Electrophoretic characterization of Heterobranchus longifilis, Clarias gariepinus, Clarias anguillaris and their intergeneric and interspecific hybrids were carried out using 12% sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Twenty seven fish samples (three from each mating combination) were used and a total of 16 electrophoretic protein bands were scored. There were variations in the protein banding patterns especially among the hybrid mating combinations. The 14th, 2nd and 9th band resolved in H. longilis, C. gariepinus and C. anguillaris respectively are the only differentiating electrophoretic bands for their biochemical identification using SDS-PAGE. The interspecific and intergeneric hybrids also resolved the 6th and the 7th band respectively which were however absent in their putative parental species. Only the intergeneric hybrids resolved the 14th protein band also found in the parental H. longiflis in addition to the 2nd and 9th bands resolved in C. gariepinus and C. anguillaris, thus showing they are true fusion of two different species. Visual scoring of the protein bands shows that the hybrids resolved more of the maternal protein bands. The molecular phylogenetic tree constructed by Unweighted Pair-group Method with Arithmetic means (UPGMA) revealed that the various mating combinations generally have high genetic similarity. The similarity coefficients were 0.96 and 0.84 for the interspecific hybrids and the putative Clarias species, respectively. The parental H. longifilis was the most divergent with the least similarity coefficient of 0.75. This study recorded for the first time, the use of fish blood serum analysed using SDS-PAGE in the identification of H. longifilis, C .gariepinus, C. anguillarisand their various hybrid combinations.
Key words: Electrophoresis, Heterobranchus longilis, Clarias gariepinus, Clarias anguillaris, sodium dodecyl sulphate polyacrylamide gel electrophoresis.
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