Achatina fulica

Geographic Range

Achatina fulica originated in the coastal areas and islands of East Africa, where it presumably got the nickname, “Giant African Snail.” The snail inhabits countries ranging from Mozambique in the south, to Kenya and Somalia in the north. It is not only found in East Africa on the coastal areas and islands, but it has also been introduced to many other countries in Africa, along with many countries worldwide. The snail has been introduced into countries as far apart as the United States to Australia, and countries in-between. Achatina fulica is not a migratory species and has therefore been introduced through other means to the countries outside of East Africa, possibly through agricultural transportation, commerce, trade, vehicle attachment, smuggling, and other accidental and purposeful ways.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• palearctic palearctic
  • introduced introduced
• oriental oriental
  • introduced introduced
• ethiopian ethiopian
  • native native
• neotropical neotropical
  • introduced introduced
• australian australian
  • introduced introduced

Habitat

The giant African land snail has a natural habitat located in Africa, where there is a tropical climate with warm, year round temperatures, and high humidity. The snail has adapted and has been able to thrive in temperate climates as well. This species prefers areas of low to mid-elevation, with temperature preference between nine degrees Celsius and twenty-nine degrees Celsius. Achatina fulica can survive less ideal conditions, such as two degrees Celsius by hibernation and thirty degrees Celsius by aestivation. The snail can be found in agricultural areas, coastal areas, wetlands, disturbed areas, forests, urban areas, and riparian zones. The snails need temperatures above freezing and preferably high humidity in order to thrive the best. They have adapted to dry and cooler areas, however, by being able to hibernate in soft soil during the unfavorable weather conditions.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

• Other Habitat Features
• urban urban
• agricultural agricultural
• riparian riparian

Physical Description

The giant African snail can be distinguished from other snails due to their large size; when mature, the snail can reach up to eight inches (30 centimeters) in length with a diameter of four inches (10 centimeters). The snail can reach up to thirty-two grams in weight. The snail has the physical features that are associated with the phylum Mollusca , including a shell. The shell of Achatina fulica is cone-shaped and has a height that is twice that of the width. When the snail is mature and full-grown, the shell will normally consist of seven to nine whorls. The color of the snail differs depending on the environment, as some are primarily brown or dark colored, with dark stripes and streaks that run across the whorls, while others are reddish-brown with pale yellow vertical markings.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

Development

The fertilized eggs of A. fulica are laid in a nest, or in the dirt and leaves, so as to protect and disguise the eggs. The eggs then hatch and become immature snails, which grow to adulthood in about six months. Achatina fulica is one of many land snails, which do not have a larvae phase like other Gastropod species.

Reproduction

Achatina fulica is hermaphroditic; each individual snail has both male and female reproductive parts. There are no distinguishing parts separating sexes because each snail contains both sex reproductive systems. They do not self-fertilize, so the snails need to mate with another snail of their species. As a Stylommatophiora , Achatina fulica does not mate randomly; the snails mate with respect to age and size of other snails. Immature, small snails that are still growing produce only spermatozoa, while larger, mature adults produce both spermatozoa and ova. There is an age dependent mate choice when it comes to young snails because they need and prefer older adults to mate with. Young giant African snails copulate at all hours of the night, while older adults mate in the middle of the night. The snails choose their mates with respect to size and age, but the reproductive stage-dependent mate is a more attractive mate than the body size-dependent mate choice. Mating occurs when one snail encounters a prospective partner that the individual snail deems acceptable to mate with. When two individual snails mate, there is a possibility that gametes will be transferred to each one by the other simultaneously. However, this is only the case if the snails are around the same size. If there is a size difference, the larger snail will act as the female and the gametes will only be transferred from the smaller snail to the larger snail, mating unilaterally.

When two A. fulica encounter and deem each other worthy mates, they will mate by one mounting the shell of the other. The mating will begin once the two snails exchange sperm with one another. The sperm is used to fertilize the eggs in the snails, but it can also be stored inside the body for up to two years. The fertilized eggs are laid between eight and twenty days after mating has occurred, and are deposited in nests or among rocks and soils on the ground. The eggs usually hatch at temperatures above fifteen degrees Celsius. The eggs, under the right conditions, will hatch after eleven to fifteen days into small snails. The number of eggs that an individual snail lays often depends on the maturity and age of the snail and is between 100 to 500 eggs. Giant African snails have no specific season of mating, as they are able to produce new clutches every two to three months.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• sequential hermaphrodite
  • protandrous protandrous
• sexual sexual
• induced ovulation induced ovulation
• fertilization fertilization
  • internal internal
• oviparous oviparous
• sperm-storing sperm-storing

The parents of Achatina fulica do not contribute to the lives of their offspring except for fertilization and laying of the eggs in nests or soil. Once the eggs are hatched, the small individuals are on their own and adopt the territory that their parent provided them.

• Parental Investment
• pre-hatching/birth
  • provisioning

Lifespan/Longevity

Achatina fulica can live on average between three and five years, with some individuals reaching as old as ten years. There is not much difference between the lifespans in the wild and in captivity. In their natural habitat, predators are a main cause of mortality of Achatina fulica , however as they have become an invasive species, their new habitats contain close to zero predators. The snails usually die due to natural causes or non-favorable living conditions. Recently, there have been developments in molluscicides that have been impactful on killing this species, in order to better control their population in unwanted areas.

Behavior

Achatina fulica is a solitary species. The parents do not have an impact in their offsprings’ lives once the eggs are hatched, so the solitary behavior is intact from the beginning. It is not possible for A. fulica to self-fertilize, so courtship and interaction is a necessary aspect of their lives. Movement is an important aspect of their lives as it is necessary for mating, finding food, and escaping threats. Achatina fulica secretes a slime-like substance that allows for smooth and easy travel during its movement. The substance protects and allows travel across rough and sharp surfaces. Achatina fulica is a nocturnal species and lies dormant during the day. The snails often bury themselves in soil, in order to stay cool and remain hidden from threats. Giant African snails can also survive cold conditions by aestivating; they become slow and sluggish as they wait for warmer and more desired conditions to occur.

• Key Behaviors
• terricolous
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• aestivation
• solitary solitary

Communication and Perception

Achatina fulica does not need to communicate often, as it is not a social species. The time of communication among the species takes place in the process of mating, as one will mount the back of another individual. Communication takes place as there is a change in the position of the head, along with changes in the movement of the body. The changes in the body and head are communication cues that indicate that the mating process will continue. Achatina fulica does not have hearing as a sense, so it relies on its other senses to perceive the environment. This species also has caudal tentacles; the upper pair of tentacles have eyes at the tips and the lower pair have the sensory organ that allows for smell. This species has a strong sense of smell, which assists in finding food sources. The combination of smell and sight is how this species perceives the environment around them and allows for the detection of food, mates, and potential threats.

• Communication Channels
• visual visual
• tactile tactile

• Perception Channels
• visual visual
• chemical chemical

Food Habits

Giant African snails are herbivores. Achatina fulica feeds primarily on vascular plant matter, having no preference whether it is living or dead matter. This snail species has a strong sense of smell that assists in attracting and leading the individuals to garden crops and other plant resources. These snails have different preferences with their ages; young members of this species feed on decaying matter and unicellular algae. They also prefer soft textured Musa (bananas), Beta vulgaris (beets), and Tagetes patula (marigolds). More mature and developed African snails prefer to feed on living plants and vegetation. The mature snails broaden their spectrum of preferred plants to consume including: Solanum melongena (eggplant), Cucumis sativus (cucumber), Cucurbita pepo (pumpkin), and many others. This species has also been found to feed on other snails, lichens, fungi, and animal matter. The radula, a distinguishing characteristic of Gastropods, is essential in the ability to eat a variety of foods. The radula is a toothed ribbon used to scrape or cut food, and allows for the ability to pick up food and begin the digestive process with ease.

• Primary Diet
• herbivore herbivore
  • folivore folivore
  • frugivore frugivore

• Animal Foods
• mollusks

• Plant Foods
• leaves
• wood, bark, or stems
• seeds, grains, and nuts
• fruit
• flowers
• lichens
• algae

• Other Foods
• fungus
• detritus detritus

Predation

Achatina fulica has a shell from the beginning of its life until the end. The shell is used for protection against the environmental conditions and potential predators. The shell also provides protection for the internal organs against outside forces. The colors of A. fulica tend to be more earthy tones, as to not stand out in its environments and to be more camouflaged from the sight of their predators. Predators of Achatina fulica includes many species of rodents, wild boars, terrestrial crustaceans, and other species of snails.

Ecosystem Roles

Achatina fulica has several different ecosystem roles. This species decomposes and consumes dead vegetation. The benefit of this ecosystem role is that the snail assists in recycling nutrients and the building blocks essential to life. Giant African snails are also part of the food chain, as they are a source of food to many predators. This species is also a host to parasitic organisms, such as Angiostrongylus cantonensis , the rat lungworm. The parasitic organisms live and thrive on this host and can be transported to other hosts, such as humans, through the consumption of the snails.

• Ecosystem Impact
• biodegradation biodegradation

Economic Importance for Humans: Positive

Snails are often seen as a delicacy for humans and A. fulica is no exception. Humans around the world consume giant African snails as a source of protein when prepared correctly. This species is also a cheap alternative in some regions as a source of fish feed in fish farming, as they breed quickly and in large amounts. Achatina fulica can also be beneficial in making fertilizer, chicken feed, and biological compounds in clinical and experimental laboratories.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Giant African snails are an invasive species across that world. It has become illegal to have possession of these snails in countries where it has been introduced. Achatina fulica has a large and broad diet preference; the dietary habits of this species cause a high loss in crops for farmers. They are considered an agricultural pest, costing farmers not only their crops but also economic costs. This species is also a carrier of many parasitic organisms, including organisms that harm people and plants. Serious illness and diseases can erupt in humans if they consume giant African snails. Achatina fulica also destroys and pollutes its surroundings, including soil. When an individual of this species dies, the calcium carbonate found in the shells neutralizes the soil; the neutralization of the soil and the altering of its properties affect the types of plants that can grow in the soil. Achatina fulica can cost cities, states, or countries millions of dollars in not only agricultural costs, but also in attempts to control this invasive species.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans
• crop pest

Conservation Status

Achatina fulica is not currently vulnerable, threatened, nor endangered.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Taylor Hoffman (author), Grand View University, Nicole Pirie (author), Grand View University, Felicitas Avendano (editor), Grand View University, Dan Chibnall (editor), Grand View University, Angela Miner (editor), Animal Diversity Web Staff.

References

Carvalho, O., H. Teles, E. Mota, C. Lafeta, G. Mendonca, H. Lenzi. 2003. Potentiality of Achatina fulica Bowdich, 1822 ( Mollusca : Gastropoda ) as intermediate host of the Angiostrongylus costaricensis Morera & Céspedes 1971. Revista da Sociedade Brasileira de Medicina Tropical , 36/6: 743-745. Accessed March 06, 2014 at http://www.scielo.br/pdf/rsbmt/v36n6/a17v36n6.pdf .

Cowie, R. 2010. " Achatina fulica (mollusc)" (On-line). Global Invasive Species Database. Accessed March 06, 2014 at http://www.issg.org/database/species/ecology.asp?si=64&fr=1&sts=sss&lang=N. .

Egonmwan, R. 2007. "Recent Advances in the Biology of Giant African Land Snails" (On-line pdf). Federal University of Agriculture, Abeokuta. Accessed March 05, 2014 at http://unaab.edu.ng/netgals/downloads/Egonmwan.pdf .

Stokes, H. 2006. "Introduced Species Summary Project" (On-line). Columbia University. Accessed March 04, 2014 at http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Achatina_fulica.htm#Introduction_Facts .

Tomiyama, K. 1996. MATE-CHOICE CRITERIA IN A PROTANDROUS SIMULTANEOUSLY HERMAPHRODITIC LAND SNAIL ACHATINA FULICA (FÉRUSSAC) ( STYLOMMATOPHORA : ACHATINIDAE ). Journal of Molluscan Studies , 62: 101-111. Accessed March 07, 2014 at http://mollus.oxfordjournals.org/content/62/1/101.full.pdf+html .

Vogler, R., A. Beltramino, M. Sede, D. Gregoric, V. Nunez, A. Rumi. 2013. The giant African snail, Achatina fulica ( Gastropoda : Achatinidae ): Using bioclimaticmodels to identify South American areas susceptible to invasion. American Malacological Bulletin , 31/1: 39-50. Accessed March 04, 2014 at http://www.academia.edu/2602901/The_Giant_African_Snail_Achatina_fulica_Gastropoda_Achatinidae_Using_Bioclimatic_Models_to_Identify_South_American_Areas_Susceptible_to_Invasion .

2014. " Achatina fulica " (On-line). Encyclopedia of Life. Accessed March 09, 2014 at http://eol.org/pages/452699/details .

2014. " Achatina fulica " (On-line). Institute for the Study of Invasive Species. Accessed March 07, 2014 at http://www.tsusinvasives.org/database/giant-african-snail.html .

2014. " Lissachatina fulica " (On-line). Invasive Species Compendium. Accessed March 07, 2014 at http://www.cabi.org/isc/?compid=5&dsid=2640&loadmodule=datasheet&page=481&site=144 .

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