First occurrence of tetrodotoxin in a dendrobatid frog (Colostethus inguinalis), with further reports for the bufonid genus Atelopus.

The water-soluble toxin present in skin of Colostethus inguinalis (Dendrobatidae) was identified as tetrodotoxin by fluorometric HPLC analysis. The amount of tetrodotoxin per frog skin was estimated by HPLC, mouse toxicity, and inhibition of [3H]saxitoxin binding to brain membranes as 0.1 to 1.2 micrograms. Small amounts of anhydrotetrodotoxin and 4-epietrodotoxin also were present. Tetrodotoxin-like activity was not detected by inhibition of [3H]saxitoxin binding in other species of Colostethus nor in other dendrobatids (Aromobates, Dendrobates, Phyllobates). Tetrodotoxin-like activity was present in extracts of skin of five species of Atelopus (Bufonidae). HPLC analysis identified tetrodotoxin as the major toxic component in Atelopus spumarius and A. varius, as a minor component in A. spurrelli, and as a trace component in A. ignescens and A. zeteki. The major tetrodotoxin-like compounds in the last three species were not identified. Tetrodotoxin-like activity was not detected by inhibition of [3H]saxitoxin binding in skin extracts from three other genera of bufonids.