Accuracy of a prey-specific DNA assay and a generic prey-immunomarking assay for detecting predation

Abstract

Predator gut examinations are useful for detecting arthropod predation events. The accuracy and reproducibility of two different gut assays are tested on various predator species that consumed Chrysoperla carnea (Stephens) that was externally labelled with rabbit immunoglobulin (IgG). Each predator homogenate was examined in triplicate for prey remains by both a conventional PCR assay to detect for C. carnea DNA and a generic ELISA to detect for rabbit IgG-marked prey. The ability of each method to detect predation over time was compared among predators, and between assay types were determined using a novel three-dimensional contingency table approach. Both assays reliably detected prior predation (e.g. at least one of the three subsamples yielded a positive reaction) for 6-12 h after feeding. However, the generic ELISA was more reproducible (e.g. all three subsamples yielded the same outcome) than the PCR. This shows that it was important to assay the predators in triplicate by PCR to avoid a high occurrence of false-negative reactions. Conversely, reproducible results from the ELISA procedure were not dependent on duplicate subsamples. Overall, the generic immunomarking gut assay procedure proved an effective method to assess predation.