Yuta Kudo, Mari Yotsu‐Yamashita, Dietrich Mebs
For three German newt species, Ichthyosaura alpestris , Lissotriton vulgaris , and Triturus cristatus , low levels of tetrodotoxin (TTX) have been reported. However, information on TTX resistance of their voltage-gated sodium channels (Na v ) has remained scarce. In the present study, TTX levels of the three species were reassessed and a 4,000-bp sequence of the skeletal muscle Na v 1.4 α-subunit including the pore region was analyzed. Although many specimens exhibited toxin levels below the detection limit, TTX concentrations were generally low and did not exceed 7.9 μg/g. All three newt species were found to possess four resistance-associated substitutions in the Na v 1.4 channel located in domains III and IV. These findings suggest that substitutions associated with TTX resistance are retained in the Na v 1.4 channel despite low levels of TTX in German newts.