38th Annual Meeting of the Society for Invertebrate Pathology

Entomopathogenic nematodes (EPNs) search through the soil for hosts. They respond to cues produced by hosts and make infection decisions based upon these cues. Cues vary based upon host species and infection status. EPNs respond most strongly to host species that support high levels of reproduction. More recent work suggests that EPN infective juveniles (IJs) respond to infected hosts differently than non-infected hosts. We now ask how infection decisions are linked with fitness when an IJ is presented with the opportunity to join an ongoing infection. We have measured the temporal course of infection decisions of three EPN species in two host species. The rate of infection varies both with EPN species and with the relative permissiveness of the host. EPN IJs continue to join conspecific infections almost until IJs begin to emerge from the host, albeit at rates that gradually decline as the infection progresses. However, when presented with the chance to join heterospecific infections, S. glaseri will infect whereas S. carpocapsae will not. When hosts were held until IJ emergence, S. glaseri was a superior competitor inside the host, reinforcing their decisions to enter heterospecific infections. Thus, the link between fitness and infection decisions is again supported.