Японский тритон огненнобрюхий (Cynops pyrrhogaster)

Species of amphibian

based on specimens brought from Japan to Europe. He compared it to the smooth newt, saying he would have mistaken the former for the latter, had he not known it was from Japan. None of the specimens he studied were fully mature. Pyrrhogaster is derived from Greek, purrhos and gastēr Salamandra subcristata was described by Coenraad Jacob Temminck and Hermann Schlegel in 1838 and transferred to Cynops later that year by Swiss naturalist Johann Jakob von Tschudi,

The Integrated Taxonomic Information System lists sixteen synonyms for Cynops pyrrhogaster. Common names of the species include Japanese fire bellied newt,

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On the newt's upper body, the skin is dark brown, approaching black, and covered in wartlike bumps. The underbelly and the underside of its tail are bright red, with black spots. An entirely red variant exists: that coloration is believed to be inherited and recessive. This variant is not confined to any single population, but is more common in the western half of Japan overall. The vomeropalatine teeth, a group of teeth in the upper back of the mouth, are arranged in two series. The tongue is relatively small, half the width of the mouth. The nostrils are positioned anteriorly (toward the head), closer to each other than to the eyes and hardly visible when viewed from above. The toes of males are longer than those of females, although the females themselves are longer. The tail is tightly compressed, with fins on both the top and bottom. A smooth ridge runs from their nape to their tail. The full body length of adults is There is also an introduced population on Hachijō jima, believed to be descended from individuals from Shikoku. Their introduction is thought to have occurred in the 1970s, although exactly how it happened is unknown. It has been recorded in the United States three times, in Florida and Massachusetts. Every instance was either an escape or deliberate release, and no populations have been established. Of the four clades, the northern is found in the districts of Tohoku and Kanto. This does not overlap with the range of the central clade, which is found in Chubu, northern Kansai, and eastern Chugoku. The central's range has a small amount of overlap with the western, which is found in southern Kinki, western Chugoku, Shikoku, and central Kyushu. The western also has some overlap with the southern clade, which is found in western and southern Kyushu. females have their own variety, named imorin by its discoverers (from the Japanese term imo, , and rin from sodefrin). These are released from the cloaca, and were the first peptide pheromone to be identified in a vertebrate and first to be identified in a female vertebrate, respectively. Courtship begins when the male approaches the female, sniffing its sides or cloaca. The male then brings its tail to the female and rapidly vibrates it. The female responds by pushing the male's neck with its snout. At this point, the male slowly moves away, undulating its tail, and the female follows, touching the tail with its snout when close enough. The male then deposits two to four spermatophores, one at a time, moving several centimeters after each, which the female attempts to pick up with its cloaca, sometimes unsuccessfully. The young hatch from their eggs after about three weeks, as swimming, gilled larvae, with dorsal tailfins. They grow around in the first three months of their lives. At between five and six months, they stop eating and undergo metamorphosis, losing their gills and fins, and becoming juveniles. Juveniles cannot remain submerged in water like larvae or they drown. Newts at lower altitudes mature faster than those at higher ones. Male newts of higher altitude populations tend to live longer after reaching maturity, but their fully grown size is not as large as that of lowland newts. Wild individuals as old as twenty three have been found.

Cynops pyrrhogaster is regarded as an ideal vertebrate model for investigating the mechanism(s) involved in the transition from mitosis to meiosis during spermatogenesis. In males, this transition involves expression of PCNA, a DNA polymerase delta auxiliary protein employed in DNA replication and DNA repair. Adults at one particular sub alpine moor in the Azuma Mountains of Fukushima Prefecture were found to like both live prey and carrion. They consume many insect varieties, such as members of Odonata, which include dragonflies and damselflies, whose larvae have been found whole in newt stomachs, but only pieces of adults; Brachycera, a suborder of Diptera (flies); Hymenoptera, which include sawflies, wasps, bees, and ants; and Coleoptera (beetles). They also eat Rhacophorus arboreus tadpoles and the eggs of their own kind. The makeup of their diet varies seasonally and from year to year, suggesting changes in the small animals in and around the ponds that they dwell in.

Newts in Mainland Japan have different antipredator behavior than newts on smaller islands. Individuals on smaller islands (for instance, Fukue Island) generally use a maneuver called the unken reflex, where they expose their bright red underbelly to attackers. As their main predators are birds, which are capable of distinguishing the color red, this technique is effective. In Mainland Japan the newts must also avoid mammalian predators, which cannot distinguish colors as well as avian hunters. This leads these populations to use the maneuver less, as it can result in death if attempted. Against snakes, newts from Fukue Island tend to perform tail wagging displays, designed to bring a predator's attention to their replaceable tail rather than their more vital head; those from Nagasaki Prefecture in Mainland Japan tend simply to flee. Snakes are present in both areas. This behavior difference is likely because newts from the mainland are adapted to escape from mammalian hunters, which are less likely to be repelled by such a display.

Wild Japanese fire bellied newts contain high levels of the neurotoxin tetrodotoxin (TTX). In a follow up experiment by the same team, captive reared newts were given food containing the neurotoxin. They readily consumed TTX laced bloodworms when offered, not showing any symptoms after ingesting the poison. It was detectable in their bodies afterward, further indicating food to be the source of the toxin. No TTX producing organisms are known from their habitat, but their existence is likely, and would explain the origin of TTX in wild newts.

The International Union for the Conservation of Nature (IUCN) has ranked it as near threatened. This assessment was made in 2020, It successfully reproduces in Australian zoos. A variety, believed to be found exclusively on the Atsumi Peninsula, was thought to have become extinct in the 1960s. Then, in 2016, a trio of researchers discovered that newts on the Chita Peninsula were very likely the same variant due to their similar morphological traits. Both groups share a preference for cooler temperature and have smooth and soft bodies, pale dorsal regions, and yellowish undersides. Even if still alive, this form is highly threatened and will soon be wiped out without immediate protection.

Japanese fire bellied newts serve as a highly useful model organism in laboratory settings, but they become more difficult to care for after metamorphosis. An experiment supported by the Japan Society for the Promotion of Science found that thiourea (TU) can prevent this process from occurring, allowing the animals to stay in their pre metamorphosis form for as long as two years, while still capable of metamorphosizing when removed from the TU solution. This did not have any impact on their regeneration capabilities. This species, as well as other Urodele amphibians, is capable of regrowing missing body parts, including limbs with functional joints and the lower jaw. When this process occurs, the regenerated tissue tends to mirror intact tissue in form. It is also able to regrow missing lenses, taking thirty days to do so as a larva and eighty days as an adult. The difference in time is purely due to the size of the eye, and regenerative ability does not change; the discovery of this fact contradicted a popular claim that juvenile animals are quicker to regenerate than adults.

Cynops pyrrhogaster can be kept in captivity. Doctor of Veterinary Medicine Lianne McLeod described them as "low maintenance", noting that captive newts enjoy bloodworms, brine shrimp, glass shrimp, Daphnia, and, for larger individuals, guppies.