Abstract:
Division of labor and caste formation has evolved across multiple groups of social
animals, including parasitic flatworms of marine snails. Individual animals in separate castes are
often different sizes or shapes and represent reproductive and non-reproductive morphs. This
project observed whether trematodes in freshwater snails exhibit similar caste formation as
trematodes in marine snails. Caste formation based on body size would result in the secondary
morphs being much smaller than the primary morphs with no overlap in body volume or width.
Specifically, I determined whether the rediae of freshwater trematodes exhibit size differences
within snail host species. The freshwater snail species, Elimia livescens and Physa acuta, were
collected in the White River, Delaware County, IN, USA. Snails were identified to species, the
shell lengths were measured, and they were dissected to find parasitic trematodes under a
dissecting microscope. Length and width measurements of rediae were taken using a Nikon
imaging program and an image processing program. A scatterplot was constructed from rediae
length and width measurements. The volume of the rediae bodies were calculated by
approximating the shape of the rediae to a cylinder. The volume of rediae bodies varied
extensively, but the trematode parasites did not appear to exhibit distinct size difference within
the freshwater snail hosts.
