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Phylum Cnidaria > Class Anthozoa > Subclass Alcyonaria/Octocorallia > Order Pennatulacea
Spiky sea pen
Pteroeides sp.*
Family Pennatulidae
updated Mar 13
Where seen? This feathery colony is sometimes seen on our Northern shores. In soft silty sand and near seagrasses. The colony does not harbour symbiotic algae (zooxanthellae) and can thus thrive in murky water.

Features: Those seen on our shores are about 15-20cm long (but some species of Pteroides are said to grow to 60cm long!). According to Reef Corals of the Indo-Malayan Seas globally, there are about 17 species of Pteroeides.

Each colony is stout and feather-like. Made up of a sausage-like 'stem' some are plain, others with brown blotches. Some have an orange 'foot', usually buried and seen only in uprooted sea pens. Short (2-3cm) leaf-like structures symmetrically on both sides of the 'stem'. These 'leaves' supported by rays of many long needle-like sharp spikes that stick out of the leaf edge. When exposed at low tide, the central stalk is often bent over in half so the colony looks like a limp feather.

Tiny feeding polyps (autozooids) with 8 branched tentacles emerge from these 'leaves' when submerged. The autozooids can retract completely, leaving tiny bumps on the 'leaf' edges. The colony also has another kind of polyp that sucks in water (siphonozooids) and which are minute, numerous and crowded near edges of the 'leaves'.

Pen pals: The tiny Painted porcelain crab (Porcellanella picta) is often found in pairs in this sea pen.
Washed up sea pens sometimes seen with colourful brittle stars and other brittle stars.

Sometimes seen uprooted with orange foot.
Pasir Ris, Dec 08

Tiny polyps on the sea fan.

Bent over at low tide
Changi, Jul 04

The Painted porcellain crab is often
seen in this sea pen.

Tiny coloutful brittle stars.
Changi, Oct 11

Changi, Jul 12
Autozooids emerging from the 'leaf' edge.

Pulau Sekudu, Aug 13

Pulau Sekudu, Aug 13

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Spiky sea pens on Singapore shores

Photos of Spiky sea pens for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map

Tanah Merah, Aug 09
Photo shared by James Koh on his blog.

Pulau Ubin, Dec 09
Photo shared by James Koh on his blog.

Tuas, Jun 10
Photo shared by Toh Chay Hoon on her blog.

Tanah Merah, Feb 09

Shared by Loh Kok Sheng on his blog.

East Coast, Jun 06
Tiny coloutful brittle star.



  • Erhardt, Harry and Daniel Knop. 2005. Corals: Indo-Pacific Field Guide IKAN-Unterwasserachiv, Frankfurt. 305 pp.
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