The Crustaceans are animals with jointed legs. Crabs, lobsters and shrimp are all crustaceans, but it’s the crabs that we find easily here on the rocky shore. “Imagine an animal wearing its skeleton on the outside,” Dad says, “like a coat of armor.” He points at a little crab crawling across the bottom of a tide pool. “The armor is made of a material something like your fingernail. It’s called an exoskeleton, and it can’t stretch as the animal grows bigger. Crustaceans have to shed their armor now and then and grow a new set. This is called molting.”
Dad peers into a shallow tide pool and says “Hey, there are hermit crabs (photo right) in here carrying their own houses around!” I look, but I see only snail shells. Suddenly, some of the shells sprout legs and start to crawl! “Remember our summer trip when we pulled our mobile home behind us?” Dad asks. “Well, these hermit crabs do something like that.” As we watch them lurch across the tide pool, Dad explains that the lower half of the hermit’s body is tucked inside the shell, wrapped neatly around the spirals. There are hermit crabs in every tide pool we examine. But only the head, antenna and legs stick out of the “mobile home.” “Does a hermit crab ever come out of its shell all the way?” I ask. “Sure. Soon it will need a larger home. Then it’ll jump out and move into its new shell quick as a wink so it doesn’t get caught out in the open.”	Hermit crab
“Look, there’s a true crab,” Dad points out. “The others were fakes?” I ask. “No, smarty. A true crab is one that doesn’t live in a snail shell. It has a flat, oval-shaped body called a carapace, and five pairs of legs, four mainly for walking, and one pair ending in pincers.” A big red crab is hiding under some kelp. When I kneel down for a closer look, it waves its claws at me. “Those claws are an important weapon for self-defense,” Dad explains. “And if we could follow this crab for awhile, we’d see it use them to catch food too.”	Shore crab
The crab finally gets tired of us and scuttles away sideways through the tangled kelp. It‘s the biggest one I’ve seen. “How big do crabs get?” I ask. “Well, the northwest Dungeness crab gets pretty large. It’s also good to eat; we humans are predators too! But crabs are more important for the job they do when they’re alive.” Dad calls the crabs and other crustaceans the “sanitary engineers of the sea,” because they clean up their surroundings by eating dead and decaying things. “Remember that every creature has a role to play in nature.” Dad says. I understand, but I’m glad I’m not a crustacean.	Dungeness crab
I thought I’d figured out the crustaceans. They crawl around on jointed legs, right? Wrong. Dad confuses me by saying that the barnacles belong to this group. Weird. A barnacle looks nothing like crab! “Think of a barnacle as a crab in a closet,” Dad says, “or maybe a shrimp-like creature standing on its head inside a cone-shaped house, using its legs to kick food into its mouth through the front door.” (I’ll have to think about that one awhile!) Barnacles are everywhere around us, even up high, clustered on dry rocks. Barnacles attach to a hard surface when they’re young, and stay there for life. They can close their shell plates tightly when they’re exposed to air, pounding waves, and temperature changes during low tide. We examine something very strange, what looks like a cluster of bird beaks all pointed upward. “Those are barnacles too,” Dad says.
[Left] The gooseneck barnacles are raised on stalks that bend. This way, the barnacle can position its legs to take advantage of passing water. Most barnacle species are very sociable; usually, they live in large crowded colonies, sometimes attaching to other animals like mussels. [Photo right]
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