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Phylum Mollusca > Class Gastropoda > sea slugs > Order Nudibranchia
Semper's armina nudibranch
Armina semperi
Family Arminidae
updated May 2020

Where seen? This slug in pajamas is sometimes seen on our Northern shores, burrowing in sandy areas near seagrasses where there are sea pens. It is more active at night.

Features: 2-6cm long. Body long, narrow with narrow black-and-white stripes (which are actually ridges). The blue foot has a yellow or orange border. The wedge-shaped flap over its mouth (oral veil) is also blue with a yellow or orange border. The oral veil has no bumps on it. Rhinophores with yellow or red tips and fine black stripes. According to Bill Rudman, the coloured wiggly lines seen on the underside of the body are not gills although gas exchange may take place. These act like the cerata of aeolids, a place where the digestive gland can expand. These lines often are the same colour of their sea pen food.

Changi, May 14

Colourful oral veil without bumps.
Changi, Jun 06

Changi, Oct 07

Gills under the mantle skirt.
Chek Jawa, Jun 05
Sometimes mistaken for the bumpy-faced armina nudibranch, that has a plain oral veil and foot and has bumps on its 'face'. The Tiny striped nudibranch (Dermatobranchus sp.) is also striped but is much smaller.

What does it eat? As a group, the armina nudibranchs eat soft corals and sea pens. Bill Rudman has a post sharing how an armina nudibranch feeds on a sea pen and is dragged down into the sand when the sea pen retracts.

About to eat this Flowery sea pen?
Changi, Aug 14

About to eat this Spiky sea pen?
Beting Bronok, Jun 18

Semper's armina nudibranch on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

About to eat this Flowery sea pen?
Changi, Aug 19
Photo shared by Loh Kok Sheng on facebook.

Eating a Sea pencil?
Changi, Jul 20
Photo shared by Toh Chay Hoon on facebook.

Changi, Oct 20
Photo shared by Marcus Ng on facebook.

Pulau Sekudu, May 12
Photo shared by Toh Chay Hoon on facebook.

Beting Bronok, Jul 07
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.
  • Coleman, Neville. 2001. 1001 Nudibranchs: Catalogue of Indo-Pacific Sea Slugs. Neville Coleman's Underwater Geographic Pty Ltd, Australia.144pp.
  • Humann, Paul and Ned Deloach. 2010. Reef Creature Identification: Tropical Pacific New World Publications. 497pp.
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