Cook Islands Biodiversity & Natural Heritage

Uca tetragonon

Kō‘iti Raukura

a fiddler-crab

Multimedia & Additional Resources

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Open this image in pop-up window Image: Males - dark and pale morphs 73KB
Open this image in pop-up window Image: Male courting female 60KB
Open this image in pop-up window Image: Pale-morph males (Pukapuka) 77KB
Open this image in pop-up window Image: Pale-morph male (Pukapuka) 53KB

General Information

COMMON NAMES: a fiddler-crab

TRADITIONAL NAMES: Kō‘iti Raukura (RR), Koro‘iti (AK), Kohitihiti Kula (TS), Kohitihiti Kura (TW), Fetike (MH RK), Kalama ?ID (PK)

GLOBAL DISTRIBUTION: NATIVE e.Africa - Indonesia - Cooks - Tuamotu; n. to Taiwan

COOK ISLANDS STATUS: Native; S.Group - common; N.Group - common; Marine, near-shore; mud-flats, intertidal

SIGNIFICANCE LIST: oil production;

KEY FEATURES: Carapace 21x34mm (LxW); fiddle to 55mmL. CARAPACE very narrow between the eyes (a "narrow-fronted fiddler-crab"). COLOUR contrasting morphs - blue-black with pale lattice or blotches, and yellow with cream blotches and dark spots. MALE "fiddle" (=chela or cheliped) red to pink base with dark band over base of fixed-finger (=pollex); an indistinct long-triangular depression extending about 25% along the fixed-finger (pollex); a granular surface on the base of the fiddle; and a dorsal spine on the wrist segment (=merus). FEMALE has patch of hairs on each posterior corner of carapace.

SIMILAR SPECIES: Uca crassipes has a broad projection between the eyes (vs. narrow projection); sharp-edged short-triangular pit at the base of the fixed-finger (vs. indistinct long-triangular depression); without dark-bar on base of fixed-finger (vs. usually with dark bar).

Enlarged Image of 'Uca tetragonon'

Cook Islands Distribution

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Southern Group: Present    Makatea:

Northern Group: Present

Key to Symbols

Scientific Taxonomy

Uca tetragonon (Herbst, 1790)
SYNONYMS: Uca tetragonum; Gelasimus tetragonon; Uca duperreyi

TAXONOMY: ANIMALIA; ARTHROPODA; CRUSTACEA; MALACOSTRACA; EUMALACOSTRACA; Eucarida; Decapoda; Reptantia; Brachyura; Brachygnatha; Brachyrhyncha; OCYPODIDAE

More Information

POSITIVE SIGNIFICANCE: oil production;. Comments: Used in production of scented coconut oil (Rakahanga-Sims84)

GENERAL NOTE: The common and large fiddler on Rarotonga and Aitutaki is the narrow-front Uca tetragonon which has a typically minimal vertical wave in which it barely raises its body and simply moves the fiddle up and down. They court on the surface and mate on the surface or in their burrows. Females sometimes build chimneys.

Vouchers & References

Tongareva:TCrocker39 as Uca duperryi; fieldspecimen+photo, both morphs, c.2002, G.McCormack with ID as Uca tetragonon. Manihiki: BPBM-AccNo.1971.201 with ID as Uca tetragonon; probably includes Uca annulipes of Bullivant74, 2006/02 G.McCormack Pukapuka: fieldspecimen+photo, 2/2004, G.McCormack with ID as Uca tetragonon. Suwarrow: fieldspecimen+photo, dark morph female, 1985, G.McCormack with ID as Uca tetragonon 2006/02.

None recorded.

Data Update History (information):
zTX, zB02, zM02, zupM06a, zD02, zupD06a

Web Resources

Citation Information

McCormack, Gerald (2007) Cook Islands Biodiversity Database, Version 2007.2. Cook Islands Natural Heritage Trust, Rarotonga. Online at Copy citation to system clipboard
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