The spring cavefish (''Forbesichthys agassizii'') is the only member of the genus ''Forbesichthys'' and is one of seven

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the family

Amblyopsidae The Amblyopsidae are a fish family commonly referred to as cavefish, blindfish, or swampfish. They are small freshwater fish found in the dark environments of caves (underground lakes, pools, rivers and streams), springs and swamps in the easter ...

. This species is listed as state endangered in

Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...

, but it is considered to be of

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

Red List due to its relatively large population size and number of subpopulations. The spring cavefish inhabits caves, springs, spring runs, and spring seeps. It is subterranean, emerging at dusk and retreating underground an hour or two before dawn. The species is located within areas of the

central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

and

southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...

. It stays underground after dawn, but then emerges into surface waters at dusk. They are a carnivorous fish and are well adapted to their environment. The species' breeding behavior is rarely documented.

Spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...

occurs underground and in darkness between January and April. The status and distribution of cave-obligate species is incomplete or lacking entirely, which makes conservation and management decisions difficult.

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

and Missouri are the two main states that have their agencies managing this species in some way.

Geographic distribution

Originally found in a deep well in

Lebanon, Tennessee Lebanon is the county seat of Wilson County, Tennessee, United States. The population was 38,431 at the 2020 census. Lebanon is located in Middle Tennessee, approximately east of downtown Nashville. Lebanon is part of the Nashville Metropolit ...

, the spring cavefish is distributed within the central and southeastern United States.Hill, L.G. 1969. ''Feeding and Food Habits of the Spring Cavefish,'' Chologaster agassizi. American Midland Naturalist:83:110-116. It inhabits select springs, spring runs/seeps, and caves from central and western Kentucky, west towards the Tennessee River, to south central Tennessee. It also is located in areas west across southern Illinois to southeastern Missouri. The spring cavefish's distribution has decreased from within its original streams and springs. This species is affected by the activities on the surface of the ground. Any activity that reduces water quality or quantity affects the spring cavefish. It is vulnerable to pollution from many different sources. Some of these sources include nearby agricultural fields, pastures,

septic tank A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater (sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatme ...

s, sewage lagoons,

urban runoff Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precipit ...

, mines, and livestock waste.Missouri Department of Conservation. 2000. Policy Coordination Section. Some of the springs fluctuate drastically in flow and turbidity as a result of direct connections with surface drainage or they were enclosed as water supplies or otherwise modified by man.

Ecology

Spring cavefish stay underground after dawn, but then emerge into surface waters at dusk. They are dark brown dorsally and fade to a creamy brown towards the pelvis and reach a maximum length of . The head is sloped, and it has a protruding lower jaw. The fish has no

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

adipose fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

. Its dorsal fin is set further back compared to most fish. This species is susceptible to developing

retinoblastoma Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from the immature cells of a retina, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively fo ...

s. The spring cavefish is well adapted to its environment, as it has a well-developed sensory system. This system occurs in clusters on the head. Most fish detect food by sight, taste, touch, or smell, or by a combination of these senses. Sight is important in the detection of food by most species, but this is presumably excluded with the slightly blind spring cavefish. They use their underdeveloped eyes to distinguish between light and darkness. However, spring cavefish cannot readily distinguish between edible and inedible substances by touch alone, but once in contact with the lips, the sense of taste enables the fish to distinguish among these items. Another hurdle for this species is food is often lacking in their habitats, so they compensate for this scarcity of food with cannibalistic behavior. Cannibalism in the spring cavefish presumably serves two purposes: it enables the adults to survive in an environment where food is the principal limiting factor, and it serves as a means of population control. The spring cavefish can be considered its own predator, because of the cannibalism behavior and the lack of natural predators within the caves. However, they eat a wide range of

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

, small

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

, smaller fish, and some

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

.Science Encyclopedia. 2011. Cave-Fish. ''Science Encyclopedia'' 1290 pp. Cave environments provide a relatively stable habitat in terms of temperature fluctuations. However, the different species living in caves are reliant on food being brought to them by underground streams. This makes spring cavefish highly vulnerable to external factors as subterranean

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

s are becoming increasingly tapped for irrigation purposes, and many sites may be at risk from drying out either temporarily or permanently.

Life history

The breeding behavior of spring cavefish is sparsely documented. Spawning occurs underground and in darkness between January and April. Spring cavefish are

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

; however, the eggs are carried in gill chambers of the females. Females produce roughly 100 young per female. The average spring cavefish lives for about three years and typically reaches a length of about 1.8 to 2.6 in.

Conservation

The status and distribution of cave-obligate species is incomplete or lacking entirely, which makes conservation and management decisions difficult. This species is listed as endangered in Missouri. The IUCN Red List considers the spring cavefish to be of least concern due to its relatively large population size and number of subpopulations. This species is declining, but many of the reasons are unknown. The Kentucky Department of Fish and Wildlife Resources is proposing to investigate the status, distribution, ecology, phylogenetic relationships, and threats to populations of three cave-associated fishes in the family Amblyopsidae in Kentucky. Kentucky and Missouri are the two main states with agencies managing this species in some way. Missouri has purchased Cape LaCroix Bluffs Conservation Area to provide habitat for the state endangered spring cavefish. This 63.21-acre area supports natural wetlands, limestone bluffs, and beech mesophytic forests unique to eastern Missouri.

References

{{Taxonbar, from1=Q3023750, from2=Q19826986 Amblyopsidae Cave fish Endemic fauna of the United States Freshwater fish of the Southeastern United States Fauna of the Plains-Midwest (United States) Taxa named by Frederic Ward Putnam Fish described in 1872