Description

DESCRIPTION:

Stereochilus marginatus are slender, medium-sized salamanders with a snout-vent length of 27 – 50 mm and a total length of 65 – 115 mm (Bruce 1971) with a narrow head. Like many aquatic salamanders, Stereochilus marginatus have tails with a dorsal keel and that are laterally compressed near the tip. The front limbs have four toes, and hind limbs have five toes.

DIAGNOSIS:

By salamander standards, adult Stereochilus marginatus are relatively unique in appearance and are unlikely to be confused for other species within their range. They can usually be distinguished from sympatric dusky salamanders (Desmognathus) by their more elongate and narrow head, the absence of a light line connecting the back of the eye to the back of the jaw, and the presence of fine stripes across the dorsum. They can be distinguished from sympatric dwarf salamanders (e.g., Eurycea quadradigitata) by their larger size and the presence of five toes on the hind feet. They can be distinguished from mud salamanders (Pseudotriton montanus) by their more slender build and their more elongate and narrow heads (Bruce 1971, Rabb 1966, Petranka 1998, T. Pierson pers. comm.).

COLORATION:

In life, Stereochilus marginatus have a brown dorsum and yellowish venter with darker flecks. There is often a dark, indistinct line running through the eye and continuing onto the body, which is usually covered by a series of thinner, parallel stripes that may be absent or often difficult to distinguish. Often, a thicker, cream-colored stripe runs across the side near the separation of the dorsal and ventral color (Bruce 1971, Rabb 1966, Petranka 1998, T. Pierson pers. comm.).

VARIATION:

There is no sexual size dimorphism (Bruce 1971), and sexes may not be easily differentiated through gross morphology alone (Rabb 1966; Sever 1986). There are no described subspecies, and geographic variation in morphology and coloration is poorly documented.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: Florida, Georgia, North Carolina, South Carolina, Virginia

View distribution map in BerkeleyMapper.

Stereochilus marginatus are found in the Atlantic Coastal Plain from northern Florida to southeastern Virginia of the United States of America. These salamanders are nearly fully aquatic and are primarily found in lentic (especially gum and cypress swamps) and slow-moving lotic habitats at low elevations (Rabb 1966; Means 2000; Ryan and Bruce 2000).

Life History, Abundance, Activity, and Special Behaviors
Adult Stereochilus marginatus are most often found in thick organic matter (e.g., leaf packs or Sphagnum moss) in aquatic habitats. However, adults have occasionally been found under terrestrial organic matter near the margin of the water (Foard and Auth 1990; Petranka 1998; Ryan 2005).

Seasonal variation in activity and habitat use is not well-described. Courtship is likely concentrated in the autumn (Bruce 1971; Petranka 1998). Noble and Brady (1930) provide some limited descriptions of courtship behavior; although they note behaviors involving the contact of the mental gland, Stereochilus marginatus - like their close relatives in Pseudotriton and Gyrinophilus - lack this secondary sexual character (Sever 1986; Sever et al. 2016).

Oviposition occurs in the winter (Schwartz and Etheridge 1954; Rabb 1956; Wood and Rageot 1963; Bruce 1971), and descriptions of oviposition sites and parental care vary substantially. Clutches of eggs have been discovered in both aquatic microhabitats and terrestrial microhabitats near water, and eggs are attached singly to plant structures (e.g., roots, stems, moss fibers) or detritus (e.g., pine needles or logs; Petranka 1998). Some reports of terrestrial nests note that these eggs are more closely clumped together and occasionally brooded by females (Schwartz and Etheridge 1954; Rabb 1956). When oviposition is aquatic, eggs are often laid singly or in loose groups, attached to moss or bark under 8 - 15 cm of water, and are not brooded (Bishop 1943; Wood and Rageot 1963). Clutch sizes may vary from 6 - 92 eggs (Noble and Richards 1932; Wood and Rageot 1963; Bruce 1971), and incubation lasts 1 - 2 months (Bruce 1971).

Metamorphosed juveniles and adults eat a variety of invertebrate prey including isopods, amphipods, and insects (Foard and Auth 1990). Most documented prey are aquatic, but the presence of terrestrial adult invertebrates (e.g., Lepidoptera, Coleoptera) in the stomachs of adults following heavy rainfall could suggest either feeding upon terrestrial insects swept into the water or occasional feeding in terrestrial habitats (Ryan 2005).

There are no known instances of predation upon Stereochilus marginatus, perhaps because this species is relatively secretive and poorly studied. However, it is speculated that common predators of other amphibians in these habitats (e.g., aquatic snakes, fish, large invertebrates, and birds) are likely predators (Bruce 1971; Petranka 1998). Although skin toxins have been demonstrated in their closest relatives (Pseudotriton and Gyrinophilus: Brandon et al. 1979; Brandon and Huheey 1981), they have not been described in Stereochilus, which also lack the bright coloration found in some populations of these other species.

Stereochilus marginatus is sympatric with several species of plethodontid salamanders, including various members of dusky salamanders (Desmognathus), brook salamanders (Eurycea), and mud salamanders (Pseudotriton montanus). Other amphibians present in the same habitat include sirens (Siren), amphiuma (Amphiuma), and a variety of frogs and toads (Petranka 1998; Means 2000).

Larva
Stereochilus marginatus has a biphasic life history that includes an aquatic larval stage. Hatchlings are approximately 8 mm in snout-vent length and have functional limbs (Bruce 1971). Larvae have a characteristic “pond-type” morphology, including a high caudal fin (extending nearly to the head in young larvae) and large filamentous gills (Schwartz and Etheridge 1954; Bruce 1971; Ryan and Bruce 2000).

Young larvae have a dark brown dorsum and yellow venter, and older larvae have a color pattern more similar adult (Bishop 1943).

The larval period is variable and be approximately 13 - 16 months or 25 - 28 months (Bruce 1971). Larvae are often found in aquatic organic matter (e.g., moss or leaves) in shallow water around the edge of wetlands, where they eat a variety of invertebrate prey. (Rabb 1966; Bruce 1971; Foard and Auth 1990).

Metamorphosis occurs between 27 - 42 mm (Bruce 1971; Foard and Auth 1990; Ryan and Bruce 2000).

Trends and Threats
The conservation threats of Stereochilus marginatus is not well-documented. Past and ongoing destruction of wetlands and other suitable habitats in the Atlantic Coastal Plain is likely the largest conservation threat (Means 2000; Ryan 2005). It is possible that enigmatic declines of other plethodontid salamanders - including from apparently suitable habitat in the same region (Means and Travis 2007; Graham et al. 2010; Maerz et al. 2015) - may also be affecting Stereochilus marginatus, but there exist only sparse data about the status of this secretive and poorly studied salamander.

Comments

PHYLOGENETIC RELATIONSHIPS:

Stereochilus marginatus is the sole member of the genus Stereochilus and belongs to the tribe Spelerpini within the subfamily Hemidactyliinae. Although the close relationship among the genera Stereochilus, Pseudotriton, and Gyrinophilus has long been recognized, the exact relationships of these three taxa remains contentious. Conclusions drawn from some morphological characters (e.g., cloacal anatomy; Sever 1986) are equivocal, but cranial osteology (Wake 1966) suggests that Gyrinophilus and Pseudotriton are more closely related to each other than either is to Stereochilus. Indeed, several molecular analyses (e.g., Bayesian, maximum likelihood, and maximum parsimony analyses of mitochondrial DNA [mtDNA] sequence data in Mueller et al. 2004; Bayesian analysis of mtDNA and nuclear markers in Steffen et al. 2014) have supported Gyrinophilus + Pseudotriton together as the sister group of Stereochilus, but other studies have recovered different relationships. Neighbor-joining (Baldwin 2002), maximum parsimony (Baldwin 2002; Macey 2005), and maximum likelihood (Baldwin 2002) analyses of mtDNA sequence data found support for Gyrinophilus as the sister group of Stereochilus, as did neighbor-joining and maximum likelihood inferences from a single nuclear locus (Baldwin 2002). In contrast, Camp et al. (2009) and Wray and Steppan (2017) used Bayesian analyses of mtDNA and nuclear DNA sequence data and estimated a sister relationship between Stereochilus and Pseudotriton, while Bonett et al. (2014) found a sister relationship between Stereochilus and P. montanus (and thus, the non-monophyly of Pseudotriton) using a Bayesian analysis of a single nuclear locus.

ETYMOLOGY:

The genus name comes from the Greek "stereos", which means “firm” or “solid” and the Greek "cheilos," which means “edge” or “lip”. Although the etymology was not explained in the description of the genus (Cope 1869), it may refer to the attachment of the tongue, which the author considered an important anatomical character (Rabb 1966).

The species epithet comes from the Latin "marginatus," which means “bordered” or “lined” (Rabb 1966). Likewise, the etymology was not explained in the description, but it likely refers to the “dusky white margined with black” pattern found on some individuals (Hallowell 1856).

References

Baldwin, A. S. (2002). Systematics of salamander genera Stereochilus, Gyrinophilus, and Pseudotriton (Plethodontidae) and phylogeography of Pseudotriton ruber (Order No. 3065618). Available from ProQuest Dissertations & Theses A&I; ProQuest Dissertations & Theses Global. (275991360). https://www.proquest.com/dissertations-theses/systematics-salamander-genera-i-stereochilus/docview/275991360/se-2

Bishop, S. C. (1943). Handbook of salamanders: the salamanders of the United States, of Canada, and of Lower California. Cornell University Press.

Bonett, R. M., Steffen, M. A., & Robison, G. A. (2014). Heterochrony repolarized: a phylogenetic analysis of developmental timing in plethodontid salamanders. EvoDevo, 5(1), 1-18. [link]

Brandon, R. A., & Huheey, J. E. (1981). Toxicity in the plethodontid salamanders Pseudotriton ruber and Pseudotriton montanus (Amphibia, Caudata). Toxicon, 19(1), 25-31. [link]

Brandon, R. A., Labanick, G. M., & Huheey, J. E. (1979). Relative palatability, defensive behavior, and mimetic relationships of red salamanders (Pseudotriton ruber), mud salamanders (Pseudotriton montanus), and red efts (Notophthalmus viridescens). Herpetologica, 35(4), 289-303. [link]

Bruce, R. C. (1971). Life cycle and population structure of the salamander Stereochilus marginatus in North Carolina. Copeia, 1971, 234-246. [link]

Camp, C. D., Peterman, W. E., Milanovich, J. R., Lamb, T., Maerz, J. C., & Wake, D. B. (2009). A new genus and species of lungless salamander (family Plethodontidae) from the Appalachian highlands of the south‐eastern United States. Journal of Zoology, 279(1), 86-94. [link]

Cope, E. D. (1869). A review of the species of the Plethodontidae and Desmognathidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 21, 93-118. [link]

Foard, T., & Auth, D. L. (1990). Food habits and gut parasites of the salamander, Stereochilus marginatus. Journal of Herpetology, 24(4), 428-431. [link]

Graham, S. P., Timpe, E. K., & Laurencio, L. R. (2010). Status and possible decline of the Southern Dusky Salamander (Desmognathus auriculatus) in Georgia and Alabama, USA. Herpetological Conservation and Biology, 5(3), 360-373. [link]

Hallowell, E. (1856). Descriptions of two new species of urodeles, from Georgia. Proceedings of the Academy of natural Sciences of Philadelphia, 8, 130-131. [link]

Macey, J. R. (2005). Plethodontid salamander mitochondrial genomics: a parsimony evaluation of character conflict and implications for historical biogeography. Cladistics, 21(2), 194-202. [link]

Maerz, J. C., Barrett, R. K., Cecala, K. K., & Devore, J. L. (2015). Detecting enigmatic declines of a once common salamander in the Coastal Plain of Georgia. Southeastern Naturalist, 14(4), 771-784. [link]

Means, D. B. (2000). Southeastern US Coastal Plain habitats of the Plethodontidae: The importance of relief, ravines, and seepage. The biology of plethodontid salamanders, 287-302. [link]

Means, D. B., & Travis, J. (2007). Declines in ravine-inhabiting dusky salamanders of the southeastern US coastal plain. Southeastern Naturalist, 6(1), 83-96. [link]

Mueller, R. L., Macey, J. R., Jaekel, M., Wake, D. B., & Boore, J. L. (2004). Morphological homoplasy, life history evolution, and historical biogeography of plethodontid salamanders inferred from complete mitochondrial genomes. Proceedings of the National Academy of Sciences, 101(38), 13820-13825. [link]

Noble, G. K., & Brady, M. K. (1930). The courtship of the plethodontid salamanders. Copeia, 1930(2), 52-54. [link]

Noble, G. K., & Richards, L. B. (1932). Experiments on the egg-laying of salamanders. American Museum Novitates; no. 513. [link]

Petranka, J. W. (1998). Salamanders of the united States and Canada. Smithsonian Institution Press.

Rabb, G. B. (1956). Some observations on the salamander, Stereochilus marginatum. Copeia, 1956(2), 119-119. [link]

Rabb, G. B. (1966). Stereochilus and S. marginatus. Catalogue of American Amphibians and Reptiles (CAAR).

Ryan, T. J. (2005). Stereochilus marginatus. Amphibian Declines: The Conservation Status of United States Species, 862.

Ryan, T. J., & Bruce, R. C. (2000). Life history evolution and adaptive radiation of hemidactyliine salamanders (pp. 303-326). Springer US. [link]

Schwartz, A., & Etheridge, R. (1954). New and additional herpetological records from the North Carolina Coastal Plain. Herpetologica, 10(3), 167-171. [link]

Sever, D. M. (1986). Disparate sexual variation among Gyrinophilus, Pseudotriton and Stereochilus (Amphibia: Plethodontidae). Herpetologica, 42(3), 301-323. [link]

Sever, D. M., Siegel, D. S., Taylor, M. S., & Beachy, C. K. (2016). Phylogeny of mental glands, revisited. Copeia, 104(1), 83-93. [link]

Steffen, M. A., Irwin, K. J., Blair, A. L., & Bonett, R. M. (2014). Larval masquerade: a new species of paedomorphic salamander (Caudata: Plethodontidae: Eurycea) from the Ouachita Mountains of North America. Zootaxa, 3786(4), 423-442. [link]

Wake, D. B. (1966). Comparative osteology and evolution of the lungless salamanders, family Plethodontidae. University of Southern California. [link]

Wood, J. T., & Rageot, R. H. (1963). The nesting of the many-lined salamander in the Dismal Swamp. Virginia Journal of Science, 14(1963), 121-125.

Wray, K. P., & Steppan, S. J. (2017). Ecological opportunity, historical biogeography and diversification in a major lineage of salamanders. Journal of Biogeography, 44(4), 797-809. [link]

Species Account Citation: AmphibiaWeb 2023 Stereochilus marginatus: Many-lined Salamander <https://amphibiaweb.org/species/4200> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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