Georgette Douwma / Boxer Crab (Lybia tessellata) with sea anemones in its claws for defense. Lembeh Strait, North Sulawesi, Indonesia.

Nick Upton / Common prawns (Palaemon serratus) and a Rock goby (Gobius paganellus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Magnus Lundgren / Wild Wonders of China / Boxer crab (Lybia tessellata) carrying a sea anemone around in each of its claws, Xiaoliuqiu Island, Taiwan

Alex Mustard / Close up of a tiny Boxer crab (Lybia tessellata) as it waves the stinging anemones it holds in its claws for defence. Tulamben, Bali, Indonesia. Java Sea.

Pascal Kobeh / Olive purse crab / pebble crab (Leucosia pubescens) burying itself in the sand at night, Sulu Sea, Philippines

Nick Upton / Montagu's / Furrowed crab (Xantho hydrophilus) from English Channel. South Devon, England, UK. September.

David Fleetham / Splendid round crab (Etisus splendidus) holding pieces of coral that it has broken off with its lobed claws. Philippines.

David Fleetham / Pebble crab (Leucosia pubescens) can bury itself completely in the sand to escape predators, Komodo, Indonesia.

Sue Daly / Risso's crab (Xantho pilipes) Sark, British Channel Islands, September.

Nick Upton / Common prawns (Palaemon serratus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Common prawns (Palaemon serratus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Common prawns (Palaemon serratus) and a Shanny (Lipophrys pholis) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Common prawns (Palaemon serratus) feeding on a dead Montagu's crab (Xantho hydrophilus) in a rockpool, with a a Rock goby (Gobius paganellus) swimming past, Cornwall, England, UK, September.

Nick Upton / Montagu's crab (Xantho hydrophilus) in a rockpool, showing threat posture with open claws raised, walks out of frame, Cornwall, England, UK, September.

Nick Upton / Two Montagu's crabs (Xantho hydrophilus) competing for a crevice to hide in within a rockpool, with a young Velvet swimming crab (Necora puber) moving away nearby, Cornwall, England, UK, September.

Nick Upton / Two Montagu's crabs (Xantho hydrophilus) competing for a crevice to hide in within a rockpool, Cornwall, England, UK, September.

Nick Upton / Montagu's crab (Xantho hydrophilus) moving behind a stone in a rockpool to hide in a rockpool low on the shore, near Falmouth, Cornwall, England, UK, September.

Constantinos Petrinos / Mosaic boxer crab (Lybia tesselata) female carrying its red eggs Lembeh Strait, North Sulawesi, Indonesia

Constantinos Petrinos / Juvenile mosaic reef crab (Lophozozymus pictor) Lembeh Strait, North Sulawesi, Indonesia.

Linda Pitkin / Mosaic reef crab (Lophozozymus pictor), on the reef at night Aljui Bay, Raja Ampat, West Papua, Indonesia.

Pascal Kobeh / Boxer / Pompom crab (Lybia tessellata) holding its eggs on hard coral, Manado, Indonesia. Sulawesi Sea.

Pascal Kobeh / Boxer / Pompom crab (Lybia tesselata) with eggs underneath, Manado, Indonesia. Sulawesi Sea.

Sue Daly / Montagu's or Furrowed Crab (Xantho hydrophilus) on sea shore, Sark, British Channel Islands.

Sue Daly / Risso's crab (Xantho pilipes) on sea shore, Guernsey, British Channel Islands.

Franco Banfi / Button crab (Paractaea monodi) on encrusting red sponge, Ponza Island, Italy, Tyrrhenian Sea, Mediterranean

Fred Bavendam / Splendid Pebble Crab (Etisus splendidus) photographed at night, Bali, Indonesia

Gary Bell/ Oceanwide / Boxing Crab (Lybia tessellata) holding sea anemones used for defense, Anilao, Philippines

Gary Bell/ Oceanwide / Boxing Crab (Lybia tessellata) holding sea anemone for defense, Bali, Indonesia

Gary Bell/ Oceanwide / Boxing Crab (Lybia tessellata) female with eggs holding sea anemone for defense, Bali, Indonesia

David Fleetham / Splendid pebble crab (Etisus splendidus) defensively hiding in crevice, Hawaii, USA, Pacific Ocean.

Joel Sartore / Photo Ark / Boxer crab (Lybia tessellata) portrait, National Aquarium, Abu Dhabi. Captive, occurs in Indo-Pacific Ocean.

Alex Mustard / Shaggy crab (Zalasius dromiaeformiss) resting on the seabed at night, Bitung, North Sulawesi, Lembeh Strait, Molucca Sea.

Andy Trowbridge / New Zealand kingfisher (Todiramphus sanctus) in flight with Mud crab in beak, Banks Peninsula, South Island, New Zealand.

Alex Mustard / Hoary rubble crab (Banareia palmeri) gripping on to a sea rod, Grand Cayman, Cayman Islands, Caribbean Sea.

David Fleetham / An endemic Hawaiian pom-pom crab / Boxer crab (Lybia edmondsoni) carrying a juvenile Anemone (Triactis producta) in its claws as a defense mechanism. A mutualistic symbiosis, with the anemone being tr...

David Fleetham / Pom-pom crab / Mosaic boxer crab (Lybia tesselata) carrying large egg mass and its associated Anemone (Triactis producta), used for defense. that it carries around in its claws, using them for defense...

David Fleetham / Endemic Hawaiian pom-pom crab / Boxer crab (Lybia edmondsoni) on reef, waving anemones (Triactis sp.) in its claws, North Pacific, Hawaii, USA.

Franco Banfi / Round crab (Euryozius sp.), Punta Campanella Marine Protected Area, Costa Amalfitana, Italy, Tyrrhenian Sea, Mediterranean.

Magnus Lundgren / Wild Wonders of China / Blue-eyed coral crab (Cymo quadrilobatus) molted out of old shell Kenting Nationalpark, Kenting, Taiwan.

Francisco Marquez / American Pebble Crab ( Daria americana ) on white background, Islas Marias Archipelago, Marias Biosphere Reserve, Mexico.