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USING COMMON-GARDEN EXPERIMENTS TO TEST THE EFFECTS OF INFECTION BY THE TREMATODE METAGONIMOIDES OREGONENSIS ON LARVAL PLETHODONTID SALAMANDERS (DESMOGNATHUS AMPHILEUCUS) IN APPALACHIAN STREAMS

Abstract

Amphibians are the most endangered group of vertebrates, with recent declines and extinctions driven primarily from anthropogenic habitat loss and emerging pathogens. In addition, amphibians, like all vertebrates, are parasitized by a multitude of macroparasites which can pose detrimental effects to survival either directly or indirectly through interactions with environmental stressors. For instance, the Southern Black-bellied Salamander (Desmognathus amphileucus), a member of the family Plethodontidae and one of the most abundant amphibians inhabiting southern Appalachian streams, commonly serves as the second intermediate host for the trematode flatworm Metagonimoides oregonensis. We tested the hypotheses that this trematode affects (1) survival and (2) growth of these salamanders. To determine the potential impacts of this macroparasite on host performance, we conducted two replicated common-garden experiments with larval D. amphileucus to evaluate the effects of infection on larval growth and survival. Larvae originating from trematode-free and naturally infected populations were reared under symmetrical, controlled conditions at 16o° C in 100-mL jars with aerating bubblers. The first replicate (Spring 2025) was terminated at 50 days due to an unforeseen power outage to bubblers which resulted in substantial mortality; nonetheless, significant survival differences had already emerged with nearly all parasitized individuals perishing prior to this event. The second replicate (Fall 2025) was terminated at 90 days using a population with a lower average parasite load, revealing no detectable differences in survival and growth. Although trends suggest the possibility of a larger disparity in growth over the species’ entire larval period of approximately 3 years, another replication must be conducted with the use of a more heavily infected population to clarify possible effects. Overall, if such trematode-mediated fitness consequences continue to arise, these results indicate the necessity of additional experimentation and reevaluation of amphibian conservation in the hands of presumptuously innocuous macroparasites.

Acknowledgements

Piedmont University Department of Natural Sciences

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