Haematological profile, food composition and digestive enzyme assay in the gut of the African bonytongue 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, potassium,
magnesium, phosphorus) concentrations of pond-cultured H. niloticus
were established. Correlations were found between some blood parameters and
standard length.
KEY WORDS: dietary habit, digestive enzymes, haematological profile, bony-tongue
fish, H. niloticus.

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