Morphological and Genetic Diversity Studies of Chrysichthys Nigrodigitatus from the Cross River, Nigeria, Using Microsatellite Markers

Morphometric and genetic diversity studies were carried out on Chrysichthys nigrodigitatus sampled from middle and lower Cross River. The aim was to provide information on variations between these two populations and also augment the limited information currently available on genetic diversity in this species. A total of 79 fish samples were used for the morphometric analysis out of which 30 were used for the genetic study. Genomic DNA was extracted from caudal fin using a modified cetyltrimethylammonium bromide method and amplified using microsatellite markers.Twenty-three morphological features were studied from each fish sample out of which 19 showed significant differences (P<0.05) between the two populations. Principal Component Analysis identified head length, head width, caudal peduncle depth, standard length, preventral distance, snout length and anal fin length as key contributors to variation. Genetic analyses indicated low variability in the populations studied as evidenced by low Shannon`s information index (mean of 0.944 – 1.034), and positive coefficients of inbreeding (FIS) across both populations suggesting the presence of greater homozygosity in this species. Gene flow of 3.507 was observed between the lower and middle Cross River indicating the possibility of free mating between the two populations. The low levels of genetic diversity call for urgent management and conservation strategies to ensure long term survival of the species.