Archachatina marginata

Archachatina marginata
The shell of Archachatina marginata
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
(unranked):	clade Heterobranchia clade Euthyneura clade Panpulmonata clade Eupulmonata clade Stylommatophora informal group Sigmurethra
Superfamily:	Achatinoidea
Family:	Achatinidae
Genus:	Archachatina
Species:	A. marginata
Binomial name
Archachatina marginata (Swainson, 1821)

Archachatina marginata, common name the giant West African snail or banana rasp snail, is a species of air-breathing tropical land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae. They can grow up to 20 cm long, and live up to 10 years.

Distribution

This species occurs in Western Africa: Cameroon through Democratic Republic of the Congo, and can be found in the Caribbean, in Martinique.^[1]

How the species reached Martinique is unknown, but it is possible they were intentionally introduced as "pets" or by workers returning from West Africa.^[2]

The natural spread of this species is very slow; however, unintentional spread by individuals for food and as folk medicine is very common.^[3] The USDA routinely checks for the species in the luggage of travelers from West Africa, Nigeria particularly, Ghana and Cameroon.

This species has not yet become established in the United States, but it is considered to represent a potentially serious threat as a pest, an invasive species which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine significance in the United States.^[4]

Archachatina marginata var. ovum (Pfeiffer, 1858)

Description

The snail has a bulbous protoconch that is large and broad, with a white or bluish-white columella, parietal wall and outer lip. The shell of the snail can grow up to 21 centimeters in height, and 13 centimeters in diameter. The shell, when magnified, has the appearance of a woven texture.^[5]

Invasive species

The snail feeds on a large variety of plants, mainly fruits. Plants included in the snail's diet are bananas, lettuce, peanuts, and peas, some of which are important crops in certain economies.^[6] The giant West African snail is one of the worst invasive species in the world and is extremely devastating to any species that it affects. However, the more prevalent problem with the spread of the snail as an invasive species is that it is often a carrier of the disease rat lungworm. Within humans this causes the disease eosinophilic meningoencephalitis, which is what makes the snails' spread to North America problematic. If the snails continues to spread it could potentially be a problem for the health of people all throughout North America from Cuba to the United States.^[7] Archachatina marginata can live up to 10 years, and attain sexual maturity at 9–10 months under laboratory conditions. In addition to being an agricultural pest, they act as the reservoir host of rat lung parasites which cause eosinophilic meningoencephalitis in humans and are seen as a threat to public health because of this.^[8]

Archachatina marginata var. suturalis (Philippi, 1849)

Ecology

Achatinids are nocturnal forest dwellers but can adapt to disturbed habitats. The snails prefer concealed habitats and if overcrowding occurs, they may colonize more open habitats. During periods of high humidity, Achatinids are more active but if the individuals are found during broad daylight it is most likely due to high population density.

Eggs of Achatinids are normally laid in the soil, but can be found under leaves or rocks. They produce as many as 40 eggs which are yellow in color with dark blotches and an incubation period of approximately 40 days.

Mating

Mating for the Archachatina marginata species varies in the three separate states of Nigeria: Enugu, Edo, and River. The rate of snail mating across the three states is low at 20 percent because most A. marginata snails have homotypes rather than heterotypes. As a result, the reproductive rate for A. marginata is relatively slow.^[9]

In pre-mating process, male A. marginita attempts to exhibit mating behavior while the female A. marginita must respond to the male A. marginita positively in order to proceed with mating. In wet season (from March), A. marginita begin their reproductive process. After the A. marginita baby hatches, it usually takes up to four weeks for the growing traits to develop. During the first few weeks of life, the A. mariginita eats less than an adult due to the slow process of gaining weight.^[10]

Diet

Wild snails eat plants at a ferocious rate. Often times this leads to property destruction and damage to homes. Studies have shown that the snails will eat during the day but they prefer to eat at night. Wild snails have a very wide appetite on a whole and they are known to eat up to 500 different species of plants. Snails that have become domesticated typically consume food that is high in protein and low in fats. Studies from 2005 that were done to test food on domesticated snails have shown that poultry droppings have been the most effective meal to both grow and gain weight.^[11]

Nervous system

In this organism's nervous system, there are two main types of nerves: pallial nerves and visceral nerves. Pallial nerves are the subject of the majority of scientific research. Visceral nerves are split into two subcategories: the main visceral nerve and the rectal visceral nerve. The main visceral nerve is on the snail's back and connects to a large group of nerve cells to transmit information in the body. The rectal visceral nerve starts further down under the main visceral and extends a short length before branching off near the rectum.^[12]

Heat can stimulate reactions in the West African snail as a result of the snail's nervous system. The nerves produce warm responsive fibers when the temperature exceeds 25°C and produce cold responsive fibers when the temperature falls below 19° C. The ideal temperature range for this species falls between 13° and 32° C; this is also formally known as the thermopreferendum of the species.^[13]

Subspecies

• Archachatina marginata var. Ovum
• Archachatina marginata var. Suturalis
• Archachatina marginata var. Egregia
• Archachatina marginata var. Eduardi
• Archachatina marginata var.Candefacta
• Archachatina marginata var. Grevillei
• Archachatina marginata var. Icterica

References

1. "Archachatina marginata (Swainson, 1821)" (PDF). United States Department of Agriculture. USDA/APHIS. Retrieved October 29, 2015.
2. Robinson, David G. "The Giant African snail (Lissachatina fulica); its history and reported biology" (PDF). USDA APHIS National Malacology Laboratory and The Academy of Natural Sciences. Retrieved October 29, 2015.
3. Let Them Eat Snail: Nutritional Giant Snails Could Address Malnutrition (ScienceDaily, November 20, 2009)
4. 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.
5. "Archachatina marginata" (PDF). United States Department of Agriculture. Retrieved October 29, 2015.
6. Mead, Albert (1961). The Giant African Snail: A Problem In Economic Malacology. Chicago, Illinois: The University of Chicago Press. pp. 40–49.
7. Vázquez, Antonio A.; Sánchez, Jorge (2015-04-03). "First record of the invasive land snail Achatina (Lissachatina) fulica (Bowdich, 1822) (Gastropoda: Achatinidae), vector of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae), in Havana, Cuba". Molluscan Research 35 (2): 139–142. doi:10.1080/13235818.2014.977837. ISSN 1323-5818.
8. White-McLean, J.A. (September 2, 2011). "Archachatina marginata". Terrestrial Mollusc Tool. USDA/APHIS/PPQ Center for Plant Health Science and Technology and the University of Florida. Retrieved October 29, 2015.
9. Ogbu, C.C (2011). "Evaluation of pre-mating reproductive isolation in Archachatina marginata from three populations in the humid tropics" (PDF). http://www.academicjournals.org/AJAR. Department of Animal Science, University of Nigeria. Retrieved October 29, 2015. External link in |website= (help)
10. Ibom, L.A. (2011). "Evaluation of growth and body traits of snailets obtained from the crossbreeding of black skinned × white skinned snails (Archachatina marginata (S)) in the Niger Delta area of Nigeria" (PDF). www.academicjournals.org. Retrieved October 29, 2015.
11. Ademolu, K. O.; Idowu, A. B.; Mafiana, C. F.; Osinowo, O. A. (2005-03-21). "Performance, proximate and mineral analyses of African giant land snail ( Archachatina marginata ) fed different nitrogen sources". African Journal of Biotechnology 3 (8): 412–417. ISSN 1684-5315.
12. Nisbet, R. H. (1961-05-09). "Some Aspects of the Structure and Function of the Nervous System of Archachatina (Calachatina) marginata (Swainson)". Proceedings of the Royal Society of London B: Biological Sciences 154 (955): 267–288. doi:10.1098/rspb.1961.0032. ISSN 0962-8452.
13. Voss, M.; Schmidt, H. (2001-02-01). "Electrophysiological responses to thermal stimuli in peripheral nerves of the African giant snail, Archachatina marginata S.". Journal of Thermal Biology 26 (1): 21–27. doi:10.1016/S0306-4565(00)00021-8.

External links