The Eastern Newt (Notophthalmus viridescens) is a common amphibian found across eastern North America. These small salamanders, including the brilliant orange juvenile stage known as the Red Eft, are toxic. Their toxicity is a defensive mechanism concentrated in skin secretions, making them unpalatable and often lethal to most predators. This chemical defense allows the newt to move slowly and openly, as its striking coloration serves as a clear warning sign.
The Specific Neurotoxin
The substance responsible for the Eastern Newt’s defensive power is Tetrodotoxin (TTX), a non-proteinaceous neurotoxin also found in pufferfish. TTX disrupts the nervous system by targeting voltage-gated sodium channels in nerve and muscle cells. The toxin acts as a molecular plug, binding to the channels and blocking the influx of sodium ions, which prevents the transmission of electrical signals. This blockage causes paralysis, leading to muscle weakness and potentially respiratory failure if a sufficient dose is ingested. The newt does not produce TTX itself, but instead harbors symbiotic bacteria that synthesize the compound.
Toxicity Levels in Red Efts and Adults
The concentration of Tetrodotoxin varies significantly across the Eastern Newt’s life stages. The terrestrial juvenile stage, the Red Eft, is a brilliant orange-red color, which warns predators of its toxicity. This stage is where the newt is most vulnerable to land-based predators, and accordingly, the Red Eft possesses the highest concentration of TTX in its skin. Studies show that the Red Eft can have concentrations seven to ten times higher than those found in the aquatic adult newt. After living on land, the eft transforms into the duller, olive-green adult, which is fully aquatic and contains lower, though still present, levels of the toxin.
Practical Safety and Handling
The risk posed by the Eastern Newt to humans and pets depends almost entirely upon ingestion. The toxin is not absorbed through intact human skin, meaning simply touching the newt is unlikely to cause serious harm. However, the toxin can cause irritation if it contacts mucous membranes (eyes, nose, or mouth) or enters an open wound. Severe poisoning occurs when the newt is swallowed by a pet or a small child.
Symptoms of ingestion begin with numbness and tingling around the lips and tongue, quickly progressing to the face and extremities. More severe symptoms include dizziness, muscle weakness, difficulty speaking or swallowing, and potential paralysis, including the muscles needed for breathing. If ingestion is suspected, immediate medical attention is required, as supportive care is the only treatment, given that no antidote exists for Tetrodotoxin. Handling should always be minimized, and thorough hand washing is necessary after any contact.