Eastern newt

The eastern newt (Notophthalmus viridescens) is a common newt of eastern North America. It frequents small lakes, ponds, and streams or nearby wet forests. The eastern newt produces tetrodotoxin, which makes the species unpalatable to predatory fish and crayfish.[2] It has a lifespan of 12 to 15 years in the wild, and it may grow to 5 in (13 cm) in length. These animals are common aquarium pets, being either collected from the wild or sold commercially. The striking bright orange juvenile stage, which is land-dwelling, is known as a red eft. Some sources blend the general name of the species and that of the red-spotted newt subspecies into the eastern red-spotted newt (although there is no "western" one).[3][4]

Eastern newt
Aquatic adult male
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Family: Salamandridae
Genus: Notophthalmus
Species:
N. viridescens
Binomial name
Notophthalmus viridescens
(Rafinesque, 1820)
Range of N. viridescens subspecies:

Yellow: N. v. viridescens
Purple: N. v. louisianensis
Magenta: N. v. dorsalis
Black: N. v. piaropicola

Subspecies

The eastern newt includes these four subspecies:[5]

  • Red-spotted newt (Notophthalmus viridescens viridescens)
  • Broken-striped newt (Notophthalmus viridescens dorsalis)
  • Central newt (Notophthalmus viridescens louisianensis) - Central newts measure from 2.5 in (6.4 cm) to 4 in (10 cm) in length. They are brown or green, with fine black dots all over the body. There may be a row of red spots on each side of the body. The belly is yellow or orange and is noticeably lighter than the rest of the body. The skin of newts is not as slippery as the skin of salamanders and may appear to be rough and dry for parts of their lives.
  • Peninsula newt (Notophthalmus viridescens piaropicola)

Life stages

Eastern newts have three stages of life: (1) the aquatic larva or tadpole, (2) the red eft or terrestrial juvenile stage, and (3) the aquatic adult.

Larva

The larva possesses gills and does not leave the pond environment where it was hatched. Larvae are brown-green, and shed their gills when they transform into the red eft.

Red eft

The red eft (juvenile) stage is a bright orangish-red, with darker red spots outlined in black. An eastern newt can have as many as 21 of these spots. The pattern of these spots differs among the subspecies. An eastern newt's time to get from larva to eft is about three months. During this stage, the eft may travel far, acting as a dispersal stage from one pond to another, ensuring outcrossing in the population. The striking coloration of this stage is an example of aposematism — or "warning coloration" — which is a type of antipredator adaptation in which a "warning signal" is associated with the unprofitability of a prey item (i.e., the saturation of the eft's tissues with tetrodotoxin) to potential predators.[6]

Adult

After two or three years, the eft finds a pond and transforms into the aquatic adult. The adult's skin is a dull olive green dorsally, with a dull yellow belly, but retains the eft's characteristic black-rimmed red spots. It develops a larger, blade-like tail and characteristically slimy skin.

It is common for the peninsula newt (N. v. piaropicola) to be neotenic, with a larva transforming directly into a sexually mature aquatic adult, never losing its external gills. The red eft stage is in these cases skipped.

Homing

Eastern newts home using magnetic orientation. Their magnetoreception system seems to be a hybrid of polarity-based inclination and a sun-dependent compass. Shoreward-bound eastern newts will orient themselves quite differently under light with wavelengths around 400 nm than light with wavelengths around 600 nm, while homing newts will orient themselves the same way under both short and long wavelengths.[3] Ferromagnetic material, probably biogenic magnetite, is likely present in the eastern newt's body.[4]

Habitat and diet

Eastern newts are at home in both coniferous and deciduous forests. They need a moist environment with either a temporary or permanent body of water, and thrive best in a muddy environment. During the eft stage, they may travel far from their original location. Red efts may often be seen in a forest after a rainstorm. Adults prefer a muddy aquatic habitat, but will move to land during a dry spell. Eastern newts have some amount of toxins in their skin, which is brightly colored to act as a warning. Even then, only 2% of larvae make it to the eft stage. Some larvae have been found in the pitchers of the carnivorous plant Sarracenia purpurea.[7]

Eastern newts eat a variety of prey, such as insects, small mollusks and crustaceans, young amphibians, worms, and frog eggs. They also eat a lot of snails, beetles, ants, and mosquito larvae.[8] Their dietary habits prove to be very beneficial to humans because they help to control insect populations. They are very active animals and they tend to feed every two to three days.

Survival advantages

Secretion of toxins through the skin protects the newt from predators, and should therefore not be handled with bare hands. The red colors of the adult newt also act as a warning sign for predators.[9] Its ventral surface has poison glands, which makes it reluctant for predators to eat.[10] This special toxin is known as tetrodoxin. Several studies have found that newt larvae increase the production of this toxin while in the presence of predators (dragonflies). Tetrodoxin is known to cause muscle paralysis, skin irritation, and even death in predators. The Eastern newt also has a greater tail depth and is capable of swimming quickly away from aquatic predators.

Limb regeneration

Eastern newts are able to regenerate their limbs that were lost to an injury. Forelimb regeneration has been considered to be close to the forelimb development; genes that play a role in forelimb regeneration are known to also be expressed in its developmental stages.[11]

Conservation concerns

Although eastern newts are widespread throughout North America, they, like many other species of amphibians, are increasingly threatened by several factors including habitat fragmentation, climate change, invasive species, over-exploitation, and emergent infectious diseases.[12] The biodiversity of amphibians across the United States is considered to be threatened due to the loss of wetlands and furthermore, their connectivity;[13][14] since the 1780s, more than 53% of wetlands in the United States have been lost.[15] Wild eastern newts are known hosts of Batrachochytrium dendrobatidis and Ranavirus. They are also highly susceptible to the newly emergent chytrid fungus Batrachochytrium salamandrivorans.[16]

  • Terrestrial juvenile stage ("red eft")
  • Aquatic larval stage
  • Eft near Northfield, Massachusetts
  • Eft navigating over leaves near Thomasville, Alabama
  • Eft on North Fork Mountain in eastern West Virginia
  • Eft seen along a trail in Harriman Park, New York
  • Swollen cloaca and large hind legs in a reproductive adult male
  • Adult female central newt
  • A red-spotted newt among the autumn leaves not far from Bolton, Vermont

References

Citations
  1. IUCN SSC Amphibian Specialist Group (2015). "Notophthalmus viridescens". IUCN Red List of Threatened Species. 2015: e.T59453A78906143. doi:10.2305/IUCN.UK.2015-4.RLTS.T59453A78906143.en. Retrieved 19 November 2021.
  2. Marion, Zachary H; Hay, Mark E (2011). "Chemical Defense of the Eastern Newt (Notophthalmus viridescens): Variation in Efficiency against Different Consumers and in Different Habitats". PLOS ONE. 6 (12): e27581. doi:10.1371/journal.pone.0027581. PMC 3229496. PMID 22164212.
  3. Phillips, J; Borland, S (1994). "Use of a Specialized Magnetoreception System for Homing by the Eastern Red-Spotted Newt Notophthalmus Viridescens". The Journal of Experimental Biology. 188 (1): 275–91. doi:10.1242/jeb.188.1.275. PMID 9317797.
  4. Brassart, J; Kirschvink, J. L; Phillips, J. B; Borland, S. C (1999). "Ferromagnetic material in the eastern red-spotted newt notophthalmus viridescens". The Journal of Experimental Biology. 202 Pt 22 (22): 3155–60. doi:10.1242/jeb.202.22.3155. PMID 10539964.
  5. Behler, John L.; King, F. Wayne (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians (Chanticleer Press ed.). New York: Knopf. p. 276. ISBN 978-0-394-50824-5. Retrieved 4 September 2012.
  6. Santos, J. C; Coloma, L. A; Cannatella, D. C (2003). "Multiple, recurring origins of aposematism and diet specialization in poison frogs". Proceedings of the National Academy of Sciences. 100 (22): 12792–7. doi:10.1073/pnas.2133521100. JSTOR 3148039. PMC 240697. PMID 14555763.
  7. Butler, Jessica L; Atwater, Daniel Z; Ellison, Aaron M (2005). "Red-spotted Newts: An Unusual Nutrient Source for Northern Pitcher Plants". Northeastern Naturalist. 12 (1): 1–10. doi:10.1656/1092-6194(2005)012[0001:rnauns]2.0.co;2. JSTOR 3858498.
  8. Wood, J. T., & Goodwin, O. K. (1954). OBSERVATIONS ON THE ABUNDANCE, FOOD, AND FEEDING BEHAVIOR OF THE NEWT, NOTOPHTHALMUS VIRIDESCENS VIRIDESCENS (RAFINESQUE), IN VIRGINIA. Journal of the Elisha Mitchell Scientific Society, 70(1), 27–30. http://www.jstor.org/stable/24334334
  9. https://www.dec.ny.gov/animals/67022.html
  10. Hurlbert, Stuart H. “Predator Responses to the Vermilion-Spotted Newt (Notophthalmus Viridescens).” Journal of Herpetology, vol. 4, no. 1/2, 1970, pp. 47–55, https://doi.org/10.2307/1562702. Accessed 27 Apr. 2022.
  11. Vlaskalin, T., Wong, C.J. & Tsilfidis, C. Growth and apoptosis during larval forelimb development and adult forelimb regeneration in the newt (Notophthalmus viridescens). Dev Genes Evol 214, 423–431 (2004). https://doi.org/10.1007/s00427-004-0417-1
  12. Collins, James P; Storfer, Andrew (2003). "Global amphibian declines: Sorting the hypotheses". Diversity and Distributions. 9 (2): 89–98. doi:10.1046/j.1472-4642.2003.00012.x. JSTOR 3246802.
  13. Semlitsch RD, Bodie, JR 2001. Are Small, Isolated Wetlands Expendable? Conservation biology. https://doi.org/10.1046/j.1523-1739.1998.98166.x. Retrieved 27 April 2022.
  14. Gallant AL et al 2007. Global Rates of Habitat Loss and Implications for Amphibian Conservation, BioOne Complete. https://doi.org/10.1643/0045-8511(2007)7[967:GROHLA]2.0.CO;2. Accessed 27 April 2022
  15. Dahl, T.E.,1990. Wetlands Losses in the United States 1780's To 1980's. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 21 pp.
  16. Martel, A; Blooi, M; Adriaensen, C; Van Rooij, P; Beukema, W; Fisher, M. C; Farrer, R. A; Schmidt, B. R; Tobler, U; Goka, K; Lips, K. R; Muletz, C; Zamudio, K. R; Bosch, J; Lotters, S; Wombwell, E; Garner, T. W. J; Cunningham, A. A; Spitzen-Van Der Sluijs, A; Salvidio, S; Ducatelle, R; Nishikawa, K; Nguyen, T. T; Kolby, J. E; Van Bocxlaer, I; Bossuyt, F; Pasmans, F (2014). "Recent introduction of a chytrid fungus endangers Western Palearctic salamanders". Science. 346 (6209): 630–1. doi:10.1126/science.1258268. PMC 5769814. PMID 25359973.

Further reading
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