Little crawlers grow up

Six-week old Cornu aspersum (a.k.a Cantareus aspersus or Helix aspersa), the common garden snail. Born transparent, they began developping shell pigmentation after a couple of weeks, starting with the bands. The final pattern of their shells however won’t be certain until they have fully grown: until then the bands continue evolving as the shell grows and may become thicker or thinner, darker or lighter, and adjacent bands may merge into a single, broader one while others may simply fade and disappear. As such, even if apparently all juveniles developped five bands at first, adults may have less.

Their bodies are still light coloured: body pigmentation will take a few months to become apparent, starting with their head and dorsal stripe.

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Eaters of the dead

Crawling in a wood in broad daylight, two Arion slugs approach a lucky meal: a dead conspecific. Many snails and slugs are saprophagic, i.e. feed on decaying matter and dead animals. And some of them, like Arion slugs, won’t hesitate to eat dead snails or slugs of their own kind.

Cannibalism in some form or another is not infrequent among gastropods: several snails (including Pomacea bridgesii and other common aquarium snails) will feed on the remains of dead conspecifics, and sibling cannibalism has been observed among hatchlings (e.g. newborns of the common garden snail, Cornu aspersum, will sometimes eat the other eggs that haven’t hatched yet). Few species, however, hunt live individuals of their same species: Schizoglossa novoseelandica being an example. By contrast, despite being known as “cannibal snail”, Euglandina rosea (rosy wolfsnail) will rarely prey upon individuals of the same species.

GLOSSARY

Intraspecific predation: from Latin intra “within”, predation within the same species = cannibalism
Adelphophagy: from Ancient Greek ἀδελφός (adelphos) "brother" & φάγος (phagos) "eater" = sibling cannibalism

Literature:

Mother & baby

Adult Cornu aspersum, carrying one of its newborns

Close-up

More pictures of the hatchlings.

Hatchlings

Barely 3mm in size, these Cornu aspersum explore the world for the first time. Eggs hatched after 12 days of incubation, and the fully formed and self-sufficient baby snails emerged from the ground, crawling their way to food and shelter.

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