Richard Robinson / Large sea pen (Pteroeides bollonsi) in Doubtful Sound, Fiordland National Park, New Zealand.

Pascal Kobeh / Commensal shrimp (Periclimenes magnificus) on Sea pen (Pteroeides), Manado, Indonesia. Sulawesi Sea.

Franco Banfi / Sea pen, (Pteroeides sp.) , Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Jeff Rotman / Sea pen (Pteroeides sp) in sand at night, Bismarck Sea, Papua New Guinea

Juergen Freund / Sea pen (Pteroeides sp) on seabed at night, Komodo NP, Indonesia.

Georgette Douwma / Sea pen (Pteroeides sp) on sandy sea bed. Komodo National Park, Indonesia

Georgette Douwma / Sea pen (Pteroeides sp) on sandy seabed, Komodo National Park, Indonesia

Georgette Douwma / Sea pen (Pteroeides sp) on sandy sea-bed. Komodo National Park, Indonesia

David Shale / Brittle star {Ophiurida} on Seapen (Pennatulidae), deepsea, from the Mid-Atlantic Ridge

Albert Lleal / Sea Pen (Pennatula sp) tentacles made up of polyp colony, Spain

Fred Bavendam / Orange Peel Nudibranch (Tochuina tetraquetra) eating an Orange Sea Pen (Ptilosarcus gurneyi), British Columbia, Canada

Fred Bavendam / Sea Pen (Sarcoptilus grandis) field with an Ocellate Sea Star (Nectria ocellata) crawling among them, Port Davey, Tasmania, Australia