Two-spined Burrowing Sand Crab, Flower Moon Crab, Reticulated Surf Crab
This species has a tropical distribution around northern Australia from North-western Western Australia to the Sydney region of New South Wales. It appears to be more common in northern Australia (NSW, NT, WA, QLD).Features:
The Two-spined Burrowing Sand Crab is a beautifully patterned surf crab; it is distinguished by its rounded carapace, which is armed with a strong spine on each side, and the functional paddles formed by the flattened hind limbs. This species reaches a carapace width of 65 mm, and a length of 50 mm. It may resemble swimming crabs of the family Portunidae, because of their flattened hind limbs and the spine on each side; however, in species of Matuta all the limbs are slightly flattened and the mouth is triangular. The basic colour of these crabs matches their habitat; it ranges from white to yellow, with a range of spots, rings and mottling in colours varying from dark purple through dark red to brown.Ecology/Way of Life:
The Two-spined Burrowing Sand Crab occurs on sandy beaches from low tide level down to depths of about 7 metres. Although it is an excellent swimmer, its flattened rear legs are used as digging tools to burrow quickly backwards into the sand. Hale (1976) described these crabs as being able to "slip themselves under the sand in a moment". These flattened hind limbs are not fringed by hairs, such as occur in other crab species, and seem to be more adapted for digging into sand. The joints of the other legs may have fringes. Unlike other crabs, Matuta takes in oxygen-rich water near its eye-sockets, which is guided through a hair-lined channel to an opening at the base of the chelipeds - the limbs bearing the claws - where a mat of dense hairs acts as a filter to remove unwanted sediments.Interaction with Humans/Threats:
This species is often seen in shallow water along long sandy beaches. It is unknown if it is threatened by human activity.Other Comments:
Matuta planipes (Meirs). The genus is named after Matuta, the Roman goddess of the dawn; the species name comes from the Latin: planus = flat or level, and pes = foot, and refers to the flattened limbs of these crabs.Further Reading:
Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. p. 50. New Holland Press.
Hale, H.M. (1976). The Crustaceans of South Australia. Pt. I & II. p. 188-9. SA Govt. Printer.
Jones, D. & Morgan, G. (1994). A Field Guide to Crustaceans of Australian Waters. p.141. Reed.
Text, map & photograph by Keith Davey.Sponsorship welcomed:
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