Limitation and failure of immunological technique (ELISA) in resolving thediet of the South African rock lobster Jasus lalandii

Declines in rock-lobster (Jasus lalandii) growth have prompted a re-assessm ent of their diet, for which we employed an immunological approach (enzyme- linked immunosorbent assay, ELISA). Antisera were raised against 26 prey sp ecies, and their specificity was determined using ELISA. Antibody-binding w as compared using Western blots. The antisera showed high specificity to un digested prey with cross-reactions among antisera being reduced to < 4%. Ho wever, crossreactivity increased to 49% when tested against digested prey, with some antisera even failing to recognise homologous prey. Sodium dodecy lsulphate (SDS) gel electrophoresis demonstrated that excess rock-lobster d igestive enzymes prevented the identification of digested prey by ELISA. Ho wever, "inhibition ELISA" (modified ELISA) did demonstrate species-specific proteins in the digested extracts and could be used to identify digested p rey accurately. Nevertheless, the problem of enzyme interference has to be solved before large-scale screening of rock-lobster diets by ELISA is feasi ble.