Species specificity between the trematoda Fasciola hepatica and the molluscan host


Abstract Larval development of Fasciola hepatica in abnormal snail intermediate host Lymnaea palustris was studied. This incompatible host-parasite relationship was investigated under Transmission Electron Microscopy (TEM) to determine the fate of penetrated miracidia. It is believed that no larval development beyond the sporocyst was allowed to proceed by the defense system of L. palustris. This reaction was in the form of defense cell (haemocytes) aggregation around sporocyst. These haemocytes vary in appearance under TEM, some have a vary electron dense cytoplasm, others are much more electron lucid. These appeared to correspond to granulocytes and amoebocytes respectively, as described by other workers. Intermediate cells XXZAAAre were found in close contact with sporocyst and pore cells were also reported. In L. palustris 18 days old, the location of sporocyst proved to be difficult. This could be due to the very efficient defense mechanism of the snail at this age and its capability to destroy and remove the sporocyst within three days post exposure, thus snails 0 day old was used.