We were thrilled and mesmerized to film this this flamboyant cuttlefish Metasepia pfefferi while scuba diving in the southern Philippines. This cephalopod’s electro-neuromuscular system controls the expansion or contraction of thousands of individual color cells (chromatophores) in its skin. That’s how it flashes waves of color across its body like a digital video screen in Times Square.
The Original Mobile Home
More than 65 million years ago, the hermit crab, which is more closely related to certain kinds of lobsters than true crabs like the blue crab, was an early inventor of the mobile home. Using its soft, spiral tail, it will quickly back into empty snail shells or even small bottles it finds on the ocean floor.
Why has this way of life been so successful for hermit crabs? No one is sure, but here’s one guess: Many predators, including fish with strong molar-like teeth, can bite into a more conventional crab (Yum! Crunchy on the outside, soft on the inside). But a predator needs some serious jaw strength to crush a snail shell, which provides a durable, spiral form that withstands structural stress.
Perhaps the hermit crab saves metabolic energy by avoiding the need to build a shell around its tail-like abdomen. It simply collects a shell that another creature has invested time and energy into its architecture.