Karyological studies of Arvicanthis niloticus (Rodentia: Murinae) in Egypt [electronic resource].

Includes reference.

The karyotype and C-banding pattern of the unstriped grass rat, Arvicanthis niloticus, from four localities in Egypt are presented. All karyotyped individuals have, as a rule, the same diploid number of 2n = 62 and autosomal fundamental number of aFN = 62. All chromosomes have a large centromeric block of fairly uniform size. An additional interstitial or telomeric small C-band is scored in some chromosomes. However, frequent polymorphism in the morphology and heterochromatin of both the homologous chromosomes of the pair no. 1 and the X chromosome is scored in some individuals from four localities and led to an aFN = 63. Accordingly, four forms or cytotypes, namely ANl-la, ANI-lb, ANI-Ic and ANI-ld, are recognized based on this variation, which may indicate the occurrence of either addition or deletion of a heterochromatic segment as a result of pericentric inversions. Of these four forms, the ANI- r is considered ancestral for A. niloticus in Egypt and is closely similar to that of the Ethiopian A. dembeensis, regardless the contradiction concerned with the morphology of the X chromosome, while the karyotypes of the other forms are synapomorphy of the form ANI-1°. These forms also showed a relative resemblance to those of the Ethiopian A. abyssinicus and A. blicki. Therefore. it is concluded that the genus Arvicanthis could be represented by an Egyptian- Ethiopian radiation (A. niloticus, 'A. dembeensis', A. abyssinicus and A. blicki) and by a Central-Western African one including the karyotypes described as 'A. centralis' and 'A. solatus'. Moreover, A. niloticus should no longer be regarded as a single species but as a cluster of several proper species.

Summary in Arabic.

1