Blind Cave Fish (Astyanax mexicanus)

IUCN Conservation Status: Least Concern

Ecology

As the name suggests, this fish is characterized by a lack of eyes and its body is white in color! The Blind Cave Fish is a fantastic example of evolution at work, as it is a variant of the Mexican Tetra. Although this fish’s territory expands throughout parts of Mexico and some Midwestern States of the US, this particular variant is mostly found in the cave systems of Northeast Mexico. [1,2] Although this fish lacks eyes, it is still able to sense movement through its lateral line*, and its movement is not inhibited by its blindness. [2,3] Despite the big phenotypic* differences, the Blind Cave Fish is able to interbreed with its surface-dwelling variants (which have functioning eyes).

Fishery

Almost all individuals of this species in the aquarium trade are aquacultured from a line of Blind Cave Fish initially collected in the Cueva Chica Cave in the Sierra del Abra system in 1936. [4]

In Aquaria

The Blind Cave Fish has become a popular schooling fish for aquarists, as it is one of the few cave-dwelling species that fare well in the aquarium. It is very hardy and does not require live plants to thrive. And although it is not aggressive, it can nip at other fish occasionally, and should not be kept with smaller or slower moving fish. It can grow to be about 3-4 inches long and should be kept in groups of 4 or more, so a minimum tank size of 20 gallons is recommended. [5]

*Lateral line: a sensory organ in fish that often appears as a series of dots along the length of the body.

*phenotypic: the appearance/physical traits of an organism.

Works Cited

[1] NatureServe. 2013. Astyanax mexicanus. The IUCN Red List of Threatened Species 2013: e.T62191A3109229. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T6... Accessed on 09 September 2022.

[2] Herman, A., Brandvain, Y.J., Weagley, J.S., Jeffery, W.R., Keene, A.C., Kono, T.J., Bilandžija, H., Borowsky, R.B., Espinasa, L., O'Quin, K.E., Ornelas-García, C.P., Yoshizawa, M., Carlson, B.M., Maldonado, E., Gross, J.B., Cartwright, R.A., Rohner, N., Warren, W.C., & McGaugh, S.E. (2018). The role of gene flow in rapid and repeated evolution of cave-related traits in Mexican tetra, Astyanax mexicanus. Molecular Ecology, 27, 4397 - 4416.

[3] Yoffe, M., Patel, K., Palia, E., Kolawole, S.O., Streets, A., Haspel, G., & Soares, D. (2020). Morphological malleability of the lateral line allows for surface fish (Astyanax mexicanus) adaptation to cave environments. Journal of experimental zoology. Part B, Molecular and developmental evolution.

[4] Keene, A.; Yoshizawa, M.; McGaugh, S. (2016). Biology and Evolution of the Mexican Cavefish. pp. 68–69, 77–87. ISBN 978-0-12-802148-4.

[5] Astyanax mexicanus (Blind Cave Tetra) — Seriously Fish. (n.d.). Retrieved September 10, 2022, from https://www.seriouslyfish.com/species/astyanax-me...