Solemya velum
Solemya velum, the Atlantic awning clam, is a species of marine bivalve mollusc in the family Solemyidae, the awning clams. This species is found along the eastern coast of North America, from Nova Scotia to Florida.
Like other species of the genus Solemya, the gills of S. velum contain sulfur-oxidizing chemosynthetic bacteria which fix carbon dioxide to support their hosts nutritionally. This is an example of chemosynthetic symbiosis. The bacteria produce the energy to fix carbon by oxidizing hydrogen sulfide found in the environment. The metabolic pathway that they use for carbon fixation is the Calvin cycle. The genome of the symbiotic bacteria has been sequenced and contains genes for bacterial motility, suggesting that it may also be able to live outside of its host.
The clams themselves live in coastal sediments, where they build Y-shaped burrows. These burrows allow them to access both oxygen from the overlying seawater, and hydrogen sulfide from deeper sediment laters, both of which are needed by their symbionts to produce energy. The mitochondrial genome of S. velum has been sequenced, and has features that are closer to ancestral mollusks than other bivalves.
