Eugregarine parasitism of Erythemis simplicicollis (Say) at a constructed wetland: a fitness cost to females? (Anisoptera: Libellulidae)

Eugregarine parasites infect a wide variety of invertebrates. Some authors suggest that eugregarines are rather harmless, but recent studies suggest otherwise. Among odonate-eugregarine investigations, Zygoptera have been more frequently studied than Anisoptera. Adult dragonfly populations were surveyed for eugregarines at a constructed, flow-through wetland system and the fitness cost of infection was assessed in a common and widespread dragonfly host sp., E. simplicicollis. Populations were sampled weekly throughout the flight season. Host fitness parameters measured included wing load, egg size, clutch size, and total egg count. Of the 22 host spp. surveyed, 8 hosted eugregarines and 2 of these odon. spp. were previously undocumented as hosts. While eugregarine parasitism has been shown to exhibit seasonality, parasite prevalence and intensity in E. simplicicollis in this study showed no seasonal trend. The fitness parameters measured were not correlated with the presence or intensity of eugregarines. These findings suggest that either eugregarines do not affect wing loading and egg production in E. simplicicollis, or that virulence depends on parasite intensity and/or the specific eugregarine spp. infecting the hosts.