Overview
The Striped Shore Crab (Pachygrapsus crassipes), also widely known as the Lined Shore Crab, is the supreme acrobat and sentinel of the Pacific intertidal zone. Inhabiting sun-drenched rocky cliffs and boulder reefs from Oregon to Baja California, this lightning-fast decapod is famed for its transverse green-and-black tiger stripes and remarkable ability to scuttle across vertical rock faces out of water.
Biology and Physical Characteristics
Pachygrapsus crassipes features a square, flattened carapace adorned with prominent, parallel transverse ridges and alternating dark green, brownish-purple, and black stripes. Its powerful walking legs are flattened and tipped with sharp, hooked dactyls that grip wet rock like climbing crampons. Its robust claws are reddish-purple with pale fingertips, capable of delivering a formidable defensive pinch.
Behavior and Ecology
Unusually terrestrial for a marine crab, the Striped Shore Crab can remain out of water for up to 70 hours by circulating a reservoir of seawater stored inside its gill cavities. During low tide, it roams exposed cliff faces, grazing on turf algae with its claws. When threatened, it sprints sideways at blinding speed, squeezing into paper-thin rock crevices.
Conservation and Human Impact
Unassessed by the IUCN Red List due to its vast population across thousands of miles of Pacific coastline, the Striped Shore Crab is robust and secure, playing an indispensable role as an intertidal herbivore and prey for black oystercatchers, raccoons, and octopuses.
Interesting Factoid
The Striped Shore Crab carries its own scuba tank of seawater inside its body: it can spend three whole days exploring dry land above the ocean waves by recycling moisture through its internal gill chamber.