1.陆地上爬行的螃蟹为什么要吐沫?螃蟹是生活在水中的动物,它和鱼一样是用鳃进行呼吸的,与鱼不同的是它的鳃长在脑部的两侧,由头胸甲覆盖着。螃蟹在水中呼吸时,水从鳌足和步足的基部进入鳃中,氧气和二氧化碳在鳃内完成气体交换后,水又从口的两边吐出。螃蟹到陆地上觅食或爬行时 1. Why does the crab crawling on land whip? Crab is an animal that lives in the water. It is like a fish. It uses a dragonfly for breathing. Unlike a fish, its dragonfly grows on both sides of the brain and is covered by a head breastplate. With. As the crabs breathe in the water, the water enters the cocoon from the base of the lameness and the foot and foot. After oxygen and carbon dioxide exchange gas in the cockroach, the water spits out from both sides of the mouth. When crabs grazing or crawling on land