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

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

Pascal Kobeh / Porcelain crab ((Porcellanella triloba) living commensally on Purple sea pen (Virgularia gustaviana). Flores Sea, Indonesia.

Pascal Kobeh / Three-lobed / Painted porcelain crab (Porcellanella triloba) in a Sea pen (Pteroeides or Pennatula sp) Sulu Sea, Philippines

Franco Banfi / Porcelain crab (Porcellanella triloba) on a sea pen, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Juergen Freund / Sea pen porcelain crabs (Porcellanella triloba) in sea pen (Pteroides sp.). Lembeh Strait, North Sulawesi, Indonesia.

Georgette Douwma / Pen Crab (Porcellanella triloba) perched in Sea Pen (Virgularia sp.), from where the crab filter feeds in the current. Rinca, Indonesia. October.

Georgette Douwma / Pen Crab (Porcellanella triloba) perched in Sea Pen (Virgularia sp.). Filter feeding setae mouthparts of the crab are visible. Rinca, Indonesia, October.

Georgette Douwma / Sea pen porcelain crab (Porcellanella triloba) in Sea pen (Virgularia gustaviana) Porcelain crabs are filter feeders and climb in the sea pen to take advantage of current. When the Sea pen retreats in...

Georgette Douwma / Sea pen porcelain crab (Porcellanella triloba) in Sea pen (Virgularia gustaviana) Porcelain crabs are filter feeders and climb in the sea pen to take advantage of current. When the Sea pen retreats in...

Georgette Douwma / Hydroid or Fairy crab (Hyastenus bispinosus) on Sea pen (Pteroides sp.) where it has climbed to feed on plankton floating past. It has decorated its body with hydroid polyps. Majidae - Spider or Decor...

Georgette Douwma / Pen crab (Porcellanella triloba) resting in Sea pen (Pteroeides) to feed on plankton, Rinca, Indonesia

Georgette Douwma / Hydroid / Fairy crab (Hyastenus bispinosus) on Sea pen (Pteroides sp) where it has climbed to feed on plankton floating past, it has decorated its body with hydroid polyps, Rinca, Indonesia

Chris Newbert / Porcelain Crab (Porcellanella sp) camouflaged on Sea Pen (Virgularia sp), Indonesia

Chris Newbert / Porcelain Crab (Porcellanidae) on Sea Pen (Scytalium sarsii), Papua New Guinea

Georgette Douwma / Unidentified porcelain crabs (Pteroeides sp.) on Sea pen, Rinca, Indonesia

GEORGETTE DOUWMA / Hydroid / Fairy crab (Hyastenus bipinosus) on Sea pen (Pteroides sp.) where it has climbed to feed on plankton floating past. It has decorated its body with hydroid polyps, Indonesia

David Hall / Porcelain crab (Porcellanella haigae) on Sea pen (Veretillum sp). Pantar, Alor Archipelago, Lesser Sunda Islands, Indonesia.