For many animals in the ocean, crabs are food. That's a problem for crabs. How can they stay off the dinner menu? One type of crab, known as the decorator crab, has found a clever solution. It "decorates" itself. Decorator crabs use seaweed to change their appearances so that predators (捕食者) will not recognize them.
More than 100 species of decorator crabs are found all over the world. One species, commonly called the longnose spider crab, takes decorating to a whole new level. The ocean floor was covered in seaweed, but these crabs wouldn't use just any kind they found. "They were very, very picky, and things they pick were quite uncommon. "says Dr. Stachowicz of the University California.
He noticed that longnose spider crabs would grab a piece of seaweed and take a little bite. Sometimes they would just eat the seaweed. Other times, they would reach back and attach the piece to the small hairs on their back. These crabs were choosing to decorate themselves with seaweed that has a peppery-tasting (胡椒味) chemical in it. Most fish find this chemical unappetizing. "If the crabs just decorated to look like the background, they would be giving their predators a little side salad with the main course. "says Dr. Stachowicz. But by carefully choosing the peppery seaweed, these decorator crabs look less tasty and predators avoid them.
Once a longnose spider crab has put together ai good suit to protect itself, it is set for a while. The seaweed continues to grow even while it's stuck to the crab's back. When a crab sheds (去除) its old shell, it has to redecorate, often using seaweed from its old shell. Basically, the crab recycles.
