ambience: Seashore
Walking along the shore, you can sometimes find a shell that has a perfectly round hole in it, as if it had been drilled. Well as a matter of fact, it probably was. I’m Jim Metzner and this is the Pulse of the Planet, presented by DuPont. The shells of snails, clams, and other mollusks have many functions. Scallops, for example, can “swim”, in a manner of speaking, by squeezing the two sides of their shell together. But shell expert Geerat Vermeij says that shells are primarily a form of armor, to protect the animal from some very determined predators, especially in warm waters. “Fish can take them in the jaws and simply crush the shell, or they can swallow them and crush them in the throat. Crabs take them in the claws and break them that way. There are animals called Manta shrimp that actually hammer shells with a specialized appendage they have. Sea otters can bang shells against rocks — some birds do this as well, and break them that way. There are other animals that swallow the shell and the enclosed animal whole.” And as for those perfect little holes in certain shells… “There are snails, and also some octopuses, that actually drill through the shell and then proceed to digest the soft tissues within the shell. The mechanism involves literally some mechanical drilling by a tongue-shaped structure, and this is aided and abettted by secretions from the accessory boring organ. They are acidic, so they help dissolve the minerals from which the shells are made.” Well it’s a tough world out there for mollusks, but they’ve responded over time by evolving better shells — thicker in some cases, or easier to camouflage. Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I’m Jim Metzner.