bivalviák

Bivalvia is a class of aquatic molluscs that are characterized by their shells, which are composed of two hinged parts, or valves. These valves are typically symmetrical and are secreted by a specialized tissue called the mantle. Bivalves are found in all marine environments, from shallow coastal waters to the deep sea, and also inhabit freshwater habitats. They are filter feeders, meaning they strain small food particles, such as plankton and organic detritus, from the water using their gills.

The two valves of a bivalve's shell are held together by a ligament, which can be internal or external. Powerful muscles, known as adductor muscles, are used to close the valves tightly against predators or to regulate water flow for feeding and respiration. Many bivalves are sessile, attaching themselves to substrates like rocks, shells, or even other animals. Others are mobile, using a muscular foot to burrow into sand or mud, or to move slowly across the seafloor.

Reproduction in bivalves typically involves external fertilization, where males release sperm into the water and females release eggs. The resulting larvae are often planktonic before settling to the bottom and developing into adult forms. Some bivalve species are commercially important as food sources, such as oysters, mussels, and clams. They also play crucial roles in marine ecosystems, filtering large volumes of water and serving as prey for various other organisms.