Description

DESCRIPTION:

DIAGNOSIS:

Desmognathus organi occupies drier, colder environmental conditions and is more robust and heavier compared to its sister taxon D. wrighti, which occurs south of the French Broad River. Unlike D. wrighti, which features complete speckled iridophores, D. organi have incomplete or absent iridophore formation on the abdomen (Crespi et al. 2010). In literature prior to Crespi et al. (2010), D. organi can be distinguished from D. wrighti by the location of the specimen.

COLORATION:

Desmognathus organi have bronze to dark brown dorsal coloration, darker brown intervertebral costal grooves, and light underside with typically some gold iridophores present on the abdominal musculature between the forelimbs to the anterior tip of the cloacal vent (Crespi et al. 2010).

VARIATION:

Females have a more rounded snout than males and tend to be lighter in color but larger, heavier, and more robust. Individuals may vary in iridophore presence ranging from a few golden speckling on the abdomen to none. Some individuals may have a lighter brown, wavy dorsal strip that runs along the ventral dorsal area to the tip of the tail (Crespi et al. 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: North Carolina, Tennessee, Virginia

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (4 records).

Desmognathus organi is endemic to the Southern Appalachian mountains of the Eastern United States. The largest populations occur in mature, high elevation spruce-fir forests of the Blue Ridge Mountains between the French Broad River Valley and Mt. Rogers, while smaller concentrations can occur in lower elevation north-facing slopes and deciduous forests (Rossell et al. 2018). Populations can be disjunct due to their affinity for higher elevation forests and the varying locations which suitable habitat occurs. The highest densities typically occur above 1500 m but have been observed up to 2082 m and down to 762 m (Bruce 2019, Harrison 2000, Crespi et al. 2010).

Life History, Abundance, Activity, and Special Behaviors

Desmognathus organi like its sister species D. wrighti, is typically associated with wet forest floors during warmer months. While a rare species overall, D. organi is most common under small cover-objects such as logs, bark, rocks, or moss. These habitats allow them to avoid predation and interspecific competition (Rossell et al. 2018).

Microarthropods such as oribatids and collembolans make up a large portion of D. organi's diet, hence their association with moss carpets, round wood, and leaf litter (Bruce 2019). Foraging occurs mainly at night due to increased moisture and decreased visibility to predators. During colder months, they relocate to overwinter in springs and seepages near stream headwaters (Bruce 2019, Organ 1961).

When exposed to or touched by a predator, D. organi will flip over onto its back and become immobile (Harrison 2000).

Reproduction occurs in late summer when larger populations congregate in more aquatic environments where females nest and oviposition occurs (Organ 1961). During courtship, males grasp and hold females with their jaw, rhythmically tugging back and away while undulating his tail. The female turns towards the male and places her chin on his tail, forming a circle - this process can happen two or more times per encounter. After releasing the female, the male slides his head under the female's body and moves forward in a tail-straddle walk as he deposits his spermatophore, which is taken up by the female’s cloaca (Verrell 1999).

The spermatophore is 2.5 mm tall, slender, "glass-like", and flares at the base. The sperm cap is a thin milk-white sheath at the tip of a slender stalk (Organ 1961). The number of testes in males increase with body size with up to nine testes being recorded (Crespi et al. 2010).

Females guard their clusters of 3 to 8 eggs, which are attached to small rocks in cavities in mud or gravel in seepages and headwater streams (Organ 1961).

Hatchlings show direct development, lacking a larval stage with embryos completely absorbing their gills prior to hatching - a unique feature to Desmognathus species (Organ 1961). Sexual maturation is reached in 2 - 3 years (Bruce 2019).

Trends and Threats
While local populations of D. organi remain somewhat stable, especially since 65% of known D. organi occurrences in North Carolina occur in Pisgah National Forest and 85% of these are within permanently protected areas like inventoried roadless areas or designated wilderness, their habitat has been severely affected. Specifically, habitat loss and fragmentation from recreational development and logging (USFS 2014), introduced insects like Choristoneura fumiferana (spruce budworm) and Adelges piceae (balsam woolly adelgid) causing spruce tree declines, and canopy cover reduction from environmental changes like acid rain. This significantly harms D. organi since relative abundance of the species is higher in spruce fir forests (as well as northern hardwood forests) compared to mountain cove forests (Rossell et al 2018).

Relation to Humans
There are reports of this species being over-collected (along with D. wrighti) for the pet trade, reducing population numbers (Rossell et al 2018).

Possible reasons for amphibian decline

General habitat alteration and loss
Urbanization
Subtle changes to necessary specialized habitat
Habitat fragmentation
Intentional mortality (over-harvesting, pet trade or collecting)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments

PHYLOGENETIC RELATIONSHIPS:

ETYMOLOGY:

Desmognathus is derived from Greek – “Desmos”, meaning “ligament”, and “gnathos”, meaning “jaw”. This refers to jaw morphology unique to Desmognathus salamanders (Virginia Herpetological Society).

The species epithet, “organi” stems from James Organ’s surname, who first described D. organi’s life history in 1961 (Crespi et al. 2010). At the time D. organi and D. wrighti were not considered separate species, but Organ’s study location only coincides with D. organi’s range and habitat.

References

Bruce, R.C. (2019). “Life history evolution in Plethodontid salamanders and the evolutionary ecology of direct development in dusky salamanders (Desmognathus).” Herpetological Review, 50(4), 673-682.

Crespi, E. J., Browne, R. A., Rissler, L. J. (2010). “Taxonomic revision of Desmognathus wrighti (Caudata: Plethodontidae).” Herpetologica, 66(3), 283-295. [link]

Crespi, E. J., Rissler, L. J., Browne, R. A. (2003). “Testing Pleistocene refugia theory: phylogeographical analysis of Desmognathus wrighti, a high‐elevation salamander in the southern Appalachians.” Molecular Ecology, 12(4), 969-984. [link]

Harrison, J.R., III (2000). ''Desmognathus wrighti.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 704.1-704.7.

Organ, J. A. (1961). “Life history of the pygmy salamander, Desmognathus wright, in Virginia”. The American Midland Naturalist, 66(2), 384-390.

Rossell, C.R., Haas, I.C., Williams, L.A., Patch, S.C. (2018). “Comparison of relative abundance and microhabitat of Desmognathus organi (northern pygmy salamander) and Desmognathus wrighti (southern pygmy salamander) in North Carolina.” Southeastern Naturalist, 17(1). 141-154. [link]

USFS (2014). “Potential Species of Conservation Concern for the Nantahala and Pisgah NFs Plan Revision Including Botanical and Animal Species.” United States Department of Agriculture. [link]

Verrell, P. (1999). “Bracketing the extremes: courtship behaviour of the smallest‐and largest‐bodied species in the salamander genus Desmognathus (Plethodontidae: Desmognathinae).” Journal of Zoology, 247(1), 105-111. [link]

Virginia Herpetological Society “Pygmy Salamander, Desmognathus organi.” Accessed February 11, 2021 from http://www.virginiaherpetologicalsociety.com/amphibians/salamanders/pygmy-salamander/pygmy_salamander.php. [link]

Species Account Citation: AmphibiaWeb 2021 Desmognathus organi: Northern Pygmy Salamander <https://amphibiaweb.org/species/7527> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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