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Title: IMMUNOLOGICAL EXAMINATIONS OF SPECIES VARIABILITY IN PREDATOR GUT CONTENTS:THE EFFECT OF THE PREDATOR: PREY PROTEIN RATION ON IMMUNOASSAY SENSITIVITY.

Author
item Hagler, James
item Naranjo, Steven
item ERICKSON, MELISSA - UNIVERSITY OF ARIZONA
item MACHTLEY, SCOTT - UNIVERSITY OF ARIZONA
item WRIGHT, SALLY - FORMER ARS EMPLOYEE

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Predaceous insects, those that feed on other insects, are thought to play an important role in decreasing the population of insect pests. However, due to the small size and elusive behavior of predators and pests, it is difficult to measure predation in the field by direct observation. We have developed tests, similar to those used in medicine to screen urine for drug gresidues and test for pregnancy at home, which enable us to precisely, rapidly, and economically analyze the stomach contents of predatory insects. These tests are called gut content enzyme linked immunosorbent assays (ELISAs). In this study we identified some variables that can affect the outcome of a gut content ELISA. Specifically, we examined what effect the predator:prey protein ratio has on the outcome of an ELISA. The gut content ELISA was more effective at detecting prey remains in small predators than in large predators. The predator:prey protein ratio had a profound effect on the sensitivity of our gut content ELISA. Our results suggest that care must be taken not to overload the ELISA with extraneous predator proteins. Predator samples should be diluted to less than 125 ug of total protein per sample. In another experiment, we compared the efficacy of our gut content immunoassay with another immunoassay technique known as a dot blot immunoassay. The dot blot immunoassay was more reliable than the gut content ELISA for detecting the presence of minute traces of prey remains in the stomachs of large predators.

Technical Abstract: In qualitative predator gut content immunoassays, sensitivity of immunoassay is important for detecting whether a predator contains a targeted prey antigen. If immunoassay employed is insensitive, probability of obtaining a false negative reaction is high. Sensitivity of an indirect enzyme linked immunosorbent assay (ELISA) developed to detect pink bollworm megg(s) in whole-body homogenized predators varied in efficacy between species. The indirect ELISA was more effective at detecting egg antigen in small predators than large predators. We examined the effect predator:prey protein ratio has on the sensitivity of an indirect ELISA. Results suggest when assaying whole body homogenized predators, care must be taken not to overload an ELISA microplate with non-target (predator) proteins. Predator samples should be diluted to less than 125 ug of total protein per sample. Any protein concentration above 125 ug/ELISA microplate will likely result in an ELISA false negative reaction. In another experiment, we compared efficacy of an indirect ELISA with a dot blot immunoassay. Adult Hippodamia convergens Guerin-Meneville that had eaten one pink bollworm egg were homogenized in variable dilutions of phosphate buffered saline (PBS) and each sample was analyzed using both immunoassays. The dot blot immunoassay was more reliable than indirect ELISA for detecting presence of minute traces of egg antigen in samples.