A karyological study of three typhlopid species with some inferences on chromosome evolution in blindsnakes (Scolecophidia)

tBlindsnakes are poorly studied reptiles from the karyological point of view since chromosomal dataare only known for eight out of more than 420 species. The present paper shows the results of a kary-ological study conducted by means of standard and banding staining (Ag-NOR-banding and C-bandingplus CMA and DAPI fluorochromes) on three typhlopid species, Madatyphlops arenarius, Xerotyphlopsvermicularis and the parthenogenetic blindsnake, Indotyphlops braminus. Madatyphlops arenarius has con-served the primitive snake karyotype of 2n = 36 with 16 biarmed macro- and 20 microchromosomesand NORs on a microchromosome pair. The karyotype of X. vermicularis differed in showing a reducednumber of microchromosomes (16) and NORs on the long arms of the third macrochromosome pair.The parthenogenetic I. braminus exhibited a triploid karyotype of 3n = 42 with seven macro- and sevenmicrotriplets and NORs on a microtriplet. Comparison with chromosome data from the available literaturesuggests that the primitive snake karyotype of 2n = 36 occurred in the common ancestor of Leptotyphlopi-dae + Typhlopidae and in the common ancestor of Typhlopidae. In the latter family chromosome evolutionmay well have proceeded towards a decrease in the chromosome number from 2n = 36, 34, 32 until itreached 2n = 28, mainly involving micro- to microchromosome and/or macrochromosome translocations.Furthermore, these chromosome rearrangements occurred independently and repeatedly in the differ-ent evolutionary lineages of this family and are partially concordant with phylogenetic relationships.Cytologically identifiable sex chromosomes were not revealed by either standard or C-banding staining.