Fischer's clawed salamander

Onychodactylus fischeri

Onychodactylus fischeri is an East Asian amphibian species from the family of angles tooth newts. The species is found in the Russian Far East, Korea and China. The larval is relatively long in this kind of up to 3 years. It has 2n = 78 one of the largest chromosome numbers among the tailed amphibians ( Caudata ).

Description

Adult animals

The species reaches a head-body length of 58-90 mm ​​and an overall length of 125-184 millimeters. Head and body taken together are slightly shorter than the tail. The palate teeth are separated by a small gap. On both sides of the body are 14-15 ribs furrows. Onychodactylus fischeri is brown or grayish brown in color and has spots and a golden or brownish, slurred Dorsalband on. This can also consist of larger spots. In males compared with females the tail is shorter and the front legs are longer. Between the fifth toe and tibia is located on the hind legs of the male, a lateral fold, which is the most striking distinguishing feature between males and females. The cloaca of the male is longer and more swollen than those of the females. The tail of the male is rounded, which pointed to the females. Leg creases and sewers of the males are very conspicuous in the breeding season. The maturing egg cells ( oocytes ) are recognizable in the females through the abdominal skin through.

Scrim

The nest consists of paired Eisäcken, each containing 3 to 7 eggs. A gelatinous stalk connects the individual Eisäcke; with this the Eisäcke also be stapled to stones. A Eisack together with gelatinous stalk is about 45 millimeters long, possibly even slightly longer. The diameter is 5 to 6 mm.

Larvae and juveniles

The smallest known larval stage has already fully formed front and rear legs, short gills and Schwanzsäume. From a total length of larvae of 40 to 45 millimeters put a first metamorphosis processes. When the animals have reached a length of 76-78 mm, the metamorphosis is completed. Immediately after the metamorphosis, the animals do not have claws and Schwanzsäume.

Chromosomes

The study of the chromosome numbers of animals from Korea showed 2n = 78 At the time of the study (1994 ), this was the largest known chromosome number for a representative of the Salamanders ( Caudata ).

Dissemination

The area of Onychodactylus fischeri includes the Russian Far East, Korea and China. In Russia, the northernmost part of the range, type in the Sikhote -Alin Mountains and in Pogranitschnij Mountains are home. Probably runs along the 45th parallel or slightly north of it through the Sikhote -Alin Mountains, the northern and north- western boundary of the site. In the northeast put between the Khanka and the Pacific, the river valleys of Rasdolnaja and Ilistaja the border dar. reserves are only known from the mainland, not from islands. The vertical distribution ranges 350-1684 m above sea level.

Habitat

Onychodactylus fischeri is a highly specialized art your living space provide fast-flowing mountain streams in mixed forests Represents the substrate of the waters consists of layers of gravel or gravel- like material. Due to the rich riparian vegetation prevails shade and high humidity of 75 % to 92 %. There are also observations of Onychodactylus fischeri from mountain lakes. The shadiest areas in the waters close to sources where there are plenty of hiding places and access to underground sources to adult animals to keep. Here, yes 10 m² are found at low population density places a 2-5 adults. In the south of the area Onychodactylus fischeri is more common than in the north. Of the sources bach down decreases the frequency of the species. This may be due to higher water temperatures and predators.

Way of life

Larvae and animals shortly after metamorphosis are most active during dusk. Adult animals live from late summer to early fall usually terrestrial and in spring, early summer and autumn months in the mid -aquatic. From October to April holds Onychodactylus fischeri probably hibernation. Getting active animals after winter were found between late April and early May.

There is little data on the propagation of Onychodactylus fischeri. So far, only once a single nest was discovered. This was the beginning of August and was found on the back of a large stone in a stream. From April to mid-July and August-September large oocytes are present in the females. It is believed that is spawned in underground springs or the layers of gravel in the stream bed. The reproductive period of the species lasts from late spring until the whole summer, with a peak in June and July.

The larval is relatively long in the way. The larvae spend a year or more in the waters in which they are hatched. An examination of larvae in their waters showed an age 0-3 years. Specimens with a head-body length of more than 30 millimeters disappeared in September from the waters. It is believed that in these two to three years of animals at the time takes place metamorphosis.

Larvae make a total length 34-39 mm by the transition from endogenous nutrition through embryonic yolk applied towards active foraging. As a dietary serving the larvae mainly flow- loving crustaceans as well as larvae of mayflies Gammaridae and stoneflies. During metamorphosis, the diet of animals is limited. In this phase, arthropods are accepted as a food, but it is still largely of aquatic animals. Following metamorphosis, the juveniles feed mainly on land-dwelling arthropods. The diet of adult animals varies according to their habitat. Over the summer and early autumn, they feed mainly on land animals such as spiders, centipedes or beetle. Immediately before and after hibernation they feed mainly from aquatic invertebrates.

Predators and parasites

The larvae are mainly captured by predators. So there is a negative correlation between the presence of Onychodactylus fischeri and the Siberian bullhead and Dolly Varden Salvelinus; that is, where the two types of fish occur, absent Onychodactylus fischeri. Other predators of the larvae are the two pit viper species Gloydius blomhoffii and Gloydius saxatilis and the river dippers. From carnivorous mammals such as the Asian badger and the Asiatic is known that they also prey on adult specimens of Onychodactylus fischeri. In captive animals cannibalism was observed among the larvae. An endoparasite of the species is the nematode Cosmocercoides pulcher.

System

Onychodactylus fischeri was first described in 1886 by Boulenger. We distinguish between no subspecies. A synonym is Onychodactylus rossicus Nikolsky, 1914.

A phylogenetic study of Onychodactylus fischeri and Onychodactylus japonicus based on the mitochondrial cytochrome b showed that both species are sister species, Onychodactylus fischeri consists of three genetically distinct populations in Russia, Northeast China and Korea, and is not monophyletic in its current scope. The results of the study suggest that Onychodactylus fischeri, as Onychodactylus japonicus, consists of several cryptic species.

Threats and conservation

In the IUCN Red List the species is listed as not at risk (least concern) in South Korea it is considered endangered ( nationally threatened ). The abundance of the species decreases sharply. The reason for this seems to be mainly the loss of their very special habitat, for example by cutting down trees to sources. Other potential threats include pollution sources and the extraction of gravel from the waters.