Calyptogena

Calyptogena is a genus of large deep-sea clams in the family Vesicomyidae. Members of this genus are bivalves that inhabit chemosynthetic environments such as hydrothermal vents and cold seeps in oceans around the world. They commonly occur on soft sediments or attached to substrates on continental margins, often in aggregations near seepage sites.

Morphology and biology: Calyptogena species have robust, elongated shells and well-developed siphons for drawing in water from above the seabed. They possess a mantle and gills that accommodate symbiotic bacteria. A defining feature is a digestive system that is greatly reduced, with nutrition largely provided by intracellular chemoautotrophic bacteria housed in the gill tissues.

Ecology and symbiosis: The key adaptation of Calyptogena is its symbiotic relationship with sulfur-oxidizing bacteria. The bacteria reside in the gill cells and convert sulfide-rich fluids from vents or seeps into organic nutrients that feed the clam. In exchange, the clam supplies a habitat and access to chemical energy sources, forming a mutualistic relationship that supports life in otherwise food-poor deep-sea environments.

Habitat and distribution: Calyptogena species are associated with hydrothermal vent and cold-seep ecosystems and are found at depths ranging from several hundred to thousands of meters. Their distribution includes various ocean basins, with communities typically tied to active seepage or venting activity.

Life cycle and significance: Reproduction is sexual, with adults producing free-swimming larvae that disperse before settlement. Calyptogena and related vesicomyids are important components of vent and seep communities, contributing to the chemosynthetic-based food webs and providing structural habitat in extreme deep-sea environments.