April 17, 2021

Welcome to our Cool Critters series, where Marine Ecologist Jeff Adams shares the unique features of his favorite marine animals native to the Pacific Northwest. Today’s Cool Critter is the Purple Shore Crab!

The Purple Shore Crab (Hemigrapsus nudus) is a small (<2″), hairless crab common among larger rocks. When you pick up beach rocks, these crabs can often be seen scuttling quickly away. They prefer to be high on the beach where they eat mostly algae, but also some small animals. They are normally purple with spotted claws, but can be plain green or red without spots. Purple shore crabs can be found along the Pacific Coast, from Alaska down to Mexico. 

This picture shows their green color when they morph.

Their claw tips are brown because they are hardened with bromine (Br). 

Photo Credits: Jeff Adams, Marine Ecologist, Washington Sea Grant