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*L3 as 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).