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Snail eggs on a stalk of grass
Image: Veer
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The life cycle of a snail is straightforward. There is no metamorphosis, with markedly distinct larval and adult forms, as in such organisms as frogs or butterflies.
The young snail within the egg has a shell and the same basic form as an adult. The shell is transparent initially, but becomes opaque soon after hatching, when the snail starts eating food containing calcium. Thereafter, the snail looks like a small version of an adult. From the beginning, a snail adds layers to the rim of its shell so that it grows in a coil, round and round, larger and larger.
After reaching maturity, female and hermaphrodite snails lay eggs (see figure, left). In those types with separate sexes, one or more males have fertilized the eggs. Hermaphrodites usually mate with each other, but self-fertilization can occur.
As the eggs start to develop, the life cycle of a snail begins again.
Snail facts:
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Snails make up the molluscan class Gastropoda;
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All land snails are hermaphroditic;
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Some snails, such as the Maiden Campeloma (Campeloma parthenum), reproduce via parthenogenesis.
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A few snails, such as the Japanese Trapdoor Snail (Viviparus malleatus), give live birth, but the great majority are oviparous.
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