Feeding Mechanism of Tilapia nigra

Abstract

EXAMINATION of the gut and rectal contents of Tilapia nigra (Günther) has shown that this fish, like T. esculenta Graham¹, feeds mainly on phytoplankton or epiphytic algæ, digesting the diatom fraction, but passing the green and blue-green algæ untouched through the gut. (Rectal smears from T. nigra have in fact yielded cultures of both green and blue-green algæ, as has been reported for the closely related T. mossambica Peters².) T. esculenta, which has simple and moderately widely spaced gillrakers, feeds on suspended plankton³, and this fact has led to speculation on the method by which the finer food particles are strained out. Greenwood⁴ considered the interdigitation of the gillrakers sufficient to retain only the coarser elements which sometimes appear in the stomach, for example, copepods. He suggested that the smaller particles are entangled in a film of mucus secreted especially by cells lying along the posterior mid-dorsal surface of the mouth and pharynx and on the gill arches.