Helminth community structure in tadpoles of northern leopard frogs (Rana pipiens) and Woodhouse's toads (Bufo woodhousii) from Nebraska.

Abstract

Currently, little information is available on helminth community structure in tadpoles, the ephemeral, feeding, non-reproductive larva stages of anurans. We examined the helminth community structure in tadpoles of northern leopard frogs, Rana pipiens, and Woodhouse's toads, Bufo woodhousii, from a first-order stream in Western Nebraska. Specifically, we were interested in how species-specific difference in size, time to metamorphosis, and habitat partitioning among larval anurans affect their helminth community structure. From June-July 2009, we collected 30 tadpoles of northern leopard frogs, R. pipiens, and 50 tadpoles of Woodhouse's toads, B. woodhousii, from Cedar Creek, Keith County, NE, USA. The compound helminth community was dominated by trematode metacercarial stages (echinostomatids and plagiorchids) and the nematode Gyrinicola batrachiensis with only a single non-gravid adult trematode, Gorgoderina attenuata, present in low numbers. The helminth component communities were depauperate and isolationist in nature, with a maximum of four helminth species/types per component community. Although no species-specific helminth infections were observed, clear differences were found in overall abundance of nematode versus trematode infections among tadpoles of these two anuran species. The component community of tadpoles of R. pipiens was dominated by nematodes, whereas the component community of tadpoles of B. woodhousii was dominated by trematodes. Although differences in tadpole susceptibility of these two anuran species could not be ruled out, differences in the reproductive strategy of G. batrachiensis in tadpoles of R. pipiens and B. woodhousii and anuran species-specific habitats partitioning among tadpoles of these two anuran species were important factors in structuring their helminth communities. Our study indicates that time to metamorphosis (older tadpoles) play a significant role in structuring helminth communities of tadpoles within species at the infracommunity level with older tadpoles having higher helminth species richness and/or abundances. However, species-specific differences in anuran tadpole habitat partitioning outweighed the effects of differences in time to metamorphosis at the component community level. Finally, our study is the first to report deformities in hind limb development in a tadpole from Nebraska. Of the 30 northern leopard frog tadpoles collected, a single individual contained an extra hind limb and was infected with two plagiorchid metacercariae located in the musculature above the hind limbs.