National Geographic : 1994 Nov
they exist in a symbiotic rela tionship with gardens of bacte ria living in their interior sac. The red hemoglobin in a worm's plume has components that bind hydrogen sulfide from vent fluids and carry it to the bacteria within. The bacteria have the ability to oxidize the hydrogen sulfide and convert large amounts of carbon dioxide from seawater into organic car bon. The carbon is absorbed by the worms in a process that we do not yet understand. The question also remains as to how the tube worms acquire the bac teria in the first place. Other bacteria living freely outside a host provide fodder for tiny crustaceans. Whenever we used a "slurp gun" to suck up bacteria samples for study, we also captured hundreds of minute crustaceans feeding on the microbes. Tube worms have distinct but indistinguishable-sexes, and we and our colleagues observed them spawning on sev eral occasions. Females expel clouds of eggs, males puffs of sperm. We were amazed to see that these animals had grown to sexual maturity and were spawning in only 21 months. Many questions about vent ecology are still unanswered. How, for instance, do bivalves and attached worms colonize vents? Do their larvae float from nearby vents? The East Pacific Rise is continuous from the Galapagos region to the Gulf of California, and we find many of the same species from one vent area to the next. Are some larvae able to ride on currents for great distances, delaying metamorphosis to adulthood until chemicals from vents cue them to settle and grow? We hope clues to relation ships among far-flung vents will come from genetic studies of vent creatures. In the meantime, we continue to study the 300 new species in 90 new genera, 20 new fam ilies, and one new phylum-that we have already sampled and identified.