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Phylum Mollusca > Class Gastropoda > sea slugs > Order Nudibranchia
Slender ceratosoma nudibranch
Ceratosoma gracillimum
Family Chromodorididae
updated May 2020

Where seen? This large chunky hard nudibranch is more commonly seen by divers and sometimes seen on the intertidal on coral rubble near reefs.

Features: 6-8cm long. The body is stiff, narrow with a long, slender tail. There is a pair of elongated lobes on the sides (looks like 'wings'). At the body end over the tail, a large horn-like lobe, where the feathery gills emerge. The head is flat wedged-shaped with a pair rhinophores. The edges of the lobes and head are generally slightly wavy with a fine line of bright orange. The rest of the body generally speckled (orange, pink) with blotches of darker colour over a pale background.

Like other members of the Family Chromodorididae, the Ceratosoma nudibranch absorbs the toxic chemicals in their sponge food and incorporate these chemicals into the mantle glands. According to Bill Rudman, most species of Ceratosoma have a long 'horn' that sticks out and curves towards the head. This acts as a defensive lure attracting and sacrificed to potential predators. This 'horn' contains most of the distasteful chemicals stored from the sponges that they feed on.

Beting Bronok, Aug 15


Feathery gills.

Side 'wings', large lobe over the tail and wedge shaped head.
Beting Bronok, Jul 19
Sometimes mistaken for the 'Jolly Green Giant' nudibranch (Ceratosoma sinuatum) which has regular undulating lobes along the edge of the mantle from the head to the tail.

What does it eat? It is eats sponges.

Slender ceratosoma nudibranchs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

East Coast PCN, Jul 20
Photo shared by Loh Kok Sheng on facebook.

Beting Bronok, Jul 19
Photo shared by Marcus Ng on flickr.

Sentosa Serapong, Jun 18
Photo shared by Abel Yeo on facebook.

St. John's Island, Feb 15
Photo shared by Neo Mei Lin on her blog.

Sentosa Serapong, May 12
Photo shared by Marcus Ng on facebook.

Pulau Hantu, Jul 07
Photo shared by Toh Chay Hoon on flickr.

Pulau Hantu, Mar 08
Photo shared by Toh Chay Hoon on flickr.

Pulau Semakau (South), Apr 18
Photo shared by Jianlin Liu on facebook.

Pulau Semakau (North), Jul 20
Photo shared by Marcus Ng on facebook.

Beting Bemban Besar, Jun 15
Photo shared by Toh Chay Hoon on facebook.

Beting Bemban Besar, Jun 15
Photo shared by Toh Chay Hoon on facebook.

Terumbu Raya, May 09
Photo shared by Loh Kok Sheng on his blog.



  • Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore (pdf), Raffles Museum of Biodiversity Research, National University of Singapore.
  • Debelius, Helmut, 2001. Nudibranchs and Sea Snails: Indo-Pacific Field Guide IKAN-Unterwasserachiv, Frankfurt. 321 pp.
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