Amphibians
Japanese Fire-belly Newt
Cynops pyrrhogaster · also called Japanese fire-belly newt, Japanese fire newt, Japanese newt, imori
The Japanese fire-belly newt is small, slow, and easy to catch — and it carries pufferfish poison in its skin, advertised by a belly the colour of hot coals. It is also one of the animal kingdom’s great healers, able to regrow a leg, an eye lens, or a piece of its heart, over and over.
Overview
Japanese fire-belly newts are endemic to Japan — Honshu, Shikoku, and Kyushu — living in still and slow water such as rice paddies, ponds, ditches, and marshes and the damp woodland around them. They are 8–13 cm, dark and warty above with a scarlet, black-marbled belly, and eat insects, worms, tadpoles, and amphibian eggs.
Pufferfish poison
The skin contains tetrodotoxin — the same lethal neurotoxin as fugu, with no antidote. It is harmless to hold with intact skin but dangerous if the newt is eaten or the secretions reach the eyes, mouth, or a cut. The red belly, flashed in an arched unken reflex, warns predators that have learned the lesson.
A champion regenerator
The newt regrows limbs, tail, jaws, spinal cord, and heart tissue, and can rebuild the eye lens from iris cells. In one experiment the lens was removed and regrown 18 times from the same eye over 16 years with no loss of quality — which is why it is a classic regeneration model animal.
Status
The Japanese fire-belly newt is Near Threatened and declining from the loss of rice-paddy and pond habitat, agricultural chemicals, introduced predators, and past over-collection.
Japanese Fire-belly Newt: common questions
Is the Japanese fire-belly newt poisonous, and can you handle it?
It is genuinely poisonous. Its skin secretes tetrodotoxin, the same neurotoxin that makes pufferfish (fugu) dangerous, and it is among the deadliest natural poisons known — there is no antidote, and it works by blocking nerve signalling. However, the newt cannot inject it and it is not absorbed through unbroken human skin, so simply holding one briefly is not dangerous. The real risks are eating the newt or any part of it, letting the skin secretions get into your mouth, eyes, nose, or an open cut, or a pet biting one. The sensible rule is to handle as little as possible, with clean wet hands, and to wash your hands thoroughly afterwards and keep them away from your face. Keeping them with other amphibian species is a bad idea because the toxin can harm tankmates.
Why is the belly bright red?
It is a warning signal, or aposematism. The newt's dark, warty back camouflages it against mud and leaf litter, but its underside is vivid red or orange marbled with black, colours it normally keeps hidden. When a predator threatens it and it cannot escape, it can bend its body into a sharp upward arch and raise its head and tail so the bright belly is displayed — the unken reflex. A predator that has previously bitten a fire-belly newt and been sickened by the tetrodotoxin learns to associate that red-and-black pattern with a bad experience and leaves it alone. Several unrelated newts and toads have evolved the same red-belly-plus-arch strategy.
How good is the Japanese fire-belly newt at regenerating body parts?
Exceptional, and unusual even among salamanders for keeping the ability throughout a long adult life. It can regrow a lost leg, its tail, parts of its jaws, its spinal cord, and damaged heart muscle, and it can regenerate the lens of the eye from cells of the iris. In a famous long-term experiment, researchers removed and regrew the lens from the same newt's eye 18 times over 16 years, and the regenerated lenses remained normal each time, with no sign of the process wearing out or the tissue ageing. Because of this the species has been a standard model animal for regeneration research for over a century, alongside the axolotl.
Can I keep a Japanese fire-belly newt as a pet?
They have been popular in the aquarium trade, but there are strong reasons to be cautious now. Wild populations are declining and the species is listed as Near Threatened, and Japan has restricted exports, so animals offered for sale abroad may be wild-caught or of uncertain origin. They are also long-lived — commonly 25 years or more — so it is a serious commitment. If kept, they need a cool (they dislike warm water), clean, well-filtered aquarium that is semi-aquatic with easy land access, a secure lid because they climb and escape, a varied diet of worms and other invertebrates, and no tankmates. Captive-bred stock should always be chosen, and the tetrodotoxin means careful hygiene and no housing with fish or other amphibians.