Gersemia rubiformis is a colonial coral that grows in the form of knobbly clumps. The colonies are erect and branch from one main stalk. The polyps are concentrated near the ends of the narrower terminal branches and are non-retractile in their calyces. The branches are not rigid but are stiffened by the presence of sclerites, and can sway gently in the current. The sclerites are red, some being irregular and shaped like miniature capstans. Gersemia rubiformis does not contain the symbiotic alga zooxanthella. In Puget Sound, juvenile basket stars (Gorgonocephalus eucnemis) have been found to be living, growing and feeding inside the pharynges of Gersemia rubiformis polyps, only becoming free-living when they have grown large enough to catch food for themselves. Learn more about Sea Strawberry