CHARACTERISATION OF THE AFRICAN MUD CATFISH (Clarias gariepinus (Burchell 1822) IN SOME RIVERS IN SOUTH WEST NIGERIA USING MITOCHONDRIA DNA MARKERS

Abstract

The versatility in the nature of Clarias gariepinus, poor stock, genetic erosion and contamination of gene pool necessitate periodic characterization of its phenotypic and genotypic structure. Mitochondria markers were chosen because of rapid rate of mutation and it shows more variation than nuclear markers. This study was carried out to investigate the extent of variation among and within three populations of C. gariepinus using both molecular and morphological approach. Thirty (30) individuals were collected from three rivers: Ogbese, Aago and Asejire, DNA extraction was done using Urea- SDS protocol, polymerase chain reaction products was checked with 1% agarose gel. Sequences obtained from Cytochrome-b gene and 16S rDNA were treated by deleting regions of low quality and rectifying ambiguities. In the present study, results from morphometric characterisation showed that population from Asejire and Ogbese were somewhat related while population from Aago showed no relatedness, meristic character of all the three stations were all related to each other, however, Aago and Ogbese showed more relatedness. High positive correlation r = 0.872, b = 2.10 was observed in Aago and Ogbese population while low correlation and negative allometric growth r = 0.425 and b= 1.38 was observed in Asejire population using New Duncan Multiple range test. Eye diameter and distance between orbital and dorsal fin accounted for variation within the populations using Principal Component Analysis. On the other hand, Cytochrome B and 16S rDNA markers were used to assess the genetic diversity. Asejire river showed highest nucleotide diversity, all the populations were A - T rich and low in G - C content, high level of genetic diversity was observed in the population from Asejire while moderate level were observed in the Aago and Ogbese, phylogenetic separation was evident, phylogenetic tree when compared with reference strain was separated into two major clads and Asejire 2 suggests a monophyletic lineage, Population from Asejire were different from other populations. Low level of genetic structuring was observed among the three populations. This study established that there were differences in the genetic variation of Clarias gariepinus from three populations as revealed by molecular and and morphological analysis.