DIFFERENTIAL ANTIGEN DECAY-RATES DURING DIGESTION OF MOLLUSCAN PREY BY CARABID PREDATORS

Carabid beetles (Coleoptera:Carabidae) were fed upon slugs (Mollusca:P ulmonata) in the laboratory, and their crop contents analysed for moll usc remains, using an enzyme-linked immunosorbent assay (ELISA) with a n anti-Arion ater (L.) haemolymph antiserum. Crop weight loss and anti genic recognition of prey proteins were examined as separate variables in a series of validatory experiments. Two model predators, Abax para llelepipedus Piller and Mitterpacher and Pterostichus madidus F., were fed upon two species of pest slugs, Deroceras reticulatum (Muller) an d Arion hortensis Ferussac. The fitting of regression equations to the transformed antigenic response data allowed the 'half-life' and detec tion period to be calculated for each predator-prey combination. Follo wing a one hour feeding interval, the half-life of the antigenic respo nse to D. reticulatum remains was almost twice as long in P. madidus a s that in A. parallelepipedus, and the detection period more than 2.5 times as long. However, covariant analysis showed that there was a sig nificant difference between predator species in the rate at which dete ctability declined, but not in the rate of crop weight loss. When A. p arallelepipedus was allowed to feed upon A. hortensis for eight hours, prey remains were still detectable at the end of the experiment, 13 d ays after feeding. Calibration of the differential rates of antigen de cay and crop weight loss could potentially be used to calculate the si ze of the original meal, but only if prey species, and the time since feeding, can be determined. Potential solutions to these problems are discussed.