Pascal Kobeh / Hard coral (Porites lutea) with Christmas-tree worms (Spirobranchus giganteus), New Caledonia, Pacific Ocean.

Georgette Douwma / Christmas tree worm (Spirobranchus giganteus). North Sulawesi, Indonesia.

Georgette Douwma / Christmas tree worm (Spirobranchus giganteus). North Sulawesi, Indonesia.

Alex Mustard / Christmas tree worm (Spirobranchus giganteus) growing out from a coral, next to a bed of algae. East Of Eden, Similan Islands, Thailand. Andaman Sea, Indian Ocean.

Pascal Kobeh / Christmas tree worm (Spirobranchus giganteus) Maldives, Indian Ocean.

Alex Mustard / High magnification detail of filter feeding appendage of Christmas tree worm (Spirobranchus giganteus) Misool, Raja Ampat, West Papua, Indonesia. Ceram Sea, Tropical West Pacific Ocean.

Solvin Zankl / Christmas tree worms (Spirobranchus giganteus) on Porites coral (Porites sp) Raja Ampat, West Papua, Indonesia, Pacific Ocean.

Roland Seitre / Christmas Tree Worms (Spirobranchus giganteus) Jokin, Lifou, Loyalty Islands Province, New Caledonia

Franco Banfi / Christmas tree worm (Spirobranchus giganteus) Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Georgette Douwma / Christmas tree worms (Spirobranchus giganteus) on Porites coral boulder, Andaman Sea, Thailand

Pete Oxford / Christmas tree worm (Spirobranchus giganteus) on Star coral (Montastraea cavernosa) Bonaire, Netherlands Antilles, Caribbean

Pete Oxford / Christmas tree worm (Spirobranchus giganteus) on Star coral (Montastraea cavernosa) Bonaire, Netherlands Antilles, Caribbean