Foraging Response of Blind Cavefish and Eyed Facultative Cavefishes in Surface and Subterranean Conditions

Cave environments impose strong selective pressures upon the organisms that reside within. One of the most obvious pressures is complete darkness: it influences the evolution of troglomorphic traits such as enhanced non-visual sensory systems, reduced metabolic rates, eye degeneration, and pigment loss. Fishes in the family Amblyopsidae are comprised of cave-obligate, cave-facultative, and surface-dwelling species. This family provides a powerful system for examining adaptive responses across environmental gradients. In this study, feeding trials were conducted on three amblyopsid species: the blind cave-obligate Typhlichthys subterraneus and two eyed cave-facultative species, Forbesichthys agassizii and Forbesichthys papilliferus. Using live amphipod prey, time to capture of the prey item and the number of unsuccessful strike attempts were quantified under simulated surface and subterranean conditions. Results demonstrate that facultative cavefishes appear to exhibit behavioral flexibility in response to environmental conditions. Eyed facultative-cave species parallel the foraging accuracy of blind cavefishes in dark conditions. Under light conditions, facultative species displayed an increased predatory aggression, characterized by faster capture times and more frequent strike attempts. In contrast, under dark conditions, their behavior shifted toward a more energy-conservative strategy that more closely resembled that of the cave-obligate T. subterraneus. These findings suggest that behavioral flexibility within the facultative species may facilitate their resilience across contrasting environmental gradients.