Chromosomal Polymorphism in Thracian Populations of Rattus rattus (Linnaeus, 1758) (Rodentia: Muridae)


Abstract: The black rat (Rattus rattus L.) from Thrace is an Oceanian type (2n = 38). Chromosomal analyses show that a polymorphism occurs in chromosome pairs no. 9, 10, and 13 due to pericentric inversions. In the studied populations, the frequencies of homozygous and heterozygous individuals did not differ from the Hardy-Weinberg equilibrium for chromosome pair no. 13. In both Gelibolu and Pınarhisar populations of R. rattus, a polymorphism due to the supernumerary B-chromosome was found. The R. rattus karyotype with supernumerary chromosomes is reported here for the first time in Turkey. The number of diploid chromosomes are 2n = 38, 2n = 38 + B, and 2n = 38 + 2B. The chromosomal differences were recorded in the number of autosomal arms (NFa), ranging from 58 to 62. The supernumerary metacentric chromosomes were similar in morphology and size to the small metacentric chromosomes of the standard complement of 2n = 38 chromosomes.

Keywords: Rattus rattus, karyology, polymorphism, Thrace

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