ABSTRACT
This chapter focuses on the gill morphology in relation to the respiratory function, the adaptations to ionic disturbances and the interference in the gas transfer. Internally, a cartilaginous rod provides support for the gill filament and the filament striated abductor and adductor muscles connected to the gill arch bones, the epibranchial and ceratobranchial, adjust the position of filaments during ventilation. The blood supply to gill tissue consists of an arterio-arterial and an arterio-venous pathway. Icefish gills have large blood spaces in the lamella and a prominent and continuous marginal channel; noradrenaline increases the diameter of blood spaces and lamellar height, and the pillar cells control lamellar perfusion. The gills of most teleost fish are similar in their general structure but interspecific variability of the gill components, the blood pathway inside the lamellae and the thickness of water-blood diffusion distance influence the effectiveness of gas transfer.
