Grotto Salamander, Ozark Blind Cave Salamander
© 2006 Michael Graziano (1 of 20)
Distribution and Habitat
Country distribution from AmphibiaWeb's database: United States
U.S. state distribution from AmphibiaWeb's database: Kansas, Missouri
Life History, Abundance, Activity, and Special Behaviors
The larval period lasts from 1 - 3 years (Brandon 1971) or 2 - 6 years or longer depending on locality and conditions. Adults are known to live for at least 12 years in captivity, but their lifespan in the wild is unknown. If E. spelaea is comparable to cave fish and crayfish their lifespan may be considerably longer, 20 - 25 years, than terrestrial salamanders as a response to energy resource limitations (Fenolio et al. 2014, Fenolio, personal communication).
This species is unique in that it starts life as a fully sighted larva but then metamorphoses underground into a terrestrial adult that loses its pigment and becomes blind, with the eyelids eventually fusing (Brandon 1970; 1971; Petranka 1998; Besharse and Brandon 2005). However, it is likely that some light sensitivity remains in the eye structures because adults have photophobic behavior. There three main hypotheses explaining why the eye forms but then becomes vestigial and loses its color. The first is that there is a link between the genes that code for skin pigment and eye pigment. However, this would not explain the loss of the structure in the eye. The second hypothesis is that early development of the eye plays a role in skull development. This hypothesis is supported by the fact that many blind cavefish also have eyes early in development that are completely loss after the skull is formed. The third hypothesis is that the loss of the eye helps the species conserve energy (Fenolio personal, communication). The energy economy hypothesis for loss of eyes was reviewed by Jeremy Niven (2015), who argued that the cost of developing and maintaining eyes is substantial as illustrated by a positive correlation in eye and brain size in fish in comparisons of cave, intermediate/hybrid, and terrestrial fish, which indicates that when eyes are present a substantial portion of the brain is needed for visual processing, and oxygen consumption rates. Energy savings from loss of eyes could reduce the amount of time needed for foraging and allow energy to be re-invested in other physiological processes, including reproduction. This hypothesis is reasonable for E. spelaea considering the resource limitation it experiences. Lastly, hypotheses two and three are not mutually exclusive and may both be accurate explanations (Fenolio, personal communication).
Grotto salamanders are most active during spring and summer months when moisture levels in caves are high, food is abundant, and courtship is taking place. Adults feed on aquatic and terrestrial invertebrates, including flies, mosquito larvae and beetles. Adults may function as a top predator in some cave systems. Predators have not been reported although larvae are likely to be vulnerable to crayfish (Brandon 1971; Petranka 1998).
The grotto salamander is most abundant in caves that harbor high numbers of bats (Hendricks and Kezer 1958; Bonett and Chippindale 2004; Brandon 1971). From late April to October, and particularly during the summer, gray bats (Myotis grisescens) make use of caves as maternity roosts (Hendricks and Kezer 1958; Bonett and Chippindale 2004; Brandon 1971). Bats deposit feces (guano) within the cave, leading to an increase in invertebrates associated with the guano. Grotto salamander larvae eat isopods, fly larvae, and snails (Brandon 1971; Petranka 1998), but in a highly unusual move for animals that are normally thought of as strictly carnivorous, grotto salamander larvae also consume bat guano (Fenolio et al. 2006). Bat guano is a source of high nutrition in a resource-poor environment (the cave) since bats have short digestive tracts and fast digestion times and do not extract the full nutritive value of food items. Guano has been found to contain twice the protein content and about two-thirds the calories of an equivalent volume of Big Mac hamburger. Microbial biofilms on the guano may provide extra nutritive value. The nutritive value of guano was found to be higher in terms of protein content, caloric density, and essential mineral content than a potential prey item, cave-dwelling gammarid amphipods (Fenolio et al. 2006).
Multiple species of helminth parasites (protozoans, trematodes, cestoids, nematodes, acanthocephalans) infecting E. spelaea have been noted (Dyer 1975; McAllister et al. 2006).
Trends and Threats
Possible reasons for amphibian decline
Habitat modification from deforestation, or logging related activities
Recent molecular studies have shown that it is a close relative of species of the genus Eurycea that occur nearby. It differs strikingly from these species in its larger size and cave-related features, but because it is phylogenetically nested within the Euryea multiplicata complex, Bonett and Chippindale placed it in Eurycea. Thus its name was change from Typhlotriton spelaeus to Eurycea spelaea (Bonett and Chippindale 2004).
In an alternative to Linnean classification, the name Typhlotriton could be retained as a clade name, for example in Phylocode. Because mitochondrial DNA sequence divergence within E. spelaea is relatively great, some of the populations might be recognized as distinct species (two additional species were described in the past but now included within E. spelaea; Bonett and Chippindale 2004).
Besharse, J. C., and Brandon, R. A. (2005). ''Postembryonic eye degeneration in the troglobitic salamander Typhlotriton spelaeus.'' Journal of Morphology, 144(381-405).
Bonett, R., and Chippindale, P. T. (2004). ''Speciation, phylogeography, and evolution of life history and morphology in plethodontid salamanders of the Eurycea multiplicata complex.'' Molecular Ecology, 13(5).
Brandon, R. A. (1970). ''Typhlotriton and T. spelaeus.'' Catalogue of American Amphibians and Reptiles. American Society of Ichthyologists and Herpetologists, 84.1-84.2.
Brandon, R. A. (1971). ''Correlation of seasonal abundance with feeding and reproductive activity in the Grotto Salamander (Typhlotriton spelaeus).'' American Midland Naturalist, 86(1), 93-100.
Dyer, W. G. (1975). ''Parasitism as an indicator of food sources in a cave-adapted salamander habitat.'' Bulletin of the Southern California Academy of Sciences, 74, 72-75.
Fenolio, D. B., Graening, G. O., Collier, B. A., and Stout, J. F. (2006). ''Coprophagy in a cave-adapted salamander; the importance of bat guano examined through nutritional and stable isotope analyses.'' Proceedings of the Royal Society B, 273, 439-443.
Fenolio, D.B., Niemiller, M.L., Bonett, R.M., Graening, G.O., Collier, B.A., Stout, J.F. (2014). ''Life history, demography, and the influence of cave-roosting bats on a population of the Grotto Salamander (Eurycea spelaea from the Ozark Plateaus of Oklamhoma (Caudata: Plethodontiade).'' Herpetological Conservation and Biology, 9(2), 394-405.
Hendricks, L. J., and Kezer, J. (1958). ''An unusual population of a blind cave salamander and its fluctuation during one year.'' Herpetologica, 14(1), 41-43.
Johnson, T.R. (2000). Amphibians and Reptiles of Missouri: 2nd Edition. Conservation Commission of Missouri, Jefferson City.
McAllister, C. T., Bursey, C. R., Trauth, S. E., and Fenolio, D. B. (2006). ''Helminth parasites of the grotto salamander, Eurycea spelaea (Caudata: Plethodontidae), from northern Arkansas and southern Missouri, U.S.A.'' Comparative Parasitology, 73, 291-297.
Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
Stejneger, L. (1892). ''Preliminary description of a new genus and species of blind cave salamander from North America.'' Proceedings of the United States National Museum, 15, 115-117.
Trauth, S. E., Robison, H. W., and Plummer, M. V. (2004). The Amphibians and Reptiles of Arkansas. The University of Arkansas Press, Fayetteville, Arkansas.
Written by Meredith J. Mahoney, additions by David B. Wake and K. Whittaker (molge AT yahoo.com), Museum of Vertebrate Zoology, UC Berkeley
First submitted 2004-03-20
Edited by Kellie Whittaker; updated by Ann T. Chang (2016-02-22)
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