Subterranean Fishes of the World

6013

2023

Journal of Ichthyology

41-47

63

Sinocyclocheilus bicornutus is a valid cave–dwelling cyprinid species with small eyes from Guizhou province, southwest China, the close relatives of which are also small eyed and obligate cave–dwelling. Our expeditions in 2015 to 2017 found the intraspecific variability of eye degeneration based on total 114 specimens collected from one lighted and two dark caves with an altitude of about 1350 m. Three morphotypes, the small eyed, the rudimentary eyed, and the eyeless, co-occurred in each cave. The eye size closely correlates with the standard length SL in the lighted cave, while the correlation of the eye size and SL become loosely related in the dark caves which associated with increased proportion of significantly degenerative eyed morphotypes. It implies that the developmental retardation occurs in the darkness and remains in adult stage. The variable eye-reduced populations of S. bicornutus provide an interesting model to address the involvement of potential epigenetic mechanisms with the regressive evolution of cavefish. Keywords: cavefish, regressive evolution, phenotypic variation, epigenetics

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