GENETIC DIVERSITY OF TILAPIA IN NIGERIA USING AVAILABLE COI SEQUENCE IN THE GENE BANKS

Abstract

Tilapia importance in global aquaculture and fisheries has motivated the study and assessment of their genetic
diversity in Nigeria. In this article, attempt was made to retrieved all available mitochondrial cytochrome c
oxidase subunit I gene (COI) sequences of tilapia species from Nigeria deposited in BOLD and NCBI, to quantify
their available DNA barcoding information. It appears output of tilapia species barcoding studies in Nigeria were
not much as we got only 112 hits. Maximum likelihood analyses of the sequences with three tilapia reference
genomes and three distant outgroups (669 bp fragment; N=112+3+3) showed two groups of Nile tilapia
Oreochromis niloticus, identification of some unidentified Tilapia spps and Oreochromis as Coptodon
camerunensis, Coptodon dageti and Oreochromis aureus, presesnce of Blue tilapia Oreochromis aureus in both
species of O. niloticus and Sarotherodon galilaeus groups independently. These species are readily utilized for
aquaculture in Nigeria and could escape from farms into the wild due to poor waste management or flooding.
Hence, this may explain why the BLAST search identified an unplaced sequence from Ondo, Nigeria as Coptodon
camerunensis (99.2%), a strain endemic to Northern Cameroonian rivers. However, O. niloticus individual from
River Benue could be pure based on placement with its genome. Considering the limitations of mtDNA, we
recommended an exome gene capture approach in addressing issues of introgressive hybridization, for better
informed conservation of tilapia pure stocks.