Temperature affects predation of schistosome-competent snails by a novel invader, the marbled crayfish Procambarus virginalis

The human burden of environmentally transmitted infectious diseases can
depend strongly on ecological factors, including the presence or absence
of natural enemies. The marbled crayfish (Procambarus virginalis) is a
novel invasive species that can tolerate a wide range of ecological
conditions and colonize diverse habitats. Marbled crayfish first appeared
in Madagascar in 2005 and quickly spread across the country, overlapping
with the distribution of freshwater snails that serve as the intermediate
host of schistosomiasis–a parasitic disease of poverty with human
prevalence ranging up to 94% in Madagascar. It has been hypothesized that
the marbled crayfish may serve as a predator of schistosome-competent
snails in areas where native predators cannot and yet no systematic study
to date has been conducted to estimate its predation rate on snails. Here,
we experimentally assessed marbled crayfish consumption of uninfected and
infected schistosome-competent snails (Biomphalaria glabrata and Bulinus
truncatus) across a range of temperatures, reflective of the habitat range
of the marbled crayfish in Madagascar. We found that the relationship
between crayfish consumption and temperature is unimodal with a peak at
~27.5°C. Per-capita consumption increased with body size and was not
affected either by snail species or their infectious status. We detected a
possible satiation effect, i.e., a small but significant reduction in
per-capita consumption rate over the 72-hour duration of the predation
experiment. Our results suggest that ecological parameters, such as
temperature and crayfish weight, influence rates of consumption and, in
turn, the potential impact of the marbled crayfish invasion on snail host
populations.