David Shale / Detail of deepsea Sea pen (Pennatulacea) from coral seamount, Indian Ocean, December 2011

Alex Mustard / 2020VISION / Phosphorescent Seapen (Pennatula phosphorea) extends out of the muddy seabed in the calm waters of the upper reaches of a Scottish sea loch. Loch Duich, Ross and Cromarty, Scotland, UK, April

Juergen Freund / Sea pens (Virgularia sp) on sandy seabed, Palawan, Philippines.

Juergen Freund / Sea pen octocoral (Veretillum sp) with polyps out, feeding, Misool, Raja Ampat, West Papua, Indonesia

Georgette Douwma / Loki whip goby (Bryaninopss loki) on Sea pen (Virgularia gustaviana). Komodo National Park, Indonesia

Georgette Douwma / Purple sea pen (Virgularia gustaviana) on sandy sea bed. Rinca, Indonesia

Georgette Douwma / Sea pen (Virgularia gustaviana) with a small porcelain crab on sandy sea bed, purple form. Rinca, Indonesia.

Alex Mustard / Common ghost goby (Pleurosicya mossambica) hiding in the branches of a sea pen (Pteroeides sp.). Anilao, Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Tropical West Pacifi...

Alex Mustard / Common ghost goby (Pleurosicya mossambica) hides in the branches of a sea pen (Pteroeides sp.). Anilao, Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Tropical West Pacific...

Georgette Douwma / Kaleidoscopic image of Brittlestar (Ophiothrix sp.) on Sea pen (Virgularia sp.). Rinca, Indonesia.

David Hall / Mozambique ghostgoby (Pleurosicya mossambica) living commensally with Sea pen (Pennatulacea). Komodo, Indonesia; November, 2006

David Hall / Haig's porcelain crab (Porcellanella haigae) living commensally on Sea pen (Pennatulacea) Crab recently emerged from exoskeleton. Pantar, Alor Archipelago, Indonesia.