Chromosomes of three prosobranch gastropods from Viviparidae, Pilidae and Cyclophoridae (Order: Mesogastropoda)

Post - Graduate Department of Zoology, Berhampur University, Berhampur - 760 007, Orissa, India.



Mitotic and meiotic chromosome preparations of Bellamya bengalensis f. doliaris (Viviparidae), Pila globosa (Pilidae) and Cyclophorus polynema (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 with the chromosome formula n = 7m + 4 sm and FN = 44 for Bellamya bengalensis f. doliaris 2n = 28 with the chromosome formula n = 9m + 5sm and FN = 56 for Pila globosa and 2n = 28 with the chromosome formula n = 13m + lsm and FN = 56 for Cyclophorus polynema were obtained. Chromosome numbers of each species was confirmed from the respective metaphase-1 spreads and behaviour of their meiotic chromosomes were studied. The data obtained for each species were compared with the available chromosomal information on other confamilial species and the role of the possible mechanisms of karyotypic evolution in them have been discussed. Conservativeness with regard to chromosomal change at higher taxon level has been discussed.

Caryologia, 50(3-4): 341-353.

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