If you are the curious type that likes to hop over tide pools and investigate puka, why not pause for a moment and take a deeper look into what you may find. There are many living animals you may not see at first, such as animals that are camouflaged in a variety of ways and reusing “homes” as protection.
The hermit crab is a land or water dwelling crustacean, a crab that does not have the hard shell you normally think they have. They actually need and use (or reuse) the empty shells of snails to move into, carefully selecting the right size and then backing themselves into it. Their abdomens are very soft and need protection, and their tails are not as long as lobsters but longer than other types of crabs. They have a total of 10 legs, larger ones outside to help them move quickly and smaller legs in the back to help hold onto the shell. The hermit crab can also use its large front claw to help seal the hole once it is inside the shell, protecting it from potential danger. The shell can help as camouflage as well. Even the cuttlefish has been recorded mimicking the hermit crab as a disguise.
Being meticulous bargain hunters, hermit crabs are known to pick through and use a variety of snail shells such as augers, spindles, cones and even the Triton’s trumpet. In a few cases, they have even been seen with a glass bottle or debris covering their body while they look for a more suitable residence. The jeweled anemone crab is a special and decorative one, named simply by placing and carrying multiple sea anemones on its shell. Since the anemones themselves eject pink stinging threads, this helps protect the crab within, being able to use each other in a symbiotic relationship. If a dominant one comes into contact with another anemone crab, it is known to steal away the others’ anemones by using its claw to remove and place them on its own shell and then run off.
The list of hermit crab species varies, depending on where they are found in the ocean. You can easily see them on the shoreline, but they can also be found in water as deep as 1,000 feet. Many scavenge on what’s on the sea floor, like fish and scraps from other foragers, while others choose only algae to eat. As with other arthropods (insects and crustaceans), they molt or shed their exoskeleton periodically in order to grow. They may not eat and are inactive while molting. Once the new exoskeleton has hardened, they will continue on their vigorous way, particularly after night fall.
There are many things we can learn from the hermit crab and try to look for things to reuse. And the next time you are walking on the beach and glimpse into the curious world of tide pools, you may see a coveted shell that is not common to find. As hard as it may be, please leave it there. . . . there’s probably a hermit crab that needs it more than you do!
* Larissa Treese is the head aquarist at Maui Ocean Center. “Ka Mo’olelo Moana,” or “The Ocean Story,” is a monthly column submitted by the Maui Ocean Center, which is open from 9 a.m. to 5 p.m. daily in Maalaea. For more information, call 270-7000.
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