Alabama Cavefish | Encyclopedia of Alabama

The Alabama cavefish (Speoplatyrhinus poulsoni) is an extremely rare and critically endangered species of fish endemic to Alabama. It has only been found in five underground pools in Lauderdale County's Key Cave in the Key Cave National Wildlife Refuge in the northwestern part of the state. The fish is considered so unusual that a new genus, Speoplatyrhinus, was created to designate it (speos and platyrhinus are Greek for "cave" and "flat-nosed," respectively).

The fish was discovered in 1967 by biologist John E. Cooper while on a collecting trip with his wife. During subsequent trips to Key Cave, he recovered eight more specimens, and in 1974 published his findings, with fellow researcher Robert A. Kuehne, in "Speoplatyrhinus poulsoni, a New Genus and Species of Subterranean Fish from Alabama." Since that time, scientists have observed fewer than 10 specimens of the fish in the cave's pools.

Cavefish (also often written as cave fish) belong to the family Amblyopsidae, with more than 170 species found all over the planet except Europe and Antarctica. Although most of the species are not related, they all share the characteristics of being adapted to living underground with no source of light. Scientists refer to this characteristic as troglobitic, loosely translated as "cave-living" from the Greek. Only six species are members of the Ambylopsidae family, and all are native to the southeastern United States. The Alabama cavefish is the rarest known North American cavefish and believed to be one of the rarest of all freshwater fish. It is also the most specialized of all known cavefish, existing in a fragile ecosystem that is dependent upon nutrients from the guano of the endangered gray bat, which also inhabits the cave. No specimens of the Alabama cavefish have been found in any other location, suggesting it is a unique adaptation to its very isolated environment.

The Alabama cavefish lacks eyes and practically all pigment, making it appear pinkish white with a slight bluish tint, and it has completely translucent fins. Adults average 1.2 to 2.5 inches (30-60 mm) in length. It is the only species in its genus (Speoplatyrhinus) and can be distinguished from other cavefish by its elongated flattened head, the lack of rays (spines) in its fins, and the incisions that give its fins a spiky appearance.

The cavefish navigates and finds its food using an elaborate system of small rounded protuberances called sensory papillae that are arranged in ridges on its head and sides. The nerve centers in these organs allow the fish to detect minute changes in water pressure and temperature, as well as vibrations caused by the movement of its prey. It subsists on a diet of tiny crustaceans such as copepods, isopods, and amphipods, which in turn subsist on the nutrient-rich bat guano. The cavefish also occasionally feeds on other small organisms such as mites, spiders, and insects that fall into the water. It has no predators other than itself, placing it at the top of the food chain in its enclosed ecosystem.

The life cycle of the cavefish remains poorly understood. Scientists have speculated that it has the slowest reproductive rate of any cave-dwelling aquatic species, and its longevity is predicted to be between five and ten years. It has a large mouth cavity and likely reproduces like the northern cavefish, which incubates its young inside its mouth, but this behavior has yet to be observed. Because the Alabama cavefish's reproductive cycle appears to be based on various environmental triggers, it is possible that it does not reproduce every year. Its reproductive cycle may be triggered by seasonal flooding in the cave, which causes hormonal changes in the species.

There are likely fewer than 100 Alabama cavefish in existence. Because its known range is limited to a single cave, the Alabama cavefish has an uncertain future. It is threatened by changes in groundwater quality and level and most notably threats to the gray bat population from white-nose syndrome, a newly emergent fungal disease that is devastating bat populations all over North America. In 1988, the Alabama cavefish was reclassified from threatened to "endangered" by the U.S. Fish and Wildlife Service.

Additional Resources

Mettee, Maurice F., and Patrick E. O'Neil. Fishes of Alabama and the Mobile Basin. Birmingham, Ala.: Oxmoor House, 1996.

Cooper, John E., and Robert A. Kuehne. " Speoplatyrhinus poulsoni, a New Genus and Species of Subterranean Fish from Alabama." Copeia 1974 (June 1974): 486-93.