Haematological profile, food composition and digestive enzyme assay in the gut of the African bony-tongue fish, Heterotis (Clupisudis) niloticus (Cuvier 1829) (Osteoglossidae)

Analyses of stomach contents of (1093) Heterotis niloticus (Cuvier 1829) in the River Ogbese, Owena Reservoir and Mahin Lagoon (southwestern Nigeria) established it as a benthic feeder in the river and a planktonic feeder in the reservoir and lagoon. There was a preponderance of zooplankton, accounting for > 80% occurrence and > 25% of total volume in the stomachs of specimens from all habitats; this suggests a microphagous habit. Digestive enzyme assays in the different gut regions (oesophagus, stomach, pyloric caeca, ileum, rectum) of H. niloticus revealed an array of glycosidases (amylase, sucrase, maltase, lactase, cellulase); proteases (pepsin, trypsin, chymotrypsin) and lipases were also detected. The pattern of distribution and relative activity of the enzymes is consistent with its planktophagous diet. Haematocrit values, haemoglobin concentrations, erythrocyte and leucocyte counts, mean cell haemoglobin concentration, plasma protein, glucose and albumin, inorganic ion (sodium, chloride, calcium, ...