Arcidae
Arcidae is a family of saltwater clams, marine bivalve mollusks. The family is large and contains about 200 species in 30 genera. These clams are commonly known as ark clams, ark shells, or just arks. They are characterized by their sturdy, often rectangular or oval shells with prominent, well-defined, radial ribs or ridges. These ribs provide the shells with strength and protection, helping the clams withstand the rigors of their marine environment.
Characteristics
Ark clams have a distinctive shell morphology. Their shells are typically thick and solid, with a prominent beak or umbo at the anterior end. The shells are usually equivalve (meaning both valves are similar in shape and size), and they are often covered with a periostracum, a thin, outer layer of organic material. The hinge line of the shell is straight and strong, featuring a series of teeth that interlock with those of the opposing valve.
Environments
Ark clams are found in a wide range of marine habitats, from shallow intertidal zones to deep-sea environments. They are common on sandy or muddy bottoms, often living in areas with strong currents. Some species are also found in rocky habitats and coral reefs. Many arc clams are epifaunal, living on the surface of the seafloor, while others are infaunal, living partially buried in the sediment.
Distribution
Arc clams are distributed globally in all oceans, with a wide range of temperature tolerance. They are particularly abundant in tropical and subtropical waters.
Notable Genera
Some notable genera of Arcidae include:
- Arca: The type genus of the family, containing many common ark clams.
- Anadara: A genus of ark clams known for their edible value in some regions.
- Barbatia: A genus of ark clams characterized by their elongated, narrow shells.
- Scapharca: A genus of ark clams with a distinctive, spoon-shaped shell.
Ecological Importance
Ark clams play a vital role in marine ecosystems. They are important food sources for a variety of marine animals, including fish, birds, and other invertebrates. They also contribute to the bioturbation of the seafloor, which helps to maintain the health of the ecosystem.
Economic Importance
Some species of ark clams are commercially harvested for food, particularly in Asia and other parts of the world. They are also popular in the aquarium trade due to their attractive shells.