Garden snails

We have found many different garden snails this spring, in various shades of white, brown, tan and pink.  Many were already picked over by the birds, and some of them were bleached by the sun.  We found several active snails, and we brought them home to observe them in an unused goldfish bowl with moss, soil, a little bottlecap of water, and some pulpy fruit.

An interesting thing about snails is that they are either right-swirled or left swirled.  All of the snails we have found were right-swirled, which means that starting from the center, the swirl twists clockwise.  This is the more common type.

Garden snails usually have two sets of tentacles.  The upper set are eyestalks and the other pair is a set of olfactory organs for smell.

Garden snails can hibernate in winter and aestivate during the summer.  Aestivation means they retreat into their shells, and form a mucus door to preserve moisture.  Both hibernation and aestivation are forms of dormancy.  They build up an anti-freeze-like substance in the winter to avoid being frozen.

source of diagram: Wikipedia

Garden snails are pulmonates, which means they have a lung and breathe air.  You can see the air hole of this snail below.  It is easy to see it expand and contract with the naked eye.

One question we had was why the snail shells were in so many different colors.  My guess was that the food they ate had something to do with their outer color, similar to flamingos.  It turns out that it might have a little to do with food, but it is probably an evolutionary tactic snails use to make it harder for the birds to recognize them.  If all snails were the same color, birds would quickly develop a pattern recognition scheme and be able to wipe them out.  With varying colors and striations, some snails can escape being eaten.

Since most snails are hermaphrodites, they inseminate each other and are all able to lay eggs.  One snail will shoot a love dart into another, which simply increases the possibility that the other’s mucus will be hospitable to reproduction; it is actually a precursor to mating, which occurs later.  It does not matter where the love dart lands – the snail simply needs a contact shot.  Snails find each other for mating by finding each other’s slime trails.  The reproductive opening of a land snail is in its head.