Haematological characteristics -including red and white blood cells counts, haemoglobin, haematocrit, mean cell haemoglobin concentration, mean cell volume, mean cell haemoglobin, protein, glucose, albumin, sodium, chloride, potassium, magnesium and phosphorus -were established from an examination of 25 adult Heterotis niloticus collected at a fish farm. The red and white blood cell counts did not positively correlate with the physical parameters of length and weight. There were significant correlations between the blood cells, haemoglobin and pack cell volume. The blood group, genotype and agglutination test results were 92% Rh-O + and 8% Rh-O -, respectively, and were similar to the pattern in humans.

Thirty-nine morphometric and five meristic comparisons were carried out on 12-month-old interspecific and intergeneric hybrids of the African clariid catfishes Heterobranchus longifilis, Clarias gariepinus and Clarias anguillaris from experimental earthen ponds in Nigeria. Canonical discriminant analysis accounted for 89.4% of the variations, with eigenvalues of 151.69 and 9.06, respectively, the highest loading in the two axes coming from only 12 variables. A re-analysis based on those 12 variables revealed four major groups among the nine genetic combinations from a plot of axes 1 and 2, which accounted for 95.2% of the variations. The Mahalanobis square distance (D 2 ) between the offspring of the various mating combinations also revealed the varying levels of relationship between them based on their morphometric and meristic characters. The interspecific hybrids showed some level of heterosis only in the inheritance of the length of the frontal fontanelles compared to that of the putative Clarias species. The study shows the level of similarities in many of the morphometric and merisitic features, especially among the hybrids, and the distinguishing features that can be used to identify the hybrids from their putative parents.

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