An enzyme‐linked immunosorbent assay to detect the presence of paralytic shellfish poison using an induced crab protein marker

A purified, high molecular weight protein (referred to as saxitoxin‐induced protein, SIP), was obtained from crabs, Hemigrapsus oregonesis, by affinity chromatography prior to use in a homologous crab SIP enzyme‐linked immunosorbent assay (ELISA) procedure. The SIP measured in H. oregonesis control crabs given acute saxitoxin (SAX) challenge injections (SAX range 0–50 ng), was less than the amount of SIP present in H. oregonesis crabs exposed to a natural toxic dinoflagellate outbreak. The latter were collected from a paralytic shellfish poison (PSP) contaminated coastal area which also contained PSP toxic butterclams (2000 μg PSP per 100 g shellfish), tested by the conventional mouse lethality bioassay procedure. These ELISA results were confirmed by an immunoblotting procedure using anti‐SIP antibody. An immunoblotting procedure of purified SIP and crude SIP antiserum revealed no cross‐reactivity with control, SAX uninjected crabs, thereby indicating specificity of the assay. The method is fast and useful for the screening of antigens expressed in crabs as a consequence of PSP, and represents a procedure that will complement the standard mouse bioassay.