Macro Monday: Cantareus apertus

A lucky encounter with a juvenile Cantareus apertus, also known as the green snail. Native of the Mediterranean and North Africa, these snails spend most of their life underground, but emerge after rain. Subadults like this one have a yellowish-green shell and body, which will darken with time: as adults they are almost black fleshed and have uniformely brown shells.

In spite of their small size (about 2,5-3 cm in diameter), these snails are highly prized for culinary purposes, especially in southern Italian peninsula of Salento, where they are known as municeddhi, municedde or moniceddi. (They are said to be far superior to other edible snails, even Helix pomatia)

 

 

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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.

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:

• A predatory snail distinguishes between conspecific and heterospecific snails and trails based on chemical cues in slime
• First report of cannibalism in Triplofusus giganteus (Gastropoda: Fasciolariidae)
• Influence of egg cannibalism on growth, survival and feeding in hatchlings of the land snail Helix aspersa Müller (gastropoda, pulmonata, stylommatophora)
• Sibling Cannibalism in Juveniles of the Marine Gastropod Nassarius festivus (Powys, 1835)

Polynesian tree snails – saved from oblivion?

Extinct in the wild in its native French Polynesia, Partula faba, a small tree snail, is being given a second chance at Bristol Zoo Gardens, where the last 88 surviving specimens are being nurtured and cared for in an attempt to save the species through conservation breeding.

Newborn Partula faba:15 snails hatched in April 2010 at Bristol Zoo Gardens
(Photo credit: Jenny Spencer)

Double disaster: in the 70s Achatina fulica, a highly prolific species of giant African land snails, was introduced into French Polynesia as a source of food but soon turned into a pest. To keep the highly invasive Achatina under control, a predator snail, Euglandina rosea (rosey wolfsnail) was introduced into the islands. Euglandina however disregarded Achatina and instead devoured local species into oblivion.

According to the IUCN Red List of Threatened Species, of the many Partula species endemic to the islands, by 2009 , 13 were critically endangered, 11 extinct in the wild and 51 extinct (including Partula affinis, P. auriculata, P. bilineata, Partula candida, P. citrina, P. dolichostoma, P. turgida, P. umbilicata and more).