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.
During the middle of June, the water temperature and tidal stage initiate the spawning process of the sexually mature worms. They swim to the surface of the water where the males emit sperm and the females burst releasing their eggs. Box sexes of worms die after spawning.