This beautiful pink urchin with unique spiny spines is seasonally
common on some of our Northern shores, in seagrass meadows. Sometimes
many are seen during a visit, and then none for a while. Broken spines
of this sea urchin may also be seen washed ashore.
Features: Body diameter 4-5cm.
It has spines on its spines! The thick spines are long (4-5cm to 10-12cm),
armed with small spines and may be colourful and banded in pink and
yellow or beige. Because of its thick spines, it is sometimes called
the Pencil sea urchin. Several different kinds of spines may be seen
even on the same sea urchin. On the upper side, some long spines have
sharp tips and sharp small spines. Other long spines may be blunt
or or even square-tipped and have blunt small spines. On the upperside,
there are five short, sharp pointed spines usually held crossed over
one another forming a tent over the centre of the body. Long tube
feet may emerge from the sides of the spherical body when the sea
urchin is submerged in water. On the underside, the mouth is surrounded
by short flattened blunt spines. Other longer spines on the underside
have blunt tips too, possibly used for burrowing?
In some, the longer spines are covered sediments. Sometimes, tiny
brittle stars are seen wrapped around its spines. Or encrusting
ascidians may grow on the spines.
Status and threats: Prionocidaris
baculosa is listed as Vulnerable in the Red List of threatened
animals of Singapore. The other species recorded for Singapore is
Pulau Sekudu, May 08
Upperside with five short sharp spines.
Mouth surrounded by flattened spines.
sea urchins on Singapore shores
Cyrene Reef, Mar 09
shared by James Koh on his
species recorded for Singapore
Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in
in red are those listed among the threatened
animals of Singapore from 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.
Prionocidaris baculosa (VU:
- Lane, David
J.W. and Didier Vandenspiegel. 2003. A Guide to Sea Stars and
Other Echinoderms of Singapore. Singapore Science Centre.