A gut analysis technique for identifying egg-specific predation events

Authors: Hagler, James; MOSTAFA, AYMAN - University Of Arizona

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2019
Publication Date: 6/7/2019
Citation: Hagler, J.R., Mostafa, A.M. 2019. A gut analysis technique for identifying egg-specific predation events. Journal of Insect Science. 19(3):1-7.

Interpretive Summary: The lygus bug is a major pest threat to many important crops. It reduces crop yields or values via fruit deformation or fruit loss by feeding preferentially on the fruiting structures of plants (i.e., cotton boll, alfalfa seed, strawberry fruit, etc.). An ARS scientist at Maricopa, Arizona developed a novel method for studying predation on the egg stage of lygus. The method consists of tagging lygus eggs with a unique protein biomarker. In turn, protein-marked eggs consumed by predators can be detected in their guts by protein-specific assays. In proof-of-concept studies, two predatory beetle species were exposed to two cohorts of lygus eggs, each of which contained a specific protein biomarker. The bioassays were able to detect protein-marked egg remnants in the guts of the predators for several hours after a feeding event. The technique also proved useful for identifying the most effective predator of the lygus egg stage. The methods described in this study will be used in the near future to identify the key predators of the lygus bug in cotton, alfalfa, and strawberry agroecosystems.

Technical Abstract: A universal food immunomarking technique (UFIT) is described for post-mortem gut analysis detection of predation on the egg stage of Lygus hesperus Knight (Hemiptera: Miridae). Collops vittatus Say (Coleoptera: Melyridae) and Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) were fed a single Lygus egg that was marked with rabbit and chicken sera proteins. The protein-marked egg remnants were detectable in the guts of the majority of the predators by each sera-specific enzyme-linked immunosorbent assay (ELISA) for 3 to 6 hours after a feeding event. A technique was then developed to expose protein-marked eggs to predators that simulated the Lygus bug’s endophytic oviposition behavior. The novel procedure entailed embedding Lygus eggs in an artificial substrate that mimicked the stem of a plant. A predator feeding choice study was then conducted in cages that contained a cotton plant and artificial stems containing an endophytic (concealed) and exophytic (exposed) egg patches. The endophytic and exophytic eggs were marked with chicken and rabbit protein, respectively. The gut analyses revealed that higher proportions of both predator populations contained remnants of the endophytic egg treatment and Lygus eggs were more vulnerable to C. vittatus than H. convergens. This study shows how the UFIT can be a useful tool for investigating complex predator-prey interactions.