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Earthworms
In the absence of a heart, earthworms have five pseudohearts that wrap around their esophagus and help circulate their blood throughout the body. Their moist skin allows them to absorb oxygen from air trapped in the soil or aboveground after rain. This oxygen is then drawn into the cells and blood system, where it is pumped around the body by the red blood containing hemoglobin, a protein that carries oxygen. This circulation process is facilitated by an open circulatory system.
