Cynops pyrrhogaster (Boie, 1826)

Taxonomy

This species, Cynops pyrrhogaster, is a newt first described by Boie in 1826.

Dorsal Skin Characteristics

On the upper body, the skin is dark brown, nearly black, and covered with wart-like bumps.

Ventral Coloration

The underbelly and underside of the tail are bright red with black spots.

Juvenile Coloration

Young juveniles have creamy coloration instead of red, though most larger juveniles already show some red.

Geographical Ventral Color Variation

Adults from smaller islands typically have more red on their ventral (belly) regions than adults from larger islands, and sometimes have extremely small black spots or none at all.

Sex-Based Color Differences

In general, males have more red coloration than females.

Male Morphological Traits

Males can also be told apart from females by their flat, wide tails and swelling around the ventral region.

Red Color Variant

An entirely red color variant of this newt exists; this color trait is thought to be an inherited recessive characteristic.

Variant Distribution

The variant is not limited to any single population, but it is more common across the western half of Japan.

Oral Dentition

The vomeropalatine teeth, a group of teeth located in the upper back of the mouth, are arranged in two separate series.

Tongue Characteristics

The tongue is relatively small, measuring half the width of the mouth.

Nostril Positioning

The nostrils are positioned anteriorly toward the snout; they are closer to each other than to the eyes and are barely visible when the newt is viewed from above.

Sex-Based Limb and Body Differences

Males have longer toes than females, though females have a longer overall body length.

Tail Structure

The tail is tightly compressed, with fins along both the upper and lower edges.

Dorsal Ridge

A smooth ridge runs from the nape of the neck to the tail.

Adult Body Length Range

Full adult body length ranges from 8 to 15 cm (3.1 to 5.9 in).

Snout-Vent Length by Sex

Snout–vent length ranges from 43.0 to 64.0 mm (1.69 to 2.52 in) for males, and from 48.5 to 75.0 mm (1.91 to 2.95 in) for females.

Geographical Size Variation

Populations from more northern, higher elevation regions tend to grow larger than populations from southern, lower-altitude regions.

Unfertilized Egg Size

Unfertilized eggs measure 2.1 to 2.3 mm (0.083 to 0.091 in) in length.

Native Distribution

Cynops pyrrhogaster is endemic to Japan, where it occurs on multiple islands of the Japanese archipelago, including Honshu, Shikoku, and Kyushu.

Congeneric Range Comparison

It mainly inhabits the larger Japanese islands, while its close relative Cynops ensicauda lives in the Ryukyu Islands.

Genus Range Extremity

This species has the northernmost natural range of any member of the genus Cynops; all other Cynops species, aside from C. ensicauda, are native to southern China.

Introduced Hachijō-jima Population

An introduced population of C. pyrrhogaster exists on Hachijō-jima, and this population is believed to descend from individuals originating from Shikoku.

Hachijō-jima Introduction Details

The introduction is thought to have taken place in the 1970s, but the exact method of introduction remains unknown.

United States Occurrences

C. pyrrhogaster has been recorded three times in the United States, in Florida and Massachusetts.

United States Population Status

Every recorded occurrence was the result of either escape from captivity or deliberate release, and no established wild populations exist in the US.

Genetic Clade Structure

There are four distinct genetic clades of C. pyrrhogaster.

Northern and Central Clade Ranges

The northern clade is found in the Tohoku and Kanto regions, and its range does not overlap with that of the central clade, which occurs in Chubu, northern Kansai, and eastern Chugoku.

Central and Western Clade Ranges

The range of the central clade has a small amount of overlap with the range of the western clade, which is found in southern Kinki, western Chugoku, Shikoku, and central Kyushu.

Western and Southern Clade Ranges

The western clade also has some range overlap with the southern clade, which occurs in western and southern Kyushu.

Elevation Range

The newts are found at elevations ranging from 30 to 2,020 m (98 to 6,627 ft).

Natural Habitat Types

Ecosystems that host this species include forests, grasslands, shrublands, wetlands, lakes, marshes, and cultivated areas.

Anthropogenic Habitat Use

They can also live in human-made bodies of water, such as aquaculture ponds.

Breeding Habitat

Breeding takes place in paddy fields, ponds, brooks, pools, and streams.

Breeding Season

Females respond to male courtship behavior from spring to early summer.

Mating Pheromones

When ready to mate, both males and females produce peptide pheromones to attract the opposite sex.

Known Pheromone Types

Males produce a pheromone called sodefrin, named from the Japanese term sodefuri meaning 'soliciting'; females produce their own distinct pheromone named imorin by its discoverers, from the Japanese term imo meaning 'beloved woman', with the suffix -rin taken from sodefrin.

Pheromone Release Site

Both pheromones are released from the cloaca.

Pheromone Scientific Significance

Sodefrin was the first peptide pheromone identified in any vertebrate, while imorin was the first peptide pheromone identified in a female vertebrate.

Initial Courtship Behavior

Courtship starts when the male approaches the female and sniffs her sides or cloaca.

Male Courtship Display

The male then positions his tail toward the female and vibrates it rapidly.

Female Courtship Response

The female responds by pushing the male's neck with her snout.

Courtship Lead Behavior

At this stage, the male slowly moves away while undulating his tail, and the female follows.

Spermatophore Deposition Trigger

When she is close enough, she touches his tail with her snout.

Spermatophore Deposition Process

The male then deposits two to four spermatophores one at a time, moving several centimeters away after each deposition.

Spermatophore Uptake

The female attempts to pick up the spermatophores with her cloaca, and sometimes this attempt is not successful.

Egg Laying Behavior

Females lay eggs individually on underwater objects, such as leaves and submerged grass roots.

Egg Fertilization

Each egg is fertilized separately using sperm from the spermatophores the female has picked up.

Fecundity

A female can lay up to 40 eggs in a single laying session, and 100 to 400 eggs total over one breeding season.

Larval Hatching

Larvae hatch from the eggs after approximately three weeks; they are swimming, gilled larvae with a dorsal tail fin.

Larval Growth

They grow to around 3 cm (1.2 in) long during their first three months of life.

Metamorphosis

Between five and six months of age, they stop eating and undergo metamorphosis, losing their gills and fins to become juveniles.

Juvenile Physiological Trait

Unlike larvae, juveniles cannot stay fully submerged in water without drowning.

Altitude-Based Maturation Rate

Newts at lower altitudes reach sexual maturity faster than newts at higher altitudes.

Altitude-Based Adult Traits

Males from higher-altitude populations tend to live longer after reaching maturity, but their fully grown size is smaller than that of lowland newts.

Lifespan

Wild C. pyrrhogaster individuals have been recorded reaching 23 years of age.