Resistibility of a toxic crab Atergatis floridus possessing paralytic shellfish poison (PSP) and of five nontoxic crabs, Pilumnopeus indica, Pachgrapsus crassipes, Leptodius exaratus, Eriphia laevimona and Gaillardiellus orientalis, against PSP and tetrodotoxin (TTX) was examined. The results showed that A. floridus is highly PSP resistible, the minimum lethal dose (MLD) being 5, 000-10, 000 MU/20 g body weight. This crab showed essentially the same resistibility against scallop PSP mainly consisting of gonyautoxins and gaginst crab PSP Mainly consisting of saxitoxins. A. floridus exhibited also a fairly high TTX resistibility, with an MLD of 1, 000-2, 000 MU/20g.
On the other hand, the nontoxic crabs had no resistance against PSP and TTX at all; most of their MLDs were assayed to be only several MU/20g.