learn only 3 things about them ...
These colourful crabs are poisonous to eat! Their toxins
are NOT destroyed by cooking.
They are generally secretive and slow-moving.
are not venomous but it's best not to touch them.
group includes the most colourful large crabs that you might commonly
encounter on the shore. The
Egg crabs (Atergatis sp.) are often encountered on many of
our shores and can be quite common in coral rubble areas. Others
are only sometimes seen. They are more active at night, but nevertheless,
usually slow moving and always near some hideaway into which they
scuttle at the first sign of danger.
width 5-10cm. Many members are colourful or strikingly patterned.
This probably serves as a warning. The group includes among the
most poisonous crabs in Singapore. Their
toxins are not destroyed by heat or cooking. These crabs should
never be eaten. Eating
them can cause Paralytic Shellfish Poisoning which can lead to death.
is no antidote to their toxins.
While these crabs
may be poisonous, they are not venomous. That is, they cannot introduce
their toxins by stinging or biting. But nevertheless, it's best
to leave these crabs alone.
For example, those who are allergic might get a reaction by even
touching these crabs.
How do they make their toxins?
The process is not well understood but it is believed that the poisons
are produced by bacteria that live in symbiosis with the crabs.
toxins are similar to the neurotoxins of puffer fishes, and just
What do they eat? Most of these
crabs are said to be vegetarians, but at least one was seen chomping
happily on a fish.
Human uses: The study of the unique toxins in these crabs
may help develop new drugs or achieve better understanding of human
Status and threats: Several of these crabs are listed
among the threatened animals of Singapore. Like
other creatures of the intertidal zone, they are affected by human
activities such as reclamation and pollution. Trampling by careless
visitors also have an impact on local populations.
A Red egg crab eating a sea urchin.
Tanah Merah, Jun 09
Juvenile Floral egg crab
Tuas, Nov 03
Floral egg crab eating a fish.
Sentosa, Sep 04
crabs on Singapore shores
Xanthidae recorded for Singapore
Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity
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.
sp. (Spiny-legged rock crabs)
Actaea aff. ruppelloides
Atergatis sp. (Egg crabs)
(Floral egg crab) (VU: Vulnerable)
integerrimus (Red egg crab) (VU:
Banareia subglobosa (EN:
(Hairy coral crabs)
Cymo andreossyi (Hairy coral
Etisus laevimanus (Smooth spooner
Etisus utilis (Saw-edged spooner
Euxanthus exsculptus (Lumpy
sp. (Rock crabs)
Liomera venosa (Ruby reef crab)
(Mosaic reef crab) (EN: Endangered)
Neoxanthops lineatus (EN: Endangered)
Novactaea bella (EN: Endangered)
Palapedia valentini (VU: Vulnerable)
(Pilodius rock crabs)
(Curry puff crab) (EN:
Zalasius horii (Paddington Bear crab)
(CR: Critcially Endangered)
Xanthid Crabs, Liomera,
Rock Crab (Leptodius), Actaeodes
Egg Crab (Atergatis integerrimus) Tan, Leo W. H. &
Ng, Peter K. L., 1988. A
Guide to Seashore Life. The Singapore Science Centre,
Singapore. 160 pp.
...an ancient alkaloid from the sea by Jim Johnson on Molecule
of the Month of the School of Chemistry, University of Bristol
website: lots of details about the toxin's effects, creatures
that carry it and how it came about, with LOTS of links to more
- Ng, Peter
K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema
Brachyurorum: Part 1. An annotated checklist of extant Brachyuran
crabs of the world. The Raffles Bulletin of Zoology. Supplement
No. 17, 31 Jan 2008. 286 pp. (Online
PDF on the Raffles Bulletin of Zoology website).
- Lim, S.,
P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life
and Times of Labrador Beach. Division of Biology, School of
Science, Nanyang Technological University & Department of Zoology,
the National University of Singapore. 160 pp.
P., 1990. A
Colour Guide to Dangerous Animals.
Venom & Toxin Research Group, Faculty of Medicine, National
University of Singapore. 156 pp.
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.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
- Jones Diana
S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of
Australian Waters. Reed New Holland. 224 pp.
Helmut, 2001. Crustacea
Guide of the World: Atlantic Ocean, Indian Ocean, Pacific Ocean
IKAN-Unterwasserachiv, Frankfurt. 321 pp.
Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral
Reef Animals of the Indo-Pacific: Animal life from Africa to Hawai’I
exclusive of the vertebrates
Sea Challengers. 314pp.