DECAY-RATES FOR SLUG ANTIGENS WITHIN THE CARABID PREDATOR PTEROSTICHUS-MELANARIUS MONITORED WITH A MONOCLONAL-ANTIBODY

The rate at which prey antigens decay within a predator during digesti on must be calibrated, for a given assay system, in order to define th e period within which predation must have occurred. Monoclonal antibod ies have great advantages in terms of target specificity, but have oft en in the past demonstrated impractically abbreviated antigen detectio n periods. However, the DrW-2D11 monoclonal antibody, which detects al l three genera of pest slugs (Mollusca: Pulmonata) in Britain, could c learly identify predation by Pterostichus melanarius Illiger (Coleopte ra: Carabidae) after 2.5 days at 16 degrees C, a longer interval than has been recorded for any other monoclonal antibody used in predation studies. The half-life, detection period and decay rate were calibrate d with and without subsequent feeding on alternative prey. Unrestricte d feeding on earthworm, following consumption of the slug Deroceras re ticulatum (Muller), significantly reduced the decay rate of slug antig ens. These results appear to contradict the assumptions, based on prev ious studies, that indicate reduced digestion rates in response to sta rvation. Possible reasons for this failure to comply with the predicti ons of optimal foraging theories are discussed.