Term of Award

Fall 2009

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

Lance A. Durden

Committee Member 1

William S. Irby

Committee Member 2

Alan W. Harvey

Abstract

Ectoparasites were collected from cotton rats (Sigmodon hispidus) in 20 sites in the Southeastern United States (FL, GA, MS, NC and SC). Prevalence and mean intensity of parasitism by sucking lice (Anoplura) and fleas (Siphonaptera) of cotton rats were recorded at all sites. The geographical distribution of S. hispidus and its main louse and flea ectoparasites range from the neotropical region to the southeastern USA. It was hypothesized that the abundance of the cotton rat associated louse (Hoplopleura hirsuta) and flea (Polygenis gwyni) would increase the further south and closer to the distribution centers of each of these ectoparasite species. In addition, it was hypothesized that male cotton rats would exhibit higher infestations (mean intensities and prevalence) by ectoparasites than females. Because males of many ectoparasites are more mobile than females and may experience more periods off the host than females, I further hypothesized that sex ratios of both flea and louse populations would be female-biased. Data collected during this study supported the hypothesis that populations of Polygenis fleas on S. hispidus increased further south (closer to the center of distribution for this flea) and thus were dependent on site location. Conversely, there was not a significant trend in abundance noted for Hoplopleura lice on S. hispidus, which was unexpected given that this ectoparasite is a more permanent ectoparasite than P. gwyni. Male cotton rats were not parasitized by statistically greater numbers of H. hirsuta or P. gwyni than were female cotton rats. Thus, the male host bias hypothesis was not supported for either ectoparasite species in this study. Populations of both H. hirsuta and P. gwyni were significantly female-biased, with about twice as many females as males on cotton rats. Overall, this study provides the first evidence for larger populations of an ectoparasite (P. gwyni) of a vertebrate towards the geographical center of distribution of the ectoparasite. Higher on-host populations of female versus male sucking lice and fleas in this study conform to similarly sex-biased data reported for several previous studies of ectoparasites on mammals. Conversely, the lack of significant differences for louse and flea infestations on male versus female cotton rats recorded during this study differs from some previous mammal-ectoparasite studies in which male hosts were more heavily infested.

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