What is the breathing method of a bony fish?

1. Water Intake: Bony fish open their mouths and actively draw water into their oral cavity through a process called suction. This water contains dissolved oxygen, which is necessary for respiration.

2. Gill Structure: Inside the fish's mouth and along its sides are specialized structures called gills. Gills consist of bony arches that support delicate filaments known as gill filaments. These gill filaments are covered in tiny blood vessels called capillaries.

3. Gas Exchange: As water passes over the gill filaments, oxygen from the water diffuses across the thin membranes of the capillaries into the bloodstream. At the same time, carbon dioxide, a waste product of cellular respiration, diffuses out of the bloodstream and into the water. This exchange of oxygen and carbon dioxide is facilitated by the large surface area of the gill filaments.

4. Gill Ventilation: To ensure a continuous flow of oxygen-rich water over the gills, bony fish employ a ventilation mechanism. They have specialized muscles associated with the gill covers (opercula) that rhythmically contract and relax. This creates a pumping action that draws water in through the mouth and forces it out through the gill slits.

5. Opercular Movements: The operculum (plural: opercula) is a flap of skin that covers the gills on both sides of the fish's head. During inhalation, the operculum opens to allow water to enter the oral cavity. During exhalation, the operculum closes to expel water through the gill slits.

By utilizing gills and employing gill ventilation, bony fish efficiently extract oxygen from water and release carbon dioxide, enabling them to breathe and obtain the oxygen they need for cellular respiration.