Purple Shore Crab
Hemigrapsus nudus
Classification
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Malacostraca
- Superorder: Eucarida
- Order: Decapoda
- Infraorder: Brachyura
- Family: Grapsidae
- Genus: Hemigrapsus
- Species: nudus
Pronunciation
How to pronounce Hemigrapsus nudus: //ˌhɛmɪˈɡræpsəs ˈnuːdəs//
These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.
Images
Summary
Hemigrapsus nudus, commonly known as the Purple Shore Crab, is a small amphibious crab often found on the Pacific coast. It displays distinct coloration and feeding behaviors, primarily inhabiting rocky coastal areas.
Physical Characteristics
Carapace width up to 5.6 cm in males and 3.4 cm in females. The dorsal shell is generally purple, olive green, or red with white or cream markings. Legs match the carapace color but chelipeds are lighter with purple or red spots; male abdomen is narrow and triangular, female abdomen is wide and flap-like.
Identification Tips
Distinct purple or red spots on white-tipped claws differentiate from similar crabs such as Pachygrapsus crassipes.
Habitat
Found in inter-tidal and sub-tidal areas of beaches, commonly sheltering under rocks and in seaweed.
Distribution
Southeastern Alaska to northern Mexico along the Pacific coast, less commonly found south of Morro Bay, California.
Diet
Primarily feeds on sea lettuce and other green algae, occasionally scavenges dead animals.
Life Cycle
Females carry eggs from January to mid-July, with hatching dependent on water temperature. Undergo 5 zoeal stages and a juvenile stage.
Reproduction
Mating occurs between December and January; females lay between 400 and 36,000 eggs after fertilization.
Predators
Preyed upon by seagulls, seabirds, larger crabs, and other marine predators.
Ecosystem Role
Acts as both a grazer of algae and as prey for various marine animals.
Collecting Methods
- Hand collection
- Trap methods
Preservation Methods
- Freezing
- Alcohol preservation
Evolution
Evolved mechanisms for osmoregulation and tolerance to hypoxia, suggesting adaptations to fluctuating environments.
Similar Taxa
Misconceptions
Often confused with other shore crabs due to similar coloration and morphology.
Tags
- crustacean
- marine biology
- intertidal species
- ecology