Question

Contrast the mechanism that freshwater and saltwater animals use to osmoregulate

Answer 1

Osmoregulation is important to maintain cell structure because :
- If the osmotic pressure inside the cell is more, then cell swells and bursts because of movement of water into the cell.

- If the osmotic pressure inside the cell is less, then cell shrinks.

The composition of the extracellular fluid is different in different animals, so cells are different are in different environments. So mechanism for freshwater and saltwater animals use to osmoregulate are different for different animals. They have different osmoregulatory organs to help maintain their internal environments.

Let's take first, freshwater animals. Salt concentration inside freshwater animal is higher as in the surrounding water. It contains more salt than the water in which they live. So, water flows continuously into the body of a freshwater animal through its skin and gills and therefore animal don't need additional water by drinking, they remove excess water from body tissues by producing large amounts of urine. As kidney produces a large amount of urine, which means loss of salts.

To maintain a sufficient salt level, special cells in the gills called as chloride cells take up ions from the water, that are transported into the blood.

In contrast, saltwater animals face has low salt content in their blood than that of saltwater. Therefore they lose water and build up salt. So to replace the water loss, they continuously need to drink saltwater. t
Their small kidney can only excrete relatively small amount of urine, so the excretion of salt takes place in the gills also where chloride cells work in opposite as in freshwater animals ...