A soft-sided creature, typically about six inches long with a long, slim forked end, used by organic Denobulan healers like Phlox for internal treatments to cleanse the humanoid lymphatic system with no side effects. He only has about a half-dozen in a reddish slime in his Sickbay menagerie during the Xindi mission, kept in a clear canister; they are hard to replace. During the elaborate futuristic ruse to win Degra's trust initially, Phlox and Archer implant one in Degra's left arm to reinforce a story that the worms are used as "truth serum" by the Xindi-Insectoids, thanks to the mucous liquid they secrete when injected under the skin.

A century later, the Klingon officer Korax famously does not compare James T. Kirk to a Regulan bloodworm.