1. Water Intake: Guppies open their mouths and actively draw water into their oral cavity. This water flows over the gills through the action of muscles and pressure differences.
2. Gas Exchange: The gills consist of numerous thin, feathery filaments called gill filaments. Each filament is covered in tiny blood vessels known as capillaries. As water passes over the gill filaments, dissolved oxygen in the water comes into close contact with the thin walls of the capillaries.
3. Diffusion: Oxygen diffuses passively across the capillary walls and into the bloodstream. Simultaneously, carbon dioxide, a waste product of cellular respiration, diffuses out of the blood and into the water. This gas exchange occurs due to the concentration gradient of oxygen and carbon dioxide across the capillary walls.
4. Blood Circulation: The oxygen-rich blood is then transported throughout the guppy's body by the circulatory system. It delivers oxygen to the cells and tissues, supporting their metabolic processes.
5. Water Expulsion: After gas exchange, the guppy expels the water that has passed over the gills. This is achieved by closing the mouth and contracting the operculum (gill cover), pushing the deoxygenated water out through the gill slits.
6. Repetition: The entire process of water intake, gas exchange, and water expulsion is repeated continuously to maintain a constant flow of oxygenated water over the gills.
By efficiently extracting oxygen from the surrounding water, guppies meet their respiratory needs and obtain the oxygen necessary for maintaining their activities, growth, and survival.