Zoological Studies

Karyotype Variations in the Genus Pollicaria (Caenogastropoda: Pupinidae)

Bangon Kongim, Chirasak Sutcharit, Piyoros Tongkerd, Shau-Hwai Aileen Tan, Nguyen Xuan Quynh, Fred Naggs, and Somsak Panha (2010) The karyotypes of 4 recognized Southeast Asian species of 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 genus.