You may be planning to wear a costume at Halloween, but many marine animals wear disguises throughout the year.
Several types of crabs change their appearance to give them greater protection. Hermit crabs live in empty shells to protect their tender backsides. A hermit crab may change its shell when it finds a more attractive or better-fitting one. Some hermit crabs put anemones on their shells. The anemone's stinging cells help protect and disguise the crab, and the crab helps the anemone by providing "leftovers" from his meals. One small Xanthid crab carries sea anemones around in its claws. When frightened, it waves the anemones like boxing gloves to ward off predators. Sponge crabs carry sponges to camouflage themselves. The sponge is held above the body by the crab's rear pair of legs. The small Decorator crabs have many hooks on their bodies which they use to attach pieces of algae, sponges, and hydroids. This practice makes them very hard to spot among algae-covered rocks or reef flats.
Several fish change their appearance as part of their life-cycle or as a defense. Pufferfish (o'opu-hue) and Porcupinefish (kokala) can make very dramatic changes. When alarmed, they distend themselves with water into round, prickly balloons, making themselves larger and more difficult to eat. Parrotfish (uhu) can secrete a thick mucus "sleeping bag" at night. This may protect them by containing their scent and warding off parasites.
The collector urchin (hawa'e) gets its name because it collects small pieces of shell, rock, seaweed, and whatever debris is available--sometimes even plastic or bottle tops. It holds these with the suction cups of its tube feet, thus creating an original "costume."
In the mollusk group, Cowries (leho) have beautiful shells and a membrane, the mantle, that can completely cover the shell. The mantle secretes the shell, polishes it, and provides camouflage as well, since it often matches the surrounding habitat.
The champion of change is the Octopus (he'e). No other animal can change color as fast. It changes to match its surroundings or to reflect its mood. When at rest, an octopus may be a mottled, brownish gray. When frightened, it may turn almost white. When angry, it can become a rich, reddish-brown. When a day octopus is about to catch a crab, it often flashes dark brown with white spots. An octopus can even change the texture of its skin from smooth to bumpy.
So Waimanalo is not the only place where dressing up will occur this month. There are always plenty of tricks and treats beneath the sea!