What is the respiration system of a prawn?

Answer 1

Praws have gills (special gas exchange surfaces) at the base of each walking leg. In order to pass a constant supply of oxygenated water over the gas exchange surface the gills are ventilated by movement of the walking and swimming legs. A prawn has 5 pairs of walking legs (located on thorax) and 5 pairs of swimming legs (located on the abdomen)

Answer 2

Prawns -like us- need oxygen to live, and to achieve this, they use gills that act as gas exchange surfaces. Their gills are complex outgrowths holding blood vessels that significantly increase the surface area for gas exchange. The prawn's gills are arranged in a number of plates and are on the surface of the prawn's body, covered and protected by the carapace.

Water is very dense, making both the intake and extraction of dissolved gases from it more difficult and water also has a low oxygen concentration, in fact, there is 5% of the amount of oxygen in the air then under water; therefore, it is difficult to pass water through the gills. To overcome this, prawns have gills on the top of their walking legs or the appendages from the second maxilla to the fifth pereiopod. So the amount of oxygenated water passing through their gills is increased whist they move or swim. However, since prawns are cold blooded, they do not need a large supply of oxygen.

The prawn's gills contain gill arches that act as a support to hold the other gill parts, gill filaments that bring deoxygenated blood to the surface of the gill to become oxygenated and branching off the filaments are blood capillaries called lamellae. The lamellas are smaller branches that divide into even smaller branches and so forth. They are a great number of branches that provide a huge surface area for the oxygen to diffuse into the blood. This is one of the reasons behind the gills success in extracting the maximum amount of oxygen out of the water.

As the prawn swims forward, the water is passed over the branchial chamber and into its gills. The gill lamellas take the oxygen from the water and pass it through the blood vessels to re-oxygenate the bloodstream. The carbon dioxide also passes through the thin walls of the lamellae and into the water.

The flow of blood in the gills of a prawn travels in an opposite direction from the water when it passes over the gills. This is called countercurrent flow and allows prawn's to obtain more oxygen from the water than if the blood and water flowed the same way.