Experiment Two
Algae, snail eggs, and snail hatchlings were quantified using the same methodology as the first experiment. At the end of the experiment (week 12), we recorded the number and mass of live predators and snails. All snails and macroinvertebrates were collected and subsequently preserved in 70% ethanol. We determined snail infection under a dissecting microscope by cracking each snail’s shell and inspecting the hepatopancreas and gonad. We estimated snail tissue biomass (mg dry weight) using a mass-shell length (mm) regression where mass = 0.0096*Las fully described by (Civitello, Fatima, Johnson, Nisbet, & Rohr, 2018). To assess parasite production in the second experiment, we randomly collected 24 snails from each tank between 9 – 12 AM on September 10 and September 24 (days 45 and 59 post initial egg introduction, respectively) using a small net, measured their mass (g), and then shed them individually in artificial spring water in 30 mL beakers in the field for 1 hr. After shedding, snails were returned to their tank of capture. Collected cercariae were stained with Lugol’s solution and counted in the laboratory under a microscope. At the end of both experiments, we added pool shock (71.8% trichloro-s-triazinetrione, Recreational Water Products , Buford, GA, USA) to each tank at 0.15g/L to kill any snails or infective schistosome cercariae (Halstead et al., 2018).