Binds specifically to voltage-gated sodium channels (Nav), thereby delaying their inactivation during signal transduction (By similarity). Is highly toxic to crabs (by intrahemocoelic injection) (PubMed:2568126, PubMed:22015268), but without effect upon mice (by intraperitoneal injection) (PubMed:2568126). LD(50) is 0.3 ug/kg by intrahemocoelic injection. Belongs to the sea anemone sodium channel inhibitory toxin family. Type II subfamily.