 T-D-T-R-O-D-O-T-O-X-I-N, tetrodotoxan T-D-X is a potent neurotoxan. Its name derives from tetraodontiforms, an order that includes pufferfish, porcupina fish, ocean sunfish, and triggerfish. Several of these species carry the toxin. T-D-T-R-O-D-O-T-O-X-I-N was discovered in these fish and found in several other aquatic animals, e.g., in blue-ringed octopuses, rough skin nudes, and moon snails that is actually produced by certain infecting or symbiotic bacteria like Pseudoaltyrimonas, Pseudomonas, and Vigrio as well as other species found in animals. Tetrodotoxan is a sodium channel blocker. It inhibits the firing of action potentials in neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions responsible for the rising phase of an action potential into the neuron. This prevents the nervous system from carrying messages and thus muscles from flexing in response to nervous stimulation. Its mechanism of action, selective blocking of the sodium channel, was shown definitively in 1964 by Toshio Narahashi and John W. Moore at Duke University, using the sucrose gap voltage clamp technique.