Digestion and Assimilation of Periphytic Detrital Aggregate by Tilapia mossambica

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Abstract
T. mossambica in Lake Valencia, Venezuela, feeds almost exclusively on periphytic detrital aggregate (PDA), a complex aggregation of detritus, algae and bacteria. The food passes unaltered through the buccal cavity to the stomach. Gastric acid at a pH uncommonly low for fish (pH < 1.5) decomposes large amounts of inorganic matter and liberates some protein. Intestinal digestion and assimilation of most organic matter are completed in the 1st half of the intestine. Assimilation efficiencies determined by a field technique were total organic matter 63%, protein 77% and carbohydrate 63%. When compared to available literature, these results indicate that the 2 best known detritivorous fish, I. mosambica and Mugil cephalus, confront similar obstacles in digestion of detrital aggregate, but have overcome these obstacles by physiologically divergent digestive processes.