Fig. 1

Octocorals as habitat providers. a–c Gorgonians form three-dimensional structures in a range of environments, such as a Leptogorgia sarmentosa on sandy bottoms, b Corallium rubrum on the walls and ceilings of caves and overhangs, and c Paramuricea clavata forming “marine animal forests” on rocky substrates. Close-up of the gorgonian colonies of d Paramuricea clavata with open (front) and retracted (back) polyps and e C. rubrum, showing their eightfold body symmetry. f Colonies can consist of thousands of polyps forming large three-dimensional structures. Together colonies can form vast “forests” providing refuge and habitat for numerous marine organisms (photos a and f by Eric Béraud and photos b–e by Sergio Rossi)