Mud Shore Crab
Pioneer River, Queensland, southwards through New South Wales, Victoria, Tasmania, to the mouth of the River Murray, Port Adelaide, and Port Augusta, South Australia. (QLD, NSW, VIC, TAS, SA,)Features:
The Mud Shore Crab has a broad rectangular-shaped carapace, with a fairly smooth edge. The upper surface of the carapace is smooth and convex, and the body is deep. Mature males measure 25-30 mm across the carapace. The orbital tooth behind each eye is notched. Beneath the carapace and under each eye is a feature used to create sound - the stridulation ridge. Mature males have very large claws. Each finger bears a low crest along its upper and lower margins, and a swollen ridge is present on the inner face of the claw. The Mud Shore Crab is honey-coloured and may appear almost translucent, especially the claws of big males. This is typical in New South Wales estuaries. The carapace of younger crabs is dark grey with lighter markings, especially on southern shores. Colouration may be estuary or habitat dependent.Ecology/Way of Life:
Mud Shore Crab are abundant in sheltered bays and estuaries, often well above high tide level in areas of mud. They may burrow in a variety of sediments, ranging from dirty sand to moist clay, and shelter under debris or rocks. Such burrowing may create quite distinct systems of interconnecting burrows in muddy estuaries. These crabs can be abundant on saltmarsh flats, and some are found well up-river in fairly low salinity areas. They are also found among mangrove roots, especially those of Avicenna marina, often in association with the Red-fingered Marsh Crab, Sesarma erythrodactyla and the Semaphore Crab, Heloecius cordiformis. Eggs are carried by females in summer, each measuring about 0.3 mm in diameter. After hatching in experimental tanks, they took 23 days to pass through 6 stages as zoea larvae, and a final stage called a megalopa, becoming juvenile crabs.Interaction with Humans/Threats:
The Mud Shore Crab can live in areas greatly affected by pollution carried in from storm-water run-off. They may often shelter under pieces of wood and litter stranded high on the shore. The greater the pollution, the more drab the colour of the crab seems to be. These crabs appear to be more orange-coloured in pristine environments, especially in NSW estuaries.Other Comments:
This species was described by Thomas Whitelegge in 1889, in his outstanding "List of the Marine and Fresh-water Invertebrate fauna of Port Jackson and Neighbourhood", which became the marine zoologist's "bible". The genus name comes from the Greek: helos = marsh and grapsaeo = a crab; the species name honours William Haswell, formerly Professor of Biology at the University of Sydney.Further Reading:
Bennett, I. (1987). W.J. Dakin's classic study: Australian Seashores. p.231, Angus & Robertson.
Campbell, B.M. & Griffen, D.J.G. (1966). The Australian Sesarminae (Crustacea: Brachyura): Genera Helice, Helograpsus nov., Cyclograpsus and Paragrapsus. Memoirs of the Queensland Museum, 14(5), 127-74.
Davey, K. (1988). A Photographic Guide to Seashore Life of Australia. p.55, New Holland Press.
Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p.214, Reed.
Hale, H.M. (1876). The Crustaceans of South Australia. Pts. I & II. p.177, South Aust. Govt. Press.
Jones, D. & Morgan, G. (1994). A Field Guide to Crustaceans of Australian Waters. p.187, Reed.
Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p.118, Museum of Victoria.
Text, map & photograph by Keith Davey.Sponsorship welcomed:
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