How do crabs breathe underwater?

Crabs and other crustaceans have adapted to their underwater environment in a number of ways, one of which is how they breathe. Unlike humans, who rely on lungs to extract oxygen from the air, crabs breathe underwater using gills, which are specialized respiratory organs.

Crab gills are located on the inside of the carapace, or shell, and are made up of thin, branching filaments that are rich in blood vessels. The gills are constantly in motion, drawing in oxygen from the surrounding water as it passes over them and releasing carbon dioxide.

In addition to their gills, crabs also have a closed circulatory system that helps transport oxygen throughout their body. The heart pumps blood to the gills, where oxygen is extracted, and then distributes the oxygen-rich blood to the rest of the crab's body.

Overall, crabs have evolved a number of specialized adaptations that allow them to survive and thrive in their aquatic environment, including their unique respiratory system that allows them to breathe underwater using gills.