Question

Compare and contrastthe internal osmotic concentration of freshwater teleostsand marine fishes, including both marine elasmobranchsand marine teleosts. Provide details on how water and ions are gained and lost in these 3fish groups. If you like, provide a sketch of cells that regulate salt levels in the gills of freshwater and saltwater fishes.

Answer 1

The concentration of ions inside the cell membrane are different in both marine and fresh water fishes. Salt concentration is higher in the blood comparative to outside environment. That is why the kidney has to produce large amount of urine for this compensation so that more salts get excreted out. The chloride cells present in the gills help in the uptake of ions and transportation to the blood.

The salt concentration is lower inside of the body comparative than the external environment in marine water fishes.These Fishes continuously lose water and build up salts. These fishes have to drink sea water to compensate and their kidney excrete only small amount of urine. Chloride cells helps in the excretion and act just opposite to fresh water fishes. Along with this two hormones named cortisol and thyroid also participate in the osmoregulation. They influences the direction and the rate of solutes or ions pumped through chloride cells. Marine water cartilagenous fishes consist of rectal gland to secrete salt they also produce TMAO to excrete out for the osmoregulation.