Two species of solitary coral are quite common at this site and share a fascinating life cycle. The juvenile coral settles out on a small mollusk shell and begins to grow, while the empty shell becomes occupied by a sipunculid worm. The coral eventually completely engulfs the shell, but the worm maintains holes through the coral to the outside. The worm can extend through these holes and provide locomotion to the coral, preventing it from being buried in the fine sediment. The name of the ribbed sided coral is Heterocyathus aequicostatus. 20mm
3 November 2012