It has been estimated that about 90 percent of deep-sea animals are bioluminescent. Yet in many cases, scientists do not know how these animals benefit from the energy-intensive process of producing their own light. Some jellies use bioluminescence as a defense-they glow when disturbed in order to light up their predators, making their attackers vulnerable to even larger animals. A few deep-sea fishes and squids have glowing organs that look like lures, but even these animals have never been observed actually using their glowing organs to capture prey.
MBARI marine biologist Steven Haddock has studied glowing marine animals for over a decade, focusing on gelatinous animals such the siphonophores described in his recent article. Related to the typical round "jellyfish" that sometimes wash up on beaches, siphonophores are colonial animals, arranged in chains that in some species can be dozens of meters long. The members of a colony specialize at different tasks. Some form swimming bells, which pulse slowly, pulling the colony through the water like a long, fluid freight train. Others specialize in feeding, and sport stinging tentacles.
Almost all siphonophores are bioluminescent, but scientists know little about why and how they glow. Siphonophore colonies are notoriously difficult to study-they often break into pieces when disturbed or captured. For
Contact: Kim Fulton-Bennett
Monterey Bay Aquarium Research Institute