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Phylum Echinodermata > Class Echinodea > sea urchins
Long-spined black sea urchin
Diadema setosum
Family Diadematidae
updated Oct 2016

Where seen? This large, very scary-looking sea urchin is among our most commonly encountered sea urchins in deeper waters. It is said to be found in large groups where there is a lot of dead coral. It is believed that these gather together in groups where there are insufficient hiding places from daytime predators. It is also sometimes encountered on the intertidal on our Northern and Southern shores, usually alone, wedged in coral rubble or near large boulders. On Cyrene Reef, they may also be found among seagrasses.

Features:
Body diameter 8-10cm. It has very long primary spines, up to 30cm long, with many shorter spines in between. The spines on the underside are much shorter. The urchin can rapidly point its long spines against any potential threat (which is quite a scary thing to observe). The spines may be all black, banded black-and-white or even all white.

There is bulbous sac in the middle of the upperside. This is the anal cone through which wastes are discharged. There is an orange ring around this anal cone, sometimes the ring is pale. There are five bright white spots on the black body, with small bright blue dots forming V-shape lines from the white spots. The underside may be pale, dark or maroon or pink.

Painful poke: The long, thin spines are hollow and sharp enough to painfully pierce through clothing and gloves. The spines often break in the skin and are hard to remove. The pain, however, usually goes away in a few hours.

How to stay safe: Wear covered shoes and long pants to cover all skin exposed to water. Don't touch or pick up sea urchins.

May be confused with the Black sea urchin (Temnopleurus sp.) with much shorter spines is more commonly seen on our Northern shores, sometimes in large numbers. Thanks to Dr Frederic Ducarme for more on how to tell apart Diadema setosum and Diadema savignyi. "The orange ring is unique to Diadema setosum, even if in some cases it can be pale, and D. savignyi can, in exceptional cases, also have a pale ring around the anal papilla. But the five white dots indicate D. setosum, as well as the blue dots pattern of the iridophores, whereas D. savignyi has lines. Indeed D. savignyi generally has a thicker body with shorter spines, but the length of the spines vary according to the site, and in some places D. setosum has shorter spines as well."

What does it eat? It feeds on algae, grazing these from dead corals or rubble areas. It may also trap tiny suspended food particles with its long spines, transferring these to the mouth with tube feet.

Prickly home: The sea urchin is sometimes home to other animals such as cardinalfish (Family Apogonidae), razorfishes (Family Centriscidae) and shrimps (Saron marmoratus) and anemones (Coeloplana sp.). Small white parasitic snails are also said to be associated with it.

Human uses: In some places, the roe of this sea urchin is eaten resulting in heavy harversting.

Cyrene Reef, Jun 08


Bulbous anal sac, five white spots
and blue dots in V-shape lines.


Spines may be black, banded or even white.



Sideview with shorter spines on the underside
and longer spines on the upperside.
Cyrene Reef, Jun 08
 

Short flat spines around the mouth.

Cyrene Reef, May 08

Long-spined black sea urchins on Singapore shores

Photos of Long-spined black sea urchins for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map


Tanah Merah, Jul 09
Photo shared by Toh Chay Hoon on her blog.

Tanah Merah, Aug 09
Photo shared by Loh Kok Sheng on his blog.

Tanah Merah, May 14
Photo shared by Loh Kok Sheng on his blog.


Lazarus Island, Feb 11
Photo shared by James Koh on his blog

Seringat Kias, Apr 12
Photo shared by Loh Kok Sheng on his blog.
 


Pulau Tekukor, Jun 16
Photo shared by Loh Kok Sheng on facebook.

Terumbu Selegie, Jun 11
Photo shared by Jerome Pang on facebook.
 


Cyrene Reef, Nov 09
Photo shared by Geraldine Lee on her blog.

Cyrene Reef, Nov 08
Photo shared by Loh Kok Sheng on his blog.

Pulau Jong, Jun 12
Photo shared by Loh Kok Sheng on his blog.


Pulau Hantu, Jun 10
Photo shared by James Koh on his blog.

Terumbu Hantu, Jun 13
Photo shared by Loh Kok Sheng on his blog.

Terumbu Pempang Tengah, Jul 12
Photo shared by Loh Kok Sheng on his blog.


Pulau Semakau East, Jul 15
Photo shared by Loh Kok Sheng on facebook.

Terumbu Semakau, May 10
Photo shared by Loh Kok Sheng on his flickr.

Terumbu Bemban, Apr 11

Photo shared by Loh Kok Sheng on his blog.


Pulau Senang, Jun 10

Photo shared by Loh Kok Sheng on his flickr.

Pulau Senang, Jun 10

Photo shared by Loh Kok Sheng on his flickr.
 

Diadema species recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
*additions from Lane, David J.W. and Didier Vandenspiegel. 2003. A Guide to Sea Stars and Other Echinderms of Singapore.

  Family Diadematidae
  Diadema setosum
*Diadema savignyi

Acknowlegments
Thanks to Dr Frederic Ducarme for more on how to tell apart Diadema setosum and Diadema savignyi.

Links

References
  • Tan Heok Hui. 4 July 014. Longspine sea urchins with commensal fish and shrimps: Zanzibar urchin shrimp, Tuleariocaris zanzibarica; Urchin clingfish, Diademichthys lineatus. Singapore Biodiversity Records 2014: 179-180
  • Lane, David J.W. and Didier Vandenspiegel. 2003. A Guide to Sea Stars and Other Echinoderms of Singapore. Singapore Science Centre. 187pp.
  • Chou, L. M., 1998. A Guide to the Coral Reef life of Singapore. Singapore Science Centre. 128 pages.
  • Miskelly, Ashely. 2002. Sea Urchins of Australia and the Indo-Pacific. Capricornia Publications. 180pp.
  • Schoppe, S., 2000. Echinoderms of the Philippines. Times Edition, Singapore. 144 pp.
  • Allen, Gerald R and Roger Steene. 2002. Indo-Pacific Coral Reef Field Guide. Tropical Reef Research. 378pp.
  • Coleman, Neville.undated. Sea Stars of Australasia and their relatives. Neville Coleman's World of Water, Australia.64pp.
  • Gosliner, Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral Reef Animals of the Indo-Pacific: Animal life from Africa to Hawaii exclusive of the vertebrates. Sea Challengers. 314pp.
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