crabs

Petrolisthes elongatus (H. Milne Edwards, 1837)
Class Malacostraca Order Decapoda Infraorder Anomura Family Porcellanidae
classification
blue half-crab
morphology surface substrate habitat
1 cm
main image: Shane Ahyong inset image: Chris Woods
Carapace elongate, flattened, smooth, oval-shaped, front bluntly triangular, rear relatively
straight. Carapace margins without teeth. Antennae longer than carapace, whip-like. Eyes large
and prominent. Chelipeds very large and flattened, without large teeth or serrations. Last pair of
legs setose and reduced and folded, partially concealed under abdomen. Only 3 pairs of walking
legs. Variable colour on carapace and dorsal surface of claws and legs from black, blue, greyish,
greenish or pinkish, ventral surfaces lighter (white, yellow, blue-green).
Endemic, widely distributed around NZ, including Stewart and Auckland Islands. Introduced to
Tasmania. Common beneath boulders, mussel beds, intertidal region of rocky shores, wharf piles
and extending into estuaries. Upper littoral down to just below low tide.
It could also be……….
Petrolisthes novaezelandiae
Petrocheles spinosus
McLay, C. (1988) Crabs of New Zealand. Leigh Laboratory Bulletin 22.
Yaldwyn, J.C., Webber, R.W. (2011) Annotated checklist of New Zealand Decapoda (Arthropoda: Crustacea). Tuhinga 22: 171-272
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