Snails have either one or two pairs of pneumatic tentacles on their head, which can be retracted in the face of danger. Their mouth is formed of a radula which is a hard scraping device used to scratch food from most surfaces. You can see clear trails along stone or brickwork where snails have scrubbed them clear of algae.
Snails have a strong muscular foot covered in a thick mucus which helps them to move over rough surfaces. This mucus also prevents the soft, permeable skinned snails from drying out and can also harden to form a plug when they retract into their shell.
The Spiral Shell
Most snails are hermaphroditic, with both male and female sexual organs, and when emerging from the buried eggs, the tiny snails hatch with a complete shell. This shell will then grow in a spiral as the soft fleshy parts of its body increase in size. The shell is put together using calcium carbonate, creating a very rigid structure.
Most land snails have shells that spiral to the right, however, some are able to spiral left creating a problem for some specialised predators, as displayed in David Attenborough's Natural Curiosities.
- The largest terrestrial species, the African land snails, can grow up to 38cm and weigh 1kg.
- WHile the largest marine species, Syrinx aruanus, can grow up to 90cm and weigh up to 18kg.
- The shell is made from calcium carbonate.
- Most shells spiral to the right.
- Snails are eaten as a delicacy throughout the world.
- Snails that have very small, vestigial shells are often called semislugs.