Giant African Land Snail And Giant South American Snails: Field Recognition

  FDACS-P-01678

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Paul E. Skelley, Paul.Skelley@FreshFromFlorida.com, Biological Scientist IV, Florida Department of Agriculture and Consumer Services, Division of Plant Industry

Wayne N. Dixon, Wayne.Dixon@FreshFromFlorida.com, Assistant Director, Florida Department of Agriculture and Consumer Services, Division of Plant Industry

Greg Hodges, Greg.Hodges@FreshFromFlorida.com, Bureau Chief - Entomology, Nematology and Plant Pathology, Florida Department of Agriculture and Consumer Services, Division of Plant Industry

INTRODUCTION: Two agricultural pest snails, the giant African land snail (Achatina (Lissachatina) fulica (Bowditch)) (Fig. 1) and the giant South American snails (Megalobulimus spp. and relatives) (Fig. 2), are of regulatory significance and are not allowed to be possessed or sold within Florida, even though both are popular as pets. Both of these large snails are known to feed on many varieties of plants, in some cases causing serious damage. The giant African land snail has recently been discovered in several localities in Miami-Dade County (FDACS-DPI 2011). The giant South American snail is presently not established in Florida or the Continental US.

Any very large snail will draw attention and may be considered exotic and possibly invasive. Yet, there are native snails which are similar in appearance and occasionally reach large size (up to 3 inches in length). Immature snails or smaller specimens of these exotic snails can be easily confused with native species that are protected by state and federal laws.

The following information will assist in the field recognition of these pest snails and other common snails, support state and federal regulatory efforts to prevent establishment of the snails in Florida, and help protect our native snails by preventing unnecessary collection and destruction.

IDENTIFICATION: There are many snails in Florida which can become very large. These species are mostly aquatic or marine snails and are not the subjects under consideration.

Apple Snail (Pomacea spp.) (Fig. 1). Adults of some species can be up to 4 inches in diameter. Shell globose, thin. Coloration tan to greenish, occasionally with darker bands, rarely with stripes. Apple snails are aquatic and have a separate hardened operculum which protects the snail when retracted in the shell. They come out of the water to lay eggs on nearby structures. Their large shells are often found along the edge of waterways. Egg color and number per clutch are useful for identification. Florida has several species of apple snails: one native (P. paludosa (Say)), and three introduced species. One of these exotic species, P. insularum (d’Orbigny), is considered a serious pest of our waterways (Anonymous 2010; FWC 2006; Stange 1998, Fasulo 2011).

The giant African and South American snails are terrestrial or land snails with more elongate, conical shells. Although they may be found near water, they cannot survive prolonged submersion in water.

Rosy Predator Snail (Euglandina rosea (Ferussac)) (Fig. 6). Adults relatively large, up to 2.6 inches long. Shell narrowly elongate-lanceolate, apex conical, shell somewhat thickened. Columella smooth with a truncate apex. Coloration generally a rosy-cream color with no banding.

This snail is easily recognized by its narrowly elongate, often pinkish shell. This native snail is a predator of other snails. It has been used as a potential biological control agent and introduced into other countries (Auffenberg and Stange 1986).

Banded Caracol (Caracolus marginellus (Gmelin)) (Fig. 2). Adult width up to 2 inches. Shell flattened, sharply edged on sides. Coloration brown to reddish with varying sized black banding. This distinctive land snail occurs in a few localities in Miami-Dade County, where it feeds on algae growing on trees. It does not seem to be a pest.

Cuban Snail (Zachrysia provisoria (Pfeiffer)) (Fig. 3). Adult width 1 inch (2.5 cm). Shell globose, thick, and whorls sculptured with small ribs. Coloration dark tan, not patterned. It is common throughout the lower peninsula of Florida, where it is a voracious herbivore, occasionally causing significant damage to ornamental plants.

Rosy Predator Snail(Euglandina rosea (Ferussac)) (Fig. 4). Adults relatively large, up to 2.6 inches long. Shell narrowly elongate-lanceolate, apex conical, shell somewhat thickened. Columella smooth with a truncate apex. Coloration generally a rosy-cream color with no banding.

This snail is easily recognized by its narrowly elongate, often pinkish shell. This native snail is a predator of other snails. It has been used as a potential biological control agent and introduced into other countries (Auffenberg and Stange 1986).

Native Floridian Tree Snails (Orthalicus spp. (Fig. 5-6), Liguus fasciatus (Muller) (Fig. 7), and several species of Drymaeus (Fig. 10). Adults up to 3 inches in length, most are less than 2 inches long, Drymaeus species reach slightly over 1 inch long. Shell elongate-oval, apex conical, shell usually ceramic-like. Columella of shell usually short, smooth, and lacking free curled edge (some Liguus specimens have a thickened edge), never truncate at apex. Coloration can be quite variable (Deisler 1983, Frank 2010), entirely pale, but usually with distinct bands and stripes.

There are many terrestrial or semi-terrestrial snails that may be encountered when searching for snails. Some in southern Florida (e.g., L. fasciatus, O. reses) may be endangered and legally protected from collection wherever they occur. Many of our other native tree snails are also declining in numbers. These native snails feed on algae or other debris growing on plants. They are not known to harm plants and are considered beneficial because of their cleaning activities on plants. It is preferred that none of these native snails be collected.

Guadeloup Snail (Bulimulus guadeloupensis (Bruguiere)) (Fig. 9). Adults up to 1 inch in length. Shell elongate-oval, apex conical, shell usually ceramic-like. Columella of shell smooth, lacking free curled edge, never truncate at apex. Coloration highly variable, when present always in circular bands, never striped. This snail is introduced and extremely common around homes in Miami-Dade County. They feed on algae and other debris growing on surfaces, but not on the surface. They are not known to harm plants.

Giant African Land Snail (Achatina (Lissachatina) fulica (Bowditch)) (Fig. 10). Adults large, up to 6.7 inches in length or more. Shell elongate-oval, apex conical, shell thin and ceramic-like. Columella of shell with long, inwardly curled free edge with truncate apex. Coloration usually with regular longitudinal bands.

Achatina fulica is partially characterized by having only the regular longitudinal bands. Other species of Achatina vary in the amount of banding that is present with some almost entirely pale, but none have distinct transverse banding. King (2010) provides pictures of various Achatina spp. and some identification aids. In contrast to the giant African land snail, our native tree snails have transverse banding varying from very distinct to moderately vague. Coloration and body size also varies which makes smaller Achatina difficult to distinguish from native snails. However, none of the native terrestrial snails have the long truncate columella of Achatina. Any snails with an elongate oval shell and a truncate columella are to be considered suspect African snails.

Giant South American Snails (Megalobulimus spp.) (Fig. 11). Adults large up to 3 inches in length. Shell elongate-oval, apex conical, shell thick and calcareous. Columella broad and smooth, no free curled edge. Coloration generally cream colored, not banded, columella often pink. The thickened shell is a character not present on any of our native terrestrial snails. (See also Deisler and Stange 1982.)
BIOLOGY OF GIANT AFRICAN LAND SNAIL: This snail is able to survive in many different environments. They require areas rich in calcium, thriving in locations with limestone, marl and places with concrete and cement. Snails are able to sexually reproduce in about one year. They may live 3-5 years to a maximum of 9 years. Although adult snails have both male and female sexual organs, reciprocal copulation is necessary to produce viable eggs. A snail can begin laying eggs 8 to 20 days after mating and can lay eggs for up to 380 days producing 400 to 1000 eggs in one year. Eggs are placed in cool moist soil and under objects on the ground. After eggs hatch, juvenile snails eat their egg shells and then burrow underground for up to 2 weeks. The snails typically have a home range, feeding primarily on plants and returning to home before dawn. Larger snails feed on plants and may become detritus feeders as well. Although nocturnal, the snail may become active at twilight on overcast days with moist and warm soil. There is a risk of snails moving long distances when they cling to cargo, vehicles or machinery. During unfavorable environmental conditions, the snail can bury itself in soil and remain inactive for up to a year (USDA-APHIS-PPQ 2007).

SURVEY: Many snails, including those discussed here, are known to possess toxins or harbor parasites that can affect or infect humans. While short-term handling of a snail by the shell is probably safe, it is strongly recommended to wear gloves when handling them. Always wash hands thoroughly after handling snails and do not touch your face or mouth with dirty hands.

When conditions are damp or overcast these snails may be on the move and could be found nearly anywhere, on the ground, up in trees or on buildings. When conditions are dry or hot, they prefer to shelter on or near the ground. These sheltered areas are the best places to look for snails and include: under or in debris on the ground, water meter boxes, under dense vegetation, and similar protected locations. Look also for large slime trails or slimy feeding damage on plants to indicate potential presence of snails.

Anyone surveying for these snails must be familiar with a few characters that distinguish these large pest snails from our protected native snails. Thus, when surveying for giant African land snails, collect suspect snails that have the inwardly curled, truncate columella. When surveying for giant South American snails, collect snails that have thickened calcareous shells. If in doubt, please contact the senior author to receive instructions on sending a digital picture.

Once properly identified, a snail can be killed by placing it in a plastic bag and then placing in a refrigerator freezer. If there is a heavy infestation, snail baits containing a molluscicide are readily available in most lawn and garden supply stores (see also UF-IFAS Extension 2011, Capinera and White 2011). Unfortunately, baits kill all snails including the beneficial ones.

REFERENCES:

Anonymous. 2010. Apple Snails. (available at http://www.applesnail.net/ - accessed October 8, 2011.)

Auffenberg, K., and L. A. Stange. 1986. Snail-eating snails of Florida. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular No. 285 [Adobe PDF Document 361.99 KB]: 1-4. [accessed October 8, 2011]

Capinera, J. L., and J. White. 2011. Terrestrial snails affecting plants in Florida. http://edis.ifas.ufl.edu/in893 [accessed October 8, 2011]

Deisler, J. E. 1983. A key to the Tree Snails of Florida. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular No. 246 [Adobe PDF Document 679.33 KB]: 1-4. [accessed October 8, 2011]

Deisler, J. E., and L. A. Stange. 1982. The Giant South American Snail, Megalobulimus oblongus (Muller) (Gastropoda: Megalobulmidae). Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular No. 239 [Adobe PDF Document 787.87 KB]: 1-4. [accessed October 8, 2011]

Fasulo, T. R. 2011. Applesnails of Florida Pomacea spp. (Gastropoda: Ampullariidae). University of Florida, IFAS Extension, Publication #EENY323. http://edis.ifas.ufl.edu/in598 [accessed October 8, 2011]

FDACS-DPI. 2011. Giant African land snail. [accessed October 8, 2011]

Frank, B. 2010. Liguus fasciatus in Florida. http://jaxshells.org/phillig.htm [accessed October 8, 2011]

Florida Fish and Wildlife Conservation Commission (FWC). 2006. Non-native applesnails in Florida. http://www.myfwc.com/docs/WildlifeHabitats/FWC_applesnails_FLMS_handout.pdf  [accessed October 8, 2011]

King, P. 2010. Snail & Slug: Care, Species, Health and much more. http://www.petsnails.co.uk/ - [accessed October 8, 2011]

Stange, L. S. 1998. The Applesnails of Florida (Gastropoda: Prosobranchia: Pilidae). Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular No. 388 [Adobe PDF Document 96.05 KB]: 1-2. [accessed October 8, 2011]

UF-IFAS Extension. 2011. Giant African snail. http://solutionsforyourlife.ufl.edu/hot_topics/environment/giant_african_snail.html [accessed October 8, 2011]

USDA–APHIS-PPQ. 2007. New Pest Response Guidelines. Giant African Snails: Snail Pests in the Family Achatinidae. USDA–APHIS–PPQ– Emergency and Domestic Programs –Emergency Planning, Riverdale, Maryland. http://www.aphis.usda.gov/import_export/plants/manuals/emergency/downloads/nprg_gas.pdf [Adobe PDF Document]  [accessed October 8, 2011]

 Figure 1a. Achatina (Lissachatina) fulica, giant African land snail, adult, 3 inches (7 cm).

Figure 1a. Achatina (Lissachatina) fulica, giant African land snail, adult, 3 inches (7 cm).

 Figure 1b. Achatina (Lissachatina) fulica, giant African land snail, immature, 1 inch (2.5 mm).

Figure 1b. Achatina (Lissachatina) fulica, giant African land snail, immature, 1 inch (2.5 mm).

 Figure 2. Megabulimus sp., giant South American snail, adult, 3 inches (7.5 cm).

Figure 2. Megabulimus sp., giant South American snail, adult, 3 inches (7.5 cm).

 Figure 3. Pomacea sp., adult, 2 inches (5 cm).

Figure 3. Pomacea sp., adult, 2 inches (5 cm).

 Figure 4. Caracolus marginellus, banded caracol, adult, width 1.5 inches (3.5 cm).

Figure 4. Caracolus marginellus, banded caracol, adult, width 1.5 inches (3.5 cm).

 Figure 5. Zachrysia provisoria, Cuban land snail, adult, width 1 inch (2.5 cm).

Figure 5. Zachrysia provisoria, Cuban land snail, adult, width 1 inch (2.5 cm).

 Figure 6. Euglandina rosea, rosy predator snail, adult, 2 inches (5 cm).

Figure 6. Euglandina rosea, rosy predator snail, adult, 2 inches (5 cm).

 Figure 7. Orthalicus reses, Stock Island tree snail, adult, 2 inches (5 cm).

Figure 7. Orthalicus reses, Stock Island tree snail, adult, 2 inches (5 cm).

 Figure 8. Orthalicus floridensis, banded tree snail, adult, 2.5 inches (6 cm).

Figure 8. Orthalicus floridensis, banded tree snail, adult, 2.5 inches (6 cm).

 Figure 9. Liguus fasciatus, Florida tree snail, adult, 1 inch (2.5 cm).

Figure 9. Liguus fasciatus, Florida tree snail, adult, 1 inch (2.5 cm).

 Figure 10. Drymaeus multilineatus, many-lined tree snail, adult, 1 inch (2.5 cm).

Figure 10. Drymaeus multilineatus, many-lined tree snail, adult, 1 inch (2.5 cm).

 Figure 11. Bulimulus guadeloupensis, Guadeloup snail, adult, 1 inch (2.5 cm).

Figure 11. Bulimulus guadeloupensis, Guadeloup snail, adult, 1 inch (2.5 cm).

More Giant African Land Snail information

Pest Alert created 09-February-2010, updated 10-October-2011