Crabs are a kind of animal that we can often see.They can not only move in the water, but also stay on land for a period of time.When we look at crabs on land, we find that they always spit bubbles.When they first leave the water, the bubbles they spit are relatively small, and as time goes on, the bubbles on their bodies will become more and more, all piled up together.Of course, although crabs can persist in spitting bubbles for a period of time, they will not persist for too long, because the water they can store in their bodies is limited, and they can not move on land for too long.
As mentioned above, crabs can spit bubbles for a period of time, and the number of bubbles will accumulate more and more.This is because the breathing of crabs in the water is different from that on land.Crabs breathe through their gills, and when they are in the water, the water flows through their gills, and then the dissolved oxygen in the water enters their bodies through the tiny blood vessels in the gills.
Crabs need to keep their gills moist to breathe normally.They can also breathe for a period of time on land because their gills can store part of the water to keep their gills moist.When on land, crabs absorb air directly and then expel waste gas through their gills.In the gills, air and water combine to form bubbles.As time goes on, more and more bubbles will appear.Of course, this will also lead to less and less water in the crab's body, and ultimately can not support their breathing.Therefore, the crab's bubbles are not endless.
。
