MORPHOMERISTIC AND GENETIC CHARACTERIZATION OF Enteromius SPECIES (PISCES: CYPRINIDAE) FROM SELECTED RIVERS AND RESERVOIRS OF THE NORTH RIFT, KENYA

Abstract

The Enteromius species of the family Cyprinidae, are known to have high genetic diversity and distinct population structure. They are widely distributed in rivers and reservoirs across Africa Because of the diversity in the group, accurated identification of species remains a big challenge, hampering their sustainable exploitation and management. The study was carried out to identify Enteromius species and perform the molecular characterization of select identified populations from the North Rift region, Kenya, a region where these species exist, but are poorly documented and therefore managed. Both morphomeristic and molecular techniques were used for species identification, while the D-loop region of the mitochondrial DNA was used to determine genetic diversity and population structure of populations. Sampling was carried out in man-made reservoirs and rivers across the region, from February to July 2018 using seine nets and an electrofisher. The captured fish were identified in the field using morphological characteristics, total length and standard length of each measured in cm and photographed. The fins were clipped and preserved in 90% ethanol for genetic analysis. Each fish sample was preserved in 10% formalin for laboratory analysis. Sixteen morphometric measurements and eleven meristic counts were done on each sample. The data was entered into Excel spreadsheet and then exported to PAST for Principle Component Analysis (PCA). Mann-whitney U test was used used to test for significance. Results on morphometric characteristics revealed clear separations of polygons of Enteromius species separating Enteromius species into four: Enteromius neumayeri, E. cercops, E. apleurogramma and E. paludinosus. The factor loadings analysis revealed that Standard Length (SL), Prepectoral Length (PPECL) and PrePelvic Length (PPELL) were the factors that clearly separated the four species. Principal component analysis (PCA) of the meristic data showed no clear separation of polygons of Enteromius species. However, the factor loadings established that mostly, the lateral line scales and caudal fin rays were significantly different within the four species. A total of 287 DNA sequences of the Cytochrome oxidase I region of mitochondrial DNA for species identification identified four fish species: Enteromius apleurogramma, E. cercops, E. neumayeri, and E. paludinosus. Enteromius neumayeri had seven clusters while E. apleurogramma had five clusters. Minimum spanning network showed two clusters for E. neumayeri and and one cluster for E. apleurogramma. Pairwise comparisons for FST values among E. neumayeri populations revealed significant differentiation in 27 out of 45 comparisons while in E. apleurogramma FST values were significantly different between the three sites, indicating that these populations were genetically differentiated. There was high genetic diversity of Enteromius species in North Rift selected rivers and reservoirs, with number of hapotypes ranging from 2 to 10, while haplotype diversity ranged from 0.1539 to 0.9082 Continual monitoring of Enteromius populations is essential to track changes of Enteromius species over time. Further studies should be conducted to determine the influence of environmental factors on the number of Enteromius species and their diversity in river and reservoir populations in North Rift region, Kenya which will help relevant bodies to develop population specific conservation strategies.