National Geographic : 2012 Mar
NOW PHOTOS: MARK W. MOFFETT TOP ; MONTEREY BAY AQUARIUM RESEARCH INSTITUTE. NGM ART. SOURCE: NOAA Ant Anonymity It's nice to know your neighbors. But when a society is supersize, forget familiarity. Argentine ants---whose invasive colonies may span hundreds of miles and multiple continents--- have societies that, like ours, can be millions strong. What gives them (and us) the capacity to expand is anonymity, says an upcoming paper in Behavioral Ecology by entomologist Mark Moffett. "To cooperate," he says, "members don't need to recognize each other as individuals." For most animal societies to function, everyone needs to know everyone (think chimps or elephants). But that limits growth to maybe a hundred, says Moffett---"as many faces as one can keep track of." For Argentine ants there's no such ceiling. Yet there are territories, with pheromones defining friend and foe. So even with millions of strangers, he says, "there's no ambiguity about who's who." ---Jennifer S. Holland Members of supercolonies that have invad- ed several conti- nents, Argentine ants devour a piranha's face. SQUID SEX Promiscuity is Octopoteuthis deletron's MO. When another of these squid swims by---male or female---this five-inch cephalopod (left) slaps 50 or so sperm packets on its skin. Feckless? No. According to Henk-Jan Hoving of the Monterey Bay Aquarium Research Institute, it's an effective propagation strategy in deep seas, where encounters are few. In the inky darkness half a mile down, he adds, squid flings are brief. "Two together are larger," says Hoving, "and they're bioluminescent"---making moving on imperative to avoid predation. ---Johnna Rizzo Roughly 75 percent of the world's ocean water is deeper than 3,300 feet, where no sunlight reaches.