Feeding Structures And Associated Organs In The Cichlid Fish, Oreochromis Esculentus (graham)

Abstract

Teeth anatomy and gut morphology are described in Oreochromis esculentus (Graham) and related to the food habits of the species based on existing information and diet and food utilization. Three rows of oral teeth of different sizes are found on both the upper and lower jaws. They are either bicuspid, on the outer row, or tricuspid, on the inner and middle rows. The dentition does not seem to undergo morphological changes with size of the fish. Teeth are also borne on triangular pharyngeal bones with different lengths and are curved backwards. The toothed surface area of the lower pharyngeal bone reveals a significant positive correlation with fish standard length (r = 0.65; P0.05). The lower pharyngeal teeth are adapted for breaking colonial and filamentous algae while the dorsal ones are used for plankton maceration. The jaw teeth, however, could not be associated with any food type consumed by the species in the lake. The stomach is a distensible sac which is separated from the duodenum by a pyloric sphincter. Only limited digestion takes place there. The intestine is of considerable length, with a ratio of 1:4 - 1:14 to fish standard length and a highly positive correlation between intestine length (IL) and fish standard length (SL) described by the following equation.