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Satan eurystomusTexas blind catfish

By R. Brian Lawson

Geographic Range

Satan eurystomus is known only from the Edwards Aquifer in Bexar County near San Antonio, Texas. (Page and Burr, 1991)

Habitat

Widemouth blindcats live in the fresh waters of the subterranean Edwards Aquifer. These waters ranges from 305 to 582 m below the surface. (Page and Burr, 1991)

  • Aquatic Biomes
  • rivers and streams
  • Other Habitat Features
  • caves
  • Range depth
    -305 to -582 m
    -1000.66 to -1909.45 ft

Physical Description

Widemouth blindcats generally have similar physical characteristics to other members of the Family Ictaluridae. The most notable difference being that they have no eyes. They are white or pink in color because they lack skin pigmentation. The head is wide and flat and they have barbels. The lips thicken at the corners and the mouth appears as if they have a slight overbite. The gills have separate membranes and contain strong folds. The adipose fin is high and long while the anal fin is rounded and short, with approximately 20 rays. The caudal fin is either slightly notched or straight. (Langecker and Longley, 1993; Page and Burr, 1991)

  • Range length
    30 to 117 mm
    1.18 to 4.61 in
  • Average length
    70 mm
    2.76 in

Development

The life cycle is similar to that of other ictalurids. They reproduce sexually. Similar troglobitic fish species have fewer, larger eggs. Some of these species have a low proportion of reproductive females per reproductive event and slower growth rates. (Trajano, 2001)

Reproduction

Little is known about the mating system of widemouth blindcats. It has not been studied in the natural habitat. Specimens which have been studied appeared to be juveniles, having not reached sexual maturity. Among ictalurids, both monogamy and polygamy have been observed. Spawning season usually varies by habitat. ("Freshwater Fishes of Virginia", 2007; Langecker and Longley, 1993; Trajano, 2001)

Little is known about the reproduction of widemouth blindcats. (Trajano, 2001)

Little is known about parental investment in widemouth blindcats. In most ictalurid species, parental care has been seen, although it varies among species and sexes. ("Freshwater Fishes of Virginia", 2007; Trajano, 2001)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

Little is known about the lifespan and longevity in Satan eurystomus. Slower growth and longer life than related species has been seen in similar troglobitic fish species. (Trajano, 2001)

Behavior

Little is known about the behavior of widemouth blindcats. It has been suggested that they prey on toothless catfish (Trogloglanis pattersoni), which would be the first example of troglobitic fishes interacting as predator and prey. (Langecker and Longley, 1993; Trajano, 2001)

Home Range

It is unknown how large of an area this species occupies in its aquifer. Consequently, territorial defense and territory size are also unknown. They are assumed to be rather sedentary. (Langecker and Longley, 1993)

Communication and Perception

Little is known about communication and perception in Satan eurystomus. The species is only observed when specimens emerge from artesian wells and are caught in nets. Most that are caught are already dead by the time they are observed by scientists. Widemouth blindcats lack eyes, however, most ictalurid catfishes have well developed olfactory and tactile senses (including their barbels) that widemouth blindcats may also use to navigate their subterranean environment. There are also lateral-line canals and pores on the head, suggesting they use this mode of perception. (Langecker and Longley, 1993)

Food Habits

Widemouth blindcats are carnivores and detritivores. Upon examining the stomach contents of a few specimens, a mudlike substance was observed, as well as the exoskeletons of crustaceans. There are several known species of crustaceans found in the waters of the Edwards Aquifer, such as Stygobromus russelli. Widemouth blindcats are also able to store extra fat due to a reduced gas bladder. This helps the fish to store more energy when food is scarce. Widemouth blindcats may be top predators in the Edwards Aquifer. (Langecker and Longley, 1993; Reddell, 1994; Trajano, 2001)

  • Animal Foods
  • aquatic crustaceans

Predation

There are no known predators of Satan eurystomus.

Ecosystem Roles

Widemouth blindcats are possibly the top predators of the San Antonio pools of the Edwards Aquifer. (Langecker and Longley, 1993; Trajano, 2001)

Economic Importance for Humans: Positive

Satan eurystomus provides no positive economic importance for humans directly, although they are important members of a unique and amazing subterranean ecosystem. Cave fishes are important in the study of evolution.

Economic Importance for Humans: Negative

There are no known adverse effects of Satan eurystomus on humans.

Conservation Status

Widemouth blindcats are considered vunerable due to their extreme endemicity and the threat of pollution from agricultural and industrial runoff into the Edwards Aquifer. (Proudlove, 2001)

Other Comments

Satan eurystomas is an odd name. The Latin name is translated as "widemouth prince of darkness". Carl Hubbs, who named this species, seemed to have an affinity for giving diabolical names to cave fishes. His reasoning for this was that Hell was underground. Considering that widemouth blindcats live exclusively in darkness and may be the apex predator in this habitat, the name "widemouth prince of darkness" may turn out to be more accurate than first imagined. (Romero, 2008)

Contributors

R. Brian Lawson (author), Radford University, Karen Powers (editor), Radford 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

acoustic

uses sound to communicate

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

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

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

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

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

vibrations

movements of a hard surface that are produced by animals as signals to others

References

American Fisheries Society. 2007. Freshwater Fishes of Virginia. Bethesda, Maryland: American Fisheries Society.

Fish and Wildlife Service. Endangered and Threatened Wildlife and Plants: 90-day Finding for a Petition to List the Robust Blind Salamander, Widemouth Blindcat, and Toothless Blindcat.. 98-24120. Washington, D.C.: Department of the Interior. 1998. Accessed February 02, 2010 at http://fdsys.gpo.gov/fdsys/pkg/FR-1998-09-09/pdf/98-24120.pdf.

Hardman, M., L. Hardman. 2008. The Relative Importance of Body Size and Paleoclimatic Change as Explanatory Variables Influencing Lineage Diversification Rate: An Evolutionary Alaysis of Bullhead Catfishes (Siluriformes: Ictaluridae). Systematic Biology, 57/1: 116-130.

Hubbs, C. 1957. Distributional Patterns of Texas Fresh-Water Fishes. The Southwestern Naturalist, Vol. 2/No. 2-3: 89-104.

Hubbs, C., R. Edwards, G. Garrett. 2008. An Annotated Checklist of the Freshwater Fishes of Texas, with Keys to Identification of Species. Kerrville, Texas: Texas Academy of Science. Accessed February 02, 2010 at https://repositories.lib.utexas.edu/bitstream/handle/2152/6290/Hubbs_et_al_2008_checklist.pdf?sequence=2.

Langecker, T., G. Longley. 1993. Morphological Adaptations of the Texas Blind Catfishes Trogloglanis pattersoni and Satan eurystomas (Siluriformes: Ictaluridae) to Their Underground Environment. Copeia, No. 4: 976-986.

Lundberg, J. 1992. The Phylogeny of Ictalurid Catfishes: A Synthesis of Recent Work. Pp. 392-420 in R Mayden, ed. Systematics, Historical Ecology, and North American Freshwater Fishes. Stanford, California: Stanford University Press. Accessed February 02, 2010 at http://books.google.com/books?hl=en&lr=&id=t0urAAAAIAAJ&oi=fnd&pg=PA392&dq=satan+eurystomus&ots=JjRp9RpwpK&sig=JsXuP3Ril45HJkJPIumdTOcKt54#v=onepage&q=satan%20eurystomus&f=false.

Miquelarena, A., s. Ortubay, V. Cussac. 2005. Morphology, Osteology and Reductions in the Ontogeny of the Scaleless Characid Gymnocharacinus bergi. Journal of Applied Ichthyology, 21: 511-519.

Page, L., B. Burr. 1991. A Field Guide to Freshwater Fishes, North America North of Mexico. Boston, Massacusetts: Houghton Mifflin Company.

Peck, S. 1998. A Summary of Diversity and Distribution of the Obligate Cave-Inhabiting Faunas of the United States and Canada. Journal of Cave and Karst Studies, 60/1: 18-26.

Proudlove, G. 2001. The Conservation Status of Hypogean Fishes. Environmental Biology of Fishes, 62/1-3: 201-213.

Reddell, J. 1994. The Cave Fauna of Texas: With Special Reference to the Western Edwards Plateau. Pp. 31-50 in W Elliot, G Veni, eds. The Caves and Karst of Texas. Huntsville, Alabama: National Speleological Society. Accessed February 02, 2010 at http://www.utexas.edu/tmm/sponsored_sites/tss/PDF/Biologychapter.pdf.

Romero, A. 2008. "Satan eurystomus" (On-line). Accessed April 21, 2010 at http://clt.astate.edu/aromero/new_page_121.htm.

Romero, A., K. Paulson. 2001. It's a Wonderful Hypogean Life: A Guide to the Troglomorphic Fishes of the World. Environmental Biology of Fishes, 62: 13-41.

Suttkus, R. 1961. Additional Information About Blind Catfishes from Texas. The Southwestern Naturalist, Vol. 6/No. 2: 55-64.

Trajano, E. 2001. Ecology of Subterranean Fishes: An Overview. Environmental Biology of Fishes, 62/1-3: 133-160.

Walsh, S., C. Gilbert. 1995. New Species of Troglobitic Catfish of the Genus Prietella (Siluriformes: Ictaluridae) from Northeastern Mexico. Copeia, No. 4: 850-861.

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