The Mudcat Café TM
Thread #164314 Message #4045839
Posted By: Steve Shaw
13-Apr-20 - 12:25 PM
Thread Name: BS: Varmints
Subject: RE: BS: Varmints
They obtain oxygen and eliminate carbon dioxide via diffusion through their skin. Oxygen must dissolve in the moisture on the skin first, so worms must never dry out. There is a rich bed of capillaries under the skin to facilitate this gas exchange. Earthworms come to the surface to get food, decaying leaves for example, which they drag down. I suppose they may find it easier to obtain oxygen by coming up to the top when the soil is saturated by rain, but in decently-aerated soil they don't need to come up for air. And worm burrows are a major contribution to that aeration.