ABSTRACT
The fish gill apparatus is a marvelously functional structure for aquatic respiration. Each of four pairs of gill arches in teleosts contains posterior and anterior columns of gill filaments. Each filament bears transverse lamellae of a single cell layer of respiratory epithelium. As water is moved across the gill by the fish’s bronchial pump, the filaments extend so that their tips touch those of adjacent filaments and the lamellae interdigitate with those on the filaments above and below. In this way, inspired water is forced through very small openings lined with respiratory tissue containing venous blood.
