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Hermit crab


up to 35 milliimeters


white with orange to pink tints


carnivores: plankton, worms, small crustaceans, carrion


jealous hermit crabs, other crustaceans, fish and some birds



  • Dut: Heremietkreeft
  • Lat: Pagurus bernhardus
  • Eng: Hermit crab, soldier crab
  • Ger: Einsiedlerkrebs (Bernhardskrebs)
  • Dan: Eremitkrebs
Hermit crab, Ecomare

Hermit Crab

Hermit crabs have a 'naked' hind body. Only their front end is covered with shell. In order to protect their naked hind end from hungry animals, they hide this part in empty snail shells. The entire back end disappears in the shell; only the head, the legs and the sturdy pincers stick out of the opening. As opposed to the small hermit crab, the right claw of the common hermit crab is larger than the left claw. Because hermit crabs grow but their protective shell doesn't, they must regularly move into large snail shells. Smaller hermit crabs can be found in periwinkles. Larger ones are often found in whelks. Sometimes, you find the shells covered with a rough substance. Although it looks like algae growth, it is the animal polyp sea mat.

  • Life as a hermit crab

    Hermit crab eggs are carried in the snail shell belonging to the female until they hatch. Her hind legs have grown into fans and provide the brood with fresh water. The young hermit crabs live in the open water for a number of weeks. Afterwards, they look for an empty house from a small snail. After a number of molts, they move into larger shells.

  • Distribution and habitat

    Hermit crabs are found throughout the North Sea. They live in pools and under stones in the lower parts of the tidal zone. Sometimes, large amounts wash up onto the beaches.

  • Various kinds of utensils

    Hermit crabs have an amazing number of ways in which to eat. They have a sieve in their mouth to filter plankton out of the water. They can also extend a slimy net from their mouth to catch these one-celled plankton. The tiny animals which live between the sand grains on the sea floor are caught by sweeping them up with the help of the brushes attached to their mouth. Just like crabs, hermit crabs also eat carrion.

  • Fleeing, fighting and moving

    The hind legs of the hermit crab have developed into hooks with which the animal can anchor itself in the snail house. When in danger, it retracts into the shell. Some hermit crabs have additional ways to defend themselves. Once in awhile, you may find a hermit crab with a sea anemone on its shell. This anemone scares away enemies. When the crab moves to a new house, it takes the helpful anemone with it.

    Sometimes, hermit crabs fight over an empty or even an occupied shell. There is a lack of large suitable houses, due to the lack of whelks which are the original inhabitants of such a shell. A hermit crab that can't find a larger shell must either remain in its tight house or fight someone else for their larger accomodation. 

    When a hermit crab puts its mind into getting someone's else house, it will first take a threatening pose. It holds its claws up high, to show just how large they are. If this doesn't work, it will fight. It grabs the other hermit crab with its claws and begins to tick its house against the other shell in a rhymic manner. Just image your neighbor hammering on your house out of jealousy! It may not sound very heroic, but it often works.

    If the sea mat is sturdy enough, a desparate hermit crab can enlarge the edge of its house using this polyp for protection.

  • Hermit sack

    Hermit crabs 'squat' an empty snail house, but they aren't always the only resident. Sea mat, anemones and sea barnacles can attach themselves to the exterior side of the shell. And inside the shell can also be occupied, for example, by the hermit sack (Peltogaster paguri). This is not a nice house mate to have. In fact, it is a tormentor. This crustaceous parasite attaches itself to the hermit crab and feeds upon its organs. The parasite lives partially inside and partially outside the unfortunate hermit crab. You only see the sack on the outside, which explains its name. When a hermit crab is affected by this parasite, reproduction becomes very difficult if not impossible.