Document Type



Summer 2021

Academic Department


Faculty Advisor(s)

Dr. Diane Bridge


Species of the genus Hydra are freshwater invertebrates present in lentic ecosystems around the world. Research on the phylogeny and biogeography of the genus has identified four species groups. However, little work has been done on Hydra ecology during the last forty years, even though the freshwater habitats where they are found are often substantially impacted by human activities. Our project aimed to characterize the distribution of Hydra species in selected lakes in south central Pennsylvania. We sampled six lakes within Lancaster and Dauphin counties. Based on preliminary sampling of a lake on the Elizabethtown campus, we hypothesized that the species H. oligactis and H. vulgaris would be present in all locations. Plant material was gathered from lake bottoms near shore and examined for Hydra using stereoscopic microscopes. Hydra species were identified based on bud morphology and structure of nematocysts, and detection probabilities for each species were estimated using the program MARK. Hydra were found from all four species groups and at all six locations, although the lakes varied in size, dissolved oxygen levels, and whether an inflowing stream was present.


Scholarship, Creative Arts, and Research Project (SCARP)



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