Seashells are the protective outer layer of an animal that lives in the sea.
The shell is part of the animal’s body. Empty shells are found discarded on beaches. They are empty because the animal has died and its soft parts have become food for predators or scavenger animals, or have simply rotted away.
The term “shell” generally refers to the exoskeleton of an invertebrate (an animal without a spine). Most of the shells found on beaches are clamshells.
In addition to clamshells, other shells belong to Kamchatka crabs and brachiopods. Sea ringworms in the family Serpulidae create calcium carbonate cement shells. Sea urchin shells and molting shells of crabs and lobsters are called exuviae. Most shells are the appearance of cephalopods.
There are shells of freshwater animals, such as freshwater mussels and freshwater snails, and shells of land snails.
The word “shells” refers only to shells of marine mollusks. Shells are part of conchology. Conchologists, or serious collectors, carefully collect live animals for study so as not to disturb ecosystems.
The study of all animal mollusks (and their shells) is known as malacology;
A person who studies shellfish is known as a malacologist.
Seashells are the “shells” of marine species of bivalves, gastropods (or snails), scaphopods (or Tusk shells), polyplacophorans (chitons), and cephalopod mollusks (such as Nautilus and Spirula).
Marine species of gastropods and bivalves are more numerous than terrestrial and freshwater species. The shells of marine species, in tropical and subtropical regions of the planet, are more colorful, larger than in temperate zones and regions close to the poles.
But there are also a huge number of extremely small species – micromollusks.
Also, not all mollusks have an outer shell: some mollusks, such as some cephalopods (squids and octopuses) have an inner shell, and many mollusks have no shell at all, for example, Nudibranch.
There are over 15,000 species of bivalves, marine, and freshwater: scallops, mussels, oysters. Most bivalves consist of two identical shells that are connected by a flexible loop. The body of the animal is protected inside these two shells. Bivalves that don’t have two shells or have one sash – lack the shell as a whole. The shells are made of calcium carbonate and form mantles.
Bivalves, also known as pelecypods. They are filtration animals: they pass water through their gills, which trap tiny food particles. Some bivalves have eyes and an open circulatory system. Bivalves are used worldwide as food and as a source of pearls. The larvae of some freshwater mussels can be dangerous to fish.
Numerous small and little visible mollusk species (micromollusk) have not yet been identified by zoological nomenclature (ICZN). A large number of new species are described in the scientific literature each year. Currently, there are an estimated 100,000 species of mollusks worldwide.
We can talk about Barnacles animals that have a close relationship with lobsters and crabs. They are part of the crustacean subtype, infraclass Cirripedia. This type of arthropod can be found in tidal waters and shallow waters. They are marine animals. In all, there are about 1,220 species of mollusks.
To live, clams give their bodies a solid base at all times.
Pedunculata barnacles live by using a stem to attach their body to a solid substrate. Acorn shells, on the other hand, use growing shells to attach their bodies.
Another way of life of free-living Barnacle clams. They can be seen fixed from below, attached by cement glands to the substrate.
If you think that barnacles have a heart, you are mistaken. This animal has no true heart. The part of the body that can function as a heart is near the esophagus. A series of muscles pump blood through the sinuses.
Clams do not have any gills. Oxygen in the water is supplied through an inner membrane located on the shell and limbs. The maxillary glands are considered to be the shellfish’s excretory organs.
You can find one eye in adult clams. Thus, animals can only sense dark and light areas.
There are two larval stages in the life cycle of a shellfish, the nauplius, and the cyprid. Having survived the larval stages, barnacles will develop into adulthood.
There are only a few species of hermaphroditic clams – gonochoric or androdioecious animals. Most have the testes in the posterior part and the ovaries in the stalk or base.
One method of reproduction is sperm casting. The male releases sperm into the water and the female picks it up to fertilize the eggs.
You can find shells living in shallow water. Depths are less than 100 meters.
Some species of the mollusk are parasitic. Shellfish can often be seen on the body of crabs, whales, boat hulls, rocks, and sea turtle shells.
Most species are harmless because by attaching, they do not interfere with the food chain of the animal and do not harm the animal. Many clam species are so harmless that in fact, an animal that is covered in them may not even notice them!
Clams generally live from 5 to 10 years, but some of the larger species are much older.
Mollusks attach to animals in the larval stage. After the baby mollusk effectively sticks itself to something solid, a thin layer of flesh surrounds the mollusk with an outer shell. Once the clam baby has secured itself to something, it usually spends the rest of its life there.
Filter clams (also known as sestonophages) – feed on food particles extracted from the water. The shell of the clam consists of a series of plates (usually 6), with pinnate feet-appendages that rake water against the shell to feed.
Clams have numerous predators. Clam larvae are so small that they float along with plankton in the water. There are shells known to be edible to humans (edible clam species) in parts of Europe, Spain, Portugal.
Despite increased pollution and changes in the water, shells are believed to be one of the few animals that are not greatly affected.