Saturday, 14 June 2014

A new species of blind Cavefish from Indiana.

Cavefish (Amblyopsidae) are a group of predominantly cave-dwelling Perciform Fish from North America. Of the eight currently described species three are found at the surface, predominantly around springs, and five species are exclusively subterranean. 

In a paper published in the journal ZooKeys on 29 May 2014, Prosanta Chakrabarty and Jacques Prejean of the Ichthyology Section at the Museum of Natural Science and Department of Biological Sciences at Louisiana State University and Matthew Niemiller, also of the Ichthyology Section at the Museum of Natural Science and Department of Biological Sciences at Louisiana State University as well as the Department of Biology at the University of Kentucky, describe a new species of Cavefish from Idaho.

This species is described from previously known and well-studied populations assigned to the species Amblyopsis spelaea, which has previously been used to describe Cavefish from limestone karst caves on the Crawford-Mammoth Cave Uplands and Mitchell Plain in southern Indiana and northern Kentucky, and which has been shown by genetic studies to in fact be two separate, cryptic, species on either side of the Ohio River, which apparently presents an impassable boundary to the distribution of the Fish. Since Amblyopsis spelaea was originally described from specimens from south of the Ohio River in Kentucky, this name is retained for the Kentucky species while the Indiana species is renamed Amblyopsis hoosieri, or the Hoosier Cavefish, a term for a resident of the state of Indiana.

Distribution of Amblyopsis spp., Amblyopsis spelaea and Amblyopsis hoosieri, in the Mitchell Plain and Crawford-Mammoth Uplands of Indiana and Kentucky. Chakrabarty et al. (2014).

Amblyopsis hoosieri is completely blind, lacking eyes of any sort, and is also completely lacking in pigment. Adult specimens reach 60-80 mm in length, and being slightly more plump and fleshy than Fish from south of the Ohio River in Kentucky, which are still classed as Amblyopsis spelaea.

Photograph of Amblyopsis hoosieri in life. Matthew Niemiller in Chakrabarty et al. (2014).

Amblyopsis hoosieri has been found living in large streams and pools with depths between ten centimetres and two metres. It favours slower moving waters, and will seek refuge in crevices in the rock during periods of higher flow. It breeds between February and April, when the water levels are highest in the caves where it dwells. Females brood the eggs internally, and continue to care for the fry for several months after they hatch. Sexual maturity is thought to be reached in 3-4 years, with the fish living for at least 12-15 years, and possibly in excess of 20 years. The Cavefish feed on Isopod, Copepod and Amphipod Crustaceans, with larger individuals sometimes tackling Crayfish. They have no known natural predators. 

Amblyopsis spelaea was considered to be Endangered in Indiana by NatureServe, a designation which should now be applied to Amblyopsis hoosieri. Similarly Amblyopsis spelaea is considered Vulnerable on the International Union for the Conservation of Nature’s Red List of Threatened Species, a classification which should also be applied to Amblyopsis hoosieri. The species is known from 74 localities, but it is thought that some of these populations only exist because of replenishment by fresh Fish from a smaller number of source populations. The species is thought to be highly vulnerable to groundwater pollution, particularly from pesticides, herbicides and fertilizers. Some habitats previously occupied by the Fish have been completely destroyed by limestone quarrying, while others are prone to disturbance by commercial cave tours, with an uncertain impact on the Fish. Finally some populations were heavily collected by scientists studying adaptations to cave-dwelling in the late nineteenth and early twentieth centuries, which may have impacted upon these populations.

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