Ambystoma jeffersonianumJefferson Salamander

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Geographic Range

The Jefferson salamander is distributed in patches from southern New England, south and southwest through Indiana, Kentucky, West Virginia, and Virginia (Petranka 1998).

Habitat

The Jefferson salamander is restricted to sites containing suitable breeding ponds and shows a strong affinity for upland forests. It prefers relatively undisturbed deciduous woodlands, especially moist, well-drained upland forests (Petranka 1998).

Physical Description

The Jefferson salamander can vary from a dark brown, brownish gray or slate gray dorsum and may have light blue speckles scattered along the sides, tail, and occasionally extending onto the back. The speckling is most apparent in younger individuals and may disappear in older adults. The vent region is a grayish color and the ventrum is a pale, sometimes silvery, color. Ambystomid salamanders are generally characterized by prominent costal grooves, short, rounded heads, and stout bodies with robust limbs. The Jefferson salamander, however, has relatively long, slender limbs and toes comparatively. The tail is laterally compressed and extends almost as long as the body. The average adult length ranges from 10.7 to 21 cm, with females being in the upper part of the range, and 12 to 14 costal grooves are present. Breeding males have swollen vents and appear more slender than the egg carrying females. The tail is also longer and more laterally compressed in males. Outside of the breeding season both sexes are darker and less conspicuously marked. Larvae are a yellowish green color with dark blotches on the back. They possess a relatively uncolored caudal fin, and display external gills upon hatching. Older larvae have a mottled greenish gray dorsum and may be marked along the sides with small yellowish spots while the ventrum is pale and generally unmarked (Harding 1997, Petranka 1998).

Development

Reproduction

The Jefferson salamander is one of the earliest seasonal breeders, migrating to breeding ponds in late winter or early spring, often before the ground and ponds are completely thawed. The first group of males typically precedes the arrival of the first females. Current data suggest that while males breed annually, females may skip one or more years before breeding again. Salamanders are unique among amphibians in practicing internal fertilization. During courtship, the male deposits a spermatophore, a packet of sperm that the female picks up with the lips of her cloaca. The spermatophore is then stored in her spermatheca until she is ready to lay her eggs. While there is no direct cloacal contact, fertilization is internal. Females may begin to lay eggs one to two days after mating. The eggs are 2-2.5 mm in diameter and are encircled by a vitelline membrane and three jelly envelopes. They are generally deposited in small gelatinous clusters and are attached to underwater sticks or vegetation. If the pond should freeze, the eggs are then protected below the surface of the water. The egg masses generally vary in numbers of 20 to 30 eggs per mass but may have anywhere between 1 and 60 eggs per mass. Females will produce a total of 100 to 280 eggs in one breeding season. The length of the incubation varies. In a controlled setting with temperatures around 21oC eggs will hatch in about two weeks, but under more typical, natural conditions, may take up to 14 weeks depending on the time the eggs were laid. The average embryonic survival to hatching is observed to be positively correlated with egg mass size. Hatching success can be very high, however, larvae survival rate is generally very low due to predation. The newly hatched larvae range in length from 1.0 to 1.4 cm. In two to three months the surviving larvae metamorphosied into terrestrial salamanders. If the breeding pond threatens to prematurely dry up, metamorphosis will occur sooner with smaller larvae. The newly metamorphosized individuals range from 4.8 to 7.5 cm and are able to breed in two to three years. The average life span of the Jefferson salamander is six years or longer (Flank 1999, Harding 1997, Petranka 1998).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

One of the most interesting aspects of salamander behavior collectively is their stubbornness to move from an area. Salamanders are generally not very active and in its entire lifetime may not travel more than a mile. It is estimated that approximately fifty percent of all salamanders die during hibernation because they will remain in areas that are too cold for them rather than moving to a more suitable place (Flank, 1999).

Various defensive behaviors have been observed when this species is confronted by a predator. Its predators include owls, snakes, striped skunks (Mephitis mephitis), and raccoons (Procyon lotor). Behavioral and defensive responses to these predators include a variety of tail movements and body posturing, fleeing, biting, and the production of noxious secretions from skin glands concentrated on the upper base of the tail. Expanding on the observed body movements, this salamander has been noted to raise the tail and undulate or lash it about. The salamander may also tuck its head under its tail forming a coil or engage in body flipping. The jefferson salamander is also capable of voluntarily shedding its tail when threatened. Muscle contractions in the detached tail cause it to twitch violently in hopes of diverting the predator so the salamander has a chance to escape. The superior regenerative powers of salamanders allow for this defense to be effective with minimal consequences to the salamander itself (Harding 1997, Petranka 1998).

Breeding behaviors can be seen when groups of two to four adults begin gathering at a breeding pond. The male approaches a female first and dorsally amplexes her, positioning his forelimbs just behind hers. The sex ratio is generally greater than 3 males to 1 female within a given breeding pond. When the females out number the males, the females are observed to exhibit a form of sexual competition where the unpaired females butt and nudge the amplexed pairs. Before the courtship continues, the pair may remain amplexed for an extended amount of time. Upon continuation the male begins to simultaneously rub his snout on the female's head and undulate his tail. The male also moves his body back and forth rubbing his cloaca against the female's back and may lash about vigorously. At the peak of this activity, the male moves forward, dismounting the female, and begins to strongly undulate his tail and posterior body. The female then generally follows the male nudging his cloaca before picking up the spermatophore deposited by the male (Petranka 1998).

Food Habits

The Jefferson salamander generally feeds on insects and other invertebrate species. The larvae are found to consume small zooplankton after hatching and move on to organisms such as nematodes, aquatic insect larvae, insects, and snails. Larvae may become cannibalistic and feed on small larvae of their own kind and others. Because the adult salamanders spend most of the time, outside of the breeding season, hidden in the ground or under leaf litter their exact feeding habits are not known. It is presumed that they feed on earthworms and other invertebrates found in the soil (Pentranka 1998).

Economic Importance for Humans: Positive

Ecologically, salamanders appear to play important roles in the organization of many terrestrial and aquatic communities. They are increasingly being used as indicators of environmental heath. Salamanders have also proven to be valuable tools in examining various problems in disciplines such as evolution, ecology, animal behavior, physiology, and genetics. Probably most important to the human population is the medical research on salamanders. This includes research to understand the basis for limb and tissue regeneration in vertebrates (salamanders have extraordinary regeneration ability), the study of genetic disorder inheritance, and research exploring the possible therapeutic value of toxic skin secretions in treating human diseases such as cancer (Petranka 1998).

Conservation Status

The Jefferson salamander is not currently listed as threatened or endangered. To continue this species' survival relatively undisturbed, woodland habitats near suitable breeding ponds need to be preserved. The increase habitat fragmentation due to roads, leads to the deaths of many salamanders during their spring migration. The Jefferson salamander is also particularly vulnerable to habitat acidification. When pH levels fall too low they become lethal to the larvae and eggs (Harding 1997).

Other Comments

The Jefferson salamander is involved in a hybrid complex with three other species of mole salamanders (A. laterale, A. texanum, and A. tigrinum) throughout eastern North America. Usually the hybrids result in triploid females. These females are thought to reproduce gynogenetically, they use sperm from a sympatric, diploid male to initiate the development of the eggs without incorporating the male genome. Some females, however, do reproduce through hybridogenesis, where the maturing egg eliminates an entire genome. The embryonic mortality rates of salamanders in hybrid complexes is much higher than that of diploid salamander species. Studies have found that temperature is of great importance in the hybrid Ambystoma. At reduced temperatures triploid females are expected to reproduce by gynogenesis, while at higher temperatures hybridogenesis increases. This variation in breeding patterns has significant bearings on the genetic composition of hybrid populations (Bogart 1988).

Contributors

Sarah Kipp (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Bogart, J., R. Elinson, L. Licht. 1988. Temperature and Sperm Incorporation in Polyploid Salamanders. Science, 246.

Flank, L. Accessed November 11, 1999 at http://www.users.interport.net/~spiff/Newt%26Salamander.html.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor: The University of Michigan Press.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington: Smithsonian Institution Press.