Discuss the various type of adaptations in fresh water animals.

Explanation

Animals living in fresh waters have to tackle the problem of endosmosis. The osmotic pressure of freshwater is very low and that of the body fluids of freshwater organisms is much higher. So water tends to enter into bodies by endosmosis. To maintain the balance of water in the bodies, the freshwater organisms acquired several adaptations such as contractile vacuoles in the freshwater protozoans, large. glomerular kidneys in fishes etc., They send out large quantities of urine along which some salts are also lost. To compensate the .salt loss. through urine freshwater fishes have .salt absorbing chloride cells.-in. their gills. The major problem in freshwater ponds is - in summer most of the ponds dry up. To overcome this problem most of the freshwater protists undergo encystment. The freshwater sponges produce asexual reproductive bodies, called gemmules, to tide over the unfavourable conditions of the summer. The African lungfish Protopterus, burrows into the mud and forms a gelatinous cocoon around it, to survive, in summer.