Ambystoma texanum (Matthes, 1855)
Small-Mouthed Salamander, Smallmouth Salamander
|Species Description: Matthes, B. 1855. Die Hemibatrachier im Allgemeinen und die Hemibatrachier von Nord-Amerika im Speciellen. Allgemeine Deutsche Naturhistorische Zeitung, Neue Serie 1: 249–280.|
© 2006 Henk Wallays (1 of 47)
In comparison to other salamanders in the Ambystoma genus such as A. jeffersonianum, A. talpoideum, and A. laterale, A. texanum has much shorter toes and a smaller snout and head. Ambystoma texanum also has a unique groove from the nostril to the lip that separates it from similarly patterned lungless salamanders (Conant and Collins 1998). The most similar species to A. texanum is A. barbouri, however they differ in habitat preferences and oviposition locations, where A. texanum prefers ponds and they deposit their eggs on vegetation above the water, A. barbouri prefers streams and they deposit their eggs cryptically underneath flat rocks such as limestone. The most consistent difference between the two is that A. barbouri has short cusps on their maxillary-premaxillary teeth and A. texanum has long cusps (Kraus and Petranka 1989).
In life, A. texanum is a very dark brown or black with a gray lichen-like pattern (Conant and Collins 1998). These markings tend to be emphasized on the lower sides of the body and the dorsum. The ventral skin is the same dark brown color, but it doesn’t have the strong gray markings (Petranka 1998).
Females are in general slightly larger than males by about 3 - 11%, and during breeding season, males have obviously swollen, papillose vents (Petranka 1989). Their coloration also varies depending on the population. Ambystoma texanum from the northeastern part of the range are more black with very few gray markings, and ones from Texas are extremely speckled with the pattern being large (Conant and Collins 1998).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Canada, United States
U.S. state distribution from AmphibiaWeb's database: Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Michigan, Missouri, Mississippi, Nebraska, Ohio, Oklahoma, Tennessee, Texas, West Virginia
Canadian province distribution from AmphibiaWeb's database: Ontario
Ambystoma texanum is found in the northern and midwest regions of the United States, specifically in the Great Lakes region in Michigan, most westerly in eastern Nebraska, most southerly in Texas, and most easterly in Tennessee (Conant and Collins 1998). There are geographically isolated populations in southeastern Indiana, southern Ohio, and western West Virginia (Petranka 1998). There is also a population in Canada on Pelee Island, Ontario in Lake Erie (Conant and Collins 1998). They are most commonly found in the bottomland forests and the associated wetlands of floodplains (Petranka 1989).
Life History, Abundance, Activity, and Special Behaviors
In response to predators, A. texanum tends to seek refuge in substrate that matches its color in order to camouflage (Garcia and Sih 2003). Their main predators are predatory fish that have been introduced to their pond habitats, but they have been observed to have a prolonged larval period and increased reproductive success once the fish have been removed (Walston and Mullin 2007).
Ambystoma texanum is a late winter and spring breeder, and has been observed to travel to floodplains for this season and then travel back (Conant and Collins 1998; Plummer 1977). In a particular Kansas population, they travel south to the fields of the Wakarusa River floodplain and then back north as the season progressed (Plummer 1977). Females also have more incidences of multiple mating than males, and a correlation between reproductive success and mating success has been found (Gopurenko et al. 2007).
Females tend to deposit their eggs in small clumps on vegetation near lentic water and clutch size varies from 350 to 900 eggs (Kraus and Petranka 1989).
Ambystoma texanum hatch at Harrison stage 39 and have total length ranges from 7 to 14 mm (Petranka 1998; Kraus and Petranka 1989; Harrison 1969).
Hatchlings are an olive green to brownish color (Petranka 1998; Kraus and Petranka 1989; Harrison 1969). They have about three to six saddle markings in an olive green to light yellowish color along the midline of the dorsum. Older larvae become a light brown color and the saddle markings become diffuse and they gain a weak brown stripe along the sides of the body. Metamorphs are brown to brownish gray, and juveniles gain the lichen-like light gray pattern of the adults a few weeks after transforming (Petranka 1998).
Trends and Threats
Ambystoma texanum is currently listed as “Least Concern” by the IUCN. Similar salamander species, such as A. barbouri, that live in similar habitats have been under threat by urbanization and thus habitat fragmentation and destruction (Kraus and Petranka 1989).
Recently, a parasite has been found to be infecting a certain genome of unisexuals Ambystoma, as well as A. texanum. This parasite is part of the order Dermocystida, however the full effects of this parasite on these populations is still unknown (Adamovicz 2020).
The main predators of A. texanum are introduced predatory fish. This tends to result in a shorter larval period and decreased reproductive success, but they have been observed to recover once the fish have been removed (Walston and Mullin 2007).
Ambystoma texanum is part of the subgenus Linguaelapsus, and its relationship to A. barbouri is not entirely clear. Originally, they were thought to be two sister species, however due to recent Maximum Likelihood and Bayesian analyses using D-loop mitochondrial, it has shown the possibility of A. texanum being nested in a A. barbouri clade. In contrast, using genome-wide SNP data, the original idea of them being sister species is supported. These contradicting analyses make the relationship between the two species unclear (Hubbs et al. 2022).
The confusion in the phylogenetic placement of A. texanum maybe in part because 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).
The genus name “Ambystoma” comes from the Greek roots “amblys” for blunt and “-stoma” for mouth (Illinois Natural History Survey).
The species epithet “texanum” comes from New Latin meaning “of Texas” (Illinois Natural History Survey).
Adamovicz, L., Woodburn, D. B., Herrera, S. V., Low, K., Phillips, C. A., Kuhns, A. R., Crawford, J. A., and Allender, M. C. (2020). "Characterization of Dermotheca sp. Infection in a midwestern state-endangered salamander (Ambystoma platineum) and a co-occurring common species (Ambystoma texanum)." Parasitology, 147(3), 360-370. [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]
Conant, R. and Collins, J.T. (1998). A Field Guide to Reptiles and Amphibians of Eastern and Central North America. 3rd Edition. Houghton Mifflin Company, Boston, Massachusetts.
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]
Gopurenko, D., Williams, R. N., and DeWoody, J. A. (2007). "Reproductive and Mating Success in the Small-Mouthed Salamander (Ambystoma texanum) Estimated via Microsatellite Parentage Analysis." Evolutionary Biology, 34, 130-139. [link]
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]
Illinois Natural History Survey (2022). "Ambystoma texanum (Matthes, 1855)." "." INHS Herpetology Collection [link]
Kraus, F. and Petranka, J.W. (1989). "A New Sibling Species of Ambystoma from the Ohio River Drainage." Copeia, 1989(1). [link]
Matthes, B. (1855). “Die Hemibatrachier im Allgemeinen und die Hemibatrachier von Nord-Amerika im Speciellen.” Allgemeine Deutsche Naturhistorische Zeitung, Neue Serie 1: 249–280.
Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.
Plummer, M. V. (1977). "Observations on breeding migrations of Ambystoma texanum." Herpetological Review, 8, 79-80.
Walston, L. J. and Mullin, S. J. (2007). "Responses of a Pond-breeding Amphibian Community to the Experimental Removal of Predatory Fish." The American Midland Naturalist, 157(1), 63-73. [link]
Originally submitted by: Nessa Kmetec (2022-11-15)
Description by: Nessa Kmetec (updated 2022-11-15)
Distribution by: Nessa Kmetec (updated 2022-11-15)
Life history by: Nessa Kmetec (updated 2022-11-15)
Larva by: Nessa Kmetec (updated 2022-11-15)
Trends and threats by: Nessa Kmetec (updated 2022-11-15)
Comments by: Nessa Kmetec (updated 2022-11-15)
Edited by: Ann T. Chang, Michelle S. Koo (2023-01-01)
Species Account Citation: AmphibiaWeb 2023 Ambystoma texanum: Small-Mouthed Salamander <https://amphibiaweb.org/species/3849> University of California, Berkeley, CA, USA. Accessed Oct 2, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Oct 2023.
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