African amphibious fishes and the invasion of the land by the tetrapods

Abstract

Many species of amphibious fishes (fishes that live both in and out of water as normal parts of their life histories), belonging to a diverse array of families, occur in both freshwater and marine habitats in many parts of Africa. Some of the best studied forms are common in widely occurring intertidal habitats along much of the African seacoast. Several species of mudskippers (family Gobiidae, subfamily Oxudercinae) occur in mangrove areas and in other protected muddy or sandy habitats. A larger and more diverse group of blennies (family Blenniidae), some of which are called rockskippers, occur in mainly rocky habitats. The primary focus of this paper is on both the mud- and rockskippers. None of the living amphibious fishes are directly related to or descended from the ancient sarcopterygian fishes that appear to have been the ancestors of all tetrapods. However, studies of the biochemical, ecophysiological, functional morphological, and behavioural adaptations shown by the living forms for amphibious modes of life provide us with diverse examples of evolutionary successful, functional suites of adaptations that might also have been used, in varying combinations, by ancestral forms that could have occupied similar habitats.