ABSTRACT
This chapter summarizes the main points related to behavior and adaptation of air-breathing fishes. It presents an account environmental changes that can affect such fish group. Air-breathing fish species are distributed among 49 families belonging to the Subclasses Sarcopterygii and Actinopterygii. The evolution of air-breathing fishes is close-related to changes in the composition of atmosphere and water. Air-breathing activity, as a supplement to water breathing or as the main pathway for gas exchange, has independently evolved several times in fishes. In many aquatic air breathers, the mechanical coupling of exhalation and inhalation has essentially reduced the air-breath cycle to a single component, an air-holding phase. Behavioral and physiological strategies related to air-breathing adaptation are close related events, sometimes difficult to separate between them. Among the fossils of air-breathing fishes, the most ancient are the Actinopterygian fossils from Paleozoic.
