Purple Shore Crab
Scientific Name: Hemigrapsus nudus
Category: other
Brief Description
A small, common intertidal crab often found under rocks along the Pacific coast of North America.
Characteristics
Features a smooth, square-shaped carapace that is typically dark purple, reddish, or olive green. The claws (chelipeds) often have characteristic purple or reddish spots on the palms. The legs are smooth and hairless, which distinguishes it from related species.
Habitat
Rocky intertidal zones, specifically the high and middle tide areas. They are frequently found hiding under stones, in crevices, or among seaweed.
When to Find It
Visible year-round, most easily observed during low tide.
Conservation Status
Common / Least Concern
Ecological Role
Serves as both a scavenger and a predator of small invertebrates, playing a key role in the intertidal food web. They are a primary food source for shorebirds, gulls, and larger predatory fish.
Easily Confused With
Hairy Shore Crab (Hemigrapsus oregonensis), which has hair on its legs and lacks the purple spots on its claws. Also similar to the European Green Crab, an invasive species with 5 teeth on the side of the carapace.
Observation Tips
Look under loose flat rocks during low tide in the Puget Sound area. Always return rocks gently to their original position to protect the habitat. Handle with care to avoid being pinched.
Interesting Facts
Unlike many other crabs, the Purple Shore Crab can survive out of water for extended periods by keeping its gills moist. Their color can vary significantly to help them camouflage against different types of rock and algae.
User Notes
Puget Sound