Respiration and circulatory system Nemerteans lack specialized gills, and respiration occurs over the surface of the body, which is long and sometimes flattened. Like other animals with thick body walls, they use fluid circulation rather than diffusion to move substances through their bodies. The circulatory system consists of the rhynchocoel and peripheral vessels, while their blood is contained in the main body cavity. The fluid in the rhynchocoel moves substances to and from the proboscis, and functions as a fluid skeleton in everting the proboscis and in burrowing. The vessels circulate fluid round the whole body and the rhynchocoel provides its own local circulation. The circulatory vessels are a system of coeloms.
Respiration and circulatory system Nemerteans lack specialized gills, and respiration occurs over the surface of the body, which is long and sometimes flattened. Like other animals with thick body walls, they use fluid circulation rather than diffusion to move substances through their bodies. The circulatory system consists of the rhynchocoel and peripheral vessels, while their blood is contained in the main body cavity. The fluid in the rhynchocoel moves substances to and from the proboscis, and functions as a fluid skeleton in everting the proboscis and in burro!wing. The vessels circulate fluid round the whole body and the rhynchocoel provides its own l!ocal circulation. The circulatory vessels are a system of coeloms.