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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Xanthid crabs
Family Xanthidae
updated Dec 2019
if you 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.
They are not venomous but it's best not to touch them.

Where seen?This 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.

Body 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. There 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.
Their toxins are similar to the neurotoxins of puffer fishes, and just as deadly.

The Mosaic reef crab is the most poisonous crab on our shores.
Sentosa, Jun 07

Floral egg crab eating a fish.
Sentosa, Sep 04

A Red egg crab eating a sea urchin.
Tanah Merah, Jun 09
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 health.

Status and threats:
Several of these crabs are listed among the threatened animals of Singapore. L
ike 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.

Some Xanthid crabs on Singapore shores


Family Xanthidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
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.

+from The Biodiversity of Singapore, Lee Kong Chian Natural History Museum.
**from WORMS

  Family Xanthidae
  Actea sp. (Spiny-legged rock crabs)
Actaea alcocki=**Atergatopsis alcocki
Actaea amoyensis
Actaea depressa=**Forestiana depressa
Actaea fragifera
Actaea aff. ruppelloides
Actaea savignii
Actaea spongiosa

Actaeodes hirsutissimus
Actaeodes mutatus
Actaeodes tomentosus

Actites erythra=**Actiomera erythra?

+Actiomera erythra

sp. (Egg crabs)
Atergatis dilatatus
Atergatis floridus
(Floral egg crab) (VU: Vulnerable)
Atergatis integerrimus (Red egg crab) (VU: Vulnerable)
Atergatis roseus

Atergatopsis alcocki
Atergatopsis tweediei
Atergatopsis bidentata

Banareia armata
Banareia subglobosa
(EN: Endangered)

Chlorodiella bidentata
Chlorodiella nigra

Cymo sp. (Hairy coral crabs)
Cymo andreossyi (Hairy coral crab) (VU:Vulnerable)
Cymo melanodactylus

Demania baccalipes
Demania cultripes
Demania scaberrima

+Epiactaea cf. margaritifera
Epiactaea nodulosa

+Epixanthus dentatus

Etisus anaglyptus
Etisus laevimanus
(Smooth spooner crab)
Etisus utilis
(Saw-edged spooner crab)

Euxanthus exsculptus
(Lumpy rock crab)

Galliardellus orientalis=**Gaillardiellus orientalis
Galliardellus ruppelli=**Gaillardiellus rueppelli

Hypocolpus granulatus
aff. haani
+Hypocolpus pararugosus
Hypocolpus rugosus
(CR: Critically endangered)

Leptodius sp. (Rock crabs)
+Leptodius davaoensis
Leptodius exaratus
Leptodius gracilis
Leptodius nigromaculatus
Leptodius sanguineus
Leptodius scaber

+Liomera bella
Liomera margaritata
Liomera pallida
Liomera venosa
(Ruby reef crab)

Lophozozymus leucomanus
Lophozozymus pictor
(Mosaic reef crab) (EN: Endangered)

Macromedaeus distinguendus

Medaeops granulosus

Neoxanthops lineatus
(EN: Endangered)

Novactaea bella
(EN: Endangered)

Palapedia valentini
(VU: Vulnerable)

Paractaea rufopunctata

sp. (Pilodius rock crabs)
Pilodius harmsi
Pilodius luomi=**Pilodius miersi
Pilodius nigrocrinitus
Pilodius pilumnoides

Platypodia cristata
Platypodia granulosa
(Curry puff crab) (EN: Endangered)

Zalasius horii
(Paddington Bear crab) (CR: Critcially Endangered)

  • 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.
  • 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.
  • Gopalakrishnakone P., 1990. A Colour Guide to Dangerous Animals. Venom & Toxin Research Group, Faculty of Medicine, National University of Singapore. 156 pp.
  • 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.
  • 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.
  • Debelius, Helmut, 2001. Crustacea Guide of the World: Atlantic Ocean, Indian Ocean, Pacific Ocean IKAN-Unterwasserachiv, Frankfurt. 321 pp.
  • Gosliner, 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.
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