Otolith morphologies in the genus sinocyclocheilus

Sinocyclocheilus is a genus of Cyprinid fish found in southern China. This genus contains 68 species of which 40 species have adaptations for life in cave habitats. A common adaptation seen in fish that live in caves with no light is the loss of vision. Such cavefish must therefore rely on other sensory modalities to capture prey, communicate between conspecifics, and potentially avoid predators. Previous studies have identified sensory adaptations in cavefish, including the increase in size and number of mechanoreceptors. Sinocyclocheilus are hearing specialists, and it is possible that cave species of this genus have increased reliance on hearing when compared to their surface-living relatives.The central hypothesis that motivates this work is that the hearing system of cavefish has adapted for increased hearing sensitivity relative to surface fish, and specifically that their otoliths are larger. Otoliths are functionally important and easy to measure components of fish hearing systems. The size, shape, and volume of otoliths were measured as a first step in identifying and understanding evolutionary changes in hearing related to loss of vision. In general, the findings do not support this hypothesis - no differences in measurements of otoliths across ecotypes were observed.