Data from: Parasite and host elemental content and parasite effects on host nutrient excretion and metabolic rate

Ecological stoichiometry uses the mass balance of elements to predict
energy and elemental fluxes across different levels of ecological
organization. A specific prediction of ecological stoichiometry is the
growth rate hypothesis (GRH), which states that organisms with faster
growth or reproductive rates will require higher phosphorus content for
nucleic acid and protein synthesis. Although parasites are found
ubiquitously throughout ecosystems, little is understood about how they
affect nutrient imbalances in ecosystems. We (1) tested the GRH by
determining the carbon (C), nitrogen (N), and phosphorus (P) content of
parasitic trematodes and their intermediate host, the freshwater snail
Elimia livescens, and (2) used this framework to determine the trematode
effects on host nutrient excretion and metabolism. Snail and parasite
tissues were analyzed for elemental content using a CHN analyzer and
soluble reactive phosphorus (SRP) methods. Ammonium and SRP assays were
used to estimate N and P excretion rates. A respirometer was used to
calculate individual snail metabolism. Trematode tissues contained lower
C:P and N:P (more P per unit C and N) than the snail tissues. Snail
gonadal tissues more closely resembled the elemental content of parasite
tissues, although P content was 13% higher in the gonad than the trematode
tissues. Despite differences in elemental content, N and P excretion rates
of snails were not affected by the presence of parasites. Parasitized
snails maintained faster metabolic rates than nonparasitized snails.
However, the species of parasite did not affect metabolic rate. Together,
this elemental imbalance between parasite and host, and the altered
metabolic rate of infected snails may lead to broader parasite effects in
stream ecosystems.