The Influence of Trematode Invasion on the Thermoresistance of Lymnaea stagnalis (Gastropoda, Pulmonata) Population from the Floodplain Reservoir of Angara River

Abstract

The average terms (AT) of survival at 35°C in matured Lymnaea stagnalis with different levels of trematode invasion have been determined. There were noninvaded individuals from a natural population of L. stagnalis and laboratory culture; poorly (rear sporocysts and rediae) and heavily invaded (numerous cercariae) ones from a natural population. The AT values for both noninvaded groups were practically identical (31.6 and 32.4 hours, respectively). The AT values for the heavily invaded ones (18.0 hours) were significantly lower (p < 0.01) than for all of groups which mentioned above. The AT value for the non-selected sample from a natural population (22.5 hours) was rather low because of their strong infestation of mollusks (up to 84.6%) with cercaria. Obviously, the thermoresistance of natural L. stagnalis populations is largely determined both by the shares of invaded mollusks and the stages of trematode life cycle in them.

Keywords

• adaptation
• cercariae
• Lymnaea stagnalis
• rediae
• thermoresistance
• trematode infestation