Comal Blind Salamander
Country distribution from AmphibiaWeb's database: United States
Eurycea tridentifera Mitchell and Reddell, 1965
Paul T. Chippindale1
1. Historical versus Current Distribution. Comal Blind salamanders (Eurycea tridentifera) were described by Mitchell and Reddell (1965) from Honey Creek Cave, Comal County, Texas. Sweet (1977b, 1978a, 1984) extended the distribution of this species to include several other caves in the Cibolo Sinkhole Plain of the southeastern Edwards Plateau region (Comal and Bexar counties). Chippindale et al. (2000) listed additional cave localities for this species in the same area and suggested that this species probably extends into Kendall County. Sweet (1978a, 1984) demonstrated that populations assigned to this species cluster together based on morphometric analyses. Some authors (Mitchell and Reddell, 1965; Bogart, 1967; Mitchell and Smith, 1972) have suggested that additional species may be present within what is considered E. tridentifera. There has been some difference of opinion regarding the generic allocation of this species. Wake (1966) considered it a member of the genus Typhlomolge, but despite some external and osteological similarity to the two species that were once included in this genus, it is not as closely related to either "T." (now Eurycea) rathbuni or robusta as it is to other southeastern Edwards Plateau Eurycea. Bogart (1967), Mitchell and Smith (1972), and Sweet (1978a, 1984) discuss the placement of this species; Chippindale (1995, 2000), Chippindale et al. (2000), and Wiens et al. (in preparation) address relationships of E. tridentifera in an explicitly phylogenetic context. Generic boundaries in the central Texas hemidactyliine plethodontid salamanders have been controversial, but all species now are considered members of the genus Eurycea (see Chippindale, 1995, 2000; Chippindale et al., 2000; Chippindale and Price, 2003). All recent authors have considered this species a member of the genus Eurycea.
2. Historical versus Current Abundance. Assessment of abundance of Texas cave Eurycea is difficult, so no reliable assessments of past versus current abundance can be made. Individuals of this species appeared scarce during visits to the type locality in the early 1990s (personal observations), although Mitchell and Reddell (1965), Bogart (1967), and Sweet (1978a, 1984) were able to collect fairly large series at this site.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Unlikely to occur.
ii. Breeding habitat. Likely the same as adult habitat.
i. Egg deposition sites. Unknown; closely related species are thought to deposit eggs in gravel substrates.
ii. Clutch size. Bogart (1967) artificially induced hybridization between this species and Valdina Farms salamanders (E. troglodytes), and the resulting eggs developed and hatched. Approximately 7–18 mature ova are produced/clutch, and eggs hatch when embryos are about 7 mm SVL (Sweet, 1977b).
C. Larvae/Metamorphosis. Comal Blind salamanders are paedomorphic, and natural metamorphosis is unknown. Bogart (1967) reported that Comal Blind salamanders fail to metamorphose when treated with either thyroid hormone or pituitary implantation.
D. Juvenile Habitat. Probably same as adult habitat.
E. Adult Habitat. Comal Blind salamanders are found on rock and mud substrates in caves. Water temperature in waters of the Edwards Plateau is relatively constant throughout the year and typically ranges from 18–20 ˚C (Sweet, 1982).
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Unknown.
I. Seasonal Migrations. Unlikely to occur.
J. Torpor (Hibernation). Probably active throughout the year.
K. Interspecific Associations/Exclusions. At the outflow of the type locality, where Honey Creek Cave becomes a spring, surface Eurycea occur (Mitchell and Reddell, 1965; Bogart, 1967; Sweet, 1978a, 1984). Sweet (1978a, 1982, 1984) considered these to be Texas salamanders (E. neotenes). Chippindale (1995) and Chippindale et al. (2000) considered these a member of the E. latitans complex. At the cave entrance, individuals intermediate in morphology between E. tridentifera and the surface species have been found and hybridization between the two species seems likely (Sweet, 1978a, 1984).
L. Age/Size at Reproductive Maturity. Brandon (1971b) found that males are mature at 22 mm SVL and females at 25 mm; Sweet (1977b) reported maturity at 25–27 mm for males and 28–32 mm for females.
M. Longevity. Unknown.
N. Feeding Behavior. Prey probably consists mainly of small aquatic invertebrates, but no detailed feeding studies of this species have been conducted. Individuals often have large amounts of detritus in their stomachs, suggesting they may graze the substrate for tiny invertebrates (personal observations). Bogart (1967) found remains of insects in fecal matter and suggested that this species may eat bat guano. Specimens maintained by Bogart (1967) accepted liver as food.
O. Predators. Sweet (1978a, 1984) noted that Eurycea usually are absent from caves where fishes are present in the general area of the Edwards Plateau inhabited by Comal Blind salamanders. Bogart (1967) observed crayfish at the type locality, Honey Creek Cave, and suggested these as possible predators.
P. Anti-Predator Mechanisms. Sweet (1978a, 1984) reported that Comal Blind salamanders usually swim upward when disturbed. This contrasts with behavior of most other members of the group that swim toward the substrate or to cover when frightened. Sweet suggested that this may reflect the absence of fish predators in caves inhabited by Comal Blind salamanders.
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Assessment of abundance of Texas cave Eurycea, including Comal blind salamanders, is difficult, so no reliable assessments of past versus current abundance can be made. While historical collectors were able to collect fairly large series of individuals (Mitchell and Reddell, 1965;, Bogart, 1967; and Sweet, 1978a, 1984), Comal blind salamanders appeared scarce during visits to the type locality in the early 1990s. This species is listed as Threatened by the State of Texas, although it has not attracted federal attention.
1Paul T. Chippindale
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 14 Sep 2019.
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