Editing Marine worm (section)

==Circulation==
Marine worms have a variety of circulation and respiration processes. For example, in platyhelminths this is achieved through diffusion of oxygen (as well as other nutrients) across a moist epithelial layer, whereas annelids have a closed circulatory system with blood vessels lining the body.<ref>Collins, James J. "Platyhelminthes." ''Current Biology'' 27.7 (2017): R252-R256.</ref><ref>{{Cite web |date=Oct 24, 2023 |title=Worms: Phyla Platyhelmintes, Nematoda, and Annelida |url=https://manoa.hawaii.edu/exploringourfluidearth/biological/invertebrates/worms-phyla-platyhelmintes-nematoda-and-annelida#:~:text=Annelids%20have%20a%20closed%20circulatory,the%20cells%20of%20the%20body. |website=Exploring Our Fluid Earth |publisher=University of Hawaii at Manoa}}</ref>

Many of these worms have specialized tentacles used for exchanging oxygen and carbon dioxide which also may be used for reproduction. These specialized tentacles allow for gas exchange, further decreasing oxygen content in dead zones and in shallow water, which encourages plant and algae growth.{{citation needed|date=October 2022}}

This quality is also observed in deeper oceans, where tube worms that use respiratory plumes with tentacles perform gas exchange of hydrogen sulfide and methane around hydrothermal vents. These types of circulatory systems differ from marine worms previously mentioned that can perform gas exchange through their entire bodies. This synapomorphy of gas exchange causes even related terrestrial annelids to be restricted to moist environments.{{citation needed|date=October 2022}}