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Crabs That Live in Marine Rocks

Crabs are considered crustaceans consisting of an exoskeleton, jointed appendages and a hard shell. Crabs are predators of the sea but can also become easy prey for birds, animals and humans. Most marine crab species find shelter beneath rocks and rubble on the ocean floor. Crabs don't nest beneath rocks, but use them as they migrate for food and reproduction. Many smaller species such as the hermit crab can be found beneath dry rocks on coastal beaches.

Dungeness Crab
- The Dungeness crab is the most common marine species harvested for food along the Pacific Coast of the United States. These large crabs can grow to over 20 centimeters in body diameter. They are found throughout the West Coast from the Alaskan islands to northern parts of Mexico. Dungeness crabs prefer rocky areas with a lot of vegetation to offer protection. They will migrate inland or to more exposed areas along with their favorite food sources such as clams and crustaceans.
Marine Hermit Crab
- Marine hermit crabs are small, reaching up to 8 centimeters in diameter. They prefer sandy coastal areas, but some species are also found in the deep sea. Hermit crabs thrive in both temperate and tropical marine habitats as well as some terrestrial areas like beaches and streams. These crabs do not grow shells, but instead inhabit discarded shells from other sea creatures. These half-land
  
  half-sea-dwelling creatures can be found beneath rocks in shallow tide pools.
Green Shore Crab
- This species is often called the European green shore crab because it inhabits the Atlantic coastlines of Europe. During the 1800s the green shore crab established itself along the eastern coast of the United States and has even been spotted in California. According to the British Marine Life Study Society, these crabs are found most abundantly in the spring on rocky shores, beaches, rivers and in estuaries. During the summer season, these crabs migrate from brackish water to freshwater to breed.
Decorator Crab
- The decorator crab is a tropical and subtropical species found in shallow marine waters. Shallow bays in tropical areas are ideal places to look for decorator crabs. They hide amid rocky rubble and are almost indistinguishable from the ocean bottom. These crabs get their name from their natural inclination to "decorate" their shells with both living and nonliving sea life. Algae, coral, bryozoans, sea squirts and sponges are all items that the sea crab collects upon its shell. This partnership is symbiotic as the life on the crab's back benefits from the leftovers of the decorator crab's meals.

Animals & Science