CHROMOSOMES OF 3 PROSOBRANCH GASTROPODS FROM VIVIPARIDAE, PILIDAE ANDCYCLOPHORIDAE (ORDER, MESOGASTROPODA)

Mitotic and meiotic chromosome preparations of Bellamya bengalensis f. doliaris (Viviparidae), Pila globosa (Pilidae) and Cyclophorus polyne ma (Cyclophoridae) were made by colchicine - ovotestis cell suspension - methanol acetic acid - flame drying - Giemsa technique. Karyotypes were prepared on the basis of decreasing length of the chromosomes and their morphometric analyses were done. The diploid number 2n = 22 wit h the chromosome formula n = 7m + 4 sm and FN = 44 for Bellamya bengal ensis f. doliaris, 2n = 28 with the chromosome formula n = 9m + 5sm an d FN = 56 for Pila globosa and 2n = 28 with the chromosome formula n = 13m + Ism and FN = 56 for Cyclophorus polynema were obtained. Chromos ome numbers of each species was confirmed from the respective metaphas e-I spreads and behaviour of their meiotic chromosomes were studied. T he data obtained for each species were compared with the available chr omosomal information on other confamilial species and the role of the possible mechanisms of karyotypic evolution in them have been discusse d. Conservativeness with regard to chromosomal change at higher taxon level has been discussed.