Prawns, like other crustaceans, breathe through gills. These gills are located within a gill chamber on either side of the head, which is covered by a protective plate called the branchiostegal membrane.

Here's a breakdown of the structures involved:

* Gills: These are feathery structures that provide a large surface area for gas exchange. They are made up of thin-walled filaments with a network of blood vessels.

* Gill Chamber: This cavity houses the gills and is filled with water.

* Branchiostegal membrane: This acts as a protective cover for the gill chamber, preventing water from entering the body.

Here's how gas exchange happens:

1. Water movement: Prawns move water over their gills by using their pleopods (swimming legs) to create a current.

2. Diffusion: As water flows over the gills, oxygen diffuses from the water into the blood vessels within the gill filaments. At the same time, carbon dioxide from the blood diffuses into the water.

3. Circulation: The blood, now carrying oxygen, is circulated throughout the prawn's body by the heart.

This process allows prawns to obtain the oxygen they need for respiration and to get rid of carbon dioxide, a waste product of metabolism.