Mactra

Mactra is a genus of saltwater clams, marine bivalve molluscs belonging to the family Mactridae. These clams are characterized by their equivalve shells, meaning both valves are of equal size and shape, and their ovate to trigonal outline. The shells are typically smooth or finely ribbed and often exhibit a shiny periostracum, a thin, organic outer layer.

Species within the Mactra genus are found in marine environments worldwide, inhabiting sandy or muddy substrates in intertidal and subtidal zones. They are filter feeders, using their siphons to draw in water and extract plankton and other organic matter. Their burrowing habits help to aerate the sediment.

The genus Mactra is a well-established taxonomic group, though some species have been reclassified into related genera over time as scientific understanding of their evolutionary relationships has progressed. Common species might include Mactra stultorum, found in the eastern Atlantic, and Mactra chinensis, which occurs in the Indo-Pacific region. These clams play a role in marine ecosystems as both prey for other animals and as contributors to sediment dynamics. Their shells are also sometimes collected by humans.