Compensatory parasitism in a multiple parasite-host system: Water mites, gregarines and damselflies

The suborder Zygoptera is parasitized by many types of organisms. Their most common external parasites are water mites. As larvae these arachnids attach themselves phoretically during the hosts’ nymphal stage. When the host ecloses, the water mite crawls onto the adult host, pierces the teneral exoskeleton and starts its parasitic stage. The most common internal parasites of Zygoptera are gregarines; a group of parasitic protozoan apicomplexans that only infect invertebrates. Gregarines are ingested by their host as cysts and develop in the lumen of the mid-gut by attaching to the gut wall. We studied six species pairs in the Zygoptera in Soutern Ontario to determine whether parasitism rates are due to evolutionary relatedness, host geographic range, host habitat preference or parasite-parasite interactions. Based on preliminary analyses, prevalence of parasitism of larval water mites ranges from 0-67% and gregarine ranges from 0-75%. Species that are more closely related phylogenetically have more similar patterns of endoparasitism when controlling for collection locality. And there seems to be no relationship between the ectoparasites and endoparasites.