An adult R. pachyptila has a tough chitonous tube that grows to over 3 meters tall. At the top of the tube is a large red plume containing hemoglobin that gives R. pachyptila the appearence of a giant paintbrush . Inside the tube, the worm's body is colorless, and holds a large sack called a trophosome (along with its other organs). This sack contains billions of symbiotic bacteria that make food for the worm. The worm has no mouth, eyes, or stomach (Cary et al. 1989; Univ. of Delware Marine Studies 2000).