Tetrodotoxin concentrations in rough-skinned newts, Taricha granulosa, from populations of their northern distribution range

Tetrodotoxin (TTX), which is one of the most potent neurotoxins blocking voltage-gated sodium channels of excitable membranes, is present in newts of the genus Taricha in varying concentrations. Whether there is a genetic basis of that variability was tested by maximum likelihood phylogenetic analysis of T. granulosa specimens from the most northern distribution range in southeastern Alaska (USA), British Columbia (Canada), and from Oregon (USA), using COI and 16S RNA as markers. TTX was quantitatively assayed in methanol extracts of the newts. Whereas very low TTX concentrations were detected in newts from Alaska, high individual variations in toxin levels were found in populations from British Columbia and Oregon, ranging from non-detectable amounts to 0.838 mg per specimen. Phylogenetic analysis revealed that theses populations are genetically homogenous. Therefore variation in TTX levels is not based on genetically distinct newt phenotypes, but may be the result of unknown endogenous mechanisms and/or exogenous, e.g., environmental, influences.