Georgette Douwma / Blue club sea squirt (Rhopalaea crassa) with a small Goby, unknown species. West Papua, Indonesia.

Georgette Douwma / Sea squirts: Golden sea squirt (Polycarpa aurata) and Blue club tunicate (Rhopalaea crassa) Lembeh, Sulawesi, Indonesia.

Alex Mustard / Amphipod (Amphipoda) living inside sea squirt (Rhopalaea sp.) Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Alex Mustard / Amphipod (Amphipoda) living inside sea squirt (Rhopalaea sp.) Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Franco Banfi / Nudibranch (Nembrotha rutilans) feeding on ascidian, Rhopalaea, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Michele Westmorland / Blue tunicates (Rhopalaea sp) around cluster of other sea tunicates, Cannibal Rock, Rinca Island, Indonesia

Christian Ziegler / Tunicate (Rhopalaea sp) group on Red Mangrove (Rhizophora mangle) aerial roots provide space for a large community of invertebrates, Carrie Bow Cay, Belize

Juergen Freund / Blue Club Tunicate (Rhopalaea circula) Batangas, Philippines.

Juergen Freund / Blue club tunicates / ascidians / sea squirts (Rhopalaea crassa). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Blue club tunicates / ascidians / sea squirts (Rhopalaea crassa). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Blue club tunicates / ascidians / sea squirts (Rhopalaea crassa). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Blue Club Tunicate (Rhopalaea circula) and Golden Sea Squirt (Polycarpa aurata). Misool, Raja Ampat, West Papua, Indonesia.