Description

Ambystoma barbouri is a salamander with a standard length of around 90 mm and a total length of about 110 - 170 mm (Petranka 1998). The species is overall similar in appearance to A. texanum. Ambystoma barbouri have 14 - 15 costal grooves on each side and have a small head with a rounded snout. Their eyes are located laterally and are directed anteriorly. Their limbs are adpressed and they have four toes per limb (Kraus 1996).

Ambystoma barbouri can be distinguished from other Ambystoma species, except for A. texanum, A. cingulatum, and A. annulatum, by having multiple rows of teeth on the maxillary, premaxillary, and dentary bones. It differs from all Ambystoma species other than A. texanum and A. mabeei by its coloration and markings on its dorsum (Kraus and Petranka 1989).

The most similar species to A. barbouri is A. texanum. Originally, A. barbouri was called “the stream form”, in contrast to the typical “pond form”, of A. texanum (Petranka 1982). This is in reference to their habitat, where A. texanum inhabits pond areas and A. barbouri inhabits stream areas. They also differ in their locations for oviposition. Ambystoma texanum typically deposits its eggs on clumps of vegetation in exposed areas, while A. barbouri deposits its eggs cryptically under large, flat rocks, although some A. texanum individuals have been observed depositing eggs like A. barbouri. They also differ in larvae size and A. barbouri hatch at a later development stage. The main difference between the two is that A. barbouri has short cusps on its maxillary-premaxillary teeth and A. texanum has long cusps (Kraus and Petranka 1989). Additionally, although they look externally very similar to A. texanum, most often A. barbouri is of a darker color (Garcia and Sih 2003). They also have a more rounded tail, a wider and rounded snout, a greater distance between the nares, and more obvious costal grooves and folds than A. texanum (Petranka 1998).

In life, they are a grayish brown to grayish black on their dorsum with tan or light gray lichen-like markings overlain on top (Petranka 1998).

Ambystoma barbouri exhibits some color change to match their background, most often hiding in darker substrates and then changing to a darker color (Garcia and Sih 2003). The females are also slightly bigger than males by about eight percent (Petranka 1998). In terms of habitat, while they are most common and likely to be found in streams, there have been instances of populations inhibiting ponds (Kraus and Petranka 1989).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: Indiana, Kentucky, Ohio, Tennessee, West Virginia

View distribution map in BerkeleyMapper.

Ambystoma barbouri are found in central Kentucky, southwesternmost Ohio, southeasternmost Indiana, and there’s also geographical isolates in Livingston County, Kentucky and in westernmost West Virginia (Kraus 1996). There have also been reports of populations in central Tennessee (Altig and McDiarmid 2015). The species inhabits in upland, deciduous forests in regions with streams that have natural barriers that prevent the movement of predatory fish. The habitat also includes large, flat rocks for oviposition, most often limestone (Kraus and Petranka 1989). Adults are found in upland deciduous forests with rolling topography, and are rarely found in areas where the surrounding forest has been removed (Petranka 1998).

Life History, Abundance, Activity, and Special Behaviors

In response to predators, such as sunfish, A. barbouri prefers to hide in darker substrates, and they then change to a darker color in order to camouflage better (Garcia and Sih 2003).

They have a prolonged breeding season from late December to early April. Most frequently, they breed in streams and deposit their eggs on the undersides of large, flat rocks, such as limestone, but they have also been observed in ponds. In both cases, they deposit eggs in the same cryptic manner. Courtship is thought to occur underneath large, flat rocks, which is where males deposit spermatophores, and there is relatively less nudging behavior from females in comparison to other Ambystoma species, which is thought to be an adaptation for living in streams (Kraus and Petranka 1989).

Larva

Ambystoma barbouri hatches around Harrison stages 41 or 42 (Harrison 1969) and they weigh about 27 mg. Their egg clutches average about 262 eggs and hatch in one and a half to two months (Kraus and Petranka 1989, Altig and McDiarmid 2015). They metamorphose in about 4 to 10 weeks, depending on temperature, and have a total length of about 40 mm. The larvae also have 14 - 15 costal grooves, similar to the adults (Altig and McDiarmid 2015).

Laval A. barbouri are larger in size than A. texanum and A. barbouri hatch at a later development stage (Kraus and Petranka 1989).

Larvae are darkly pigmented with greenish brown on their dorsum and have three to six saddle-like markings on their middorsal region. These markings tend to fade as the larva develop, and metamorphs are solidly brown to brownish gray. They begin to acquire the adult color patterns three to six weeks after transformation (Petranka 1998).

The larvae respond to predators in the same manner as adults, hiding in darker substrates and changing to a darker color in order to camouflage better (Garcia and Sih 2003).

Trends and Threats
Ambystoma barbouri is negatively affected by habitat loss, pollution from pesticides, and low genetic diversity. More specifically, habitat loss to urbanization is a major threat to A. barbouri. Already several populations have been extirpated because of this, such as populations in Hamilton and Adams county, Ohio (Kraus and Petranka 1989). Ambystoma barbouri has been found to adapt poorly to environmental changes (Beer et al. 2021).

Lots of pesticides have been found to negatively affect A. barbouri. After being exposed to 40 μg/L of atrazine or greater, they had greater activity, fewer water-conserving behaviors, and they had accelerated water loss both four and eight months after the exposure (Rohr and Palmer 2009). When embryos were exposed to high concentrations of carbaryl, endosulfan, or octylphenol, hatching was delayed, larval survival decreased, growth rates decreased, larvae had limb deformities, and the nervous system would malfunction. Behavior in terms of activity level and refuge use also changed as a result of exposure to these chemicals, which is indicative of the nervous system malfunctions (Rohr et al. 2003).

Lastly, A. barbouri have isolated populations with poor gene diversity. Assisted migration has been suggested as a conservation measure (Beer et al. 2021).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Urbanization
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Long-distance pesticides, toxins, and pollutants

Comments

Ambystoma barbouri was previously thought to be a sister species to A. texanum, however, various analyses since the 1990s has called that into question (Jones et al. 1993, Hubbs et al. 2022). Furthermore, unisexual Ambystoma was also shown to be nested within A. barbouri, however, the exact relationship has not been explored. A 2022 study using genome-wide SNP data and multivariate analyses and Bayesian assignment supported the initial findings that A. barbouri and A. texanum are sister species, however, their D-loop mtDNA analyses found that A. texanum was nested within A. barbouri. Overall, the phylogenetic relationship of A. barbouri and A. texanum is unclear because of contradicting data from mitochondrial and nuclear analyses. In all of these analyses, A. barbouri was separated into three distinct clusters of its northern, central, and southern Tennessee populations. The Kentucky populations were most similar to the central and southern Tennessee populations with the northern Tennessee populations being the most different, most likely due to the barrier to gene flow of the Cumberland River (Hubbs et al. 2022).

In the Ambystoma genus, there are unisexual populations that can hybridize with A. jeffersonianum, A. laterale, A. texanum, A. trigrinum, and A. barbouri to create ploidy-elevated offspring. They can range from diploid to pentaploid and there are over 20 different nuclear genomic combinations. Most Ambystoma unisexuals have an A. laterale nuclear genome, while the other types of donated genomes can replace each other, as seen in recent populations of A. barbouri being the replacement donor for A. jeffersonianum. Ambystoma unisexuals’ mtDNA is most similar to A. barbouri, however A. barbouri is the least common sperm donor. Tetraploid and pentaploid unisexuals tend to have a higher mortality rate than triploid unisexuals (Bogart et al. 2009). Ambystoma barbouri is also the most recent ancestor of the unisexual Ambystoma, originating about 25,000 years ago (Robertson et al. 2006).

Ambystoma barbouri was named after Dr. Roger W. Barbour for his contributions to the natural history of Kentucky (Kraus and Petranka 1989).

References

Altig, R. and McDiarmid, R.W. (2015). Handbook of Larval Amphibians of the United States and Canada. Comstock Publishing, Ithaca, NY.

Beer, M. A., Kane, R. A., Micheletti, S. J., Kozakiewicz, C. P., and Storfer, A. (2021). "Landscape genomics of the streamside salamander: Implications for species management in the face of environmental change." Evolutionary Applications, 15(2). [link]

Bogart, JP, Bartoszek, J, Noble, DWA, Bi, K (2009). "Sex in unisexual salamanders: discovery of a new sperm donor with ancient affinities." Heredity, 103, 483-493. [link]

Garcia, T. S. and Sih, A. (2003). "Color Change and Color-Dependent Behavior in Response to Predation Risk in the Salamander Sister Species Ambystoma barbouri and Ambystoma texanum." Oecologia, 137(1). [link]

Harrison, R. (1969) "Harrison Stages and Description of Normal Development of the Spotted Salamander, Ambystoma punctatum (Linn)." In: Wilens, S., Ed., Organization and Development of the Embryo, Yale University Press, New Haven, 44-66.

Hubbs, N. W., Hurt, C. R., Niedzwiecki, J., Leckie, B., and Withers, D. (2022). "Conservation genomics of urban populations of Streamside Salamander (Ambystoma barbouri)." PLoS ONE, 17(6). [link]

Jones, T. R., Kluge, A. G., and Wolf, A. J. (1993). "When Theories and Methodologies Clash: A Phylogenetic Reanalysis of the North American Ambystomatid Salamanders (Caudata: Ambystomatidae)." Systematic Biology, 42(1), 92-102. [link]

Kraus, F. (1996). "Ambystoma barbouri Kraus and Petranka. Streamside Salamander." Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 621.1-621.4.

Kraus, F. and Petranka, J.W. (1989). "A New Sibling Species of Ambystoma from the Ohio River Drainage." Copeia, 1989(1). [link]

Petranka, J. W. (1982). "Geographic Variation in the Mode of Reproduction and Larval Characteristics of the Small-Mouthed Salamander (Ambystoma texanum) in the East-Central United States." Herpetologica, 38(4), 475-485. [link]

Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.

Robertson, A.V., Ramsden, C., Niedzwiecki, J., Fu, J., and Bogart, J.P. (2006). "An unexpected recent ancestor of unisexual Ambystoma." Molecular Ecology, 15(11). [link]

Rohr, J. R. and Palmer, B. D. (2009). "Aquatic herbicide exposure increases salamander desiccation risk eight months later in a terrestrial environment." Environmental Toxicology and Chemistry, 24(5). [link]

Rohr, J. R., Elskus, A. A., Shepherd, B. S., Crowley, P. H., McCarthy, T. M., Niedzwiecki, J. H., Sager, T., Sih, A., and Palmer, B. D. (2009). "Lethal and sublethal effects of atrazine, carbaryl, endosulfan, and octylphenol on the streamside salamander (Ambystoma barbouri)." Environmental Toxicology and Chemistry, 22(10). [link]

Species Account Citation: AmphibiaWeb 2022 Ambystoma barbouri: Streamside Salamander <https://amphibiaweb.org/species/3827> 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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