Abstract

Despite reports on chromosome polymorphism in Rattus rattus, chromosomal data on its populations from North-Central Nigeria is lacking. This study presents the chromosomal analysis of R. rattus from the University of Ilorin, Ilorin, Nigeria. Four specimens were caught using local traps. The specimens were injected intraperitoneally with 0.04% colchicine (0.01 ml per body weight) and left for 2 hours before being sacrificed. The air-dry method was used for chromosome preparation. 20 metaphase spread were examined and the diploid number of chromosomes obtained ranged from 32-38 with 2n=38 having the modal number represented by 55%. A karyotype formula of 2n=7m + 4sm+27t was found for R. rattus. These results contribute to the chromosomal data of R. rattus and compared with those from other regions in the country.

Key words: Rattus rattus, Chromosome, Karyotype, Kwara State, Nigeria