Abstract
Entomopathogenic nematodes (EPNs) are insect parasites used as biological control agents. Free-living infective juveniles (IJs) of EPNs employ host-seeking behaviors to locate suitable hosts for infection. We found that EPNs can differentiate between naïve and infected hosts, and that host attractiveness changes over time in a species-specific manner. We used solid-phase microextraction and gas chromatography/mass spectrometry to identify volatile chemical cues that may relay information about a potential host’s infection status and resource availability. Among the chemicals identified from the headspace of infected hosts, 3-Methyl-2-buten-1-ol (prenol) and 3-Hydroxy-2-butanone (AMC) were selected for further behavioral assays due to their temporal correlation with the behavioral changes of IJs towards the infected hosts. Both compounds were repulsive to IJs of Steinernema glaseri and S. riobrave in a dose-dependent manner when applied on an agar substrate. Furthermore, the repulsive effects of prenol were maintained when co-presented with the uninfected host odors, overriding attraction to uninfected hosts. Prenol was attractive to dauers of some free-living nematodes and insect larvae. These data suggest that host-associated chemical cues may have several implications in EPN biology, not only as signals for avoidance and dispersal of conspecifics, but also as attractants for new potential hosts.
Highlights
Entomopathogenic nematodes (EPNs) are insect-killing parasites used in biological control and are a model system for studying host-parasite interactions
We evaluated the responses of the infective juveniles (IJs) of four EPN species
S. feltiae has been described as a cruise forager[25, 26], and an intermediate forager when compared to EPNs from various genera[27], our results indicated that S. feltiae participation was similar to that of an ambusher type foragers such as S. carpocapsae
Summary
Entomopathogenic nematodes (EPNs) are insect-killing parasites used in biological control and are a model system for studying host-parasite interactions. The L2 juveniles will associate once more with the bacteria and take an alternative developmental pathway, becoming infective juveniles (IJs) rather than L3 juveniles These IJs will emerge and search for a new host to infect[2, 5] (Fig. 1E). The second strategy is an ambush foraging strategy where the IJ employs a sit-and-wait approach, waiting for a potential host to pass close by, allowing the IJ to attach and invade[7, 8]. Between these two endpoint foraging strategies there are species of EPNs that have been classified as intermediates[6, 9]. We evaluated the behavioral response of EPNs to infected hosts over time and identified odorants used by IJs to inform behavioral decisions regarding attraction to or avoidance of previously-infected hosts
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