Color and Flash in the Depths

From the underside, the deep-sea jellyfish Atolla, which can be ten inches across, looks like a flower or a chandelier, not an animal. Atolla is abundant around the world at midwater depths (500-1000 meters) and at shallower depths in the cold Southern Ocean. When touched or disturbed, Atolla is indeed a chandelier: It produces bright, rapidly-flashing circles of blue bioluminescent light that scientists think may confuse would-be hunters. WHOI scientist Larry Madin, a specialist on gelatinous plankton, photographed this jellyfish on an expedition in Antarctic waters. (Photo by Larry Madin, Woods Hole Oceanographic Institution)