| Popis: |
Publisher Summary Due to the large differences in osmolarity between body fluids and ambient medium, fish are facing water influx in freshwater or water loss in seawater. The maintenance of a low osmotic permeability to water of the integument is, therefore, essential, especially in the gills as these make up more than 10% of the body surface. This chapter discusses the effects of external calcium, osmolarity, and prolactin on the osmotic permeability to water of the gills of a euryhaline teleost fish, Sarotherodon mossambicus. The administration of prolactin, by implantation of the prolactin producing lobe of the pituitary gland in the dorsal musculature of an intact acceptor fish, leads to a prolonged decrease of the osmotic water permeability of the gills. It is suggested that the low osmotic permeability to water is maintained mainly by prolactin under conditions of low ambient calcium and mainly by ambient calcium if the concentration of calcium ions is high. |
