Who needs eyes?

The golden cave catfish (Clarias cavernicola) is a cave‐dwelling clariid (airbreathing) catfish only known to exist in Aigamas Cave, north of Otavi and west of Grootfontein, Namibia. The origin of this relict species is unknown, and its morphological, physiological, behavioral, and ecological features ensure its survival in an exclusively subterranean environment. These individuals were observed 81 m below the earth's surface, where food sources are scarce – food availability is probably the most important limitation for this species in terms of population size. Listed as critically endangered by the International Union for Conservation of Nature (IUCN), the species was previously estimated to contain only 150–400 individuals, making it the rarest fish in southern Africa and one of the most endangered fishes in the world. Like most cave‐dwelling fishes, it is devoid of pigment, and the skin color is cream flushed with pink or golden yellow. Interestingly, in some individuals (such as the one on the left) the eyes are completely absent but in others (such as the one on the right) they are variously developed. Despite the lack of any obvious use for eyes at water depths with little to no sunlight, evolutionary traits within this community that are directly or indirectly related to the subterranean life are still a mystery. Who needs eyes, and are there downsides to having eyes (eg in terms of energy expenditure to develop eyesight), especially in a species with barbels, which function as sensory organs