Confocal micrograph of a blind cavefish embryo at around five days post-fertilisation viewed from th

Confocal micrograph of a blind cavefish embryo at around five days post-fertilisation viewed from the side (lateral view) with an antibody that targets a calcium binding protein (calretinin) shown in green, which highlights different neuronal types and their processes in the nervous system. The cavefish Mexican tetra (Astyanax mexicanus) has a seeing and a blind form; the latter lives in dark environments, and relies on other senses. The blind cavefish has specially adapted traits that its sighted relation (dwelling near the surface) does not. These include a greater number of sensory receptors and taste buds along its body; these taste buds are also more efficient than the equivalent cells in the seeing cavefish. The eyes are still present at this stage of development but they will degenerate naturally during the lifetime of the fish as they live in a dark environment where eyes are redundant. Adult cavefish are blind.