Biological control of Biomphalaria glabrata by Thiara granifera under laboratory conditions.

The effect of the snail Thiara granifera on the snail Biomphalaria glabrata, intermediate host of Schistosoma mansoni in the Dominican Republic, was evaluated. Plastic aquaria, 3 and 1.5 gallons in capacity, were used. The aquaria were either unpartitioned or partitioned by a fine screen into two equal compartments, and the two snail species were introduced in different proportions. The results over a 1-year period showed that T. granifera effectively reduced the fecundity of B. glabrata, especially when the initial densitites of the two species were equal or where T. granifera was more abundant. There was still competition, although starting at a later date, when the density of T. granifera was half that of B. glabrata. The competitive interaction does not seem to be due to competition for food but to a chemical factor(s), possibly water-soluble pheromones.