Morphometric, meristic and DNA riboprinting analyses of Tilapia species and their hybrids inhabiting the River Nile were examined. Morphometric data showed striking similarities and overlapping among Tilapia species, making it impossible to differentiate these species. Meristic characteristics revealed that Tilapia species could be identified into four major groups (Oreochromis niloticus, O. aureus, Sarotherodon galilaeus and Tilapia zillii). The lateral line scales differed significantly between the four Tilapia species, while the number of fin rays in the dorsal and anal fins differed significantly, differentiating three species (but not between O. niloticus and O. aureus). Restriction fragment length polymorphisms (RFLPs) of nuclear small sub-unit ribosomal RNA (18S srRNA) gene were used to differentiate the species. Polymerase chain reaction-restriction fragment length polymorphisms data provided a unique pattern for each species with a specific restriction enzyme. Two hybrids of Tilapia designated H1 and H2 were detected. The endonucleases SacII and ApaI differentiated H1 and H2. This research revealed a monophylogenetic relationship among all the studied Tilapia species. |
