Morphometric analysis of Bulimulus bonariensis bonariensis (Rafinesque, 1833) and Bulimulus bonariensis sporadicus (D´Orbigny, 1835) (Gastropoda, Orthalicidae)

DIAZ, A.C.; BELTRAMINO, A.A.; VOGLER, R.E.; MARTÍN, S.M.

Rio de Janeiro

Congreso; XI International Congress on Medical and Applied Malacology; 2012

Sociedade Brasileira de Malacologia - SBMa

Orthalicidae (=Bulimulidae) are the largest gastropod family in the terrestrial Neotropical malacofauna, accounting for 40-60% of the landsnail diversity in many countries. They are widely distributed in the tropic and subtropical regions of South America, Australia, New Zealand and Tasmania. The aim of the present work is to analyze the conchological variation of two subspecies of the genus Bulimulus, Bulimulus bonariensis bonariensis (Rafinesque, 1833) and Bulimulus bonariensis sporadicus (d´Orbigny, 1835), estimating apex, last whorl and aperture. Material studied, Bulimulus b. bonariensis, is from collections in Florencio Varela, Buenos Aires (n=21) and specimens deposited in the MLP (n=21). The morphogeometric analysis was conducted using the deformation method, the Thin-Plate Splines (TPS) and the Relative Warps Analysis (RWA). The specimens were photographed with a digital camera. Fifteen landmarks were digitalized on each photograph, eight of which were semilandmarks. The first four morphometric variables obtained by the RWA accounted for 83.79% of the local variation observed. MANOVA test was conducted using the above variables to asses their significance in distinguishing among subspecies. Next, canonical variables (CVA) were estimated to maximize their separation. MANOVA revealed significant differences among the subspecies (lambda de Wilks = 0.761; F(4, 58) = 4.547, P less than 0.005). CVA showed that differences in the form of the subspecies were maximized. CV1 accounted for 100% of the variation observed between both subspecies, with B. bonariensis sporadicus situated on the most negative region on the axis(suboval shell), while B. bonariensis bonariensis (more stylized shell), was on the positive region overlapping the subspecies on the medium region of the CV1.