17 Juni 2009

Achatina fulica

The East African land snail, or giant African land snail, scientific name Achatina fulica[1], is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae.

It is native to East Africa, however the species has been widely introduced to Asia, to the Pacific and Indian Ocean islands, and to the West Indies. Where the snail is seen as a pest, it has been intercepted widely by quarantine officials, and incipient invasions have been successfully eradicated, for instance in the mainland USA.[2]

In recent times, the land snails have been kept as pets; however, they are illegal to possess in some countries including the United States[3]. The snails are easy to keep and, when bred in captivity, are unlikely to carry parasites.



[edit] Description

shell of Achatina fulica

The adult snails have a height of around 7 cm (2.5 inches), and their length can reach 20 cm (8 inches) or more.

The shell has a conical shape, being about twice as high as it is broad. Either clockwise (sinistral) or anti-clockwise (dextral) directions can be observed in the coiling of the shell, although the right-handed (dextral) cone is the more common. Shell colouration is highly variable, and dependent on diet. Typically, brown is the predominant colour and the shell is banded.

[edit] Habitat

The East African land snail is native to East Africa, especially Kenya and Tanzania. Its habitat includes most regions of the humid tropics, including many Pacific islands, southern and eastern Asia, and the Caribbean. It is a highly invasive species, and colonies can be formed from a single gravid individual. The species has established itself in temperate climates also, and in many places release into the wild is illegal. The giant snail can now be found in agricultural areas, coastland, natural forest, planted forests, riparian zones, scrub/shrublands, urban areas, and wetlands.

[edit] Nutrition

Achatina fulica in Hyderabad, India.

The Giant East African Snail is a macrophytophagous herbivore; it eats a wide range of plant material, fruit and vegetables. It will sometimes eat sand, very small stones, bones from carcasses and even concrete as calcium sources for its shell. In rare instances the snails will consume each other.

In captivity, this species can be fed on grain products such as bread, digestive biscuits and chicken feed. Fruits and vegetables must be washed diligently as the snail is very sensitive to any lingering pesticides.[citation needed] In captivity, snails need cuttlebone to aid the growth and strength for their shells. As with all molluscs, they enjoy the yeast in beer, which serves as a growth stimulus.

[edit] Reproduction

The Giant East African Snail is a simultaneous hermaphrodite; each individual has both testes and ovaries and is capable of producing both sperm and ova. Instances of self fertilisation are rare, occurring only in small populations. Although both snails in a mating pair can simultaneously transfer gametes to each other (bilateral mating), this is dependent on the size difference between the partners. Snails of similar size will reproduce in this way. Two snails of differing sizes will mate unilaterally (one way), with the larger individual acting as a female. This is due to the comparative resource investment associated with the different genders.[citation needed]

Like other land snails, these have intriguing mating behaviour, including petting their heads and front parts against each other. Courtship can last up to half an hour, and the actual transfer of gametes can last for two hours. Transferred sperm can be stored within the body for up to two years. The number of eggs per clutch averages around 200. A snail may lay 5-6 clutches per year with a hatching viability of about 90%.

[edit] Life cycle

Adult size is reached in about six months; after which growth slows but does not ever cease. Life expectancy is commonly five or six years in captivity, but the snails may live for up to ten years. They are active at night and spend the day buried underground.

The East African Land Snail is capable of aestivating for up to three years in times of extreme drought, sealing itself into its shell by secretion of a calcerous compound that dries on contact with the air. This is impermeable; the snail will not lose any water during this period.

[edit] Pest control

In many places the snail is seen as a pest. Suggested preventative measures include strict quarantine to prevent introduction and further spread. Many methods, including hand collecting and use of molluscicides and flame-throwers, have been tried to eradicate the giant snail. Generally, none of them has been effective except where implemented at the first sign of infestation.

In some regions, an effort has been made to promote use of the Giant East African Snail as a food resource, the collecting of the snails for food being seen as a method of controlling them. However, promoting a pest in this way is a controversial measure, as it may encourage the further deliberate spread of the snails.

One particularly catastrophic attempt to biologically control this species occurred on South Pacific Islands. Colonies of A. fulica were introduced as a food reserve for the American military during the second world war and they escaped. A carnivorous species was later introduced, but it instead heavily harvested the native Partula, causing the loss of several species within a decade.[citation needed]

[edit] References

[edit] Further reading

1 komentar:

Ngurah suta 4 April 2017 pukul 16.20  

Dimana saya bisa mendapat/membeli cangkang giant african land snail ?

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