How to be the perfect host: The physiology of chemosynthetic invertebrate-bacterial associationsShana Goffredi, Ph.D. Wednesday, February 24, 1999
Deep-sea hydrothermal vents and cold seeps are home to a variety of invertebrate species, many of which exist in symbiotic arrangements with sulfide-oxidizing bacteria. Many of these invertebrates rely entirely on chemoautotrophic symbionts for nutrition, which allows them to live in areas where phototrophic contributions are minimal. In order to maintain successful associations with these bacteria, the invertebrates must meet many unusual demands, normally not experienced by other metazoans. These biochemical demands include the uptake of inorganic carbon and sulfide, as well as the elimination of bacterial end products, including large amounts of protons and sulfate ions. Riftia pachyptila, the most conspicuous organism living at deep-sea hydrothermal vents, is able to overcome these demands because of its remarkable ability to control its extracellular pH, a suite of carbon-concentrating mechanisms, and an unusual mode of mediated sulfide uptake. In contrast, vesicomyid clams are the dominant invertebrates living in many cold seep areas, including the Monterey Canyon. An interesting feature of these clam communities is that the two predominant species, Calyptogena kilmeri and C. pacifica, presumably share similar modes of existence yet appear to live in very different chemical conditions. Physiological factors controlling their distribution within the Monterey seep sites will be discussed. These invertebrate-bacterial associations demonstrate a number of unique adaptations that enable them to dominate in areas largely unavailable to other animals. Research on these animals continues to reveal further insight into the astonishing reality that metazoan life can thrive in some of the most hostile and primitive environments known to science. Next: Biological-physical coupling in the equatorial Pacific during the 1997-1998 El Niņo Last updated: December 19, 2000 |
