Christmas tree worms are polychaetes (marine segmented worms) that live in the skeletons of corals. They retract their feeding appendage (seen above) when threatened. You can see the little trap door that closes behind them on the upper right I took this close up photo off the central Pacific island of Raiatea while on a cruise on the SSV Robert C Seamans with SEA Semester. I used the incredible new Olympus Tough camera. See more of my photos from the backreef of French Polynesia here.