The blind catfish of Aigamas Cave, Namibia.

One of the sequences to be included in the BBC Africa series is on the underground caves in Namibia. In one of these caves there exist an endemic species of blind catfish, clarias cavernicola. Around 15cm long, they have no eyesight, yet their vestigial eyes can be seen. Moving slowly to conserve energy, they will suddenly stop moving and depending on their ballast, either float motionless downwards or upwards, moving again when they touch something solid. They are definitely attracted to underwater vibrations assuming they are not too vigorous.