Animal profile

Sea Pen

Ptilosarcus gurneyi

AnthozoaSoft mud and sand bottoms from shallow subtidal to deep water

Field profile

The orange sea pen is a colonial octocoral shaped like a quill, anchored in sediment by a bulbous foot. Feeding polyps line the branches above. Colonies retract into the sediment when disturbed and glow when touched.

Published field notes

2026-04-14

Sea Pen

A sea pen's stalk is one giant polyp

The stalk buried in the mud is not a root. It is a single enormously enlarged polyp, the primary axial polyp, and every feeding polyp on the branches above is a secondary polyp budded from it and permanently attached.

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