Comparative studies on the productivity of Fasciola gigantica and F. hepatica sporocysts in Lymnaea tomentosa that died after a cercarial shedding or without emission.

A histology study was performed on Fasciola gigantica- or F. hepatica-infected Lymnaea tomentosa that died after a cercarial shedding or without emission to compare the parasite productivity of each trematode. Degenerated rediae increased in number throughout the experiment. Their number rose rapidly after day 79 in snails that died after shedding in the F. gigantica group; they increased more slowly in snails that died without shedding. In the F. hepatica group the number rose after day 63 in the former snails and after day 79 in the latter. The contents of normal rediae evolved inversely. The number of morulae, for example, dropped rapidly after day 79 in the F. gigantica group. In the F. hepatica group it dropped after day 63 in snails that died after shedding and decreased after day 79 in the other dead snails. Free and degenerated cercariae were more numerous in snails that died without emission than in those that died at shedding. They rapidly increased in number after day 77. The numbers of rediae of F. gigantica were substantially greater than those of F. hepatica. In each group considered separately, it was likewise higher in snails that died without shedding than in those that died after the shedding of cercariae.