Seepage Salamander (Desmognathus aeneus)

Seepage Salamander (Desmognathus aeneus)
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Seepage Salamander (Desmognathus aeneus)
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Seepage Salamander (Desmognathus aeneus) - eggs
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Seepage Salamander (Desmognathus aeneus) - female with eggs
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Seepage Salamander (Desmognathus aeneus) - female with eggs
Photo © by Dave Huth, some rights reserved. Click image for licensing information.

Description
Desmognathus aeneus is a small terrestrial salamander of the North American Southeast. Adults have dark bellies and a chestnut to yellow dorsal stripe flanked by darker sides. The dorsal stripe is often wavy and occasionally consists of chevrons or “herring bone” segments. Adults have 13-14 costal groves with a total length of 38-57 mm between the snout and tail tip (Petranka 1998). Like all members of the plethodontid family, D. aeneus do not have lungs and have a nasolabial groove which runs from the nares to the dorsal lip.

Distribution and Habitat
The range of Desmognathus aeneus is patchy from far southwestern North Carolina through central Alabama. There is a large western Alabama population, as well as isolated populations in Georgia and South Carolina (Petranka 1998; Livingston et al. 1995). The northern extent of its range is probably marked by the Little Tennessee River in North Carolina and Tennessee (Jones 1981). They are found in leaf litter along seepage areas of streams and springs in hardwood forests, and their egg masses are often found beneath patches of moss (Jones 1981).

Life History, Abundance, Activity, and Special Behaviors
Desmognathus aeneus is characterized as having direct development, which does not contain a free-living larval stage. Along with a precocious adult morphology at birth, D. aeneus also lacks substantial gills or a caudal fin, and forms eyelids as an embryo (Wake 1966; Marks and Collazo 1988; Collazo and Marks 1989; Marks and Collazo 1998). These features combined indicate that D. aeneus is a true direct developing salamander. This unique life history is shared with only one other member of its genus, Desmognathus wrighti. All other members of the genus exhibit the standard biphasic amphibian lifestyle with aquatic larvae and terrestrial or semi-terrestrial adults. Unlike many direct developing frogs or bolitoglossine and plethodontine salamanders, the development of D. aeneus is associated with little developmental repatterning. The embryo develops a hyobranchial apparatus, lateral line system, and limbs that at least partially resemble the larval development of metamorphosing desmognathines (Marks 1994; Wake et al. 1987; Marks et al. 1992). The development of these features is dramatically altered in the direct developing members of the plethodontine and bolitoglossine tribes (reviewed in Wake and Hanken 1996). In their revision of the desmognathine salamander phylogeny Tom Titus and Allan Larson (1996) placed both species of direct developing Desmognathus (D. aeneus and D. wrighti) as basal to the genus (see Tree of Life web page). This positioning along with the placement of the direct developing Phaeognathus as the closest out-group suggests that direct development is the ancestral condition for the genus. This controversial finding is unique in claiming that metamorphosis has re-evolved in the evolution of desmognathine salamanders.

Desmognathus aeneus young hatch between mid-June and mid-July. The clutch sizes range from 8-15 eggs. Their eggs are large with white embryos that can be seen through a transparent jelly coat and associated membranes. The adults primarily feed on arthropods with beetle larvae (Staphylinidae and Carabidae) its most common food source (Donavan and Folkerts 1972). Adult stomachs have also contained collembolas, arachnids, immature diptera, and even other D. aeneus, although cannibalism is thought to be uncommon (Jones 1981; Donavan and Folkerts1972).

The reproductive behavior of Desmognathus aeneus is similar to its congeners. Like all plethodontids the desmognathine salamanders use a tail-straddling walk to transfer a spermatophore from the male to the female. This walk is the culmination of an elaborate courtship ritual that involves inputs from both the female and male salamanders (see Verrell and Mabry 2000). Unlike most other plethodontids, D. aeneus along with D. wrighti use a “prolonged biting phase,” in which the male bites the female while forcefully restraining her. This biting is used to transfer male pheromones to the female and is associated with vigorous rhythmic thrashing of the head (Promislow 1987).

Desmognathus aeneus has a Global Heritage Status of G3G4 (16Oct2001) (natureserve.org). It is described as moderately threatened and declining due to its patchy distribution and habitat preferences. Current logging practices and habitat loss have raised concern for its status in Tennessee (Redmond and Scott 1996)and Alabama (Folkerts 1968). While there is evidence that populations of this species vacillate widely in density (Hairston and Wiley 1993) it is unlikely that these populations can survive the dried habitat of clear-cut forests (Folkert 1968).

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