Donax Clam Shells of the Donacidae Family
One Donax Clam Shell of the Donacidae Family can be found in this website:
Pitted Donax Clam Shell, Donax punctatostriatus. A representative of the Donacidae Family of Donax Clam Shells.
Phylogeny: Donax Clam Shells of the Donacidae Family are bivalve mollusks in the Cardiida order. Shells in this order are limited to marine environments. The Cardiida order consists of two superfamilies – Cardioidea and Tellinoidea. The Donacidae Family is one of five families in the Tellinoidea superfamily. There are no subfamilies in the Donacidae Family but there are six genera – Donax with sixty-one species, Galatea with seven species, Hecuba with four species, Iphigenia with six species, Latona with nineteen species, and Tentidonax with nine species. Shells in this family are also commonly known as Bean Clam Shells, Coquina Clam Shells, Wedge Shells, and Donacids.
Description: Donax Clam Shells are thick, small to medium-sized clams, which have a trigonal to elongate oval outline. Both valves are equal in size and shape (equivalve) and slightly inflated. Their anterior end is long and narrowly rounded. The posterior end is steeply sloping and somewhat truncate (chopped-off looking). The posterior end is sometimes marked with a radial keel The exterior of the shell may be smooth or sculpted with low radial ridges or fine commarginal striae. The exterior surface of these shell is usually shiny. The interior is smooth and shiny and the interior margin is often serrated. Shells in this family tend to be whitish, tan, brown, reddish, purplish, or gray, sometimes with darker or lighter radial rays. The interiors are white, often with purple or brown blushing. Each valve contains two cardinal teeth. These shells usually have a thin periostracum. Donax Clam Shells reach a maximum of 15.0 cm (5.8 inches) in width.
Habitat and Distribution: Donax Clams are found in mud and sand substrates. They live intertidally and at depths up to 70 m (230 feet). They are one of the most commonly found shells on sandy, surf-swept, beaches. Donax Clam Shells are found worldwide, in tropical and subtropical waters. There are eight species from the Donacidae Family found in Mexican waters.
Natural History: Donax Clams are suspension feeders that filter plankton and fine detritus from the surrounding water. In turn they are preyed upon by birds, crabs, rays and land mammals. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. They are well adapted to the high energy surf zone in that they are quick burrowers and can “surf” when needed, using wave energy to move quickly. To surf, these clams use their foot muscle to launch off the bottom, into the water column, and extend their siphon and foot, which is used as a sail to push them up the beach. They are unique in this ability. Donax Clam Shells are harvested as food and fishing bait.