Seashell

A seashell is usually the exoskeleton of an invertebrate (an animal without a backbone), and is typically composed of calcium carbonate[1] or chitin.

Marine annelid worms in the family Serpulidae create shells which are tubes made of calcium carbonate cemented onto other surfaces.

[2] This type of large-scale exploitation can sometimes have a strong negative impact on local ecosystems, and sometimes can significantly reduce the distribution of rare species.

In the tropical and sub-tropical areas of the planet, there are far more species of colorful, large, shallow water shelled marine mollusks than there are in the temperate zones and the regions closer to the poles.

Bivalves, also known as pelecypods, are mostly filter feeders; through their gills, they draw in water, in which is trapped tiny food particles.

Females of the cephalopod genus Argonauta create a papery egg case which sometimes washes up on tropical beaches and is referred to as a "paper nautilus".

On the other hand, some collectors buy the more widely available commercially imported exotic shells, the majority of which have very little data, or none at all.

In the US, these clubs are more common in southerly coastal areas, such as Florida and California, where the marine fauna is rich in species.

Seashells are usually identified by consulting general or regional shell-collecting field guides, and specific scientific books on different taxa of shell-bearing mollusks (monographs) or "iconographies" (limited text – mainly photographs or other illustrations).

In other words, they have not yet been differentiated from similar species and assigned scientific (binomial) names in articles in journals recognized by the International Commission on Zoological Nomenclature (ICZN).

The shells are broken or ground into small pieces in order to have the desired effect of raising the pH and increasing the calcium content in the soil.

These valentines consisted of elaborate arrangements of small seashells glued into attractive symmetrical designs, which were encased on a wooden (usually octagonal) hinged box-frame.

The patterns used often featured heart-shaped designs, or included a sentimental expression of love spelled out in small shells.

The making of shell work artifacts is a practice of Aboriginal women from La Perouse in Sydney, dating back to the 19th century.

The shellwork tradition began as an Aboriginal women's craft which was adapted and tailored to suit the tourist souvenir market, and which is now considered high art.

[12] Small pieces of colored and iridescent shell have been used to create mosaics and inlays, which have been used to decorate walls, furniture and boxes.

Large numbers of whole seashells, arranged to form patterns, have been used to decorate mirror frames, furniture and human-made shell grottos.

A very large outdoor sculpture at Akkulam of a gastropod seashell is a reference to the sacred chank shell Turbinella pyrum of India.

In 2003, Maggi Hambling designed a striking 13 ft (4 m) high sculpture of a scallop shell which stands on the beach at Aldeburgh, in England.

Sea shells found in the creek and backwater of the coast of west India are used as an additive to poultry feed.

[citation needed] Seashells, namely from bivalves[13] and gastropods, are fundamentally composed of calcium carbonate.

Along the Gulf Coast of the United States, oyster shells were mixed into cement to make "shellcrete" which could form bricks, blocks and platforms.

[15] Many arthropods have sclerites, or hardened body parts, which form a stiff exoskeleton made up mostly of chitin.

In crustaceans, especially those of the class Malacostraca (crabs, shrimps and lobsters, for instance), the plates of the exoskeleton may be fused to form a more or less rigid carapace.

After the animal dies, the flesh rots out and the spines fall off, and then fairly often the empty test washes up whole onto a beach, where it can be found by a beachcomber.

The brachiopods, or lamp shells, superficially resemble clams, but the phylum is not closely related to mollusks.

Some polychaetes, marine annelid worms in the family Serpulidae, secrete a hard tube made of calcium carbonate, adhering to stones or other shells.

This tube resembles, and can be confused with, the shell of marine gastropod mollusks in the family Vermetidae, the worm snails.

The construction of the shell-like structures of corals are aided by a symbiotic relationship with a class of algae, zooxanthellae.