Abstract
Karyological analysis was performed on Viviparus ater (Cristofori & Jan, 1832), V. acerosus Bourguignat, 1862, V. mamillatus (Kuster), V. viviparus (Linnaeus, 1758) and V. contectus (Millet, 1813), collected from different freshwater bodies of Switzerland, Hungary, Albania, Italy and Lithuania. The karyotypes of V. acerosus and V. mamillatus are described for the first time. The diploid number of chromosomes in V. contectus equals 14, whereas in diploid sets of other studied species, 18 chromosomes are present. The karyotype formula is in V. contectus (5m + 2sm, NF = 28, in V. ater, 7m + 1sm-m + 1 sm, in V. acerosus and V. viviparus, 8m + 1sm, NF = 36, in V. mamillatus, 6m + 1m-sm + 1sm-m + 1sm, NF = 36. In females of V. ater, V. mamillatus and V. acerosus, the heteromorphism of chromosome pair no. 8 was observed, with a sex-determining mechanism — ZW female /ZZ male. Although, Z and W chromosomes are metacentric, significant differences (P > 0.05, or P > 0.001) in their size were determined. The interspecific significant differences (P > 0.05) in karyotypes of V. ater, V. mamillatus, V. acerosus and V. viviparus were detected by using one-way ANOVA and Bonferroni¹s Multiple Comparison tests. Only chromosomes of the pair no. 5 were of similar shape in all of these species. The smallest interspecific difference was between V. viviparus and V. acerosus. The intraspecific karyological differences in relative chromosome length and centromeric index of V. contectus from lakes Garda (Italy), Olauka and Asveja (Lithuania) were observed in the chromosome pair no. 5
Baršiene, J