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Uca longidigita (Family Ocypodidae)

Long-digit Fiddler Crab

Distribution:

Long-digit Fiddler Crab has an extremely limited distribution being restricted to south-eastern Qld. It is found at Green Island, Moreton Bay, and the Brisbane River (QLD).

Features:

The Long-digit Fiddler Crab has a carapace that is turquoise-blue in colour with brown and cream markings. Adult males have three black diamond markings on the carapace. It grows to a carapace width of 20-30mm. The very long fingered chelae of the male crab is pale grey-blue and white, with a touch of orange on the inner face, with pure white fingers. The minor chelae are bluish-grey merging into pale grey. The eyestalks are grey-black while the legs are dark grey-black in colour. The carapace of the male looks to be and feels smooth, while the carapace of a female appears to be and feels finely granular. Long-digit Fiddler Crab has a narrow front to the carapace, with the frontal groove being deep and fairly narrow. The eyebrows are very narrow, almost absent. The eyestalks are long and thin. The mouthparts are a pale grey-blue with some white.

The upper moveable finger of the large male chelae is longer than the lower fixed finger. The median groove on the lower finger is shallow and indistinct. There is a slight trace of felted pile in the gape between the fingers.

A more full description is found in George & Jones (1982).

Ecology/Way of Life:

Long-digit Fiddler Crab is found on the banks of tidal rivers. It also occurs in mud and sandy mud along the seaward edge of mangroves. It is usually found below Uca coarctata and Uca vomeris.

Interaction with Humans/Threats:

Long-digit Fiddler Crab has an extremely limited distribution so a major chemical or oil spill in Moreton Bay and the Brisbane River could be catastrophic to the continued survival of this species. This situation needs to be continually monitored.

Other Comments:

Uca longidigita, Kingsley, 1880. Kingsley collected the type specimen in 1880 at Moreton Bay, Qld. He named it Gelasimus longidigitum. Other synonyms are Uca longidigitum, Macnae, 1966, and Uca (Australuca) bellator longidigita, Crane, 1975.

The specific name longidigita comes from the Latin word longus, meaning long, and digita from the Latin word digitus meaning finger or toe. The long fingers on the chelae of this species distinguish it from other Fiddler Crabs.

Acknowledgments:

Text, map & photograph by Keith Davey.

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