Franco Banfi / Two Mushroom coral / Commensal shrimps (Cuapetes / Periclimenes kororensis) on Mushroom coral (Heliofungia actiniformis) Lighthouse Reef, Cabilao Island, Bohol, Central Visayas, Philippines, Pacific O...

Pascal Kobeh / Commensal shrimp (Periclimenes tosaensis) in Mushroom coral (Heliofungia actiniformis) Sulu Sea, Philippines

Georgette Douwma / Mushroom coral (Heliofungia actiniformis) with polyps extended, Bunaken, Sulawesi, Indonesia.

Georgette Douwma / Close up of Mushroom coral (Heliofungia actiniformis) with polyps partially retracted. Bunaken, Sulawesi, Indonesia.

Georgette Douwma / Acoelous flatworms {Waminoa sp} on tentacles of Mushroom coral {Heliofungia actiniformis} Sulawesi, Indonesia

Georgette Douwma / Mushroom coral {Heliofungia actiniformis} with Acoel flatworms {Waminoa sp} Bunaken, Sulawesi, Indonesia

Juergen Freund / Fluorescent Hard coral {Heliofungia actiniformis} seen under normal light, Papua New Guinea

Juergen Freund / Hard coral {Heliofungia actiniformis} fluorescent under UV light, Papua New Guinea

Chris Newbert / Mushroom Coral (Heliofungia actiniformis), Indonesia

Chris Newbert / Mushroom Coral (Heliofungia actiniformis), Indonesia

Visuals Unlimited / Commensal Shrimp (Hamopontonia corallicola) on a Plate Coral (Heliofungia actiniformis), Mabul Island, Malaysia.