It is a group located within the branch of mollusks , these being only of an aquatic nature, either marine or freshwater. The name is originated by its main characteristic, two valves that have been joined together and are articulated by means of a hinge.
Characteristics of bivalves
- They were previously called as amelobranchs or pelecipods .
- They belong to the group of mollusks.
- They have a shell that in turn is divided into two valves
- The characteristics of the shells vary according to the species
- Its shell is mainly made up of calcite and aragonite
- The size of the shells increases as the size of the animal increases
- The valves of these animals are attached to the mantle, that is, the membrane that is around the body of the animal
- The mantle is in charge of segregating all the necessary components for the increase and growth of the animal’s shell.
- They have abductor muscles that are located on the inside of the shell. These muscles are responsible for sealing and closing the shell with the animal inside it.
- They have a foot that is modified according to the conditions of the animal
- They have a respiratory system made up of gills
- Their gills are called ctenidia.
- Many species of bivalves can stay out of the water for a long time, closing their shells and breathing with the water that remains inside them.
- They have an open-type circulation and lack hemoglobin
- Your nervous system is made up of two nerve cords and three ganglia.
This type of animals has a very particular diet , since they depend on particles suspended in the water such as the phytoplan. It should be noted that there are also carnivorous and predatory species and unlike mollusks, these animals do not have radula.
Examples of bivalves
- River clam