Constantinos Petrinos / Tube worm (Sabellidae) on hard coral (Euphyllia ancora) Sulawesi

Doug Perrine / Acoel flatworm {Waminoa sp} commensal on tentacles of Hard coral {Euphyllia glabrescens} Gato Island, Cebu, Philippines

Juergen Freund / Colonial hard coral {Euphyllia ancora} Papua New Guinea

Birgitte Wilms / Hard Coral (Euphyllia paraencora) polyps, 60 feet deep, Solomon Islands

Norbert Wu / Euphyllia Coral (Euphyllia ancora) a type of stony coral with distinctive polyps, Papua New Guinea

Juergen Freund / Coral {Euphyllia ancora} Pacific, Philippines

Juergen Freund / Tentacles of coral (Euphyllia glabrescens) Indo-Pacific

Gary Bell/ Oceanwide / Euphyllia Coral (Euphyllia ancora) polyps, Great Barrier Reef, Australia

David Fleetham / Commensal shrimp (Thor amboinensis) on hard coral polyps (Euphyllia ancora), Mabul Island, Malaysia.

Roberto Rinaldi / Bubble coral (Euphyllia sp), Farasan Islands, Saudi Arabia.

Chris Newbert / Euphyllia Coral (Euphyllia ancora) close-up of polyps, Coral Sea

Joel Sartore / Photo Ark / Branching frogspawn coral (Euphyllia paradivisa) portrait, Butterfly Pavilion, Colorado. Captive.