Description This salamander ranges from 6.5 to 14 cm in length. Terrestrial N. viridescens ("red efts") are juveniles and thus generally smaller in size (3.5 to 8.6 cm in length); efts are orange-red to reddish-brown in color. Aquatic adults are generally green with two dorsal rows of red to orange spots; the dorsum may also be yellow-brown, olive-green, or dark brown. The venter is yellow. Breeding aquatic males have brighter and redder spots than females (Davis and Grayson 2008), as well as enlarged hind legs, swollen vents and a broadly keeled tail, and black keratinized structures on the inner thigh and toe regions (Behler and King 1996). Terrestrial adults have granular skin, in contrast to aquatic adults, which have smooth mucous skin (Walters and Greenwald 1977).
U.S. state distribution from AmphibiaWeb's database: Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Massachusetts, Maryland, Maine, Michigan, Minnesota, Missouri, Mississippi, North Carolina, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Virginia, Vermont, Wisconsin, West Virginia
Canadian province distribution from AmphibiaWeb's database: New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec
This species is one of the most widely distributed salamanders in North America, occurring primarily from Nova Scotia to Florida, and also southwest to Ontario. It prefers ponds and lakes with dense, submerged vegetation and relatively undisturbed stretches of streams, swamps, neighboring woodlands and ditches (Behler and King 1996).
Life History, Abundance, Activity, and Special Behaviors
N. viridescens has a complex life cycle, with four distinct stages: egg, aquatic larva, red eft (terrestrial juvenile), and adult (Petranka 1998). The breeding season lasts from late winter to early spring (Behler and King 1996). A single batch of 200-400 eggs is typically laid by the females on submerged vegetation, with an incubation period of 3-8 weeks (Behler and King 1996). On hatching, a larva measures about 8 mm in size (Behler and King 1996). Larvae may develop along one of three possible pathways: metamorphosis via a terrestrial juvenile (eft) stage to an aquatic lunged adult; metamorphosis directly to an aquatic lunged adult; or paedomorphosis (maturation directly to an aquatic gilled adult with no metamorphosis) (Takahashi 2008; Takahashi and Parris 2008). Generally, following metamorphosis from the aquatic larval stage, juveniles disperse away from their home ponds and spend three to seven years as terrestrial red efts (Forester and Lykens 1991). Efts return to aquatic habitats to reproduce when they become sexually mature, and undergo a second transformation to a more aquatic adult form during breeding season. Aquatic adults become green in coloration, have smoother, mucous skin and develop large tail fins, particularly pronounced in breeding males (Gage 1891; Gill 1978a). The change from terrestrial phenotype to aquatic phenotype may take days to weeks (Grayson and Wilbur 2009). After breeding season is over, adults may remain aquatic or may return to terrestrial habitat; if they disperse terrestrially, the skin texture and color changes and the tail fin reduces in size (Brimley 1921; Walters and Greenwald 1977; Davis and Grayson 2007).
Terrestrial newts can migrate across both open and forested habitat (Healy 1973); the use of fluorescent tracking powder showed that efts meandered more while adult newts were found to make more linear trails away from the pond (Roe and Grayson 2008). After periods of rain, concentrations of efts in forest regions may be high (Behler and King 1996). Terrestrial efts and adults make use of a variety of surface or near-surface microhabitats, mostly under forest debris such as leaves, logs, and branches; they are never found in subterranean habitat or mammal burrows (Roe and Grayson 2008). Emergence from refuges and continued movement depend on having a moist surface environment (Roe and Grayson 2008). Distance traveled by efts or adults depended on the humidity and precipitation levels of the previous day (Roe and Grayson 2008). Some postbreeding newts were found to travel over 50 m in 24 hours (Roe and Grayson 2008). When out and active, individuals tracked by using fluorescent powder were often found to have climbed up ferns and logs, probably to forage (Roe and Grayson 2008).
The adult diet includes worms, insects, small crustaceans, amphibian eggs and larvae (Behler and King 1996). Feeding occurs year-round (Morgan and Grierson 1932). Adults were found to be capable of consuming an average of 316 mosquito larvae per day (DuRant and Hopkins 2008).
Cutaneous secretions of toxic substances (tetrodotoxin and its analogues 6-epiTTX and 11-oxoTTX) serve as a defense mechanism from potential predators (Webster 1960; Brodie 1968; Hurlburt 1970; Pough 1971; Brandon et al. 1979; Brodie and Formanowicz 1981; Shure et al. 1989). Although the bright coloration of juveniles (red efts) is presumed to be aposematic, one study supported that conclusion by finding that efts were more toxic than non-aposematic adults (Wakely et al. 1966), but a different study found that efts and non-aposematic adults were equally toxic (Yotsu-Yamashita and Mebs 2003). It is thought that the nontoxic plethodontid salamander Pseudotriton ruber, which is bright red, may be mimicking the coloration of efts (Howard and Brodie 1971; Huheey and Brandon 1974).
Trends and Threats
Raffel et al. (2010) found that eastern newts in 12 of 16 central Pennsylvania ponds were widely infected with the amphibian chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd), although they appeared healthy and did not show any overt signs of chytridiomycosis. N. viridescens may thus act as a reservoir species for Bd (Raffel et al. 2010). In the southeastern United States, Bd-infected N. viridescens have been found in Georgia, North Carolina, and Virginia, but sampling was negative in Louisiana and Tennessee (Rothermel et al. 2008). Eight dead Bd-infected newts were found in Virginia, although these individuals were apparently not part of a mass mortality event and newt populations did not decline between 2006 and 2008 (Rothermel et al. 2008). Padgett-Flohr et al. (2007) also reported Bd infections in commercially purchased N. viridescens, but did not note where infected individuals originated.
Recently a new species of mesomycetozoan parasite (Amphibiocystidium viridescens) was reported to be widespread (Pennsylvania, West Virginia, and Massachusetts) and to have caused mortality in eastern newt populations. Infection presents as subcutaneous cysts, visible as raised bumps under the skin and in the liver. This may be another recently emerged pathogen, like the chytrid fungal pathogen Bd. Peaks in infection prevalence were found to occur in winter and early spring (Raffel et al. 2008).
N. viridescens may be a carrier of iridoviruses. Duffus et al. (2008) examined FV3 prevalence in pond-dwelling amphibian communities of southeastern Ontario, Canada. Of five N. viridescens individuals sampled from a single pond, one was infected with frog virus 3 (FV3) but did not show clinical signs of infection, in contrast to syntopic wood frogs.
Pollutants can affect this species. Relyea and Jones (2009) found that the glyphosate-based herbicide Roundup (in the Original Max formulation, which contains the surfactant polyethoxylated tallowamine, or POEA) was moderately toxic to larval N. viridescens, similar to the toxicity for larval ambystomatid salamanders and less than the toxicity for larval anurans. In another study, adult N. viridescens exposed to sediments with low amounts of coal-tar sealant (which can originate from asphalt parking lots), as well as to UV light, showed sublethal effects including decreased righting ability and decreased swimming speed. Although these effects did not directly result in mortality, they could potentially influence survival by decreasing the ability to catch prey or evade predators (Bommarito 2009). Likewise, exposure to the insecticide endosulfan has been shown to reduce mating success in N. viridescens by inhibiting release or potency of female pheromones and by delaying male responses to female odors (Park et al. 2001; Park and Propper 2002).
Possible reasons for amphibian decline
General habitat alteration and loss Local pesticides, fertilizers, and pollutants Disease
Subspecies include N. v. dorsalis, N. v. louisianesis, N. v. piaropicola, and N. v. viridescens (Behler and King 1996) . However, phylogenetic analyses have identified clades that do not correspond to the current subspecies designations (Takahashi 2008).