Experiment: The effect of predator size on cercariae removal 
Project: Biodiversity and disease risk
Institute: NIOZ Royal Netherlands Institue for Sea research, Texel
Department: Coastal systems
Investigator: Jennifer E. Welsh
Assisting students:  Anke Hempel; Mirjinana Markovich 
Project Supervisors: David W. Thieltges; Jaap van der Meer
Date: Experiments conducted 2012, analyses conducted February 2017

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 ( 18.5C  0.2C).

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 25m 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. 

This excel file:
Model_&_R_Script:
This tab contains a copy of the analysis script to be used with R software (R Core Development Team (2013) A language and environment for statistical computing; R Studio Team (2014) RStudio: Integrated Development for R. Version 1.0.143. Boston, MA: RStudio, Inc.).

Model and R script: model explination and script used for analysis:
For manuscript: suggested model comparison table to be used in manuscript.
Survival rates: Survival rates for all species based on the best fitting model.
Searching rate: Searching rates for each for all species based on the best fitting model.


CSV:
This tab includes the raw data of the experiments in six columns. 
Experiment:
Denotes the different experiments conducted (cockle, oyster, crab, shrimp).
ConsumerPresence:
Presence or absence of a consumer or host in a treatment.
SizeTreatment: 
Size class category (A-E; small  large respectively) of the consumer or host used in a treatment or control in absence of consumers or hosts. See table right of this text box.
CercariaeAdded:
Number of cercariae added to each experimental unit.
CercariaeRemaining:
Number of cercariae remaining in experimental units after 3 hours.
CercariaeConsumed:
Number of cercariae removed ("consumed") by consumers or hosts during the experiment.


Citing this data and published manuscript details:
For further information or when refering to this data please cite the following publication.
Welsh JE, Hempel A, Markovic M, van der Meer J, Thieltges DW (2018). Consumer and host body size effects on the removal of trematode cercariae by ambient communities. Parasitology 16. https://doi.org/10.1017/S0031182018001488
