Purple shore crab

Hemigrapsus nudus

Purple shore crab

Hemigrapsus nudus

Other Common Names
Naked shore crab

Rocky Coast

Other Common Names

Naked shore crab

At the Aquarium

Rocky Coast

Appearance

Purple shore crabs are usually a purple color though they can be olive green or a reddish-brown. Their chelipeds are spotted, reddish-purple, with white-tipped claws, and soft tissues at the base of their claws. Males also have a tuft of hairs on the palm sides of their chelipads. There are 3 spines on each side of the carapace. The legs do not have any hairs.

Habitat

Mostly found under rocks and in cracks in the intertidal, though they also appear in estuaries.

Diet

Omnivore: algae, diatoms, amphipods, snail eggs.

Life History

The eggs are fertilized internally and then deposited outside the abdomen, on the flap. A female will carry an egg mass of 400 to 36,000 eggs for about 3 months. Upon hatching, the larvae are released to start life as plankton. A larva will progress through a series of larval stages, with the final stage being the megalopal stage, which will settle in the intertidal and undergo metamorphosis to the juvenile stage. A newly metamorphosed juvenile has a carapace width of 0.08 inches. The carapace of males can reach a width of 2.2 inches while females are smaller, only reaching 1.3 inches in width.

IUCN Status

Not Evaluated

Ecosystem & Cultural Importance

The predators of these crabs include staghorn and tidepool sculpins, anemones, and white-winged scoters.

Alaska to Mexico

You can find these small crabs hiding among rocks in the lower estuary and in tidepools.

Many crabs appear to be slobbering bubbles when they are out of the water because they are pumping both air and water into their gill chambers, and the outlets for these are near their mouth.

Citations & Other Resources

Invertebrates of the Salish Sea
Oregon Department of Fish and Wildlife
Wan, Hailin. “Population distribution and some aspects of the reproductive biology of two species of shore crab Hemigrapsus nudus and Hemigrapsus oregonensis at Bamfield, Vancouver Island, British Columbia, Canada.” (1990).

Purple shore crab

Purple shore crab

Other Common Names

At the Aquarium

Appearance

Habitat

Diet

Life History

IUCN Status

Ecosystem & Cultural Importance

Citations & Other Resources

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