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Uca coarctata (Family Ocypodidae)

The Compressed Fiddler Crab

Distribution:

The Compressed Fiddler Crab has a tropical Australian distribution. It ranges from Darwin, NT, east and south to Moreton Bay and the Gold Coast, Qld (NT, QLD).

Features:

The Compressed Fiddler Crab is a beautiful fiddler crab with a dark carapace and distinctive orange chelae. It has a deep-set body. The carapace of the male feels smooth but appears to be finely granular, while the carapace of the female both feels and appears to be finely granular. The carapace front is narrow, while the frontal groove is deep and narrow. The eyebrows are long and narrow and extend to between half and two-thirds the length of the eye-channel called the orbit. The eyestalks are long and thin. The major cheliped of a male crab has the moveable upper finger, called the dactyl, being slightly longer and overhanging the immoveable lower finger called the manus. A long, distinct median groove occurs on the lower front face of the manus.

The carapace is usually a uniform black, merging to grey, with white mottling on the hind third. The major chelae is mostly dull grey grey-cream with the fingers being rust-red to orange in colour. Its eyestalks are grey-brown, while its legs are grey-brown with some cream. The male has a white patch on the hind walking legs. The minor chela is a dull grey-orange. The mouthparts are grey-blue.

For a full description see George & Jones (1982).

Ecology/Way of Life:

The Compressed Fiddler Crab prefers to be high up on steep river and stream banks, where it lives above Uca polita and below Uca dussumieri, two other fiddler crabs. On more gentle sloping mudflats it is found with Uca longidigita and Uca vocans.

Interaction with Humans/Threats:

Because the Compressed Fiddler Crab is found in remote parts of northern Australia, often far from human habitation, it does not appear to be under threat.

Other Comments:

Uca coarctata H. Milne-Edwards 1852, Originally named Gelasimus coarctatus by H. Milne-Edwards. Synonyms are Uca arcuata, Grant & McCulloch 1906, and Uca coarctata, Macnae 1966.

Further Reading:

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. p.64, New Holland Press, Sydney.

George, R. W. & Jones, D. S. (1982). A Revision of the Fiddler Crabs of Australia (Ocyponinae: Uca). Records of the Western Australian Museum, Suppl. No. 14. P.37-40.

Jones, D. & Morgan, G. (1994). A Field Guide to Crustaceans of Australian waters. p.198, Reed.

Acknowledgments:

Text, map & photograph by Keith Davey.

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