Toxins extracted from Australian specimens of the crab, Eriphia sebana (Xanthidae)

Abstract

—Aqueous extracts of 75 specimens of the xanthid crab, Eriphia sebana, collected from coral reefs in the Capricorn Group, Great Barrier Reef, Australia, were assayed for toxicity to mice. Thirty-five extracts contained detectable toxicity. Toxicity was quantified by i.p. injection of mice where 1 mouse unit (MU) was defined as the amount of toxin required to kill a 20 g mouse in 15 min. Twenty-four of the extracts induced signs in mice similar to signs expected if paralytic shellfish toxins (PSTs) or tetrodotoxin were the predominant toxins. The highest toxicity found was 887.4 MU from a 98.6 g crab (=9.0 MU/g). Purification of five combined groups of extracts from crabs collected at the same time and area revealed for the first time the presence in E. sebana of toxins similar to PSTs. TLC and electrophoretic studies showed that these toxins behaved like saxitoxin, neosaxitoxin, gonyautoxin-1 and gonyautoxin-2. Two of these groups of extracts contained only one of these PST-like toxins and the remainder contained two. Eleven of the extracts caused signs in injected mice dissimilar to signs induced by PSTs or tetrodotoxin. Foregut contents of 33 crabs contained fish, crustacean and algal remains. Crustacean remains in one gut content sample included carapace fragments bearing distinctive surface features found on the smaller toxic xanthids, Actaeodes tomentosus and Pilodius areolatus. The combined gut contents of these crabs weighed 10.4 g and the aqueous extract of which contained 4.4 MU/g of toxin, supporting the suggestion of a probable dietary origin of the toxins present in the crabs.