Entomopathogenic nematodes are lethal insect parasites that have one free living stage, the infective juvenile (IJ), which leaves a depleted host and finds and infects a new host. Carbon dioxide has been shown to be an important cue in host infection. The quality of an insect as a potential host to an IJ depends on whether or not it is infected and, if infected by conspecifics, on the stage of the infection. The benefits of mass attack suggest that recently infected hosts may be preferred over uninfected hosts, but as the host becomes depleted the benefits will decrease. Previous research has indicated that IJ attraction and infection increase in response to recently infected versus uninfected insects. We hypothesize that changes in host CO2 production as a result of progression in the infection process could provide information about host status that affects nematode infection decisions. Carbon dioxide release by two insect species (Galleria mellonella and Tenebrio molitor) exposed to one of three nematode species (Steinernema carpocapsae, S. glaseri, or S. riobrave) was measured every two hours from initial exposure to nematodes to IJ emergence. Dead and living uninfected insects were used as controls. Infected insects showed two distinct peaks of CO2 production that were higher than levels produced by uninfected insects: one between 20-30 hours (before insect death) and the other at 110-120 hours after exposure to the nematodes. Behavioral assays will be conducted to determine how changes in host attraction are correlated with these peaks of CO2 production.
Species 1: Coleoptera Tenebrionidae Tenebrio molitor
Species 2: Rhabditida Steinernematidae Steinernema
Species 3: Lepidoptera Pyralidae Galleria mellonella
Keywords: carbon dioxide, entomopathogenic nematodes
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