The effect of a pathogen on the population dynamics and reproductive method of Asplanchna girodi
Reynolds, Abigial Nicole
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Studies show that the abundance of Asplanchna girodi can be affected by many factors including food density, temperature and pH. One such aspect not yet explored is the effect that parasitism has on Asplanchna girodi populations. During weekly samplings of a local lake, a parasitic oomycete was discovered to frequently infect the Asplanchna girodi population. Based on multi-year sampling data, this study supports recent work showing that parasitism of a zooplankton has the potential to have reproductive and evolutionary consequences. I show that epidemics of this parasite, Pythium, occur frequently and that an increased number of males in the population can be correlated to the presence of the parasite. Sexual reproduction involving males provides for Asplanchna girodi's only means of genetic recombination and production of diapausing eggs that overwinter. This study shows that there is a correlation between the rate of infection by Pythium and the density of males in the Asplanchna girodi population. By increasing the number of males in a population, the rate of diapause egg production is also increased. Infection by this parasite could therefore be associated with increased sexual reproduction and genetic recombination of A. girodi populations.