Meeting Abstract
Schistosoma, a family of trematodes that causes human schistosomiasis, have aquatic miracidial and cercarial life stages that depend on a fixed energy reserve to swim and locate intermediate snail hosts and humans, respectively. As small, ectothermic swimmers, these trematodes are likely affected by changes in water temperature and viscosity. However, their modes of locomotion differ; miracidia use cilia while cercariae use a forked tail. Thus, there is a need to quantify the effects of temperature gradients on miracidial and cercarial movement. We used a high-speed camera to quantify the crossed effects of temperature (10°C, 20°C, 30°C) and viscosity. We investigated the effects of temperature and viscosity independently by adding methylcellulose (MC), which maintained a viscosity of 10°C regardless of temperature. We quantified swimming mechanics of miracidia and cercariae of Schistosoma mansoni and results show a positive effect of temperature on cercarial tail beat frequency, cercarial speed, and miracidial speed. High viscosity significantly reduced cercarial tail beat frequency and speed, but not miracidial speed between 20 and 30°C. There were positive interactions between temperature and viscosity for cercarial tail beat frequency and speed, but not miracidial speed. Although high viscosity decreased miracidial speed, we found that colder temperatures allow miracidia to move with a lower cost of transport. That is, miracidia travel farther at 10°C than 30°C and thus have a higher probability of encountering a snail host. Conversely, cercariae had poor swimming performance at 10°C and did not travel far. Because miracidia emerge earlier in the year when water temperatures are cooler, our findings provide an explanation for such different body morphologies.
