Alex Mustard / 2020VISION / Light-bulb sea squirts (Clavelina lepadiformis), a colonial filter feeding invertebrate, fluoresce green when photographed under deep blue light. Shetland Islands, Scotland, UK, June. Did you know? Se...

Alex Mustard / 2020VISION / Light-bulb sea squirts (Clavelina lepadiformis), a colonial filter feeding invertebrate, fluoresce orange when photographed under deep blue light. Shetland Islands, Scotland, UK, June. Did you know? L...

Alex Mustard / 2020VISION / Light-bulb sea squirts (Clavelina lepadiformis), a colonial filter feeding invertebrate, Shetland Islands, Scotland, UK, June

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

Nick Upton / Group of Light bulb sea squirts (Clavelina lepadiformis) in rockpool low on the shore, Helford River, Cornwall, UK, August.

Sue Daly / Light Bulb sea squirt (Clavelina lepadiformis) Channel Islands, UK July

Alex Mustard / 2020VISION / Light-bulb sea squirts (Clavelina lepadiformis), a colonial filter feeding invertebrate, photographed under normal white light from a flashgun (left) and two examples photographed under blue light, on...

Sue Daly / Light Bulb Sea Squirt (Clavelina lepadiformis). Channel Islands, UK, July.

Sue Daly / Light Bulb Sea Squirt (Clavelina lepadiformis). Channel Islands, UK, June.

Sue Daly / Light Bulb Sea Squirt (Clavelina lepadiformis). Channel Islands, UK, June.

Sue Daly / Light Bulb Sea Squirt (Clavelina lepadiformis). Channel Islands, UK, June.

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

Juergen Freund / Colony of small yellow tunicates (possibly Clavelina sp). 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 / Colony of small yellow tunicates (possibly Clavelina sp). Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / A colony of Ascidians (Clavelina sp). North Raja Ampat, West Papua, Indonesia.

Juergen Freund / Yellow sea cucumber (Colochirus robustus) on a Tunicate (Clavelina robusta). North Raja Ampat, West Papua, Indonesia.

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

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

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

Chris Newbert / Sea Squirt (Clavelina sp) group, Papua New Guinea

Juergen Freund / Tunicate (Clavelina lepadiformis) Mediterranean Sea

Alan James / Light bulb tunicates {Clavelina lepadiformis} UK

Alan James / Light bulb tunicates {Clavelina lepadiformis} UK

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

Sue Daly / Light bulb sea squirts {Clavelina lepadiformis} Sark, Channel Is, UK

Angelo Giampiccolo / Colony of Tunicates (Clavelina lepadiformis), Balicasag Island, Philippines.

Angelo Giampiccolo / Nudibranch (Phyllidia sp.) on a colony of Tunicates (Clavelina lepadiformis). Balicasag Island, Philippines.

Angelo Giampiccolo / Colourful Nudibranch (Phyllidia sp.) on a colony of Tunicates (Clavelina lepadiformis). Balicasag Island, Philippines.

Roberto Rinaldi / Painted tunicate (Clavelina picta) on bright red rope sponge, Belize

Roberto Rinaldi / Colonies of Ascidians (Clavelina lepadiformis) and Zoantharians (Parazoanthus axinellae), Noli, Liguria, Italy.