When you first look at your pet hermit crab, probably the feature you notice most is its shell. Hermit crab shells appear to be prominent because of the fact that they are in effect, borrowed shells. By this I mean that your pet has had to use a discarded shell from another creature because of the simple fact that he has never had a shell of his own. Thus you will find hermit crabs moving around in all different types of shells.
But why choose a sea shell? The hermit crab’s abdomen is where his digestive glands and reproductive organs are situated and because of this it is important to protect the area. The easiest way for him to do this is by wriggling his torso into a discarded sea shell. Hermit crab shells also offer protection from predators.
One interesting feature regarding the choice of hermit crab shells, is that a juvenile crab may well be limited in his choice of available shells and hence may cram his rear end into a totally different shaped opening to that of his actual abdomen. This may well mean that his choice of shell results in him growing a straight shape instead of the traditional curl that his abdomen would normally have.
Hermit crab shells are also used by the crabs as a means of locking moisture into their bodies. Their entire cycle revolves around water for their well being and for this reason, you will mainly see hermit crabs out at night or when the rain falls. Naturally a snug fit is desired if the shell is to serve its purpose.
If you have a pet land hermit crab then it is your responsibility to fit him with a new shell every so often. To know if the shell is the right fit he needs to be able to completely withdraw into it and seal the opening with his large pincer. As long as his abdomen is protected, you needn’t worry yourself over whether you feel the shell is too large or too small. If your hermie is unhappy with the shell, he won’t move into it – simple as that. .
To measure your crab for a new shell you need to hold him in your hand and take a look at his large claw. Perfect fitting hermit crab shells will have an opening about the size of the large claw plus 1/8 inch all round. Of course an easier method is probably to measure the opening of a shell with a ruler to gauge whether it would fit your pet.
The best hermit crab shells are the ones that your crab chooses for himself, after all we all like to have a say when choosing our own houses. If you present him with a shell with a dirty interior, he will not like it. All shells you offer him should be cleaned by boiling in water for about five minutes and then leaving to cool. Crabs are especially drawn to shells with circular openings with the exception of the Ecuadorian crab. For some strange reason, hermit crabs are also very fond of shells lined with mother of pearl. No one knows why this is, although it is thought that the mother of pearl may offer better insulation.
Well, there you have it. A brief description of the whys and wherefores of hermit crab shells.