April 2006
Streetwise Magazine |
Mobile Homes and Roof Gardens |
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The housing market in Andalucia might be a little slow, but underwater it's as hot as ever. Before you all think I've lost the plot altogether, we are talking about an often-overlooked little creature called a Hermit Crab.
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With over 5000 species of crabs around the world more than 600 of them are Hermit crabs. Some of the species even live on land. What has this got to do with mobile homes and roof gardens you ask? Well most crabs (Crustacean) develop their own protection in the form of a hard shell, however the hermit crab seems to have managed to only half evolve. The head, back and claws have developed the hard shell, but the abdomen remains soft and unprotected. So for protection the crab will take the abandoned shell from a gastropod. The soft abdomen has a rough surface with which it grips the side of the shell so that it can carry it about.
The shell will not serve the life of the crab, and as it grows and moults (like other crabs) it will have to abandon its shell for something larger. Competition can be fierce for the ideal home, which must have sufficient space for development but must be light enough to carry around all day. The female will often choose a larger shell (must be a woman thing) for carrying eggs, and you can often see large shells scurrying along the seabed, but when investigated you will find a small crab lugging its new home around. Some species have one claw larger than the other and they use this to block the mouth of the shell for protection.
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Very often you will notice that certain anemones will grow on the shell of the hermit crab. This symbiotic relationship serves both parties well. The anemone provides protection to the crab with its stinging cells, while the crab provides transport and food to the anemone. The anemone plays hard to get and the crab must indulge in a little foreplay to induce the anemone to take up its new home. The crab gently strokes the anemone to relax it and to prevent it discharging its stinging cells, and then it gently peels it from the rock and places it on its shell. Don't attempt to pick these creatures up if you find them, because you will find your fingers covered in white sticky threads, which contain the stinging cells.
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Hermit crabs are active during daylight hours but usually hunt at night. As carrion feeders they are happy to finish the scraps, left by other predators. So next time you go snorkelling or diving, look out for the mobile home and roof garden bumbling across the sand, but don't touch what you cant afford.
Photographs by G Fairhurst & D Graves
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