Experiments on the life cycle of the trematode Himasthla elongata

In this experiment, we assessed the different transmission steps from the first to the second intermediate host: i) cercarial emergence from periwinkles, ii) cercarial activity and survival after emergence, iii) cercarial infectivity in mussels, and iv) susceptibility of mussels to cercarial infection. For iii) cercariae were treated but not the mussels, whereas for iv) mussels were treated but not the cercariae. The experiment was run in August-September 2017 in the climate chambers of GEOMAR in Kiel. All experiments were conducted using temperature and salinity (fully crossed) as well as time (only for cercarial output) as fixed factors, and periwinkle/mussel identity nested within water bath as random factor. Temperature levels applied were 19 and 23°C. Salinity levels applied were 13, 16 and 19.