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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Spotted-belly forceps crab
Ozius guttatus
Family Oziidae
updated Dec 2019

Where seen? This large shy crab is sometimes seen on our Southern shores near rocky shores, sea walls and among coral rubble and near living reefs. It is more active at night, but even so, very quick to scuttle back into hiding when disturbed. 'Gutta' in Latin means 'spots'.

Features: Body width 6-9cm. Body oval smooth upper surface. Edge smooth with a few (about 4) very shallow notches. Upperside reddish to dark brown, plain without patterns, underside pale orange with lots of tiny dark spots on its belly. Large pincers smooth (no pimples) with orange, reddish or brown tips, lower 'finger' tips often darker. Walking legs sparsely hairy. Eyes dark with white spots.

Armed with a can-opener and forceps: One of its pincers is much larger. In a young crab, this enlarged pincer is armed with a curved tooth on the movable finger of its pincers. This tooth fits into the opening of a snail shell, and the pincer is used like a can-opener to carve a spiral opening in the snail shell. As the crab gets older and bigger, a large molar-like 'tooth' develops on the 'finger' with several smaller 'teeth' along the cutting edge. This is used to crush snail shells. The other pincer has slim 'fingers' with several smaller 'teeth' along the cutting edge. These slim 'fingers' act like forceps or chopsticks to remove the snail after its shell is peeled open or crushed.

Sometimes confused with similar crabs in the same habitat. Here's more on how to tell apart big crabs with big pincers seen on the rocky shores and coral rubble.

Pulau Semakau, Oct 05

Plain smooth upper side.

Spotted belly on the underside.


One with a 'peeled' snail.
Sentosa, May 04

Eyes dark with pale spots.

Spotted-belly forceps crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores


Tanah Merah, Dec 09
Photo shared by Loh Kok Sheng on flickr.

Pulau Tekukor, Sep 18
Photo shared by Marcus Ng on facebook.


Lazarus, Jan 22
Photo shared by Kelvin Yong on facebook.


Small Sisters Island, Aug 21

Photo shared by Vincent Choo on facebook


Pulau Jong, Apr 11

Photo shared by Marcus Ng on facebook

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

  *Family Oziidae (previously Menippidae and Eriphiidae)
  Epixanthus dentatus
Epixanthus frontalis

*Eupilumnus (Globopilumnus) actumnoides=**Eupilumnus actumnoides
*Eupilumnus (Globopilumnus) globosus
=**Eupilumnus globosus

Ozius guttatus (Spotted-belly forceps crab)
Ozius rugulosus
Ozius tuberculosus

Acknowledgements
Grateful thanks to Crabhunter for confirmation of ID.

Links
References
  • 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.
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