Karyotype Variations in the Genus Pollicaria (Caenogastropoda: Pupinidae)

the genus Pollicaria were examined. All 7 populations studied were found to possess the same chromosome pattern: n = 13, 2n = 26. However, the fundamental chromosome number (FN) of both populations of P. elephas from the south (Malaysia) was 46, while those for the other 3 species (5 populations) were all 50. Moreover, although each species had a unique karyotype, the karyotype of the isolated species, P. elephas, differed from the other 3 northern species in exhibiting 3 distinct telocentric chromosomes (2m+6sm+2st+3t). The 3 smaller species, P. mouhoti from northeastern Thailand, P. myersii from Laos, and P. gravida from 2 localities in northern Vietnam, exhibited similar karyotypes of 6m+4sm+2st+1t, 4m+6sm+2st+1t, and (3m+7sm+2st+1t and 2m+8sm+2st+1t) respectively, with only 1 telocentric chromosome. The karyotypes of the 2 morphologically variant populations of P. gravida from Vietnam differed by 1 in the number of metacentric and submetacentric chromosomes. The genus Pollicaria exhibits slight rearrangements in the centromeric positions of the smaller chromosomes and the deletion of 1 chromosome pair. A ZZ-ZW sex-determining system is proposed for this