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).