Cuticular hydrocarbons as host recognition cues in specialist and generalist endoparasitoids

Authors: KAFLE, BASU - Texas A&M University; Adesemoye, Anthony; FADAMIRO, HENRY - Texas A&M University

Submitted to: Chemoecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2024
Publication Date: 7/29/2024
Citation: Kafle, B., Adesemoye, A.O., Fadamiro, H.Y. 2024. Cuticular hydrocarbons as host recognition cues in specialist and generalist endoparasitoids. Chemoecology. https://doi.org/10.1007/s00049-024-00410-9.
DOI: https://doi.org/10.1007/s00049-024-00410-9

Interpretive Summary: The chemical composition of cuticular hydrocarbons differs qualitatively and/or quantitatively among insect species. These differences convey species-specific information about the host's presence, quality, and suitability to foraging parasitoids, enabling them to discriminate between host and non-hosts during host recognition and acceptance. Here, we tested the hypothesis that specialist parasitoids that parasitize fewer host species use host-specific cues compared to generalists that have evolved to use general or ubiquitous cues. We evaluated two parasitoids with different degrees of host specialization for responses to the cuticular extracts of three host caterpillar species. Also, we compared the chemical composition of the cuticular profile of the three host caterpillars and found that the two closely related hosts were qualitatively similar in composition, whereas one host differed qualitatively and quantitatively, and this affected how parasitoids made a choice among the hosts. Results suggest that differences in the chemical compositions of host caterpillars and recognition of host-specific kairomones are essential for specialist parasitoids to discriminate host and non-host species during host acceptance.

Technical Abstract: The chemical composition of cuticular hydrocarbons differs qualitatively and/or quantitatively among insect species. These differences convey species-specific information about the host's presence, quality, and suitability to foraging parasitoids, enabling them to discriminate between host and non-hosts during host recognition and acceptance. It was hypothesized that specialist parasitoids that parasitize fewer host species use host-specific cues compared to generalists that have evolved to use general or ubiquitous cues. Here, we tested the above hypothesis by evaluating two parasitoids with different degrees of host specialization: Microplitis croceipes, a specialist parasitoid of Chloridea/Helicoverpa spp., and Cotesia marginiventris, a generalist parasitoid of several Noctuid genera including Chloridea, Helicoverpa and Spodoptera spp for responses to the cuticular extracts of three host caterpillar species. Also, we compared the chemical composition of the cuticular profile of the three host caterpillar species, C. virescens, H. zea, and S. exigua, and found that C. virescens and H. zea were qualitatively similar in composition, whereas S. exigua differed qualitatively and quantitatively from the other two. In contact bioassays, specialist M. croceipes was observed to utilize infochemicals in cuticular extracts to discriminate between host and non-host caterpillar species. Assessment with the coupled gas chromatography-electroantennogram detection (GC-EAD) revealed qualitative and quantitative differences in parasitoids’ antennal responses to the components of cuticular extracts of host species, where specialist M. croceipes showed greater antennal response than generalist C. marginiventris. These results suggest that differences in the chemical compositions of host caterpillars and recognition of host-specific kairomones are essential for specialist parasitoids to discriminate host and non-host species during host acceptance.