crabs

Hemigrapsus sexdentatus (H. Milne Edwards, 1837)
Class Malacostraca Order Decapoda Infraorder Brachyura Family Varunidae
classification
purple rock crab
morphology surface substrate habitat
3 cm
main image: Shane Ahyong, inset: Chris Woods
Previously known as Hemigrapsus edwardsi. Carapace polished, flattened, squarish with two teeth
on either side. Front of carapace straight edged between eye stalks. Inner surface of chelipeds in
males with pale balloon-like sac between base of fingers. Legs with few or no ‘hairs’ along margins.
Highly variable colour with juveniles purple and cream mottled becoming more solid black-purple in
adults. Darker crabs often have banded legs. Typically the front half of the carapace is darker than
the back. Eyestalks white. Ventral surface is white.
Endemic, widespread around New Zealand including Stewart Island and very common. Occurs on
relatively sheltered rocky, stony or muddy shores, usually sheltering under rocks throughout the
intertidal. Can tolerate slightly estuarine conditions. Near high-tide level down to mid-tide level.
It could also be……….
Hemigrapsus crenulatus
Leptograpsus variegatus
Yaldwyn, J.C. & Webber, R.W. (2011). Annotated checklist of New Zealand Decapoda (Arthropoda: Crustacea). Tuhinga 22: 171–272.
McClay, C.L. & Schubart, C.D. (2004). On the correct name for Hemigrapsus edwardsii (Hilgendorf, 1882) (Brachyura: Varunidae) from New Zealand. Journal of
Natural History 38: 695–704.
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