Host effects on Romanomermis (Nematoda: Mermithidae) parasites of snowpool Aedes mosquitoes (Diptera: Culicidae)

Abstract

Host effects on mermithid nematodes (Romanomermis sp.) were studied in four populations of snowpool Aedes spp. mosquitoes (Diptera: Culicidae) in western Wyoming. Two factors associated with nematode fitness, survival and adult size, were examined in relation to species and parasite load of the hosts. The proportion of entering parasites that successfully emerged from hosts was relatively high in Aedes impiger, Aedes increpitus, Aedes pullatus, and Aedes punctor, none of which produced melanotic encapsulations of parasites. Emergence success at all localities was lowest in Aedes nevadensis and Aedes hexodontus, species that commonly encapsulated nematodes. Proportionately fewer parasites were encapsulated per host as parasite load increased, and encapsulation by Ae. nevadensis and Ae. hexodontus occurred less frequently in populations in which these species constituted most of the available hosts. Mean adult lengths varied between populations but did not differ between postparasites from different mosquito species within the same site. Total volume of nematodes per host was independent of parasite load but size of individual parasites decreased with increasing parasite load. This suggests intraspecific competition for finite resources in superparasitized hosts.