Southern Cavefish

Southern cavefish washed out of Maramec Spring in 1984
Photo from collection of Don Rimbach

The Southern Cavefish Typhlichthys subterraneus is the second of Missouri's cavefishes. It is found mostly in the dolomite aquifers of the Salem Plateau in the South Central Ozarks, with another population in the center of the state. This cavefish tends to be larger (adults can be found up to a whopping 3.5 inches long) and less cave adapted in its body characteristics, (it looks more like a minnow, with a more round head and body elongation) although it, too, is blind, pigmentless, and possesses a of lateral line developed, vibration detecting mechanism to find its food.

Neither cavefish will survive long in direct sunlight, as they are quite sensitive to ultraviolet radiation. Some populations of Southern cavefish are not quite as susceptible--they are found at the bottom of shady sinkholes in several locations. There is also much more diversity among the Southern cavefish populations here. One population has an orange hue, and in another, most specimens grow to "monster" sizes (for cavefishes). Genetic work done on these diverse populations have yielded surprising results, which may one day rewrite the history of cavefishes in the state.

Other than their occurrence, where by rights, no fish should be, cavefish are fascinating for the part which they play in evolutionary history. A map of the Mississippi Embayment, the last major inundation by the ocean of the central United States, superimposed on a map of cavefish sites in Missouri, Kentucky, Tennessee and Alabama makes an interesting fit. In short, the fish survived along the shores where the ocean ended. But what drove them underground? Or were they troglobitic, even back then? Why do some fish, such as the Southern cavefish, have more characteristics of surface species, while others, like the Ozark cavefish, do not? Did all the cavefishes have surface characteristics, such as eyes, and pigment, and then lose them as they became cave adapted, or did they never adequately develop, and only those which retreated into the dark survive? These, and many other questions remain to be answered.

Southern cavefish are by no means plentiful, but their range, which extends into four states, over a larger area than the Ozark cavefish range, makes their survival more likely. One reason to be concerned with Southern cavefish, however, is, these populations have been geographically isolated for a long time. Those populations in Missouri are presumed to have been isolated at least since the draining of the Mississippi Embayment at the end of the last ice age. Scientists studying the development of new species are especially interested in these fish, and their differences.

Southern cavefish are more abundant in locations with a high organic debris influx. Presumably this is because much organic debris means more invertebrates for the fish to feed on.

Southern cavefish are protected under state non-game species laws, and do not fare well in captivity. Most major Southern cavefish sites are gated, or otherwise inaccessible.

2003 Jo Schaper.

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