Data presented in the paper "Consumer and host body size effects on the removal of trematode cercariae by ambient communities"
datasetposted on 11.06.2019, 00:00 by J. (Jennifer) Welsh, A. (Anke) Hempel, M. (Mirjana) Markovic, J. (Jaap) van der Meer, D.W. (David) Thieltges
Summary of experiment: Four intertidal species known to interfer with the transmission of hinasthla elongata cercariae were tested to see if their body size affects the number of cercariae removed. One individual was The effect of dilutor size on removal rates of cercariae was investigated in laboratory experiments by determining removal rates of five size categories of each dilutor species (Table 1). In addition, a sixth treatment without dilutors served as a control to account for potential loses of cercariae due other factors (knowing the number of added cercariae was 50) and to test for the presence of a dilution effect (control vs. dilutor size treatments). The experiments were conducted in four separate runs, with each run testing removal rates of a single dilutor species (one individual each; 6 replicates per treatment, Table 1). Each replicate consisted of a 2 l aquarium filled with 1500ml of filtered seawater and was randomly placed in a single climate controlled room ( 18.5°C ± 0.2°C). All organisms were starved and kept in the experimental aquaria for 24 hours to allow for acclimation . After acclimation, 50 cercariae (see above) were added to each replicate and left undisturbed for 3 hours. This time period ensured full swimming ability of cercariae, which is known to decrease after 8 hours (Studer and Poulin 2013; Thieltges and Rick 2006). At termination, the test organisms were quickly removed from the aquaria using long forceps. and the water from the aquaria was sieved using a 25µm sieve. The retained cercariae were backwashed into individual 100ml pots which contained 10ml of 99% ethanol for fixation and 0.5ml Rose Bengal for staining. Cercariae were later enumerated under a light stereomicroscope. In addition, all cockles were dissected under a light microscope and metercariae counted to determine infection intensity. This allowed to distinguish actual cercarial removal from cercarial loss due to infections. The data was analysed in R using a GLM with log link (see tab entitled "Model and R script"). The most complex model (M1 or M2) was tested against the least complex model (the Null model). Significances between models suggested that there was either a significant reduction int eh number of cercariae removed (compared to control) or that the size of the predator had a significant effect on the number of cercariae removed.