Behavioural Ecology of Cave-Dwelling Fishes

Abstract

The ecological conditions in caves are characterised by two main factors: nearly all caves have complete darkness and more or less constant temperature. The animals found in this habitat form a heterogeneous assembly. Some animals use caves only occasionally to avoid unfavourable conditions outside. Others, such as bats, enter caves regularly to rest during the day and in winter. But there are also many species which live permanently in caves. Omitting all the different classifications (Vandel 1965) of cave-living animals, we can call these true cave-dwellers `troglobionts'. Their striking morphological differences in comparison with their epigean relatives concern the reduction of the eye dark pigmentation. These reduction phenomena can be observed in many groups of animals. The degree of reduction in different species studied seems to be connected with the phylogenetical age of cave colonisation (Wilkens 1982).