Coral reefs occupy less than one percent of the ocean floor yet support roughly a quarter of all known marine species, a disproportion long attributed simply to the physical shelter the reef structure provides. Recent research complicates this picture, however: reef biologists have found that the coral polyps themselves engage in continuous biochemical signaling with resident algae and fish, exchanging nutrients in cycles so tightly interlocked that removing even a single common fish species can measurably slow the coral's own growth within months. The reef, in other words, may function less like a hotel that happens to house many species and more like an organism whose parts are distributed across many bodies.