PARANEURONS IN THE GILLS AND AIRWAYS OF FISHES

This chapter describes the distributional patterns of the neuroendocri ne cells in the respiratory surfaces of fishes and their bioactive sec retions which are compared with similar elements in higher vertebrates . The neuroendocrine cells in the airways of fishes differentiate as s olitary and clustered cells, but the clusters are not converted into n euroepithelial bodies which are reported in terrestrial vertebrates. T he dipnoan fish Protopterus has innervated neuroendocrine cells in the pneumatic duct region. In Polypterus and Amia the lungs have neuroend ocrine cells that are apparently not innervated. Two types of neuroend ocrine cells are found in the gill of teleost fishes. These cells are very different by their location, structure and immunohistochemistry. Advanced studies on functional morphology of neuroendocrine cells in f ish airways are still necessary to increase our understanding of their multifunctional role in the gill area. (C) 1997 Wiley-Liss, Inc.