OVERVIEW OF LIFE STAGES
Throughout most of its range, the Eastern Newt Notophthalmus viridescens typically has a three-stage life cycle. The newt spends its first summer as a gilled aquatic larva, which then metamorphoses into a juvenile terrestrial stage called an eft. After a variable time ashore, the eft undergoes a second metamorphosis as it transforms into an aquatic breeding adult. In some areas, notably on the southeastern coastal plain, the land stage is omitted and neoteny frequently occurs, in which the breeding adults will retain at least remnants of external gills. Seasonal migration ashore is common for most adults, either for the purpose of overwintering or aestivation during dry months. Every spring, adults return to their home ponds for the most important activity -- reproduction.
COURTSHIP & MATING
Courtship in Notophthalmus viridescens can occur both in spring and in late autumn, but only during the spring season are eggs laid. Male newts have three behavioral options for inseminating females (Verrell 1983, Massey 1988). It has been observed in laboratory that if the female is responsive to the male's intial approach and does not try to evade him, the male newt would proceed to perform the hula display, where he undulates his body in front of the stationary female, and deposit a spermatophore if the female nudges his cloacal region.
Females, however, are rarely immediately responsive to approaches by courting males, and the primary and most commonly observed reproductive tactic in nature entails the capture of unreceptive females by males (Verrell 1983, Halliday & Adler 1986). This usually begins with the male nudging the female's cloaca and displaying by twitching and undulating his body. The female may repreatedly swim away, only to be reapproached by the persistent male, who may follow her stealthily until he is in a position to apprehend her by surprise. The male will eventually crawl over the female and move forward until he can clasp her at the neck or just behind her front feet using his hind limbs (which are enlarged and covered with keratinized nuptial excrescences during the breeding season). While in this embrace, called amplexus, the male fans his tail to spread stimulating secretions from his cloaca toward her head. He also repeatedly rubs his cheek on her snout to stimulate her with secretions from the genial glands.
Amplexus can last for several minutes to more than 3 hours, after which the courting male releases the female. If the female nudges the male's tail and cloaca, he deposits a spermatophore and leads her forward so that her cloaca rests above the spermatophore. The sperm mass is taken up by the female's cloaca, leaving the spermatophore base behind. Fertilization is internal. Amplexus, however, does not always results in insemination (Verrell 1983). Sometimes the male is unsuccessful in stimulating the unreceptive female during amplexus, in which case the female simply leaves ensuing dismount. Other times the female nudges the male's cloaca after amplexus but either leaves prior to spermatophore deposition, or loses the cloacal-spermatophore alignment and fails to take up the sperm mass.
A thrid tactic males may deploy to inseminate females is interference (Massey 1988). Rival males may try to displace and replace courting male in amplexus. They may also interfere during spermatophore transfer by inserting themselves between the courting male and the female, inducing the courting male to deposit and deplete his spermatophore while depositing his own spermatophore for the female to take up. Pseudofemale behaviors have also been observed in male newts. These males allowed themselves to be clasped by other courting males and may induce spermatophore deposition from the deceived males by nudging their cloaca, hence depleting their limited spermatophore supply (Massey 1988).
Scramble competition between males and capture of female both select for sexual dimorphism of locomotory strucutres, namely the enlargement of tailfin in males during breeding season. The greater acceleration achieved by larger tailfins is likely advantageous for males because successful capture depends to some extent upon surprising the female. It has been demonstrated that male tailfin size in Notophthalmus viridescens is positively correlated with male amplexus frequency and indirectly correlated with insemination frequency (Able 1999). Mate choice is not a one way street in Notophthalmus viridescens. Male newts invest heavily in courtship behavior and the development of secondary sexual characters; they also have a exhaustible amount of sperm available during a breeding season. It should thus not be unexpected that Notophthalmus viridescnes males show a preference to court larger and presumably more fecund females when given the choice. They appear to use either olfactory and/or visual cues in assessing the size of potential mates (Verrell 1985).
EGGS & LARVAE
Eggs are mostly laid in late spring during the months of April and May. Soon after mating, females swim or walk to heavily vegetated sections of their breeding pond and proceed to deposit from a few dozen to 400 or more sticky eggs over a period of several days or weeks, usually meticulously folding each egg in a leaf or attaching them singly onto the stems of aquatic plants (Tyning 1990, Harding 1997). 
Notophthalmus viridescens eggs are the smallest among salamanders; the ova are 1.5 mm in diameter and the elliptical capsules 2.4 by 3.6 mm (Bishop 1943). The eggs, wrapped in leaves or attached to stems in water, show variation in their amount of pigmentation. Eggs deposited in sites exposed to sunlight have more melanin deposits in the animal hemisphere, whereas most eggs deposited in sites not exposed to sunlight lack pigmentation (Duellman & Trueb 1994). The presence of melanin in sun-exposed eggs may function to protect the embryo from ultraviolet radiation or to raise the temperature of the eggs through greater heat absorbtion. The eggs are susceptible to a number of hazards, including predation by insects and leeches, accidental damage caused by large animals walking in the shallows, bacterial and fungal attacks, and incidental ingestion by aquatic herbivores (Tyning 1990).
The incubation period lasts from two to five weeks, depending on the water temperature and degree of exposure to sunlight. At hatching, the tiny larvae measure about 7 to 9 mm in length (Bishop 1943). The external gills are developed but only slightly branched. The front limbs are short and blunt while the hind legs are absent. The dorsal keel extends anteriorly nearly to the head and is continuous posteriorly with the tail keel. Larvae are pale gray, green or brown tinged with yellow. On each side of the mid-dorsal line a gray band extends the length of the body. Dark chromatophores are scattered over the sids and dorsum (Mecham 1967). Newborn newt larvae sink to the bottom and remain relatively inactive for several days. At this stage they are vulnerable to insect predators such as the diving beetles and dragonfly larvae (Tyning 1990). Within a week of hatching, the primarily carnivorous larvae become active and feed rather indiscriminantly on a variety of small aquatic invertebrates abundant in summer ponds (Hamilton 1940). Larvae grow quickly and attain a maximum length of 35 to 40 mm just before metamorphosis.
TERRESTRIAL EFT STAGE & NEOTENY
A sexually immature, terrestrial eft stage is typical throughout much of the range of Notophthalmus viridescens, espcially in the Red-spotted Newt (subspecies N. v. viridescens). Starting late summer and early fall, larvae begin to re-absorb their gills and caudal fin, develop lungs and granular skin, and emerge from water as terrestrial efts (Tyning 1990). Individuals recently transformed from the larval to the eft stage may appear yellowish-brown or dull reddish (Conant & Collins 1991). Efts are diurnal and prefer high humidity for most of their life on land, so they are most often seen during or after rains at daytime in woodlands (click here for habitat and other ecological aspects of the juvenile eft stage). The terrestrial eft stage can last anywhere from two to seven years before a second metamorphosis transforms the eft into a sexually mature adult, at which time it resumes a largely aquatic existence (Forester & Lykens 1991). Two to three years of life ashore is most common, even though persistent drought can prevent efts from undergoing their second metamorphosis and indefinitely delay their reproduction.
Interspecific polymorphism in life history does occur in Notophthalmus viridescens, however, and in some areas the terrestrial stage is skipped. This is especially common for the Peninsula Newt (N. v. piaropicola) in Florida as well as Central Newt (N. v. louisianensis) in the southeastern coastal plain, where the efts are rarely observed (Mecham 1967). While throughout its wide range the Red-spotted Newt (subspecies N. v. viridescens) normally exhibits the terrestrial eft stage intervening aquatic larval and adult stages, distinct populations along coastal Massachussetts and on Long Island have also been found to omit the land stage from their life cycle (Mecham 1967, Healy 1974, Harris 1987). Adults of these populations are paedomorphic (Greek, paidos, "of child"; morphe, "form"), having attained reproductive maturity while retaining some larval characters such as remnants of external gills. Paedomorphosis could result from either slowed somatic (non-reproductive) development (called neoteny) or from precocious reproductive development (called progenesis). Paedomorphosis in Notophthalmus viridescens, as in most salamanders, is usually attributed to neoteny (Duellman & Trueb 1994).
Various hypotheses have been proposed to explain the respective adaptive significance of the terrestrial eft stage and neoteny. One of them concerns the relative living conditions in water and on land. Neotenous life history could be a response either to unfavorable terrestrial environment or ideal growth conditions within a pond such as low larval density (hence low competition), low risk of predation and abundant food supply (Harris 1987). Healy (1974) thus attributes the evolution of neotenous life history along coastal Massachusetts and Long Island as an adaptation to harsh and unstable terrestrial environment. On the other hand, metamorphosis into the eft could be a response by individuals that have not reached reproductive size to deteriorating growth conditions in the pond caused by pond desiccation or competition with other larvae and adults. Under such circumstances, selection would favor individuals that metamorphose and take advantage of growth opportunities in the terrestrial environment (Harris 1987). Gill (1978) alternatively proposed that the eft stage in the life history of newt serves to disperse individuals from deteriorating ponds to new ponds, especially in regions with rapid turnover of ponds. Since adults of this species have very high fidelities to their breeding ponds (see below), colonization of new ponds and formation of new demes in a metapopulation of Notophthalmus depend on dispersal during the eft stage. He attributed the evolution of neotenous forms in coastal Massachusetts and Long Island to the low turnover rate of ponds in the region; in such an environment where only large, permanent ponds are present and very few new ponds ever form, dispersal via the eft stage loses its benefit.
MIGRATION, OVERWINTERING & HOMING
Seasonal emigration from the aquatic, reproductive habitat is a common phenomenon among temperate salamanders, often in response to the advent of winter. Adult Notophthalmus viridescens has different overwintering patterns in different localities during winter. In Virginia (Gill 1978) and parts of Canada (Logier 1952) adult Eastern Newts migrate to land for hibernation, whereas newts in Ohio (Jiang & Claussen 1992) and New York (Hurlbert 1969) often remain active all year in the deeper, permanent ponds, sometimes observed to swim actively under the surface ice layer. Jiang & Claussen (1992) investigated the bioenergetic budget of adult Red-spotted Newts from southern Ohio that remain actively in water throughout winter, and found that the newts can store at least 85 mg of fat prior to winter, which could support low levels of activity for a minimum of 78 days at low winter temperature. This fat reserve is important because primary production is reduced to a minimum as temperatures decrease and the newts may not ingest food through the duration of winter. Those in shallow waters that dry up or freeze solid in the winter must migrate ashore to overwinter. On land, adults overwinter under logs, rocks or leaf litter; some may enter burrows made by other animals or follow natural crevices below ground (Tyning 1990). From mid-March to early April, they can be found emerging from their overwintering sites on land on their way back to their breeding ponds. Adult newts have very high fidelity to their home ponds (called philopatry), returning faithfully breeding season after breeding season.
The homing capability and mechanisms of Notophthalmus viridescens has been a subject of much fascination and investigation. Adult newts appear to use multiple cues in orienting themselves. Visual and olfactory cues emanating from the home pond are important (Hershey & Forester 1980), although even blinded newts with their sense of smell destroyed are capable of finding their way to water. The pineal body, an outgrowth of the brain lying just beneath the skull bones, appears to be sensitive to polarized light; newts can use the light polarization patterns in the sky to determine the position of the sun, even when the sun is hidden by a cloud (Taylor & Auburn 1978). They have also been shown to respond predictably to slope by orienting downhill, and since ponds usually lie in basins, it is reasonable to attribute their downhill orientation to use of the elevation gradient as ambient directional information (Omland 1998). Perhaps the most amazing aspect of the species' homing behavior is their capacity for true navigation (Phillips & Borland 1994, Phillips et al. 1995, Brassart et al. 1999). True navigation, also referred to as map-based homing, is the ability of an organism to return to its point of origin ("home") after displacement to an unfamiliar territory, without knowledge of the displacement route nor access to any familiar landmarks or cues from the origin. True navigation requires two things: a map sense (for the relative position between destination and current position), and a compass sense (to orient to the home-ward direction as determined from by the map sense). The mechanism of true navigation in Notophthalmus viridescens is complicated and involves the use of the earth's magnetic fields and a specialized magnetoreception system.
