The Toxicity of Newts

By Heather Björnebo

The question is often asked, are newts toxic. The answer is, of course, yes. But never has it been fully explained how toxic newts really are. I noticed that there are many speculations on the degree of toxin and how harmful it is. So I wondered whether there was any published literature on the subject. And as luck had it, I found some great research done by Edmund D. Brodie, Jr. and Edmund D. Brodie, III that may shed some light on this subject.

This first I ran across was a study by Edmund Brodie, Jr. (1968). It was a study on the skin toxin level of Taricha granulosa, the rough skinned or Oregon newt. He tested the toxin found in the skin of adult animals on cats, lab rats, lab mice, ermine (a member of the weasel family), moles, woodrats, muskrats, meadow mice, ground squirrels, nutria (“water-rats”), bobcats, starlings, snakes, lizards, robins, fish, frogs and more. A total of 30 vertebrate species were tested, many of them possible predators. Every animal that was giving the skin toxin was susceptible to it. Many of the animals died due to the toxin. The only animals that recovered from a dose of the toxin were ones given very small doses. He hypothesized that the toxin found in the skin of Taricha granulosa was tetrodotoxin.

I also discovered a paper by Edmund D. Brodie, Jr., John Hensel, Jr. and Judith Johnson (1974). This time the purpose of the experiments was to determine what toxins and at what levels are found in other Salamandridae species. They used Taricha, Notophthalmus, Cynops, and Paramesotriton. It stated: “Tetrodotoxin… is far more toxic than any known substance. … Wakeley et. al (1966) determined that tetrodotoxin-like substances [are] present in the homogenized bodies of the following newts of the Salamandridae: Taricha torosa, T. rivularis, T. granulosa, Notophthalmus viridescens, Cynops pyrrhogaster, C. ensicauda, Triturus vulgaris, T. cristatus, T.alpestris T. marmoratus. … Taricha were found to be the most toxic and Triturus were the least toxic of those tested. …” They went on and tested these results with Taricha granulosa, Cynops pyrrhogaster, Notophthalmus viridescens, and Paramesotriton hongkongensis. All newts tested carried toxin. They tested the toxins from each species on lab animals and found that all could potentially cause death. When discussing the results of their findings they said, “All species of newts tested had toxic skin… . The symptoms were typical of tetrodotoxin…. The [adult N. viridescens] were less toxic than the efts… both C. pyrrhogaster and P. hongkongensis were about ten times as toxic as adult N. viridescens or about as toxic as the juvenile eft stage.”

They also had some interesting accounts of some effects of Taricha skin toxins on humans. The first was when Brodie himself accidentally “jabbed a sharp forceps into his left index finger. Efforts were made to remove as much blood as possible from the injury. Despite these efforts, there was an intense burning sensation at the point of injury followed within a few minutes by numbness. This loss of feeling progressed up the arm, eventually involving the entire left arm and shoulder. This sensation persisted for about 30 min and was accompanied by light-headedness and dizziness.” They also told of a second account of toxin exposure when a 36-year-old man swallowed five Taricha granulosa on a dare. He had consumed a fair amount of alcohol prior to the ingestion of the newts. His symptoms progressed from dizziness to vomiting. He was admitted to the hospital, where it was noted he was “suffering from severe dizziness, ataxia, nausea, and vomiting. His face was flushed and walking was possible only with great difficulty.” He was treated and fully recovered. They also tell of another instance where someone swallowed a Taricha newt without any effects, but they stated, “In view of the high toxicity of Taricha this is unlikely.”

The other papers I discovered were recent ones published in Evolution written by both Brodies. Both papers dealt with Taricha granulosa and the resistance garter snakes have to its toxin. Both papers clearly restate that newts are toxic, and that the toxin is tetrodotoxin. The first paper, written in 1990, stated, “Tetrodotoxin (TTX) is one of the most potent neurotoxins known… Newts of the family Salamandridae are especially toxic… members of the genus Taricha from the Pacific coast of the United States and Canada are by far the most potent…”

I have personally had some experience with Taricha toxin, having gotten a small amount on the skin about a inch under my left eye. I noted numbness of the area for a few months as well as a slight hardening of the skin in that area. This was brought about when handling an ill animal. Under stress, the animal had started exuding toxin through its skin, and I made the mistake of touching the area on my face. Toxin release in newts can be detected very easily by a slight acidy foul smell and a sticky feeling to the skin. In paddletails (Pachytriton), the toxin will appear in a milky foam forming on the skin surface. But the most obvious thing is the smell. It will often be observed in stressed animals or animals that are fairly opposed to being held, as is the case with both my Pachytriton labiatus.

So when deciding what can live with your newts and when handling your newts, consider what the facts on toxicity are. Precautions should always be taken to avoid ingesting the toxin or allowing other animals to ingest it.

References:

Brodie, Edmund D., Jr. “Investigations on the Skin Toxin on the Adult Rough-Skinned Newt, Taricha granulosa.” Copeia. 1968. n2 p307-313.

Brodie, Edmund D., Jr., John Hensel, Jr. and Judith Johnson. “Toxicity of the Urodele Amphibians Taricha, Notophthalmus, Cynops and Paramesotriton (Salamandridae)” Copeia. 1974. n2. p506-511.

Brodie, Edmund D., III and Edmund D. Brodie, Jr. “Tetrodotoxin Resistance in Garter Snakes: An Evolutionary Response of Predator to Dangerous Prey.” Evolution. 1990. v44 n3. p651-659.

Brodie, Edmund D., III and Edmund D. Brodie, Jr. “Evolutionary Response of Predators to Dangerous Prey: Reduction of Toxicity of Newts and Resistance of Garter Snakes in Island Populations.” Evolution. 1991. v45 n1. P221-224.


Last edited August 5, 2002

© 2001 Heather Björnebo

 

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