Juergen Freund / Golden sea squirt (Polycarpa aurata) West New Britain, Papua New Guinea.

Juergen Freund / Golden sea squirts / ascidians / tunicates (Polycarpa aurata) on coral reef, Sulawesi, Indonesia, Indo-pacfic.

Juergen Freund / A colony of golden sea squirts / tunicates (Polycarpa aurata). Misool, Raja Ampat, West Papua, Indonesia, January.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle) internal detail. Misool, Raja Ampat, West Papua, Indonesia.

Sue Daly / Lightbulb seasquirts / tunicates (Clavelina lepadiformis) cluster on rock, Channel Isles, UK, July

SINCLAIR STAMMERS / Tunicate {Salpa maxima} plankton underwater, Mediterranean

SINCLAIR STAMMERS / Tunicate {Salpa maxima} Mediterranean

Michael Pitts / Chain of fluorescent tunicates {Salpa maxima} off Komodo Is, Indonesia

Norbert Wu / Tunicate (Megalodicopia hians) predatory deep sea species, Monterey, California

Georgette Douwma / Sea squirts {Polycarpa aurata + Rhopalaea sp} and soft coral, Banda, Moluccas, Indonesia, Indo

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

Norbert Wu / Invertebrates on pier piling, Edithburgh, South Australia, Australia

Norbert Wu / Invertebrates on pier piling, Edithburgh, South Australia, Australia

Chris Newbert / Ink-spot Ascidian (Polycarpa aurata) tunicate, Indonesia

Solvin Zankl / Sea Potato tunicate (Halocinthia papillosa) San Pietro Island, Sardinia, Italy, Mediterranean, July

Jeff Rotman / White and red Sea Peaches (Halocynthia pyriformis / papillosa) filter feeding on plankton. New England, USA, Atlantic Ocean.

Georgette Douwma / Sea Squirts (Polycarpa aurata) with soft corals and other invertebrates. Raja Ampat, Indonesia.

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

Christian Ziegler / Red Mangrove (Rhizophora mangle) aerial roots provide space for tunicates, Carrie Bow Cay, Belize

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 sea squirt (Clavelina caerulea) hosting an amphipod crustacean, Batangas, Philippines.

Juergen Freund / Blue spot ascidian (Clavelina moluccensis) Batangas, Philippines.

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

Juergen Freund / Blue sea squirt (Clavelina caerulea) hosting an amphipod, Batangas, Philippines.

Juergen Freund / A colonial tunicate / ascidian (Didemnum vexillum) invasive species that forms huge colonies, Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / A colonial tunicate / ascidian (Didemnum vexillum). An invasive sea squirt which can form huge colonies that smother shellfish beds, Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle). Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata) with a blennie sitting on top. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata). Misool, Raja Ampat, West Papua, 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 / Sea squirt / tunicate (Didemnum sp) morph black-yellow encroaching on a Golden sea squirt (Polycarpa aurata) Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle) internal detail. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle), close-up of the syphon. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Purple tunicate / sea squirt (Didemnum membranaceum) on coral reef, Misool, Raja Ampat, West Papua, Indonesia.

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

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata) showing hairs to stop large particles entering the cavity. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle). Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Stalked ascidians / tunicates (Clavelina robusta) on a fan coral. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata) with many smaller tunicates at its base. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata) with many smaller tunicates at its base. Misool, Raja Ampat, West Papua, Indonesia.

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

Juergen Freund / Golden sea squirt / tunicate (Polycarpa aurata) with many smaller tunicates at its base. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Detail of Reticulated ascidians / tunicates (Leptoclinides / Didemnum reticulatus) Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Three hole tunicate / sea squirt / ascidian (Polycarpa aurata). North Raja Ampat, West Papua, Indonesia.

Juergen Freund / Blue sea squirt / tunicate / ascidian (Clavelina caerulea) Moluccas Islands, Indo-pacific.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle). Misool, Raja Ampat, West Papua, Indonesia

Juergen Freund / Stalked ascidian / tunicate cluster (Clavelina robusta). Misool, Raja Ampat, West Papua, Indonesia

Tim Laman / Tunicates (Didemnum molle) Bali, Indonesia.

GEORGETTE DOUWMA / Colony of Tunicates / Sea squirts (Perophora modificata) Misool, Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Tunicate / Sea squirt (Polycarpa aurata) being squeezed out by a sponge. Misool, Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Tunicate / Sea squirt (Polycarpa aurata) Misool, Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Tunicate / Sea squirt (Polycarpa aurata) Misool, Raja Ampat, West Papua, Indonesia.

GEORGETTE DOUWMA / Tunicate / Sea squirt (Polycarpa aurata) Misool, Raja Ampat, West Papua, Indonesia.

Sue Daly / Seasquirt / Tunicate (Rhopalaea sp) Lembeh Straits, Sulawesi, Indonesia

Sue Daly / Seasquirt / Tunicate (Didemnum molle) Lembeh Straits, Sulawesi, Indonesia

Sue Daly / Seasquirt / Tunicate (Didemnum molle) Lembeh Straits, Sulawesi, Indonesia

Sue Daly / Lightbulb seasquirts / tunicates (Clavelina lepadiformis) cluster on rock, Channel Isles, UK, July

GEORGETTE DOUWMA / Freckled hawkfish (Paracirrhites forsteri) perched next to a Seasquirt (Polycarpa aurata). Misool, Raja Ampat, West Papua, Indonesia.

Sue Daly / Tunicate / Sea Squirts (Rhopalaea sp) Cebu, Philippines, March

David Shale / Salp chain {Salpidae} Mid-Atlantic Ridge, North Atlantic Ocean

Fred Bavendam / Yellow Sea Horse (Hippocampus kuda) near tunicates, Lembeh Strait, Indonesia

Fred Bavendam / Tunicate (Rhopalaea crassa) with Goby (Pleurosicya mossambica), Bali, Indonesia

Fred Bavendam / Tunicate (Rhopalaea sp) group surrounded by ascidians, Bali, Indonesia

Fred Bavendam / Sea Peach (Halocynthia pyriformis) pair, York, Maine

Chris Newbert / Tunicate (Polycarpa aurata) detail, Indonesia

Chris Newbert / Soft Coral (Dendronephthya sp) reef, Indonesia

Chris Newbert / Tunicate (Didemnum sp) group, Indonesia

Chris Newbert / Soft Coral (Dendronephthya sp) reef scenic, Indonesia

Norbert Wu / Brightly colored tunicates, Komodo Island, Indonesia

Norbert Wu / Brightly colored tunicates, Komodo Island, Indonesia

Norbert Wu / Brightly colored tunicates, Komodo Island, Indonesia

Doug Perrine / Tunicates {Didemnum sp} growing on coral reef, Vitu Is, Papua New Guinea

Doug Perrine / Tunicate / Sea squirt {Polycarpa aurata} Papua New Guinea

Scott Leslie / Salp floating in open ocean, Nova Scotia, Canada

Scott Leslie / Sea Peach (Halocynthia pyriformis) tunicate pair, Nova Scotia, Canada

Jeff Rotman / Urn-Synascidians tunicates (Didemnum molle) Sipadan Island, Borneo, South China Sea.

Juergen Freund / Tunicate (Clavelina lepadiformis) Mediterranean Sea

Alan James / Light bulb tunicates {Clavelina lepadiformis} UK

Alan James / Light bulb tunicates {Clavelina lepadiformis} UK

GEORGETTE DOUWMA / Tunicate / seasquirt {Polycarpa aurata} Molluccas Indonesia Banda island

GEORGETTE DOUWMA / Tunicate / seasquirt {Polycarpa aurata} Molluccas Indonesia Banda island

Doug Perrine / Colourful collection of Tunicates {Didemnum sp} on seabed, Palau, Micronesia

Doug Perrine / Tunicates / Sea squirts {Clavelina robusta} Gato Island Marine Reserve, Cebu Island, Philippines

David Shale / Deepsea solitary salp (Iasis zonaria), deep sea Atlantic ocean,

Juergen Freund / Tunicate {Rhopalea sp} with atriolum tunicates {Atriolum robustum} Indo Pacific

Juergen Freund / Close up of Tunicate {Polycarpa aurata} Indo Pacific

Francis Abbott / Chain of fluorescent tunicates (Salpa maxima) off Menorca, Mediterranean.

Jose B. Ruiz / Tunicate {Halocynthia papillosa} in the Mediterranean.

Jose B. Ruiz / Tunicate {Halocynthia papillosa} Mediterranean

Chris Newbert / Sea Squirt (Didemnum molle) and Sea Squirt (Didemnum nekozita), Palau

GEORGETTE DOUWMA / Tunicates {Polycarpa aurata} + {Rhopalaea sp} on soft coral Banda, Moluccas, Indonesia

GEORGETTE DOUWMA / Sea squirt {Botryllus sp} Sulawesi, Indonesia Kungkungan bay

Michael Pitts / Line of Salps {Salpa maxima} Mediterranean

GEORGETTE DOUWMA / Sea squirts {Atriolum robustum} living on 'fighting zone' between two corals. Sulawesi,

CONSTANTINOS PETRINOS / Sea squirt {Polycarpa aurata} with nudibranch. Sulawesi, Indonesia.