fish acts as a male and fertilizes a batch of eggs produced by the first fish.

Role Reversal

On the following night, their roles are reversed: the second fish lays eggs, and the first fish fertilizes them.

Alternation Pattern

The two fish continue alternating roles this way over several nights.

Pair Fidelity

The pair usually stays together through this whole sequence of role alternations, but occasionally each fish will find a different partner.