Crabs spit bubbles as a sign of breathing. Hairy crabs breathe mainly through gills. When they breathe, they suck water into their mouths, and then discharge water and air through the sides of their mouths, thus forming bubbles.

When crabs stay on land for a long time, most of the water in their gills is taken away by the air, and their gills are gradually dry, which makes them feel difficult to breathe. At this time, crabs will still stir their mouths and gills as hard as breathing in the water, constantly inhale air, and then spit out a little water in their gills, thus forming a lot of bubbles.

sabotage

Crab is a crustacean, belonging to the mollusk class Decapoda. Its body is protected by a hard shell and it breathes through its gills. Taxonomically, it is the same kind of animal as shrimp, lobster and hermit crab. Most kinds of crabs live in the ocean or offshore areas, and some live in fresh water or land. Common crabs are Portunus trituberculatus, Portunus trituberculatus, Eriocheir sinensis and Eriocheir sinensis (Eriocheir sinensis, Eriocheir sinensis and Eriocheir sinensis).

Crab is a fish-like gill breathing animal, and its gills are somewhat different from those of fish. It is not born on both sides of the head, but divided into many feathered gills that are soft like a sponge and grow on both sides of the body, and the surface is covered with hard head breastplate. When it breathes, it will suck in fresh water from the back of its body, and oxygen dissolved in the water will enter the capillaries of gills, while other water and substances will flow through gills and be spit out from both sides of its mouth.