Greenish newt

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Greenish newt
Greenish water newt (Notophthalmus viridescens viridescens); sexually mature male

Greenish water newt ( Notophthalmus viridescens viridescens ); sexually mature male

Systematics
Order : Tail amphibian (caudata)
Superfamily : Salamander relatives (Salamandroidea)
Family : Real salamanders (Salamandridae)
Subfamily : Pleurodelinae
Genre : East American newts ( Notophthalmus )
Type : Greenish newt
Scientific name
Notophthalmus viridescens
( Rafinesque , 1820)

The greenish water newt ( Notophthalmus viridescens ) is a species of amphibian from the family of the real salamanders (Salamandridae). He is the most common in North America occurring salamander .

features

Greenish water newt ( Notophthalmus viridescens viridescens ), Eft with reddish tint before sexual maturity

Adult animals after reaching sexual maturity

The greenish water newt reaches a length of 5.7–12.2 cm (maximum up to 14 cm) in the adult stage . The top of the "adult dress" is olive-green to yellow-brown or olive-brown to dark greenish-brown to almost black in color and interspersed with small black spots that become larger on the tail. On the flanks, depending on the subspecies, there may be red, black-edged dots or interrupted stripes. The ventral side is yellowish with black spots. During the mating season, the male has a widened tail edge, a more arched cloaca and black rutting calluses on the inside of the hind legs.

Young animals before reaching sexual maturity

The young ("Red Eft" or "Eft" for short) before reaching sexual maturity are 3.5–8.6 cm long. They are orange-red to light brown in color, yellowish-brown to pale reddish-brown shortly after metamorphosis . Young animals shortly before reaching sexual maturity are often very dark to almost black. Depending on the subspecies, red spots with a black border or reddish stripes can appear.

Larvae

As with all tailed amphibians , the lavas of the greenish water newt carry external tufts of gills. The body is not separated from the tail, as is the case with tadpoles , but gradually merges into it. The skin is gray to yellowish and can sometimes already have reddish spots. The head is small, with a more or less pointed snout and shows a characteristic dark stripe that runs lengthways over the eyes.

Research history

The species was first described in 1820 by Constantine S. Rafinesque-Schmaltz . However, Rafinesque had not yet recognized that the young and the adult stage were one and the same species and described two different species, which he even assigned to different subgenera ( Triturus (Diemictylus) viridescens = Adult and Triturus (Notophthalmus) miniatus = Eft). In 1850, Spencer Fullerton Baird placed both stages of development, still as separate species, in a common genus, Notophthalmus .

Although others had already suspected that it was not until Edward Drinker Cope in 1889 that the connection between adult animals and Eft was finally clarified. Cope had chosen the name Diemyctylus viridescens in his description . However, since Baird had previously established the valid genus Notophthalmus , the combination Notophthalmus viridescens is preferred today .

Subspecies and distribution

Distribution area of ​​the greenish newt

There are four subspecies :

  • Notophthalmus viridescens viridescens ("red-spotted newt"): southeastern Canada ( Ontario , Quebec ) and northeastern USA (south to Alabama , Georgia and South Carolina and west to Michigan , Indiana , Kentucky and Tennessee ); Typical identifying features are the red spots with a black border.
  • Notophthalmus viridescens louisianensis ("central newt"): in the west to Texas and Oklahoma , in the south to the Gulf of Mexico ; Differs from N. v. viridescens by the interrupted, black-edged red stripes.
  • Notophthalmus viridescens dorsalis ("broken-striped newt"): coastal regions of North and South Carolina; The back of the adult animal is olive green, red spots are absent or are very small.
  • Notophthalmus viridescens piaropicola ("peninsula newt"): Florida ; The back of the adult is dark brown to black, there are no red spots.

Way of life

Greenish newts can live up to 12-15 years in the wild and go through 4 stages of development during this time.

Embryonic stage

In spring, females usually lay their fertilized eggs one at a time on the leaves of aquatic plants, rotting leaves or other detritus and carefully wrap them around them. Each female lays several eggs per day and the oviposition can take several weeks. The total clutch size per female and breeding season is 200–375 eggs. The individual eggs are about 1.5 mm in diameter. The larvae hatch within about 20–35 days.

Larva with external gill tufts and already developed limbs

Larval stage

When hatching, the larvae are about 7–9 mm long. They mainly feed on small invertebrates such as flea crabs , mosquito larvae, and water fleas . Over the course of two to five months, the aquatic larvae first develop the front legs and finally the rear limbs. From a length of 3.5–3.8 cm the metamorphosis to the rural Eft takes place.

Eft stage

Efts are terrestrial and prefer to stay on the forest floor, especially in deciduous and mixed forests . They mainly feed on arthropods and small snails. At the age of 3–7 years, according to other sources also 2–8 years, Efts undergo a further metamorphosis, become sexually mature adults and return to an aquatic way of life. The young animals are active in damp weather and at night and crawl under the leaves on the forest floor, in rotting tree stumps or under dead wood when it is dry and in winter .

Adult stage and mating

Male ready to mate with swollen cloaca and black rutting calluses on the inside of the hind legs
Amplexus in the greenish water newt

Adult animals live aquatically in small lakes, ponds and ponds or in still water areas of flowing waters . They either keep the aquatic way of life permanently or, depending on the season, briefly return to a terrestrial way of life. The females show a more pronounced migratory behavior and sometimes leave the spawning waters for a whole year without mating. Migratory males that overwinter on land or survive dry periods, on the other hand, usually return to the spawning waters by the beginning of the mating season at the latest. The prey spectrum of the adult animals includes water fleas, insects living in the water, molluscs , little bristles and leeches , occasionally also small fish and fish spawn as well as the spawn and larvae of amphibians, whereby the larvae of their own species are not spurned.

The mating takes place in still waters rich in herbs. For some populations that do not hibernate on land, the mating season begins as early as autumn and continues throughout the winter until the eggs are laid in spring. The mating behavior of the greenish water newt is complex and can follow two different processes. In one case, the male presents himself to the female with winding movements ("hula") and prompts her to nudge his tail. If the female responds accordingly, the male lays down a packet of semen . The female picks up the sperm packet and stores it in her spermatheca for later fertilization of her egg cells. In this case, there is no amplexus during mating . More often, however, the pairing takes place in the course of an amplexus. The male clasps the female's body with his hind legs and touches it with his snout. In this case, the amplexus can drag on for several hours before the male separates from the female again and releases his sperm packet.

This 4-part life cycle does not necessarily run completely in all subspecies. Notophthalmus viridescens viridescens always goes through a terrestrial Eft stage. In Notophthalmus viridescens louisianensis and Notophthalmus viridescens dorsalis an eft only forms when their waters threaten to dry out. Otherwise, a sexually mature adult animal is formed directly from the larva or the larva becomes sexually mature without complete metamorphosis, while retaining larval characteristics such as the external gill tufts ( pedomorphosis ). In such cases, sexual maturity can be reached as early as 5–7 months after the larvae hatch. Notophthalmus viridescens piaropicola usually becomes sexually mature in the larval stage (pedomorphosis); Efts are known but very rare.

Toxinology

Tetrodotoxin

The skin of efts and adults can contain the nerve toxin tetrodotoxin ("TTX"). However, the poison is not universally present to the same extent in all animals. It cannot be detected at all in individual populations. If present, the concentration in Efts is up to 10 times higher than in adults. The origin of the neurotoxin is unclear, but since it does not occur in all populations, it is assumed that it is not produced by the newts themselves, but either produced by symbiotic bacteria or ingested with food and stored in the skin.

Duration

The IUCN lists the greenish water newt as not endangered (“least concern”). Roads as an obstacle to migratory movements and the introduction of the blue sunfish ( Lepomis macrochirus ) into waters in which it was not originally native are named as potential threats . However, the stock is generally rated as stable.

Individual evidence

  1. ^ Th. CH Cole: Dictionary of animal names: Latin-German-English German-Latin-English. 2nd edition, 974 pp., Springer Verlag, 2015. ISBN 978-3-662-44241-8 (reading sample)
  2. ^ A b c d R. Powell, R. Conant & JT Collins: Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. 4th edition, 608 pp., Houghton Mifflin Harcourt, 2016. ISBN 978-0-544-12997-9 (reading sample)
  3. ↑ J. Hoverman, Z. Olson, S. LaGrange, J. Grant & R. Williams: A Guide to Larval Amphibian Identification in the Field and Laboratory. 20 p., Purdue Extension Report No. FNR-496, 2015. (digitized)
  4. ↑ CS Rafinesque: Annals of Nature or Annual Synopsis of new Genera and Species of Animals, Plants, & c. discovered in North America. First Annual Number for 1820, 16 pp., 1820. (digitized version)
  5. ↑ SF Baird: Revision of the North American Tailed-Batrachia, with descriptions of new genera and species. In: Journal of the Academy of Natural Sciences Philadelphia , 2nd Series, Vol. 1, pp. 281–294, 1850. (digitized version )
  6. ^ ED Cope: The Batrachia of North America. In: United States National Museum Bulletin , No. 34, 525 pp., 1889. (Reprint from 1963)
  7. ^ ICZN (International Commission on Zoological Nomenclature): Opinion 635: Notophthalmus Rafinesque, 1820 (Amphibia); Addition to the official list as the name to be used for the Eastern North-American Newt. In: Bulletin of Zoological Nomenclature , Vol. 19, pp. 152–154, 1962. (digitized version)
  8. ↑ a b c d e f g h i j H.-G. Simon & S. Odelberg: Maintaining Eastern Newts (Notophthalmus viridescens) for Regeneration Research. In: A. Kumar & A. Simon (eds.): Salamanders in Regeneration Research: Methods and Protocols , pp. 17–25, Springer Verlag, 2015. ISBN 978-1-4939-2494-3 (digitized version)
  9. ↑ a b c d e f M. K. Takahashi: Life cycle polyphenism as a factor affecting ecological divergence within Notophthalmus viridescens. In: Oecologia , Vol. 158, pp. 23–34, 2008. (digitized version)
  10. ↑ MJ Lannoo: Amphibian Declines: The Conservation Status of Species United States. 1094 pp., University of California Press, 2005. ISBN 0-520-23592-4 (reading sample)
  11. ↑ JR Parmelee, MG Knutson & JE Lyon: A field guide to amphibian larvae and eggs of Minnesota, Wisconsin, and Iowa. 38 SUS Geological Survey, Biological Resources Division, Information and Technology Report USGS / BRD / ITR-2002-0004, 2002. (digitized version )
  12. ↑ a b c d e P. J. Sousa: Habitat suitability index models: Red-spotted newt. In: US Fish and Wildlife Service: Biological Report 82 (10.111) , 18 p., 1985. (digitized version )
  13. ^ A b c E. R. Johnson, BL Bowerman, MA Thomas, LM Thompson & KL Grayson: The influence of environmental factors on pond activity of aquatic red-spotted newts Notophthalmus viridescens. In: Journal of Freshwater Ecology , Vol. 32, Issue 1, pp. 711-720, 2017. doi: 10.1080 / 02705060.2017.1393467
  14. ^ A. Mathis: Use of chemical cues in detection of conspecific predators and prey by newts, Notophthalmus viridescens. In: Chemoecology , Vol. 13, pp. 193–197, 2003. (Abstract)
  15. ^ DM Sever: The "False Breeding Season" of the Eastern Newt, Notophthalmus viridescens. In: Bulletin of the Chicago Herpetological Society , Vol. 41, No. 8, pp. 149–153, 2006. (digitized version )
  16. ↑ a b c M. Yotsu-Yamashita, J. Gilhen, RW Russell, KL Krysko, Ch. Melaun, A. Kurz, S. Kauferstein, D. Kordis & D. Mebs: Variability of tetrodotoxin and of its analogues in the red -spotted newt, Notophthalmus viridescens (Amphibia: Urodela: Salamandridae). In: Toxicon , Vol. 59. pp. 257–264, 2012. (digitized version)
  17. ↑ a b M. M. Spicer, AN Stokes, TL Chapman, ED Brodie Jr, ED Brodie III, & BG Gall: An Investigation into Tetrodotoxin (TTX) Levels Associated with the Red Dorsal Spots in Eastern Newt (Notophthalmus viridescens) Efts and Adults. In: Journal of Toxicology , Vol. 2018, 4 pp., 2018. doi: 10.1155 / 2018/9196865
  18. ^ IUCN SSC Amphibian Specialist Group 2015: Notophthalmus viridescens . The IUCN Red List of Threatened Species 2015: e.T59453A78906143. doi: 10.2305 / IUCN.UK.2015-4.RLTS.T59453A78906143.en ( Accessed November 17, 2018)

Web links

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