Achatina fulica

East African land snail
Achatina fulica from Thailand
Conservation status
NE[1]
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia

informal group Pulmonata
clade Eupulmonata
clade Stylommatophora
informal group Sigmurethra
Superfamily: Achatinoidea
Family: Achatinidae
Subfamily: Achatininae
Genus: Achatina
Subgenus: Lissachatina
Species: A. fulica
Binomial name
Achatina fulica
(Férussac, 1821)

The East African land snail, or giant African land snail, scientific name Achatina fulica[2], is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae.

This mollusc is now known as one of the worst invasive species in the world.[3] In recent times, the land snails have been kept as pets; however, they are illegal to possess in some countries including the United States[4]. The snails are easy to keep and when bred in captivity are unlikely to carry parasites.

Contents

Subspecies

Distribution

This snail is native to East Africa, however the species has been widely introduced to Asia, the Pacific and Indian Ocean islands, and to the West Indies.

Distribution include:

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.[7]

This species is already established in the USA, and is considered to represent a potentially serious threat as a pest, an invasive species which could negatively effect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine significance in the USA.[8]

Description

A shell of Achatina fulica

The adult snails have a height of around 7 centimetres (2.8 in), and their length can reach 20 centimetres (7.9 in) 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.

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.

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. 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.

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.

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%.

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.

Pest control

Achatina fulica hamilei var. rodatzii

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.

Human use

Achatina fulica is used for religious purposes in Brazil as deity offering to Obatala as a substitute for the African Giant Snail (Archachatina marginata) that is used in Nigeria, because they are known by the same name (Igbin, also known as Ibi or Boi-de-Oxalá in Brazil) in both Brazil and Nigeria.[9]

References

This article incorporates CC-BY-2.0 text from the reference [9].

  1. ↑ IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>. Downloaded on 10 July 2009.
  2. ↑ "Achatina fulica". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=76978. Retrieved July 6, 2007. 
  3. ↑ Global Invasive Species Database: 100 of the Worst Invasive Species
  4. ↑ Should Giant African Land Snails Be Kept as Pets At All?
  5. ↑ Lv S., Zhang Y., Liu H-X., Hu L., Yang K', et al. 2009. Invasive Snails and an Emerging Infectious Disease: Results from the First National Survey on Angiostrongylus cantonensis in China. PLoS Neglected Tropical Diseases 3(2): e368. doi:10.1371/journal.pntd.0000368 figure 5.
  6. ↑ Wu S.-P., Hwang C.-C., Huang H.-M., Chang H.-W., Lin Y.-S. & Lee P.-F. (2007). "Land Molluscan Fauna of the Dongsha Island with Twenty New Recorded Species". Taiwania 52(2): 145-151. PDF.
  7. ↑ PBS "Alien Invasion". Accessed on 6 January 2008
  8. ↑ Cowie R. H., Dillon R. T., Robinson D. G. & Smith J. W. (2009). "Alien non-marine snails and slugs of priority quarantine importance in the United States: A preliminary risk assessment". American Malacological Bulletin 27: 113-132. PDF.
  9. ↑ 9.0 9.1 Neto N. A. L., Brooks S. E. & Alves R. R. N. 2009. From Eshu to Obatala: animals used in sacrificial rituals at Candomblé "terreiros" in Brazil. Journal of Ethnobiology and Ethnomedicine 2009, 5:23. doi:10.1186/1746-4269-5-23

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