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Purple Shore Crab Hemigrapsus nudus


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Purple Shore Crab
credit:  Walter Siegmund/CCSA

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Category: Crabs and Shrimp view all from this category

Description The purple shore crab, Hemigrapsus nudus, is a common crab of the family Varunidae. It can be found sheltering under rocks in inter-tidal areas along the west coast of North America, from Alaska to Baja California in Mexico. This crab primarily eats sea lettuce and other green algae, and occasionally scavenges dead animals.

A small crab, H. nudus reaches sizes of approximately 4.0–5.6 centimetres (1.6–2.2 in). Its dorsal shell (carapace) is generally a dark purple in color, although it may be olive green or red, with white or cream markings. The color of the legs matches the color of the carapace but the white-tipped claws (chelipeds) are a lighter color with purple or red spots – these spots allow H. nudus to be distinguished from a similar looking crab, the lined shore crab, Pachygrapsus crassipes, whose chelipeds lack spots. The legs of H. nudus lack setae, a distinguishing feature of the otherwise similar H. oregonensis.

Habitat Rocks, Salt marshes & estuaries, Algae.

Range Western Canada, Northwest, California, Alaska.