Croissance et reproduction de Bulinus truncatus (Gastropoda: Planorbidae) en competition intraspecifique et interspecifique avec Melanopsis praemorsa (Gastropoda: Melanopsidae)

Abstract

Under semi-field conditions, the growth and fecundity of Bulinus truncatus decline when density is higher in both intraspecific and interspecific competition with Melanopsis praemorsa. This latter considerably affects the life history traits of B. truncatus. The growth and fecundity of B. truncatus are significantly increased in the presence of M. praemorsa at Bt/Mp (B. truncatus / M. praemorsa) ratio of 1/1. In constrast, at the Bt/Mp ratios of 1/3, 1/8 and 1/17, the growth, but not the fecundity, is inhibited. This could be attributed to the distinct behaviour of M. praemorsa at the time of density changes. The niche overlap, hence the interspecific competition between the two species, becomes more important at higher densities of M. praemorsa, whereas the dietary niches of both species are different at lower densities. The data obtained suggest that high densities of M. praemorsa are involved in B. truncatus population declines in many Schistosoma haematobium focuses within the Haouz region of Morocco.