Species from the genus Mactra, belong to the family Mactridae and are commonly known in English as surf clams or duck clams and in Mauritius as tek tek, is a family of saltwater clams. Like other clams, their shells consist of two equal valves, which are connected by a hinge joint and a ligament that can be external or internal. The ligament provides tension to bring the valves apart, while one or two adductor muscles can contract to close the valves. Clams also have kidneys, a heart, a mouth, a stomach, a nervous system and an anus. Shaped like a round-cornered equilateral triangle, their shells of a relatively equal size bear interlocking teeth shaped like an inverted V. They have two short siphons each with a horny sheath. In most species, the hoof is white and wedge-shaped.
 Richmond, Matthew (ed.). 2011. A fieldguide to the seashores of Eastern Africa and the Western Indian Ocean islands. Sida/WIOMSA.
Mactra shells burrow in sand or fine gravel but never in muddy substrates. As filter feeders, clams collect tiny particles of food suspended in the water. Water is continuously drawn in through an incurrent siphon and circulated over the gills. Food particles stick to mucus that coats this respiratory organ. Cilia, tiny hair-like structures, sweep the food particles towards the clam’s mouth. Food is digested in the stomach and intestine. Wastes from digestion are excreted through the anus, and filtered water is returned to the sea by the excurrent siphon.
Their range and population numbers do not warrant any conservation status on the IUCN Red List. Nevertheless, these bivalve shells are often consumed by humans, and suffer from human activity on the beach, such as collection, trampling, coastal development and beach erosion.
When gleaning and observing life on beaches, small holes may be noticed on dead Mactra shells. These “drill holes” are the work of sea snails, which use their teeth or radula to scrape away some of the protein fibres and calcium which make up the shell of the clam, followed by acid secretion which further demineralizes the shell. The snail then extends its proboscis (sucking mouth part) through the hole, using the radula to tear up the tissues within the clam and ingesting the particles of meat.