Gastropods - Snails and Slugs
|by Marcia Malory|
Gastropods are the class of mollusks that includes snails, slugs, limpets and abalones.
A gastropod moves by sliding along on a large, flat foot that is covered with mucus.
The name gastropod is Greek for "stomach foot". It looks like they walk on their stomachs.
In fact, the internal organs of gastropods are located in a hump on their backs.
When a gastropod is young, it undergoes a process known as torsion, in which its visceral mass, mantle and shell rotate 180 degrees so that the anus is located above the head.
The visceral mass is the part of a mollusk's body that contains its internal organs
The mantle is a fold of the outer body wall that secretes the materials that make up the shell of a mollusk.
The shell of a gastropod is often coiled and asymmetrical.
Some gastropods have no shells or shells that are reduced in size.
Limpets often have conical shells.
There are more species of gastropod than any other type of mollusk.
Biologists estimate that between 60,000 and 90,000 gastropod species are alive today.
Gastropods live on land, in freshwater and in saltwater.
The garden snail, which can be found in many parts of the world, has a soft, brownish gray body and a shell that is usually brownish with yellow stripes or flecks.
It is usually nocturnal (active at night) but will come out during the day after it has rained.
The garden snail has a strong homing instinct. It will return to the same spot after feeding.
It will go inside its shell when it is threatened.
When the weather is too cold or too dry, a garden snail will withdraw into its shell and seal it with a barrier of dried mucus that is known as an epiphragm. It will then enter a state of lowered metabolic activity that is known as hibernation in cold weather and estivation in dry weather.
Garden snails are hermaphrodites - an individual snail has both female and male reproductive organs.
The garden snail is often considered a pest because it eats a large variety of plants.