Eurycea sosorumBarton Springs Salamander

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Geographic Range

Barton Springs of Zilker Park in Austin, Travis County, Texas. E. sosorum is restricted to and only found in two (Parthenia and Eliza) of the four hydrologically connected pools collectively named Barton Springs. E. sosorum is the only extant salamander species found in these two pools. No evidence exists that indicates E. sosorum is found anywhere else. This means that E. sosorum has the smallest habitat of any vertebrate in the world. (Chippindale et al 1993; Deanna Chamberlain, personal communication)

Habitat

E. sosorum prefers clear waters and is mostly concentrated near the spring openings where food supplies are abundant, water chemistry and temperatures are constant and access to surface and subsurface habitats is available. Barton Springs salamanders are also found under rocks and gravel immediately adjacent to main spring outflows and within aquatic vegetation and algae mats. E. sosorum lives in water depths ranging from 0.1 to 5 meters. The springs where the salamanders are found flow year long and remain at a constant temperature of twenty degrees Celsius. E. sosorum in generally not found on exposed on limestone surfaces or in silted areas within the pools. Monthly population counts done by the city of Austin show that the Parthenia pool population may range anywhere from 90 - 150 salamanders and the Eliza pool has an average population of 30 salamanders. (Deanna Chamberlain personal communication; Rogers 1997)

  • Aquatic Biomes
  • rivers and streams

Physical Description

The average length of the Barton Springs salamander is 6.35 cm. The organism is small and is known for its fairly small head, reduced eyes (with a golden iris and black mottling), shovel-nosed snout, slender body and elongate limbs. E. sosorum has a very distinctive dorsal coloration known as the "salt and pepper" effect. Dorsal color varies in life from dark through medium gray to purplish gray or gray-brown to yellowish brown to yellowish cream. The varied degrees of blotched and mottled specks are attributed to an irregular mixture of (or lack of) melanophores, iridophores and pigment gaps. Overall, the mottled pattern gives the salamander olive brown specks with a base color of yellowish cream. The presence of silvery-white iridophores enhances the salamanders' luster. Some salamanders appear pale due to the lack of melanophores. The trunk of E. sosorum is finely speckled with melanophores while the ventral surface is creamy to translucent in color. Sometimes the stomach contents, as well as the presence of eggs in females, can be seen through the translucent skin. Dorsally, the limbs of E. sosorum, are unevenly speckled as well as the toes. Ventrally, the limbs are not speckled. In addition the relatively short tail of E. sosorum has an uneven distribution of melanophores. On the ventral surface of the tail the salamander has a narrow, orange-yellow strip from the posterior margin of cloacal vent to the tip. Furthermore, unique traits of barton spring salamanders include: three pairs of brightly-colored, red gills, four fingers on each hand, five toes on each foot and 16 pre-sacral vertebrae. These traits set Eurycea sosorum apart from other Central Texas Eurycea. (Petranka 1998; Deanna Chamberlain, personal communication; Chippindale et al 1993)

Development

Reproduction

Not many details of the reproduction of E. sosorum are known. This is due to the secretive and nocturnal nature of salamanders in general. In the wild, females have been found holding, at the maximum, forty eggs from September through January. It is known that females carry their eggs for a year before depositing them It takes one year for larvae to reach sexual maturity and all sexually mature individuals that have been found have been longer than 22.5 mm. Also in their native habitat, young hatchlings have been found in November, March and April. This evidence suggests that breeding takes place year round. In the wild, no deposited eggs have ever been found or seen. It is believed the E. sosorum may deposit it's eggs in the Edwards Aquifer which feeds the pools where they live. The Edwards Aquifer is a karst aquifer which means that it is very porous. Due to the small size of the salamander this hypothesis could be true. However, in captivity Barton Spring salamanders deposit their eggs on plastic plants in string-like clusters. The eggs are 1.5 mm in diameter and are surrounded by two jelly layers. They are easily observed because of their white color and iridiscent properties.

(Deanna Chamberlain, personal communication; Bishop 1967; Petranka 1998)

As of 1999, in captive-breeding programs, females have deposited eggs twenty times. Of the eggs deposited, larvae only developed twice and none survived to sexual maturity. What has been noted in the embryos is that after 19 days eyes develop and then, after 38 days, limb bud and gill structure is observed.

(Deanna Chamberlain, personal communication)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

E. sosorum is neotenic and permanently aquatic. E. sosorum is also a spring surface-dweller that makes extensive use of the spring habitat but, appears well-suited for underground living also. Not much is known about the behavior of E. sosorum.

(Chippindale 1995; Petranka 1998; Deanna Chamberlain, personal communication)

Food Habits

The diet of E. sosorum consists primarily of the small invertebrate Hyalla azteca, an amphipod. E. sosorum also feeds on snails, crustaceans, black worms, leeches and bug larvae. In captivity the salamanders feed on earthworms, brine shrimp, white worms and commercial food pellets. Predators of E. sosorum are small fish and crayfish. (Deanna Chamberlain, personal communication; Bishop 1967; Rogers 1997)

Economic Importance for Humans: Negative

Since the placement of E. sosorum on the U.S. ESA endangered species list, major restrictions have taken place on the urban development within the main watersheds of the Edwards Aquifer in Austin, TX. (Rogers 1997)

Conservation Status

Barton Springs salamanders have been proclaimed an endangered species by the U.S. Fish and Wildlife Service. E. sosorum was first found in Barton Springs during the 1940's, and numbered in the hundreds. However, in the past decade, fewer than 20 specimens were observed over six month periods and none at other times. In addition, the number of dead salamanders found was increasing. The drastic decrease in the E. sosorum population was credited to the decrease in water quality and quantity of the Edwards Aquifer and even more specifically the Barton Creek Watershed which feeds the aquifer. This decline is the result of increased urbanization and environmental pollution. Also, improper cleaning of the Parthenia pool of Barton Springs (used for recreational swimming) drastically disturbed the chemical and physical equilibriums of the salamanders' habitat. In the past two to three years environmental activists have petitioned for environmentally safer ways for cleaning the pool, bringing greatly needed attention to the water quality and quantity issues concerning Barton Springs as well as the Edwards aquifer. (Rogers 1997; Deanna Chamberlain, personal communication)

Other Comments

Even though Barton Spring Salamanders have been observed in their natural habitat for the last fifty years, it was not until 1993 that E. sosorum was formally declared a separate species. In the Central Texas area other Eurycea salamanders such as E. neotenes and E. nana are in similar positions such as E. sosorum in that they are extremely environmentally sensitive organisms, limited to one or two populations, which makes them vulnerable to extinction. One major environmental disaster in any of the watersheds that feed the Edwards aquifer (that in turn feeds the springs where these salamanders live) could possibly eliminate the already dwindling populations. An interesting sidenote is that the species name of Eurycea sosorum came from Austin legislation during the early 1990's, known as Save Our Springs (S.O.S.), in regards to increasing environmental protection over Barton Springs. (Rogers 1997; Petranka 1998; Bishop 1967; Chippindale et al 1993)

Contributors

Jessica Drake (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Bishop, S. 1967. The Salamanders of the United States, of Canada and of Lower California. Ithaca, New York: Comstock Publishing Associates.

Chippindale, Paul Thomas, 1995. Evolution, Phylogeny, Biogeography and Taxonomy of Central Texas Spring and Cave Salamanders: Eurycea and Trypholomolge. University of Texas, Austin: Unpublished dissertation.

Chippindale, P., D. Hillis, A. Price. 1993. A New Species of Perennibranchiate Salamander (Eurycea: Plethodontidae) from Austin, Texas. Herpetologica, 49; 2: 248-259.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington, DC: Smithsonian Institute Press.

Rogers, J. 1997. "Final Rule, Barton Springs Salamander" (On-line). Accessed September 21, 1999 at http://www.fws.gov/r9endspp/r/fr97612.html.