Osmoregulation in Pisces| Introduction, Types, Osmoregulation in Fish

                      Osmoregulation in Pisces

Osmoregulation :-

Maintance of Internal body Concentration of salt ,minerals and water with the respective surrounding ,this process is called Osmoregulation.

Osmoregulation

Isotonic Solution :-

The Concentration of two Solutions are equal with respect to each other is called Isotonic Solution.

Hypotonic                    Isotonic                    Hypertonic

Hypotonic Solution :-

The Conentration of One solution is lower than other solution ,the lower one is called Hypotonic  solution .

Hypertonic Solution :-

The concentration of on solution is greater than other solution ,the greater one is called Hypertonic solution.

Poikilosmotic Animals :-

The organisms which has change their internal state by exchanging the mineral ,salts and water with surrounding .There are of two types –

Stenohaline  (2) Euryohaline

 1 Stenohaline :- The organism which can maintain their internal state at a narrow stage is called stenohaline . so if the organism is fresh-water living then it can not survive in marine water .

2 Euryohaline :

The organism whch can tolerate the wide range of changes in surrounding and internal state .so they survive in both fresh and marine water .

Homiosmotic :- 

Which can tolerate the surrounding enviourment into a narrow range .

Osmoregulators :-

 The organism which can regulate or change their internal enviourment according to surrounding ,so they are adapt to regulate its internal condition .

Osmoconfermers :-

The can maintain their body equilibrium with surrounding by loss of water or salt ,it can not adapt to regulate their  internal condition .

Osmoregulation in Fresh water :-

Because of hyperosmotic body fluid they are subjected to swelling by movement of water into their body owing to osmotic gradient.

Osmoregulation in Fresh water Fishes

ii. Since the surrounding medium has low salt concentration, they are faced with disappearance of their body salts by continual loss to the environment. Thus freshwater fishes must prevent net gain of water and net loss of salts. Net intake of water is prevented by kidney as it produces a dilute, more copious (i.e., plantiful hence dilute) urine.

The useful salts are largely retained by reabsorption into the blood in the tubules of kidney, and a dilute urine is excreted. Although some salts are also removed along with urine which creates torrential loss of some biologically; important salts such as KCl, NaCl, CaCl₂ and MgCl₂ which are replaced in various parts.

Freshwater fishes have remarkable capacity to extract Na⁺ and CI^– through their gills from surrounding water having less than 1 m M/L NaCl, even though the plasma concentration of the salt exceeds 100 m M/L NaCl.

Thus NaCl actively transported in the gills against a concentration gradient in excess of 100 times. In these fishes the salt loss and water uptake are reduced by the integument considerable with low permeability or impermeability to both water and salt also by not drinking the water 

Osmoregulation in Marine Water Fishes:-

In marine fishes, the concentration of body fluid and marine water is almost similar. Therefore, they do not require much energy for maintenance of osmolarity of their body fluid. The classic example is hagfish, Myxine whose plasma is iso-osmotic to the environment. Hagfish maintains the concentration of Ca⁺⁺, Mg⁺⁺ and SO₄ significantly lower and Na⁺ and CI higher in comparison to sea water.

Osmoregulation in Marine fesh

Other marine water fishes such as sharks, rays, skates and primitive coelacanth, Latimaria, have plasma which is iso-osmotic to sea water. They differ from the hagfish in having capacity to maintain very lower electrolyte (i.e., inorganic ions) concentrations.

They also have difference with organic osmolytes like urea and trim-ethylamine oxide. Kidneys of coelacanth and elasmobranchs excrete excess of inorganic salts such as NaCl.

Also rectal gland located at the end of alimentary canal takes part in the excretion of NaCl. Modern bony fishes (marine teleost) have the body fluid hypotonic to sea water, so they have tendency to lose water to the surroundings particularly from gill via epithelium. The lost volume of water is replaced by drinking salt water .

About 70—80% sea water containing NaCl and KCl enters the blood stream by absorption across the intestinal epithelium. However, most of the divalent cations like Ca⁺⁺, Mg⁺⁺ and SO4 which are left in the gut are finally excreted out.

Excess salts absorbed along with sea water is ultimately received from the blood with the help of gills by the active transport of Na⁺Cl^– sometimes K⁺ and eliminated into the sea water. However, divalent ions are secreted into the kidney .Osmoregulation in Pisces