How do squid use their mantle cavities for both breathing and swimming?

In squids, the mantle cavity serves as a dual-purpose system for both respiration and locomotion.

Respiration

The mantle cavity houses the gills, which are essential for gas exchange. By drawing water into the cavity, the squid ensures that oxygen-rich water flows continuously over the gill surfaces. These gills are highly efficient, allowing the animal to extract the oxygen necessary to support its active lifestyle and high metabolic rate.12

Locomotion

Squids utilize the mantle cavity for jet propulsion by manipulating water volume through muscular action:31

• Inhalation: The circular muscles of the mantle relax, causing the mantle to expand and increasing the volume of the cavity. This draws water in through the aperture around the neck.31
• Exhalation: The mantle muscles contract, closing the aperture and forcing the trapped water out through a mobile funnel. The high-pressure jet of water exiting the funnel propels the squid in the opposite direction, allowing for rapid movement and precise steering.31

This system effectively integrates the animal's need for oxygen intake with its primary method of high-speed travel.31