n 1997, Charles Fisher, professor of biology at Penn State, discovered this remarkable creature (also shown on the cover of this special report) living on mounds of methane ice under half a mile of ocean on the floor of the Gulf of Mexico. The flat, pink worms, one or two inches in length, use their appendages like oars to move around the surface of the ice as they graze for the bacteria also living there. The new worm species, Hesiocaeca methanicola, may have some influence on the formation of natural gas deposits on the sea floor and, if so, on how we go about mining gas as a source of energy. It has already helped redefine “life as we know it.” The bacteria the ice worms eat, and the methane both species grow on, could provide clues about early life on this and other planets.

Fisher came upon the worms by accident while collecting tubeworms near hydrocarbon seeps at the sea floor. Before the discovery, methane ice had been of most interest to geologists and energy companies, not biologists. The area where the ice worms live is under extremely high pressure and, at seven degrees C, very low temperatures. Adds Fisher, “The ice worm community is in itself a new ecosystem. We found an animal living in an environment that we never thought of as a habitat for animals.” The ice was formed when methane gas rose up from deposits deep beneath the sea floor. Ancient bacteria that may have lived beneath the Earth’s crust, feeding on this gas, migrated with it, eventually settling on the ice.

The ice worms, which are not ancient animals but are related to the common red mud worms we see after a rain, would have come along later. But the mere fact that they can survive such a harsh environment shows the long-term adaptive capabilities some animal species possess. Says Fisher, “The animals we study live in some very extreme, very strange environ-ments and they adapt to it using special physiology, special anatomy, and special behavior.”