Morphological studies on Bulinus sp. (Gastropoda: Planorbidae) from Nchout Monoun,Cameroon

Since 1990, diploid Bulinus sp. populations have been reported from many sites in the volcanic western Bamileke and Bamoun plateau in Cameroon; starch gel electrophoresis of enzymes and chromosome analyses have revealed a single band in hydroxybutyrate dehydrogenase (HBDH), isocitrate dehydrogenase (IDH), and a diploid chromosome number of 2n = 36. Several samples have been tentatively identified as B. natalensis (Küster, 1841) on the basis of observations on the shell and radula. The present study is a preliminary analysis of the characteristics of the shell and the radula of the snails from Nchout Monoun Crater Lake (Monoun Koumogoum) for adequate comparisons with the widely studied B. natalensis/tropicus complex from East and South Africa. Comparison of the ratio of shell length to aperture length (L/AL), plotted against shell length (L) in a scatter diagram, showed a 47% overlap between the dimensions of the Nchout Monoun sample and those from KwaZulu-Natal. From previous observations on the diploid chromosome number, single electrophoretic bands on HBDH and IDH enzyme systems, euphallic genital system, arrowhead-shaped mesocones and the characteristic features of the shell, we conclude that Bulinus sp. from Nchout Monoun is closely related to B. natalensis.