A species
Garden snail
Cornu aspersum
A house on its back, slime under its foot and thousands of teeth.
You and the garden snail last shared an ancestor about 580 million years ago (on 11 November, if life's history were one year).
Imagine carrying your house on your back. The garden snail does. It glides along on its own slime and rasps food with thousands of tiny teeth. Its surprise relative sits beside it on the tree: the common octopus. Both are molluscs, so a garden crawler and an octopus are distant relatives.
The shell is rounded and about 3 cm across, about as wide as a bottle top. It coils in four or five spirals and has a yellowish colour with dark brown bands broken by yellow flecks. Patterns vary from snail to snail. The soft, moist body is brownish grey and can pull right back inside its shell. Its head has four tentacles that pull in when alarmed. The top pair sense light with eye-like tips. The lower pair smell and touch.
It moves on one flat, muscular foot. Waves ripple along the foot while glands release slime that cuts friction and cushions sharp edges. The slime dries into a shiny trail. It favours damp, sheltered spots and is mostly active at night, often coming out by day only after rain. It mainly eats plants such as vegetables, roses and fruit trees.
Pearly batches of eggs
About ten days after fertilisation, it lays batches of about 50 round, pearly-white eggs, each about 3 mm wide, about as big as a sesame seed. It lays them in topsoil crevices or under stones and repeats through the season.
Seals itself in
It has no shell door. In dry or cold spells it seals the shell mouth with a thin sheet of dried slime that holds in moisture. It can sit out drought and winter cold down to about minus 5 degrees C.
World traveller
It is native to the Mediterranean region. People have carried it to many countries, including Australia, where it lives in cities and suburbs. It is farmed as a food snail, and one city festival in Spain for it draws more than 200,000 visitors a year.