GASL -a badass case of the munchies
The Misplaced
The culprit is Achatina fulica, more commonly known as the Giant African Land Snail. It is a mollusc species which resembles the widespread common garden snail (Cornu asperum) but is much much larger and its shell is more pointed. Adults of the species may exceed 20cm in shell length but generally average about 5 to 10cm. The average weight of the snail is approximately 32 grams.
The Giant African Land Snail reproduces quickly, producing about 1,200 eggs in a single year.
It is thought to have been introduced into a range of countries as a pet, which then has escaped into the wider environment to become a pest. It has also been deliberately introduced into some countries as a possible food source. It can adapt to both tropical and temperate environments, and can hibernate during temporarily harsh conditions.
In its natural environment, it is preyed upon by birds, mammals and reptiles plus a range of parasites attack it, so it is kept in check in its natural habitat.
Giant African Land Snails are included in the list of the World's 100 Worst Invasive Alien Species as determined by the ISSG, IUCN, Species Survival Commision and Bionet.
The Displaced
Ecosystems may be devastated by an invasion of the Giant African Snail with plants completely eliminated and consumer organisms out-competed for food sources. This snail is not is not particular about what it eats, hence the displaced organisms will belong many species. This very large snail has a voracious appetite and is known to eat over from 500 different species of plants. It will eat
- leaves
- flowers
- fruits
- stems
- bark
- wood
- seeds
- grains
- nuts
- seaweed
- lichens
- fungi
- other snails
The Consequences
Where is the invasion?
Native to Eastern Africa, from Mozambique to Kenya and Somalia in addition to the nearby islands, this species has spread to other African countries such as Ghana, Ivory Coast, and Morocco. It has been recorded in Hawaii, Australia, islands of the Caribbean, islands and regions of Asia, China, Bangladesh, Japan, Indonesia, Sri Lanka, Vietnam, Malaysia, Philippines, New Zealand, Samoa, Papua New Guinea, Fiji, and Vanuatu.
Achatina fulica has all the characteristics of a successful invasive species. It is destructive, it breeds quickly, it is adaptable to a range of abiotic factors and is not heavily preyed on by other species in most novel environments. One exception to the freedom of predation has been noted. Predatory hermit crabs, primarily Coenibitus perlatus, and robber crabs, Birgus latro, have made it difficult for A. fulica to become established on coral islands. Rats, centipedes, millipedes and fire ants are all known to prey on the giant African snail on Indo-Pacific Islands.((CABI datasheet))
As well as removal of plant species native to the area, the Giant African Snail alters the existing nutrient cycling carried out by native species which may impede re-establishment of the original species.
Remediation and Prevention
There have been numerous attempts to remove it from the countries which it has invaded and not been repelled by native species. This includes manual collection of snails and eggs and the use of molluscicides. Also quarantine measures have been taken to restrict how the snail is transported around the world e.g. seizing at customs, passing laws about using them as pets.
Biocontrol gone wrong
In the 1950s, an attempt to use the introduction of a new organism to control the Giant African Land Snail was made. The plan was to introduce the rosy wolf snail (Euglandina rosea), a cannibalistic species from southern USA to areas under assault by A. fulcina. What happened instead is that the rosy wolf spider preyed on native molluscs and put the entire systems into which it was introduced into even more danger.
In another example, a flatworm (Platydemus manokwari) from New Guinea, was deliberately introduced into two Pacific islands in an attempt to control an invasion of the Giant East African Snail. Since then, this flatworm has been discovered to have a detrimental impact on biodiversity. When it comes into a new habitat, it will quickly adapt and eat any snail or invertebrate it can find. It is not selective. It outcompetes other predatory flatworm species. Currently, there are no known methods for controlling the population of P. manokwari which makes the eradication of the invasive species especially difficult.
