Bloodworms are creamy pink segmented worms with small fleshy projections called parapodia. Their anterior end has a small tapered postomium with four small antennae. They can tolerate low levels of oxygen in the substrate as well as minimum salinity. Bloodworms are excellent burrowers utilizing their prostomium, short stiff parapodia and perisaltic muscle contractions.
Bloodworms can grow up to fifteen inches in length.
Their rate of growth is affected by the availability of food, temperature and salinity. The non-digestible solids are packaged within fecal pellets and regurgitated. The anterior brain is connected to a large ventral nerve cord. This cord runs from the anterior to the posterior end of the worm. Coelomic fluid containing hemoglobin is circulated by peristalic body movements.