Comparative chromosome studies in mongooses (Carnivora, Viverridae)

Abstract

The chromosomes of 45 mongooses (Herpestinae) representing 5 genera and 12 species were studied mainly in tissue cultures of skin biopsies. Karyotypes and idiograms were constructed for the different species, and every chromosome was compared through all the species. All species of the genus Herpestes have the functional Y chromosome translocated on to an autosome, and consequently the males have one chromosome less than the females. This “pseudo-XO/XX” or X1X2Y/X1X1X2X2 sex chromosome mechanism is unique among the Carnivora. All species of the other genera studied have the usual XY/XX mechanism. The most frequent chromosome number in the Herpestinae is 2n = 36, but some species have different numbers. Herpestes ichneumon has 2n = 43/44, H. sanguineus 2n = 41/42 and H. pulverulentus 2n = 39/40; the remaining Herpestes species have 2n = 35/36. Helogale parvula, Mungos mungo, Crossarchus obscurus and Cynictis penicillata all have 2n = 36/36. The karyotypes of the different species show great similarities; the deviations in chromosome number in Herpestes ichneumon, sanguineus and pulverulentus can be accounted for by centric fusion/fission events, in the last-mentioned species in combination with pericentric inversions. In six species of Herpestes the neo-Y chromosome was identified as one relatively large t chromosome, showing intraspecific morphologic variation in two of the species. The Y of Helogale, Mungos and Crossarchus is a very small m chromosome, that of Cynictis is somewhat larger. The true X chromosome (X1 of Herpestes) is most likely identical in all species: it is a medium-sized m chromosome comprising 5 per cent of the female haploid set. Two alternatives of karyotype evolution in Herpestinae are discussed. Five species, not studied by the present author, are included in the discussion. Their karyotypes fit well into the general pattern with the exception of Atilax paludinosus (2n = 35/36), which for cytogenetic reasons should be included in the genus Herpestes. Some features of the karyotypes of the mongooses are unique among the Carnivora and the karyological data support the view of elevating the subfamily Herpestinae to the rank of family Herpestidae.