How do crabs breathe in and out under water and on land?

Land Crabs. The length of time a crab can stay out of water depends on the type of crab. Some crabs, like coconut crabs and land hermit crabs, are terrestrial and breathe well without water, although they still need to keep their gills moist. As long as their gills stay moist, these crabs can spend their lives out of the water. read more

Land hermit crabs, which in the adult stage, are land (terrestrial) crabs can not breath underwater. You can place them underwater for a period of time(a few minutes), but if they stay under too long then they will suffocate. read more

True crabs are crustaceans that have a short projecting “tail” or reduced hidden abdomen, while others such as hermit crabs, horseshoe crabs and crab lice, are not true crabs. Crabs can be found in oceans all over the world, and many crabs in tropical regions live in freshwater and on land. read more

Crabs breathe through gills. For gills to work, they must be able to take in oxygen and transport it into the animal's bloodstream. The gills of crabs are located under the carapace near the first pair of walking legs. The oxygen that crabs need is taken into the gills either through water or moisture in the air. read more