''Phreatichthys andruzzii'', a species of

cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest ver ...

fish, is the only species of the genus ''Phreatichthys'', and is endemic to

Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constituti ...

. This cave-adapted fish is whitish (not pigmented) and blind. It is considered to have evolved in the cave environment for some two million years. Its name derives from the Greek words ''phreasatos'' for spring, and ''ichthys'' for fish. It grows to a maximum length of . This fish is the first animal discovered that does not adjust its biological clock with the light of the sun. It has an unusual internal clock, which measures the passage of time with an extremely long period (up to 47 hours). It is also completely blind to all light stimuli.Cavallari, N., Frigato, E., Vallone, D., Fröhlich, N., Lopez-Olmeda, J. F., Foà, A., Berti R., Sánchez-Vázquez, F.J., Bertolucci, C., Foulkes, N. S. (2011). A Blind Circadian Clock in Cavefish Reveals that Opsins Mediate Peripheral Clock Photoreception. PLoS Biology, 9(9), e1001142. http://doi.org/10.1371/journal.pbio.1001142 Two other cavefish species are found in Somalia: the cyprinid '' Barbopsis devecchi'' and the catfish '' Uegitglanis zammaranoi''.Romero, A., editor (2001). ''The Biology of Hypogean Fishes.'' Developments in Environmental Biology of Fishes.

References

Cave fish Cyprinid fish of Africa Fish of Somalia Endemic fauna of Somalia Fish described in 1924 Taxonomy articles created by Polbot {{Cyprinidae-stub