Arctica islandica L . Animals in colder water live the longest, since their metabolism is slower. One of them, the misnamed Teredo Ship worm, earned its name by ruining wooden boats. In reality, it is not a worm at all, but a clam, and it can bore through a six-inch plank of wood in less than one year. They will attack any wooden structure in the waters they live in.
Most molluscs are capable of making pearls when foreign substances enter their shell.
They coat the foreign substance with a shelly material, the same as the lining of their shell. Some molluscs can grow pearls as big as golf balls. It takes a commercial pearl oyster about two years to grow big enough to be of use to us as jewellery. The older and bigger the pearl the more valuable it becomes. Also, pearls from molluscs that don't normally produce them are particularly valuable.