| variability of tetrodotoxin and of its analogues in the red-spotted newt, notophthalmus viridescens (amphibia: urodela: salamandridae). | efts and adult specimens (n = 142) of the red-spotted newt notophthalmus viridescens from various locations in canada and usa were analyzed for the presence of tetrodotoxin (ttx) and of its analogues 6-epitetrodotoxin and 11-oxotetrodotoxin. considerable individual variations in toxin levels were found within and among populations from new hampshire, new york, pennsylvania, and virginia ranging from non-detectable to 69 μg ttx per g newt. ttx and its analogues were absent in efts and adults from ... | 2012 | 22197660 |