Spatial distribution patterns of the sporocyst infrapopulation of Schistosoma mansoni within its mollusc host (Biomphalaria glabrata): an unusual phenotype of aggregation.

A study carried out on the intramolluscan development of the larval stages of Schistosoma mansoni from Venezuela in its intermediate host Biomphalaria glabrata shows the existence of 2 patterns for the spatial distribution of daughter sporocysts within the digestive gland of the snail. Besides the normal pattern, which is a random distribution of daughter sporocysts within the gland, 11% of the infected snails harbored an infection phenotype with daughter sporocysts strongly aggregated in only the posterior half of the digestive gland. These data suggest a possible strategy allowing a better nutritional efficiency of the infected digestive gland, a process to block the supply of hemolymph toward the gonad, resulting in castration or both.