BLACK GUT PHENOMENON IN CARDINAL FISHES (APOGONIDAE, TELEOSTEI)

A study of 78 species of cardinal fishes (Apogonidae) revealed that 22 of them had black guts, 5 species had partly black guts and, in 51 sp ecies, the digestive tube was unpigmented or had dispersed melanophore s in the external tunic. The black pigmentation is caused by melanizat ion of the submucosal connective tissue which is situated between the muscularis and the basal lamina of the internal epithelium. This pheno menon was previously observed in moray eels and some pelagic fish. In nocturnal predators, it appears to serve to conceal bioluminescent pre y in the stomach cavity.