A medium-sized spider-like crab.

Also called: Common Spider Crab, Atlantic Spider Crab

Native status: Native to Atlantic coast of North America

§ Quick facts

SizeCarapace 7–10 cm (3–4 in); leg span to 30 cm
Weight200–600 g
LifespanWild 4–7 years
OrderDecapoda
FamilyEpialtidae

§ Encyclopedia

Libinia emarginata, the portly spider crab, common spider crab or nine-spined spider crab, is a species of stenohaline crab that lives on the Atlantic coast of North America.

Source: Wikipedia — Libinia emarginata Licensed under CC BY-SA 4.0

§ Identification

Field marks. Crab with triangular, sharply pointed carapace; long thin legs giving spider-like appearance; often festooned with attached marine growth.

Similar species. Other decorator crabs (different ranges; similar habit). Spider crabs in deeper water often much larger.

Voice. N/A

§ Diet & behavior

Diet. Algae, marine plants, small invertebrates, detritus.

Behavior. Common east-coast spider crab. Famous for "decorating" its carapace with bits of algae, seaweed, sponges, and other debris it cuts up with its claws — the camouflage technique earns the family name "decorator crabs." Newly captured individuals are sometimes completely covered in growth, making them nearly invisible against the seafloor. Slow-moving and harmless to humans.

§ Range

Atlantic coast

§ Habitat

Coastal marine waters

§ Threats

Habitat loss.

§ Conservation status

According to the IUCN Red List, the spider crab is currently classified as Least Concern.

§ What helps

Support coastal conservation.

Support our work More ways to help

§ Further reading

§ Sources cited

  • Smithsonian Marine Station Fort Pierce
  • Mote Marine Laboratory
  • iNaturalist