ECOLOGY OF THE INTRODUCED SNAIL MELANOIDES-TUBERCULATA (GASTROPODA, THIARIDAE) IN RELATION TO BIOMPHALARIA-GLABRATA IN THE MARSHY FOREST ZONE OF GUADELOUPE, FRENCH-WEST-INDIES

Melanoides tuberculata was introduced to several types of aquatic habi tat occurring in the marshy forest zone, Guadeloupe, as a competitor o f the snail host, Biomphalaria glabrata, of Schistosoma mansoni. Colon ization by the competitor was successful in all habitats, but the impa ct on the snail host was variable according to the site. Evolution of global prevalences, intensities and abundances of Schistosoma mansoni in the reservoir host, Rattus rattus, did not show any significant cha nges during the eight years following the introduction of the competit or. The analysis of size distribution of M. tuberculata in a release p lot showed that maximum reproduction took place during the rainy seaso n between June and November. The thiarid snail needed 4.5 months to re ach a size of 10 mm, 14 months to reach 15 mm, and more than 30 months to reach 20 mm. Calculated life expectancies were 0.74 year at the fi rst year of age, 0.9 year at the second year, and 0.5 year at the thir d year.