Fitness-related attributes and gregarine burden in a non-territorial damselfly Enallagma praevarum Hagen (Zygoptera: Coenagrionidae)

Odon. are usually infected with intestinal gregarines. Using E. praevarum adults, it was investigated whether: (a) both sexes differed in the degree of parasitism and immune ability (as shown by melanization of artificial, nylon-based implants in the thoracic region); and, (b) gamete production, survival and fat reserves correlated with gregarine burden. 2 sets of in-copula (to control for age) animals were used. One was used for estimation of egg and sperm, and the other for fat reserves. Survival was monitored as the time that field-captured insects survived under laboratory conditions in the absence of food. Gregarines were counted by dissection of the gut. Despite the case that 9 9 had more parasites than 3 3, both sexes did not differ in immune ability. Eggs, but neither sperm nor fat reserves in both sexes, correlated negatively with parasite number. Survival in both sexes also correlated inversely with gregarine burden. This, however, held only for 3 3 when the analysis was performed by sex. These results are discussed in terms of the detrimental effects of gregarine on Zygoptera hosts.