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Anonymous users2024-02-10The mantle of a beike mollusk with a special type of glandular cell whose secretion forms calcifications that protect the soft parts of the body, called a shell. The number, shape and structure of shells vary greatly, with some species having one spiral shell (e.g., snail, snail, abalone); Some species have two petal-shaped shells (e.g., mussels, cockles); Some species have 8 plate-like shells, arranged in a shingle-like arrangement (such as stone turtles); Some species have 1 shell encapsulated (e.g., squid, spear squid); Some species of shells are even completely degraded (e.g. ship maggots). The main components of shells are 95% calcium carbonate and a small amount of chitin.
Generally, it can be divided into 3 layers, the outermost layer is the black-brown cuticle (shell skin), thin and transparent, which has the effect of preventing carbonic acid erosion, and is composed of chitinin secreted by the edge of the mantle; The middle layer is a prismatic layer (shell), thicker, composed of prismatic calcite secreted by the edge of the mantle, and the outer and middle layers expand the area of the shell, but do not increase the thickness; The inner layer is nacre (bottom layer), which is made up of leaf-like aragonite (aragonite) secreted from the entire surface of the mantle, which has a beautiful luster and thickens as the body grows. The main chemical composition of calcite and aragonite is CaCO3. The outer layer of the shell has multiple concentric ring-shaped growth lines of alternating shades of color, but it does not represent age; It is formed as a result of the inability of the mantle edge to continue secreting due to some reason (insufficient food, different seasons, reproductive period, etc.).
The patterns on the shells are related to where they live and the genetic factors carried by their mothers. The shells picked up on the beach are often bright in color, and some have a variety of bright colors; Shells picked up in the mire near the lake are often dull in color.
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Anonymous users2024-02-09Hello, there are many shapes of shells, there are round, fan, petal, and there is a kind of shell that is spiral.
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Anonymous users2024-02-08Shells come in many shapes, ranging from round to fan-shaped.
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