The distribution of intestinal gregarine parasites (Apicomplexa: Eugregarinorida) in dragonflies of central Texas, USA

Dragonflies are ubiquitous members of aquatic communities and frequently carry a burden of gregarine intestinal parasites. The degree of that burden and the relationships among parasite prevalence, load, and host gender are not well known. Previous studies report that these intestinal parasites are detrimental to a broad spectrum of insect hosts. Longevity, fertility, mate selection, and territory defense may be compromised in some hosts. It is estimated that more than 1 million gregarine species exist, but little is known about their broad impact because relatively few invertebrates have been surveyed for gregarine parasites. In this study, we surveyed dragonfly species common to central Texas for gregarine parasites (trophozoites). Of the 20 dragonfly species surveyed, 11 hosted gregarines. Weekly collections of adult dragonflies from April - November, 2007 (N=2,890) show that parasite prevalence increased over the flying season in all species combined (0% in April - 100% in November). Parasite prevalence in two host species, Brachymesia gravida and Erythemis simplicicollis, was gender biased. Although parasite prevalence varied with species and time, parasite load did not. The mean parasite load was 7.5 trophozoites per host.