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Phylum Echinodermata > Class Echinodea > sea urchins
Salmacis sea urchins
Salmacis sp.
Family Temnopleuridae
updated Apr 2020

Where seen? This almost-cuddly white sea urchin is seasonally common on our Northern shores among seagrasses. At some times, many of these sea urchins are seen, and then none seen for some time. On Cyrene Reef, gatherings of many of these sea urchins are sometimes seen.

Body diameter 5-8cm, with tiny sharp spines. It has long tube feet and is often seen carrying all kinds of things from shells to seaweeds. It can quickly gather these things to cover itself. This behaviour may help camouflage it or shield it from sunlight.

What does it eat? It eats seaweeds.

Role in the habitat:
Despite being prickly, come animals can eat them. Examination of tests (skeleton of a dead sea urchin) suggest that large snails might prey on them.
Other animals live on the urchin, including Parasitic snails, the Zebra crab and sometimes, the Urchin-mouth worm is found curled around the mouth.

Sometimes gathered in large numbers.
Cyrene Reef, Apr 07

Carrying stuff.
Beting Bronok, May 06

Hole with 'burn' mark suggests the urchin
was attacked by a Helmet snail.
Changi, May 08

Worm-like thing seen on the underside.
Changi, Oct 10

Parasitic snails seen on the urchin
Cyrene, May 17
Photo shared on Singapore Biodiversity Records.

Zebra crab (Zebrida adamsii) seen on the urchin.
Changi, Jun 17
Photo shared on Singpaore Biodiversity Records.

Zebra crab (Zebrida adamsii) seen on the urchin.
East Coast Park, May 21
Photo shared by Loh Kok Sheng on facebook.

Some Salmacis sea urchins on Singapore shores

White salmacis urchin
(Salmacis sphaeroides)

Spines shorter, mostly white,
banded with green or maroon.


Passion salmacis urchin
(Salmacis virgulata)

Spines shorter, all maroon,
not banded .


Two-toned salmacis urchin
(Salmacis bicolor)

Spines longer, banded white
and maroon


Salmacis species recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
**from WORMS

  Family Temnopleuridae
  Salmacis bicolor
Salmacis dussumieri=**Salmaciella dussumieri
Salmacis sphaeroides
Salmacis virgulata

Grateful thanks to Dr Frederic Ducarme for identifying these sea urchins.



  • Neo Mei Lin. Zebra crab (Zebrida adamsii) on a sea-urchin (Salmacis sphaeroides) at Changi Beach. 28 July 2017. Singapore Biodiversity Records 2017: 96 ISSN 2345-7597. National University of Singapore.
  • Ying Lynette Shu Min. 29 Sep 2017. Parasitic snails, Vitreobalcis sp., on white sea urchins (Salmacis sphaeroides) at Cyrene Reef. Singapore Biodiversity Records 2017: 123-124.
  • Schoppe, S., 2000. Echinoderms of the Philippines. Times Edition, Singapore. 144 pp.
  • Miskelly, Ashely. 2002. Sea Urchins of Australia and the Indo-Pacific. Capricornia Publications. 180pp.
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