We measured the elemental content (%C, N and P) and ratios (C:N, C:P, N:P) of a diverse assemblage of parasitic helminths to ask whether taxonomy or traits were related to stoichiometric variation among species. We sampled 27 macroparasite taxa, spanning four phyla, infecting vertebrate and invertebrate hosts from freshwater ecosystems in New Jersey. Macroparasites varied widely in elemental content, exhibiting 4.7-fold variation in %N, 4.6-fold variation in %P, and 11.5-fold variation in N:P. Across all species, parasite %P scaled negatively and C:P scaled positively with body size. Similar relationships between parasite P content and body size occurred at the phylum level and within individual species. The allometric scaling of P across species supports the growth rate hypothesis, which predicts that smaller taxa require more P to support relatively higher growth rates. Life cycle stage was related to %N and C:N, with non-reproductive parasite stages lower in %N and higher in C:N than actively reproducing parasites. Parasite phylum, functional feeding group, and trophic level did not explain elemental variation among species. Organismal stoichiometry is linked to ecological function, and wide variation in macroparasite stoichiometry likely generates diverse patterns in host–parasite nutrient dynamics and variable relationships between parasitism and nutrient cycling.
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Acknowledgements – We thank Gary Taghon for generously allowing us to conduct elemental analyses in his laboratory. Chris Brianik, Seth Bromagen, Samantha Fagundez and Suzanne Sukhdeo assisted with parasite collection. We thank Jan Lovy at the New Jersey Division of Fish and Wildlife for providing additional samples. Peter Morin, Rana El-Sabaawi, Angélica González, Gary Taghon and members of the Morin Lab at Rutgers Univ. provided helpful comments that improved this manuscript. Funding – Grants from the Rutgers University Ecology and Evolution Graduate Program and the New Jersey Water Resources Research Institute funded this project. This material is based upon work supported by National Science Foundation Graduate Research Fellowships awarded to REP and RLG (DGE-1433187).
- body size
- ecological stoichiometry
- growth rate hypothesis