Modifies current passing through the fast sodium channel (Nav) in neuroblastoma cells, leading to delayed and incomplete inactivation. Produces a positive inotropic effect in mammalian heart muscle (By similarity). Paralyzes the shore crab (C.maenas) by tetanic contractions after intramuscular injection. Expressed in ectodermal glands. Not expressed in nematocytes. Belongs to the sea anemone sodium channel inhibitory toxin family. Type I subfamily.