Purple Shore Crab

Geographical Origin and Habitat: Found along the Pacific coast of North America, from southern Alaska to Baja California. Inhabits rocky intertidal zones, sheltering under rocks or macroalgae in wave-swept shores.

Taxonomy: Member of the family Varunidae. Characterized by a smooth carapace and legs without noticeable hair-like setae, distinguishing it from H. oregonensis. Grows to 4-4.5 cm.

Social Behavior: Semi-terrestrial and nocturnal. An active crab that emerges from the water to rest on damp rocks. Can be territorial toward other shore crabs.

Coloration and Sexual Dimorphism: Typically purple, reddish, or dark brown. Claws are large, smooth, and marked with distinctive purple or red spots. Males have a narrow abdomen; females have a wide one.

Tank Setup: Requires a paludarium or marine cold-water tank. Provide a land portion using smooth rocks, gravel, and overhangs. Water levels can be kept moderate. A secure, tight lid is mandatory.

Diet and Feeding: Omnivore, loves grazing on green algae and diatoms from rocks. Also scavenges detritus, small invertebrates, pieces of fish, and shrimp pellets.

Water Quality: Cool marine or brackish water (10-20°C). Keep pH between 7.8 and 8.4. Sensitive to high nitrate levels and requires zero copper content.

Compatibility and Tankmates: Unsuitable for tropical reef setups. Keep only with cold-water fish and invertebrates from similar biotopes. May capture small snails or slow fish.

Aquarium Breeding: Females carry orange eggs under their abdomen. The larval stages are planktonic and require specific wave action, making home breeding highly unlikely.

Risks and Diseases: Failed molts due to lack of iodine or calcium. High escape risk due to its agility in climbing filter tubes and cords.