Animal Diversity Web

Ge­o­graphic Range

The San Mar­cos Sala­man­der is en­demic to the source of the San Mar­cos River in Hays County, Texas. Dis­tri­b­u­tion for Eu­rycea nana is ex­tremely lim­ited, with pop­u­la­tions being found in ranges of only sev­eral hun­dred feet along this river within close prox­im­ity to San Mar­cos Spring. (Mitchell, 1990)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

This sala­man­der is char­ac­ter­is­ti­cally found in shal­low, al­ka­line springs carved out of lime­stone with sand and gravel sub­strates. The thick moss and algae that cover the shal­low pools around the springs pro­vide and ex­cel­lent habi­tat for Eu­ryca nana to not only find food for it­self, but also to keep it safe from preda­tors. Water tem­per­a­ture in the San Mar­cos and Comal Rivers are re­mark­ably sta­ble with tem­per­a­tures in close prox­im­ity to the springs being be­tween 21.0 to 21.5 de­grees Cel­sius. (Tupa and Davis 1976, Mitchell 1990) (Mitchell, 1990; Tupa and Davis, 1976)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• rivers and streams

Phys­i­cal De­scrip­tion

One of the lun­g­less sala­man­ders, Eu­rycea nana av­er­ages about 2 inches long, but may reach up to 3.25 inches. It is the small­est of the genus Eu­rycea. These sala­man­ders are slen­der, with short limbs, 5 toes on the rear feet, and 4 and the front. Gill fringes are promi­nent be­hind the head and there are also 16 to 17 costal grooves. It is light brown on its back, yel­low­ish white ven­trally, with pale yel­low flecks ob­vi­ous on the mid­line. Dis­tinc­tive large eyes have a dark ring around the lens. Males have more poorly de­fined men­tal and cau­dal he­do­nic glands than fe­males. De­vel­oped, pig­mented gills are main­tained through­out adult­hood, but gases are ex­changed al­most en­tirely through cu­ta­neous res­pi­ra­tion. The vents of males are lined with papil­lae, con­trast­ing with the smooth folds in fe­males. This species is voice­less and ear­less. (Mitchell 1990, Pe­tranka 1998, Bartlett and Bartlett 1999, Tupa and Davis 1976, Her­beck and Lar­son 1998)

• Other Physical Features
• endothermic
• ectothermic
• heterothermic
• bilateral symmetry

De­vel­op­ment

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

Males are sex­u­ally ma­ture at 19 to 23.5 mm and fe­males when they are longer than 21 mm. There is only vague in­for­ma­tion on the re­pro­duc­tion of Eu­rycea nana and eggs have never been found in na­ture. Strongly acyclic ovipo­si­tion and the pres­ence of gravid fe­males and very small lar­vae dur­ing every month of the year sug­gests that breed­ing oc­curs year round. There is not a pro­nounced peak in breed­ing. As has been ob­served in ar­ti­fi­cial habi­tats, the av­er­age egg clutch is 20 and the jelly-cov­ered eggs are usu­ally laid in stand­ing pools with thick veg­e­ta­tion. After a 24-day pe­riod in the eggs, lar­vae-like tad­poles emerge. (Mitchell 1990, Pe­tranka 1998, Tupa and Davis 1976) (Mitchell, 1990; Pe­tranka, 1998; Tupa and Davis, 1976)

• Key Reproductive Features
• iteroparous
• year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous

• Breeding season

  Breeding seems to occur year-round.

Be­hav­ior

The San Mar­cos Sala­man­der is typ­i­cally ac­tive in sur­face veg­e­ta­tion ex­cept in ex­treme win­ter weather where it stays be­neath un­der­wa­ter logs and boul­ders. It is often found sit­ting sta­tion­ary in algal veg­e­ta­tion wait­ing for prey, which it then quickly grabs and con­sumes. Pre­da­tion threats come mostly from local fish. The pri­mary preda­tors are sun­fish (Lep­omis), but bull­head cat­fish (Ameiu­rus melas) and large mouth bass (Mi­cropterus salmiodes) are also po­ten­tial threats. (Pe­tranka 1998, Tupa and Davis 1976) (Pe­tranka, 1998; Tupa and Davis, 1976)

• Key Behaviors
• natatorial
• motile
• sedentary

Food Habits

Lit­tle is known about the for­ag­ing be­hav­ior of Eu­rycea nana. It is car­niv­o­rous and has been found to feed mostly on am­phipods, midge fly lar­vae, and some aquatic snails (Pe­tranka 1998).

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods

• Animal Foods
• insects
• mollusks
• aquatic crustaceans

Con­ser­va­tion Sta­tus

The San Mar­cos Sala­man­der has been listed as a threat­ened species since July 14, 1980. Agri­cul­tural and urban de­vel­op­ment around the springs it in­hab­its are thought to be the biggest threats. These prob­lems, along with the fact that habi­tat is ex­tremely lim­ited, are be­com­ing more se­ri­ous as a rise in the human pop­u­la­tion in the area has also in­creased the de­mand for water in this semi-arid re­gion. Con­stant ground­wa­ter pump­ing could dry up the San Mar­cos, Aquarena, and Comal springs that sup­ply water to the San Mar­cos and Comal Rivers in a mat­ter of years. To help con­trol this grow­ing prob­lem, Hays County has been des­ig­nated a crit­i­cal habi­tat. Al­though threat­ened, the pop­u­la­tion seemed sta­ble with a count of 17,000-21,000 recorded in 1984. (Mitchell 1990)

• IUCN Red List

  Vulnerable
  More information

• US Federal List

  Threatened

Other Com­ments

Many as­pects of the be­hav­ior and life of the San Mar­cos Sala­man­der are poorly known and are under re­search at this time.

Con­trib­u­tors

Ste­fanie Pen­ning­ton (au­thor), South­west­ern Uni­ver­sity, Stephanie Fab­ri­tius (ed­i­tor), South­west­ern Uni­ver­sity.

Ref­er­ences

Bartlett, P., R. Bartlett. 1999. A Field Guide to Texas Rep­tiles and Am­phib­ians. Hous­ton, Tx: Gulf Pub­lish­ing Com­pany.

Her­beck, L., D. Lar­son. June 1999. Pletho­d­on­tid Sala­man­der Re­sponse to Sil­vi­cul­tural Prac­tices in Mis­souri Ozark Forests. Con­ser­va­tion Bi­ol­ogy, 13(3): 623-632.

Mitchell, R. 1990. WWF Guide to En­dan­gered Species. Wash­ing­ton, D.C.: Beacham Pub­lish­ing, Inc.

Pe­tranka, J. 1998. Sala­man­ders of the United States and Canada. Wash­ing­ton, D.C.: Smith­son­ian In­sti­tu­tion Press.

Tupa, D., W. Davis. 1976. Pop­u­la­tion Dy­nam­ics of the San Mar­cos Sala­man­der, Eu­rycea nana Bishop. The Texas Jour­nal of Sci­ence, 27: 179-194.