Bivalve: What are, characteristics and examples

The bivalve, lamelibranchs or pelecipods They are a class of mollusks that are characterized, as the name implies, by having a shell formed by two valves They bind dorsally and cover and protect the body of the animal. In the world there are approximately some 13,000 species And most of them are marine.

These aquatic animals are grouped into the Bivalvia class, so they are called bivalve (two valves), and belong to Mollusca or mollusc fylum. In this other article you can learn more about mollusks: characteristics, types and examples.

Here you have a list with the main characteristics of the bivalve:

• They present one Concha with two articulated lateral symmetrical valves one with another through its dorsal part. The valves are linked by a band of an elastic protein that forms the “ligament” and these close thanks to the action of adductor muscles. When the adductor muscles relax the natural elasticity of the ligament makes the wallets open.
• The Bivalve shell presents Great variations in size, colors and shapes. It is formed by a “periostraco” that covers 2 to 4 calcareous layers and protects the underlying calcium carbonate and avoids its dissolution. The periostraco can be very thick or very fine.
• The lines that are formed in the shell They provide information about the age of the animal and environmental conditions in which its growth occurred.
• They have a compressed foot laterally which gives the name to the Pelecipodos group (“ax -shaped foot”)
• Only the species that have their shell with Nácar inner layer they can produce pearls. Here we tell you how pearls are formed.
• The head is poorly developed.
• They lack Radula.
• Paleal cavity is the most spacious compared to other groups of mollusks.
• The Large gills They are not only used in the Gaseous exchangebut also They collect food.
• They have the circulatory system of a typical mollusk.
• Its nervous system is formed by three pairs of ganglia and two pairs of nerve cords.
• In some species there may be ocellos that detect changes in the intensity of light.
• The Bivalve class is divided into three groups according to the structure of its gills: protobranchies, lamelibranchies and septibranchies.

Almost all Bivalve species They live in Soft Acuícololas Sweetlands undergroundbeing protected and obtaining the food they need. Some are immediately under the surface and others can reach greater depths. Here you can learn more about seabed: what are, types and photos.

Other species are superficial inhabitants that They live attached to a substrate such as rocks, corals, shells and docks. An example of this type of bivalve is the mussels, widely known mollusks.

They also exist superficial inhabitants of free life found on the bottom surface like sea combs. These swim abruptly by opening and closing their valves, expelling water jets from their paleal cavity being able to escape from their predators.

Others, known as bivalve perforators, pierce and live under the surface of some firm substrates like wood, shells, corals, among others. Sea sweeps are the most representative within this group. These animals are locked under the selected substrate and only their siphons are peeked through a small hole.

A minor group within bivalve mollusks is the parasites. So far only one species of the genus is known in an endvalva that lives in the digestive system of sea cucumbers.

Most primitive bivalve (protobranchies) are selective detritivores And they do not have a gifted, but they remain in contact with the substrate thanks to the existence of a pair of tentacles covered with mucus that are prolongations of the mouth. Each tentacle is linked to a fold composed of two outgoing called lip palpos. At the time of feeding they extend their tentacles coming into contact with the sediments of the background and the particles adhere to them and are transported to the palps that have cilia and act classifying the food. In this other post you can know the detritivorous: definition and examples.

In some species, such as SOLEMY VELUMthis type of food does not exist since they lack tentacles and lip palpos are reduced, so They get their food thanks to bacteria inhabiting their gills that set carbon.

Nevertheless, Most bivalve are filter lamelibranchs and they feed mainly with plankton and suspended particles using their gills as filtration organs. The ventilation current serves as a filtration current and the cilia transport the particles taken to the mouth.

Most species are dioic and they present two gonads although there are Other hermaphrodite species. In this other article you can read about hermaphrodite animals: reproduction and examples.

In marine species, the formation of a swimming trocoporous larva that is followed by a veligera larva is common. The intercourse in these animals does not occur and the gon pipelines are very simple. Fertilization occurs externally In the surrounding water. Here we talk about external fertilization: what is and animals.

Next, we present four examples of bivalve molluscs.

Mitílidos

Mitílides commonly known as mussels They are a family of Bivalve filtering that live attached to substrates and there is economic and gastronomic interest in them. Most of the mussels are marine, but there are also sweet species such as the golden mussel, Limnoperna Fortuneia species that has become an invadora in South America.

Oysters

Ostrea is a genus of bivalve molluscs better known as oysters. These have two rounded unequal wallets and are one of the most valuable edible animals. Just like mitílidos are filter organisms. Some examples are:

• Common oyster (OSTREA EDULIS)
• Australian flat oyster (OSTREA ANGASI)
• Oyster horse (Ostrea Equestris)
• Ostrea Conchaphila

CARDIDOS

Cards, popularly known as BERBRECHOSthey are distinguished by having an armored shell and pronounced longitudinal ribs. This family contains well -known species, many of them edible, for example:

• Common beroat (Celastoderma Edule)
• Green berberecho (Celastoderma glaucum)
• Yellow berberecho (Dallocardia Muricata)
• Dinocardium robustum

Clams

There are a lot of species known as clams that They live buried in soft substrates And they possess, like the other species mentioned, importance in gastronomy. Among them:

• American clam (Mercenaria Mercenaria)
• Giant clam (Gigas tridacna)
• Fresh water clam (Diplodon Chilensis)
• Yellow clam (Yellowadesma Mactroids)

Now that you have learned all this about the bivalve, here you can read this other article about how the clams reproduce.

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