Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/6/2006
Publication Date: 10/1/2007
Citation: Ramos-Rodriguez, O., Campbell, J.F., Lewis, E.E., Shapiro Ilan, D.I., Ramaswamy, S.B. 2007. Dynamics of carbon dioxide release from insects infected with entomopathogenic nematodes. Journal of Invertebrate Pathology 94: 64-69. Interpretive Summary: Entomopathogenic nematodes are promising biological control agents for many species of insect pests, but efficacy may be limited due to infection strategies that lead to clumped distributions in some hosts and that leave other hosts uninfected. The host infection decisions of entomopathogenic nematodes are likely influenced by changes in chemical cues emitted from an infected host. We hypothesized that carbon dioxide (CO2) production from an insect host changes after it is infected. Carbon dioxide release over time was measured from two insect species after infection by one of four nematode species, and one or two peaks of CO2 production, depending on the insect species, were detected. Entomopathogenic nematodes have been shown to be attracted to CO2 and these peaks of production from infected hosts may lead to increased infection of already infected insects and lead to a more clumped distribution in hosts. This research provides a foundation from which to investigate the influence of these host changes on nematode infection behavior.
Technical Abstract: The quality of an insect as a host to an entomopathogenic nematode infective juvenile depends in part on whether or not the insect is already infected and on the stage of that infection. Previous research has shown that nematode response to hosts can change after infection and that, for uninfected hosts, CO2 can be an important cue used by infective stage juveniles during attraction. We hypothesized that CO2 production from an insect changes after it is infected, and that these changes could influence nematode infection decisions. Changes in CO2 released by two insect species (Galleria mellonella and Tenebrio molitor) after infection by one of four nematode species (Steinernema carpocapsae, S. feltiae, S. glaseri, or S. riobrave) were measured every two hours from time of initial exposure to nematodes up to 224 h after infection. Dead (freeze-killed) and live uninfected insects were used as controls. Infected G. mellonella showed two distinct peaks of CO2 production: one between 20 and 30 h and the other between 70 and 115 h after exposure to the nematodes. Peaks were up to two times higher than levels produced by uninfected insects. Infected T. molitor showed only one peak between 25 and 50 h. We found differences in peak height and timing among nematode and insect species combinations. The influence of these changes in CO2 production on IJ attraction and infection behavior remains to be determined.