 They can adapt to increasing water salinity, where the ionocyte increase in size, gill filaments become thicker, the surface area of the basolateral memebrane increases, and the intracellular tubular system proliferates.Teleost fish do not have the loop of Henle in the kidneys and are, therefore, not able to produce hyperosmotic urine.Instead, they secrete small amounts of urine frequently in order to prevent water loss and excrete NaCl thorough the gills.