Death Star

At the ocean’s edge, competition for food and space is fierce. But the intertidal zone also serves up stunning examples of cooperation.

From an octopus cannibalizing its mate to a sea star attacking a mussel, conflicts among ocean creatures hook our attention. Small wonder: Every compelling story ever told has been driven by conflict, from sagas spun around campfires to the space opera of Star Wars. Examples of people cooperating rarely make the news, much less lead to literature. Nevertheless, cooperation is arguably the most important factor in our species' rise from pursuing game on an African savanna to sending the International Space Station into orbit.

We are not alone in the animal kingdom in our ability to thrive through cooperation. Ants live in colonies, geese migrate in formation, wolves hunt in packs. Evolution has produced cooperation between species, as well.

Thanks to Finding Nemo, most kids understand that a clownfish avoids predators by sheltering itself among an anemone's stinging tentacles. Scientists have recently discovered that the relationship is a two-way street. The clownfish does a wiggle dance that stirs the water, circulating oxygen that the anemone needs to breathe.

A lesser-known example of sea creatures cooperating is the relationship between the rough keyhole limpet and a species of scaleworm it hosts. Disney won’t be making films about these uncharismatic animals anytime soon. Yet these creatures engage in a mutualistic dance every bit as compelling as a colorful clownfish swimming in an anemone's pretty, poisonous embrace.

The rough keyhole limpet, Diodora aspera, eats animals like bryozoans; in turn the limpet is preyed upon by sea stars. The scaleworm that lives beneath the limpet’s shell protects its molluscan host from echinoderm assassins. When the limpet is under siege, its worm cohabitant defends its shelled home by biting the tender tube feet of the attacking sea star.

There is no end to strategies of competition and cooperation among the myriad species of the ocean, and throughout nature. But life in all its glorious diversity arises from a single stark theme: the universal struggle for survival.

A limpet that is consumed by a sea star becomes a scatter of nutrients carried on ocean currents; a star that consumes its fuel fades to a dark sphere of ash. The story of every animal on Earth, and every object in the universe, is how, for a time, it avoided death.