Serranus baldwini (Serranidae), the lantern bass, is a small, gleaning carnivore found in turtle grass and rubble substrates in the Caribbean. Small S. baldwini are simultaneous hermaphrodites, but large members of this species are males. The males patrol territories in which several hermaphrodites reside. Hermaphrodites spawn as females with the resident males and rarely spawn as males themselves. Unlike the pattern in reciprocating hermaphrodites, courtship is largely a male function in S. baldwini. Males are much more active and aggressive than are hermaphrodites. In reciprocally spawning species, interactions among mates are more symmetrical. The behavior patterns found in the serranines reflect the differences in mating systems in a manner similar to that found in other organisms and is consistent with current mating system theory.