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Thick-edged
sand dollar
Jacksonaster depressum
Family Laganidae
updated
Apr 2020
Where
seen? This small sand dollar is sometimes seen on soft silty sand
in sheltered lagoons near reefs. Often only a few individuals are seen. According
to Lane, this is an uncommon species that was only found in trawl
hauls in the Southern islands. He also observed some at Pulau Semakau,
using their spines to move over soft sediments and not for burrowing. It was previously
known as Laganum depressum.
Features: Body diameter 4-6cm.
Usually somewhat pentagonal rather than circular. On the upperside it is thick
at the edges with a shallow depression around a raised centre. The
thick edge is more obvious in a dead sand dollar. The petalloid is
obvious and large even in living sand dollars. Spines at the edges
of the body are longer. The underside has long spines, the anus is
on the underside. Usually pale: rose pink, sometimes beige or purplish.
Dead or alive? Sand dollars may
appear dead, but they are very much alive. A living sand dollar is
covered with fine spines and appears velvety. The skeleton (test) of a dead one is smooth,
without any spines, and the details of skeleton can be seen more clearly.
The skeleton is fragile and will shatter at the slightest pressure.
Status and threats: This sand
dollar is listed as 'Vulnerable' on the Red List of threatened animals
of Singapore. |
East Coast,
Nov 08 |
Underside.
Mouth in the
centre. |
The thick edge is more
obvious
in a dead sand dollar.
Seringat-Kias, Jun 09 |
| Thick-edged
sand dollars on Singapore shores |
| Other sightings on Singapore shores |
Dead sand dollar.
Changi, Apr 10
Photo shared by James Koh on his
blog. |
Beting Bronok, Jul 19
Photo shared by Vincent Choo on facebook. |
Pulau Sekudu, Jul 20
Photo
shared by Toh Chay Hoon on facebook. |
Pulau Sekudu, Jun 17
Photo
shared by Loh Kok Sheng on facebook. |
Pulau Sekudu, Jul 13
Photo shared by Loh Kok Sheng on his blog. |
Pulau Sekudu, Jul 16
Photo shared by Loh Kok Sheng on his blog. |
East Coast Park (G), May 21
Photo shared by Toh Chay Hoon on facebook. |
East Coast Park-Marina Bay, May 22
Photo shared by Kelvin Yong on facebook. |
East Coast PCN, Aug 22
Photo shared by Toh Chay Hoon on facebook. |
Berlayar Creek, Oct 15
Photo shared by Jonathan Tan on facebook. |
Berlayar Creek, Oct 17
Photo shared by Marcus Ng on facebook. |
Berlayar Creek, Oct 17
Photo shared by Loh Kok Sheng on facebook. |
Berlayar Creek, Feb 20
Photo shared by Loh Kok Sheng on facebook. |
St John's Island, Apr 21
Photo shared by Loh Kok Sheng on facebook. |
Lazarus Island, Oct 24
Photo shared by Loh Kok Sheng on facebook. |
Lazarus Island, Oct 24
Photo shared by Loh Kok Sheng on facebook. |
|
Terumbu Raya, Sep 19
Photo shared by Jianlin Liu on facebook. |
Beting Bermban Besar, Nov 14
Photo shared by Loh Kok Sheng on facebook. |
Pulau Berkas, Feb 22
Photo shared by Toh Chay Hoon on facebook. |
Pulau Berkas,
May 10
Photo shared by Loh Kok Sheng on his
flickr. |
Pulau Berkas,
May 10
Photo shared by Loh Kok Sheng on his
flickr. |
Sentosa, May
09
Photos shared by Loh Kok Sheng on his
blog. |
Links
- The
Echinoid Directory by Dr. Andrew B. Smith on the London Natural
History Museum website: everything you could possibly want to
know about sand dollars and sea urchins with lots of large close-up
images and explanatory diagrams. With technical descriptions and
photos of Laganum.
- Jacksonaster
depressum in SeaLife Base: Technical fact sheet.
References
- Lane, David
J.W. and Didier Vandenspiegel. 2003. A
Guide to Sea Stars and Other Echinoderms of Singapore.
Singapore Science Centre. 187pp.
- Davison,
G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore
Red Data Book: Threatened plants and animals of Singapore.
Nature Society (Singapore). 285 pp.
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