About Gersemia rubiformis (Ehrenberg, 1834)
Gersemia rubiformis (Ehrenberg, 1834) is a colonial soft coral that grows into erect, knobbly clumps. All branches of a colony grow from a single main stalk. Its polyps are concentrated near the tips of narrow terminal branches, and cannot retract into their calyces. The branches are not rigid, but are stiffened by structures called sclerites, allowing them to sway gently in water currents. The sclerites of this species are red; many are irregular in shape, and some resemble miniature capstans. Unlike many corals, Gersemia rubiformis does not host symbiotic zooxanthellae algae.
This coral is found in polar to temperate waters, in the Arctic Ocean and the northwest Atlantic Ocean, ranging from the coasts of Canada south to Cape Hatteras, North Carolina. There is also a separate population in the Pacific Ocean, ranging from the coasts of British Columbia south to California. It can grow on sandy and muddy substrates, on bare rock, and on the hard surfaces of other benthic invertebrates such as shells.
A variety of other marine invertebrates share the habitat of Gersemia rubiformis. Juvenile Gorgonocephalus eucnemis basket stars often cling to this coral and hide in the gaps between its branches. The white sea anemone Metridium senile frequently grows in the same nearby area, and the rock scallop Crassadoma gigantea shares this coral's habitat in California. In Puget Sound, juvenile Gorgonocephalus eucnemis have been observed living, growing, and feeding inside the pharynges of Gersemia rubiformis polyps. They only become free-living once they are large enough to catch their own food.
