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The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton , which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage.
The anatomy of a common air-breathing land snail: much of this anatomy does not apply to gastropods in other clades or groups. Snails are distinguished by an anatomical process known as torsion, where the visceral mass of the animal rotates 180° to one side during development, such that the anus is situated more or less above the head. This ...
As the nautilus matures, it creates new, larger camerae and moves its growing body into the larger space, sealing the vacated chamber with a new septum. The camerae increase in number from around 4 at the moment of hatching to 30 or more in adults. The shell coloration also keeps the animal cryptic in the water. When seen from above, the shell ...
Freshwater snails are gastropod mollusks that live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs to major rivers. The great majority of freshwater gastropods have a shell, with very few
The evolution of an asymmetrical conispiral shell allowed gastropods to grow larger, but resulted in an unbalanced shell. Torsion allows repositioning of the shell, bringing the centre of gravity back to the middle of the gastropod's body, and thus helps prevent the animal or the shell from falling over. [2]
Usually they lay 20-50 eggs in rotting wood or below decaying leaves. Eggs are white and flattened, measure about 1 mm and hatch after 10–30 days. These gastropods reach their maturity only in the second or third season and can live 2–3 years. [3] Unlike many terrestrial snails they do not have a sex dart. [4]
This results in different areas growing at different rates, and thus a coiling of the shell and a change in its shape - its convexity, and the shape of the opening - in a predictable and consistent fashion. [31] The shape of the shell has an environmental as well as a genetic component; clones of gastropods can exert different shell morphologies.
The Vermetidae, the worm snails or worm shells, are a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha. [1] The shells of species in the family Vermetidae are extremely irregular, and do not resemble the average snail shell, hence the common name "worm shells" or "worm snails".