Franco Banfi / Rounded bubblegum / Bubble coral (Plerogyra sinuosa) with two Gobies (Gobiidae) on it, Lazi Pier, Dumaguete, East Negros Island, Central Visayas, Philippines, Pacific Ocean.

Constantinos Petrinos / Acoel flatworms (Waminoa sp.) on Bubble Coral (Plerogyra sinuosa) Lembeh Strait, North Sulawesi, Indonesia.

Linda Pitkin / Banggai Cardinalfish (Pterapogon kauderni), sheltering against Bubble Coral (Plerogyra sinuosa) Lembeh Strait, North Sulawesi, Indonesia, February 2016

Georgette Douwma / Acoel flatworms (Waminoa sp) on polyps of Bubble coral (Plerogyra sinuosa) Indonesia. This flatworm can cover the whole surface of some corals, leaving them no way to catch plankton and their symbioti...

Georgette Douwma / Acoel flatworms (Waminoa sp) on polyps of Bubble coral (Plerogyra sinuosa) Indonesia. This flatworm can cover the whole surface of some corals, leaving them no way to catch plankton and their symbioti...

Claudio Contreras / Inanuran Island, Danajon Bank, Central Visayas, Philippines, April

Georgette Douwma / Lined butterflyfish (Chaetodon lineolatus), pair feeding on Bubble coral (Plerogyra sinuosa). Egypt, Red Sea.

Juergen Freund / Bubble coral (Plerogyra sinuosa) with parasitic flatworms (Waminoa sp). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Bubble coral (Plerogyra sinuosa) on the reef. Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Orangutan crab (Achaeus japonicus) in bubble coral (Plerogyra sinuosa) Kimbe Bay, Papua New Guinea, Indo-Pacific.

Constantinos Petrinos / Bubble or grape coral (Plerogyra sinuosa) Sulawesi, Indonesia

Chris Newbert / Rounded Bubblegum Coral (Plerogyra sinuosa), Coral Sea

Fred Bavendam / Coral Shrimp (Vir philippinensis) living on Rounded Bubblegum Coral (Plerogyra sinuosa) green spots are Acoelous Flatworms, Manado, North Sulawesi, Indonesia

Gary Bell/ Oceanwide / Coral Shrimp (Vir philippinensis) on Rounded Bubblegum Coral (Plerogyra sinuosa), Anilao, Philippines

Gary Bell/ Oceanwide / Coral Shrimp (Vir philippinensis) on Rounded Bubblegum Coral (Plerogyra sinuosa), Anilao, Philippines

Gary Bell/ Oceanwide / Rounded Bubblegum Coral (Plerogyra sinuosa), Great Barrier Reef, Australia

David Fleetham / Bubble coral shrimp (Vir philippinensis) on Bubble coral (Plerogyra sinuosa). The brown oval objects are acoel flatworms (Waminoa sp.), Mabul Island, Malaysia.

David Fleetham / Two Commensal shrimp (Vir philippinensis) on Bubble Coral (Plerogyra sinuosa), Indonesia. The greenish brown circular markings are flatworms (Waminoa sp.)

Pete Oxford / Rounded Bubblegum Coral (Plerogyra sinuosa), Raja Ampat Islands, Indonesia

Constantinos Petrinos / Bubble coral shrimp {Vir philippinensis} on Bubble coral {Plerogyra sinuosa} Sulawesi, Indonesia

Richard Herrmann / Rounded Bubblegum Coral (Plerogyra sinuosa), Mindoro Island, Philippines

Magnus Lundgren / Bubble coral shimp (Vir philippinensis) full of eggs, resting in Bubble coral (Plerogyra sinuosa), Triton Bay, West Papua, Indonesia, Pacific Ocean.

David Fleetham / Bubble coral (Plerogyra sinuosa) on acoral reef, the Philippines.

David Fleetham / Neon dwarfgoby (Eviota atriventris) on Bubble coral (Plerogyra sinuosa) Philippines.

Georgette Douwma / Translucent coral goby (Bryaninops erythrops) resting on Bubble coral (Plerogyra sinuosa). Derawan Islands, East Kalimantan, Indonesia.

Georgette Douwma / Orangutan crab (Oncinopus sp) resting on Bubble coral (Plerogyra sinuosa). Derawan Islands, East Kalimantan, Indonesia.

Linda Pitkin / Bubble coral shrimp (Vir philippinesis) in symbiotic commensal relationship with Bubble coral (Plerogyra sinuosa). Lembeh Strait, North Sulawesi, Indonesia.