When worms compete, who wins?

In summer 2013, student Jessica Ramadin studied interactions among gastrointestinal worms of African buffalo together with mentors Sarah Budischak and Vanessa Ezenwa. Here’s the abstract from her summer project.

Abstract. Competition occurs when organisms must vie for limited resources and is often evidenced by a reduction in body size, decrease in reproductive success, change in resource use, or decline in numbers. Competition can occur within a species (intraspecific competition) or between species (interspecific competition) and plays a large role in the formation of natural communities. In this study, I investigated intraspecific and interspefic competition among gastrointestinal helminth parasites co-infecting African buffalo. Response to competition was measured by worm body length and fecundity. Specifically, I measured the length of 10 female and 10 male Cooperia from each of 10 African buffalo using digital photography and a dissecting microscope. Female length measurements and fecundity were first correlated to determine if there was a significant relationship between the two variables. Although there was no correlation between female length and fecundity, the relationship seemed to be influenced by buffalo host identity. To test for the presence of intraspecific competition, I compared worm body length and fecundity to the total number of Cooperia present in each individual host. Results indicated that both worm body length and fecundity were not affected by intraspecific competition. To test for the presence of interspecific competition, I compared worm body length and fecundity to the total number of non-Cooperia worms present in each individual host. Results indicated that interspecific competition did not affect fecundity, but competition and gender interacted to affect worm length. Moreover, this effect seemed to be driven by the presence of Parabronema worms. Overall, these results shed light on the complex interactions between parasite populations and how these interactions may influence disease transmission and severity.

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