Onychodactylus fischeri
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Onychodactylus fischeri |
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| Onychodactylus fischeri | ||||||||||||
| Boulenger , 1886 |
Onychodactylus fischeri is an East Asian amphibian species from the family of angular newts . The species occurs in the Russian Far East, Korea and China. The larval time of this species is relatively long, up to 3 years. With 2n = 78 it has one of the largest chromosome numbers among the caudate amphibians.
description
Adult animals
The species reaches a head-torso length of 58 to 90 millimeters and a total length of 125 to 184 millimeters. The body and head taken together are slightly shorter than the tail. The rows of teeth on the palate are separated from each other by a small gap. There are 14 to 15 rib furrows on either side of the body . Onychodactylus fischeri is brown or grayish brown in color and has points and a golden or brownish, indistinct dorsal band . This can only consist of larger spots. In males, compared to females, the tail is shorter and the front legs are longer. Between the fifth toe and the tibia, there is a lateral fold on the male's hind legs, which is the most striking distinguishing feature between males and females. The cloaca of the males is longer and more swollen than that of the females. The tail of the males is rounded, that of the females is pointed. Leg folds and cloaca in the males are very noticeable during the breeding season. The maturing egg cells (oocytes) can be seen in females through the skin of the abdomen.
Clutch
The clutch consists of paired egg sacs , each containing 3 to 7 eggs. A gel stick connects the individual ice sacs; with this the ice bags are also attached to stones. An Eisack including the gelatinous stem is approximately 45 millimeters long, possibly slightly longer. The diameter is 5 to 6 millimeters.
Larvae and young animals
The smallest known larval stage already has fully developed front and rear legs, short gills and tail hems . From a total length of the larvae of 40 to 45 millimeters, the first metamorphosis processes begin. When the animals have reached a length of 76 to 78 millimeters, the metamorphosis is complete. Immediately after metamorphosis, the animals have no claws or tail hems.
Chromosomes
The investigation of the chromosome number of animals from Korea resulted in 2n = 78. At the time of the investigation (1994) this was the largest known chromosome number in a representative of the caudate.
distribution
The range of Onychodactylus fischeri includes the Russian Far East , Korea and China. In Russia, the northernmost part of the distribution area, the species is native to the Sichote-Alin Mountains and the Pogranichniy Mountains . The north and north-west boundaries of the area probably run through the Sichote-Alin Mountains at the 45th parallel or a little north of it. In the northeast, the river valleys of Rasdolnaya and Ilistaja form the border between Lake Khanka and the Pacific . Occurrences are only known from the mainland, not from islands. The vertical distribution ranges from 350 to 1684 m above sea level .
habitat
Onychodactylus fischeri is a highly specialized species. Its habitat is represented by fast flowing mountain streams in mixed forests . The substrate of the water consists of layers of gravel or gravel- like material. Due to the rich vegetation on the banks, there is shade and a high humidity of 75% to 92%. There have also been observations of Onychodactylus fischeri from mountain lakes. In the shadiest areas of the water close to springs , where there are many hiding places and access to underground springs, there are adults. Here an individual density of 2 to 5 adults yes 10 m² can be found in favorable places. Onychodactylus fischeri is more common in the south of the area than in the north. The abundance of the species decreases from the sources downstream. This is possibly due to the higher water temperatures and predatory fish.
Way of life
Larvae and animals shortly after metamorphosis are most active during dusk. Adult animals usually live terrestrially from late summer to early autumn and aquatic in spring, early summer and the middle autumn months. Onychodactylus fischeri probably hibernates from October to April . The first active animals after winter were found between late April and early May.
There are hardly any data on the reproduction of Onychodactylus fischeri . So far only a single clutch has been discovered. This was found in early August and was on the back of a large stone in a stream. Large oocytes are present in the females from April to mid-July and from August to September. It is believed that spawning takes place in underground springs or in the gravel layers in the stream bed. The breeding season of the species lasts from late spring to all of summer, with a peak in June and July.
The larval time is relatively long for the species. The larvae spend a year or more in the body of water in which they hatched. An examination of larvae in their waters revealed an age of 0 to 3 years. Specimens with a head-torso length of more than 30 millimeters disappeared from the waters in September. It is assumed that metamorphosis takes place in these two to three year old animals at this point in time.
With a total length of 34 to 39 millimeters, larvae undergo the transition from endogenous nutrition through embryonic yolks to active foraging. The larvae feed on flow-loving crustaceans such as Gammaridae and the larvae of mayflies and stone flies . During the metamorphosis, the animals' diet is restricted. In this phase land arthropods are also accepted as food, but it still consists largely of animals living in water. After metamorphosis, the juveniles mainly eat arthropods living on land. The diet of adults varies depending on the habitat. Over the summer and at the beginning of autumn they mainly eat land animals such as arachnids , millipedes or beetles . Immediately before and after hibernation, the diet consists primarily of aquatic invertebrates .
Predators and parasites
The larvae are mainly captured by predatory fish . There is a negative correlation between the occurrence of Onychodactylus fischeri and the Siberian bullhead and Salvelinus malma ; that is, where the two fish species occur, Onychodactylus fischeri is missing . Further predators of the larvae are the two pit viper species Gloydius blomhoffii and Gloydius saxatilis and the river dipper . Carnivorous mammals such as the Asian badger and the collar bear are known to also prey on adult specimens of Onychodactylus fischeri . Cannibalism among the larvae has been observed in captive animals. An endoparasite of the species is the nematode Cosmocercoides pulcher .
Systematics
Onychodactylus fischeri was first described by Boulenger in 1886 . No subspecies are distinguished. A synonym is Onychodactylus rossicus Nikolsky, 1914.
A phylogenetic investigation 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 to date . The results of the investigation suggest that Onychodactylus fischeri , like Onychodactylus japonicus , consists of several cryptic species .
Hazard and protection
In the IUCN Red List the species is listed as Least Concern, in South Korea it is considered endangered (nationally threatened). The population of the species decreases sharply. The main reason for this seems to be the loss of their very special habitat, for example through the felling of trees at springs. Other potential dangers are the pollution of springs and the extraction of gravel from the waters.
Individual evidence
- ↑ a b c d e f g h i j k Sergius L. Kuzmin: The amphibians of Russia and neighboring areas. (= Die Neue Brehm-Bücherei. Volume 627). Westarp Sciences, Magdeburg 1995, ISBN 3-89432-457-0 .
- ↑ K. Iizuka, S. Yazawa: The karyotype, C-bands and AgNO 3 -bands of a lungless salamander from Korea: Onychodactylus fischeri (Boulenger) (Amphibia, Urodela) . Experientia, February 15, 1994, Volume 50, Issue 2, pp. 171-175 doi: 10.1007 / BF01984959
- ↑ Jung-Hyun Lee, Nam-Yong Ra, Junho Eom, Daesik Park: Population Dynamics of the Long-Tailed Clawed Salamander Larva, Onychodactylus fischeri, and Its Age Structure in Korea . J. Ecol. Field Biol. 31 (1): 31 - 36, 2008 ( pdf ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. )
- ↑ a b clawed salamander fischeri in the endangered Red List species the IUCN 2012. Posted by: Sergius Kuzmin, Masafumi Matsui, Zhao Wenge, Irina Maslova, Boris Tuniyev, 2004. Accessed March 24, 2013.
- ↑ Natsuhiko Yoshikawa, Masafumi Matsuia, Kanto Nishikawa, Jong-Bum Kimb, Alexei Kryukovc: Phylogenetic relationships and biogeography of the Japanese clawed salamander, Onychodactylus japonicus (Amphibia: Caudata: Hynobiidae), and its congener bondrial from the mitochondrial . Molecular Phylogenetics and Evolution, Volume 49, Issue 1, October 2008, pp. 249-259, doi: 10.1016 / j.ympev.2008.07.016
Web links
- Clawed salamander fischeri in the endangered Red List species the IUCN 2012. Posted by: Sergius Kuzmin, Masafumi Matsui, Zhao Wenge, Irina Maslova, Boris Tuniyev, 2004. Accessed March 24, 2013.