Dataset: E. depressus reaction time to prey

Eurypanopeus depressus were collected by hand from oyster reefs within the North Inlet Estuary (33°20’N, 79°10’W, Georgetown, South Carolina) 24 hours prior to experimentation. All oyster reefs were within 5 km of each other and no oyster reef was closer than 200 m to another sampled reef. Infected crabs were identified by the presence of parasite externae which signifies the parasite was mature. We only used infected crabs with a single mature externa to reduce any variation produced by multiple infections. Our sampling methods could not discern whether crabs were infected with the immature, internal phase of the parasite, so it is possible that some crabs categorized as “not infected” did have infections. We utilized male and female crabs in both infected and uninfected treatments because the effects of parasitic castration made distinguishing the sex of infected crabs difficult.  Scorched mussels, Brachidontes exustus, are an important prey item of E. depressus and were collected from the same reefs from which we sampled crabs. Crab carapace width and mussel length were measured to the nearest 0.5 mm using a Vernier caliper while weight was measured to the nearest 0.01 g with a top loading balance AEP-2500G.

Crabs were starved 24 hours prior to experimentation to standardize hunger levels and were monitored for 24 hours after the experiment to ensure none underwent ecdysis or extruded eggs. Crabs were placed in individual cylindrical glass containers (height 5 cm, radius 3 cm) and allowed to acclimate for five minutes. Following the acclimation period we introduced a single mussel into each container and recorded the amount of time taken for the crab begin manipulating the mussel (min). To reduce variations in reaction time brought about by differences in the crab:mussel size ratio we matched larger crabs to larger mussels (crab carapace width = 8  – 14 mm; mussel shell length = 3.5 – 6 mm). Five infected and uninfected crabs per trial were observed at night under red light for a maximum of six hours, with seven trials conducted over seven consecutive days (n = 35). Crabs were monitored continuously for the first hour and every 5 min thereafter. Recorded time is the minute an individual was actually observed reacting after the start of the experiment.