ABSTRACT
This chapter deals only with teleosts, which comprise the vast majority of bony fish nowadays occupying a wide variety of habitats. It focuses on showing how some environments challenge fish osmoregulation by offering extreme values of temperature, pressure, or salinity, or either fast/steep changes in those parameters, along tidal cycles. The chapter reviewes data on teleost fish osmoregulation as challenged by environments with extreme cold temperatures, high pressures, or high salinities, or either not as much extreme, but actually steeply variable coastal habitats such as estuaries and intertidal rocky shores. The sea, beyond a certain minimal depth and distance from land, is actually a very stable environment. However, even if it is environmentally stable, certain oceanic habitats offer special physiological challenges such as freezing cold water in polar seas or extremely high pressure in deep seas, which end up interfering with blood hypo-regulation of marine teleost fish.
