Typhlichthys subterraneus
southern cavefish

Typhlichthys subterraneus is restricted in its geographic range to the North American continent. Some scientists believe their range was continuous in the past and may still be, but it is difficult to determine. Many scientists agree the range is now disjunct, with species inhabiting specific cave systems in Tennessee, Alabama, Missouri, Arkansas, Oklahoma, and Kentucky, but always south of the limit of glaciation. Dispersal is presumed to be through underground water channels. (Jones, 1985; Romero, 1998; Woods and Inger, 1957)

Southern cavefish inhabit subterranean waters and are troglobitic. They prefer caves that are near the watertable and have low energy flows. These caves have water temperatures of 10 to 15 degrees C. Southern cavefish have adapted to life in an extreme habitat that includes factors such as low food supply, seasonal water level changes, and an aphotic environment. (Poulson, 1963)

Typhlichthys subterraneus is a small fish reaching a maximum length of 9 centimeters. Individuals have large broad heads with rudimentary eyes hidden under the skin. Normally there is no pigment on the body, although tests have shown that coloration does appear if a specimen is removed from its habitat and exposed to light. Southern cavefish do not have pelvic fins. There are 7-10 dorsal rays, 7-10 anal rays, and 10-15 caudal rays. The body, head, and caudal fin is covered by sensory papillae. (Etnier and Starnes, 1993; Poulson, 1963; Woods and Inger, 1957)

Eggs are held in the gills of females until they hatch. Otherwise, little is known of development in southern cavefish. (Poulson, 1963)

The expected life span is four years in the wild. (Poulson, 1963)

Little is known of behavior in southern cavefish. It has been found, however, that Typhlichthys subterraneus does have a strong thigmotaxis and keeps the top of its head touching and parallel to surfaces. They prefer to swim on substrates in quiet water. (Poulson, 1963)

Southern cavefish use touch and their thigmotaxic sense to maintain their position in the water column. Their use their sense of touch extensively to detect prey. Other sensory modalities are possible, but are unknown currently.

Food is scarce. Typhlichthys subterraneus forages using its sensory papillae in midwater and on the substrate. When prey is within 10 mm of the mouth, capture movements are commenced. Southern cavefish have distance perception and spatial memory which aid in foraging behavior. Their diet consists mainly of copepods (60-90%, by volume).

Foods eaten include trichopteran larvae, tendepedid larvae, cladocerans, isopods, crayfish, and copepods. (Poulson, 1963)

There are no known predators of southern cavefish. (Poulson, 1963)

These animals are the top predators in the environments in which they live.

There are no adverse effects of southern cavefish for humans.

Southern cavefish are important members of their ecosystems and important research subjects for understanding evolution in extreme environments.

Because the habitat of southern cavefish is so unique and because population numbers are normally low, they are regarded as a vulnerable species. Any amount of habitat that is destroyed or altered would have a significant impact. However, many of the cave systems inhabited by Typhlichthys subterraneus are protected by govenmental regulation (e.g., Mammoth Cave in Kentucky). (Poulson, 1963; Woods and Inger, 1957)

Southern cavefish are well-adapted for their environment. Low growth and metabolic rates as well as eye degeneration and pigment loss decrease the amounts of expended energy; parental care of young increases their chances of survival; and a well-developed sensory papillae network and spatial memory aids in navigation.

It has been suggested that the extent of eye and pigment degeneration may be a reflection of the length of isolation in caves and thus would be a helpful tool in determining the ancestral phylogenies of Typhlichthys subterraneus and other species within the family Ambloypsidae. (Poulson, 1963)