Productivity and biomass of trematode (Digenea) parasites in lake ecosystems.

The first estimation of the annual production and biomass of cercariae (free swimming transmission stage of digenetic trematodes) in a lake ecosystem has been performed. The biomass of cercariae is comparable with that of free-living invertebrates and may make a significant contribution to the energy flow in lake ecosystems.

[THE EMISSION OF PLAGIORCHIS MULTIGLANDULARIS CERCARIAE FROM NATURALLY INFECTED SNAILS LYMNAEA STAGNALIS IN CHANY LAKE, SOUTH OF WEST SIBERIA].

The daily cercarial output of freshwater trematode Plagiorchis multiglandularis from naturally infected snail Lymnaea stagnalis were studied. The snails were collected in the Chany Lake (South of West Siberia). The daily cercarial output from the snail of different size was determined. The average daily cercarial output ranged from 4641 ± 1829 at the snail with shell length 29 mm to 14022 ± 5198 at the snail with shell length 44 mm. The positive correlation between the average daily cercarial output and the shell of snail host was found (p ≤ 0.001). The maximum of P. multiglandularis cercariae release from the snail during daytime, that coincided with period of activity of the second intermediate hosts. Temperature-mediated increase in cercarial output of P. multiglandularis in temperature range 23-24.5 degrees C was found. The cercarial output was inhibited over the temperature optimum.