The Pomacea Project

Florida Apple Snail Basic Biology

Please note: For more information on the biology of the Florida apple snail than is presented here, see Turner and Mikkelsen’s (2004) Annotated Bibliography of the Florida applesnail, Pomacea paludosa (SAY) (Gastropoda: Ampullariidae) From 1824 to 1999.

Why Apple Snail?

The Florida apple snail belongs to the genus Pomacea. Freshwater snails of the genus Pomacea (and other members of the Ampullariidae Family) are commonly referred to as apple snails because of their overall large, globose shape (Keawjam 1986) (see picture on left below). The primary characteristic of their family (Ampullariidae) is that they have both a ctenidium (a “gill”) and an air sac, which functions as a lung when snails extend their siphon to the water surface to breathe air (see picture on right below).



The Florida Apple Snail as Prey:

The Florida apple snail is consumed by a number of the state’s prominent wildlife species. These include the endangered snail kite (Rostrhamus sociabilis plumbeus), the limpkin (Aramus guarauna), the alligator (Alligator mississippiensis), and the soft-shelled turtle (Trionyx ferox). Apple snails are also eaten by the white ibis (Eudocimus albus), the boat-tailed grackle (Cassidix mexicanus), and the redear sunfish (Lepomis microlophus). Apple snail predators are discussed in greater detail in the Predator Perspectives section.

Where they Live:

World-wide, apple snails inhabit tropical and subtropical wetlands (shown below in beige), many of which experience seasonal fluctuations in water levels, including dry downs (i.e., the water table falls below ground level). The apple snail’s dual respiratory system (having a “gill” and a “lung”) may be critical for allowing the snails to deal with dry downs (Cowie 2002), as well as daily or seasonal fluctuations in dissolved oxygen in water (McClary 1964).

Pila and Pomacea species can survive dry down conditions for 3 to 25 months (Cowie 2002). Recent work has further examined dry down survival of the Florida apple snail (Darby et al. 2008). Darby et al. (2008) found that adult snails from a pre-reproductive population (i.e., adult-sized snails that had not yet reproduced that season) had a survival rate of 94% after 6 weeks in dry down conditions, 79% after 12 weeks, and 47% after 16 weeks. They also found that juvenile snails have less of a capacity to survive drying events than do pre-reproductive adults; juvenile snail survival fell below 50% after 8 weeks in dry conditions. For additional information, see section on Dry Down Survival).



The range of the Florida apple snail in the U.S. extends from southern Georgia (in warm springs) and Alabama (introduced in Alabama in a small, artificially-heated reservoir) in the north, to the Everglades in the south (Haper 1936; Thompson 1984); it also occurs in Cuba. The distribution of the Florida apple snail in the Florida Panhandle is described as sporadic, due to the lower winter temperatures in this area (Thompson 1984). Florida apple snails occur in both lentic and lotic habitats, such as springs, lakes, and marshes. Example habitats in Florida are shown below.





Some data on habitat preferences are available. For example, in areas studied, wet prairie habitats were found to support greater densities of apple snails than slough habitats (Karunaratne et al. 2006). Darby et al. (2004) found no snails in areas dominated by Nuphar luteum, with an unconsolidated organic substrate, on a central Florida lake. Bryan (1990) found more snails in beds of Vallisneria (tape grass), compared to areas containing Eichornia (water hyacinth) or Pistia (water lettuce) mats, on a spring system.

In studies on Lake Woodruff, near Deland, apple snails were most abundant in alkaline waters that had an adequate supply of submerged vegetation (Hurdle 1973). Calcium concentration and pH has been found to affect hatchling growth rates and their shell crush weights (a measure of shell strength) (Glass and Darby 2008). Significantly higher growth rates and higher crush weights were found in snails grown in water with pH≈8.0 and calcium ion concentrations ≥ 28 mg/L. Their findings were consistent with field data that show relatively low snail densities in areas with low pH and low calcium concentrations.

The preferred food source of the Florida apple snail is not clear. Apple snails (not necessarily Florida apple snails) in the Ampullariidae family have been described as consumers of macrophytes, microscopic matter, and animal matter (Estebenet 1995). Sharfstein and Steinman (2001) examined growth and survival of Florida apple snails fed macrophyte-periphyton assemblages in the lab. Growth and survival of snails were higher for those fed a Utricularia sp./periphyton complex compared to metaphyton (loosely attached benthic algae); there were no differences for snails fed the Utricularia sp./periphyton complex versus an Eleocharis sp./periphyton complex. Shuford et al. (2005) reported that juvenile apple snails showed higher growth rates when fed periphyton, compared to food with no periphyton (e.g., sawgrass detritus). Hurdle (1973) reported that native apple snails in managed impoundments at Lake Woodruff fed readily on two species available, Chara sp. (muskgrass) and Naias marina (spiny naiad). Darby (personal communication) has found that in aquaria Florida apple snails eat most macrophytes provided, including Hydrilla, lettuce and spinach.

Egg Laying / Reproduction:

The presence of the lung may assist members of the apple snail family not only in dealing with low dissolved oxygen and dry downs, but also in allowing them to emerge from the water to lay eggs. Some species lay their eggs on exposed sediments, while others (including the Florida apple snail) lay their eggs on emergent vegetation (Keawjam 1986; Cowie 2002; Turner 1996) (see first two pictures to the left and right below). Florida apple snails, like all members of their family, are dioecious (Cowie 2002). Female Florida apple snails emerge from the water and lay eggs at night, with approximately 20-30 eggs in a clutch (e.g, Hanning 1979; Perry 1974; Turner 1996). Egg-laying generally occurs from March through October (Odum 1957; Hanning 1979; Darby et al. 1999). In general, eggs (3-6 mm each; Turner 1996) are laid about 10-20 cm above the water line (Turner 1996; Hanning 1979; Darby unpublished data). The calcified eggs are wet and soft when laid, but become hard when they dry (and turn from a pink/salmon color to white). They take approximately 16-22 days to hatch (Hanning 1979; Perry 1974); newly hatched juveniles are miniature versions of the adults (see third picture below).



Life Span:

Florida apple snails have a life span of 1-1.5 years (Hanning 1979; Ferrer et al. 1990; Darby et al. 2003). In general, young apple snails hatch in the spring, grow during the spring, summer and fall, overwinter, reproduce the following spring, and die late in the dry season (Hanning 1979; Darby 1998; Darby et al. 2003). As noted above, the majority of egg-laying occurs from March through October, with a peak in April-May (Hanning 1979; Odum 1957; Darby et al. 1999; and Darby et al. 2003). Their life cycle terminates in a post-reproductive die-off, with the majority of adults dying between approximately May and August (Darby et al. 2003; Darby et al. 2008) (see Figure 1 below).

Figure 1. Annual cycle of the relative abundances of snails hatched in the previous year (those that over-wintered and enter the new year as adults) (■), young of the year snails (those that hatched from egg clusters in the current calendar year) (□), and egg clusters (O). The relative size of the young-of-the-year symbol (□) represents the change in average size of this group of snails throughout the year. See Darby et al. (2008) for details and citations regarding snail life span, annual survival patterns, egg production and hatchling growth rates. From Darby et al. (2008).

Literature Cited:

Bryan, D.C. 1990. Apple snail densities at Alexander Springs, Lake County, and Observations on Snail Ecology. Florida Scientist 53:13.

Cowie, R.H. 2002. Apple snails (Ampullariidae) as agricultural pests: their biology, impacts, and management. Pp. 145-192, In G.M. Barker (ed.) Molluscs as Crop Pests. CABI Publishing, Wallingford, UK.

Darby, P.C. 1998. Florida apple snail (Pomacea paludosa Say) life history in the context of a hydrologically fluctuating environment. Ph.D. Dissertation. University of Florida, Gainesville, FL.

Darby, P.C., R.E. Bennetts, J.D. Croop, P.L. Valentine-Darby, and W.M. Kitchens. 1999. A comparison of sampling techniques for quantifying abundance of the Florida apple snail (Pomacea paludosa Say). Journal of Molluscan Studies 65:195-208.

Darby, P.C., P.L. Valentine-Darby, and H.F. Percival. 2003. Dry season survival in a Florida apple snail (Pomacea paludosa Say) population. Malacologia 45(1):179-184.

Darby, P.C., P.L. Valentine-Darby, H. Franklin Percival, and W.M. Kitchens. 2004. Florida apple snail (Pomacea paludosa SAY) responses to lake habitat restoration activity. Archives of Hydrobiologia 161 (4):561-575.

Darby, P.C., R.E. Bennetts, and H.F. Percival. 2008. Dry down impacts on apple snail demography: Implications for wetlands water management. Wetlands 28(1):204-214.

Estebenet, A.L. 1995. Food and feeding in Pomacea canaliculata (Gastropoda: Ampullariidae). The Veliger 38(4):277-283.

Ferrer, J.R., G. Perera, and M. Yong. 1990. Life tables of Pomacea paludosa (Say) in natural conditions. Florida Scientist 53 (supplement):15.

Glass, N.H. and P.C. Darby. 2008. The effect of calcium and pH on Florida apple snail, Pomacea paludosa (Gastropoda: Ampullariidae), shell growth and crush weight. Aquatic Ecology DOI 10.1007/s10452-008-9226-3.

Hanning, G.W. 1979. Aspects of reproduction in Pomacea paludosa (Mesogastropoda:Pilidae). M.S. Thesis, Florida State University. Tallahassee. 138pp.

Harper, F. 1936. The distribution of the limpkin and its staple food, Pomacea. The Nautilus 50(2):37-40.

Howell, A.H. 1932. Florida Bird Life. Coward-McMann, Inc. 579pp.

Hurdle, M.T. 1973. Life history studies and habitat requirements of the apple snail at Lake Woodruff National Wildlife Refuge. Proc. 27th Ann. Conf. SE Assoc. of Game & Fish Comm. 27:215-224.

Keawjam, R.S. 1986. The apple snails of Thailand: distribution, habitats and shell morphology. Malacological Review 19:61-81.

Karunaratne, L.B., P.C. Darby, and R.E. Bennetts. 2006. The effects of wetland habitat structure on Florida apple snail density. Wetlands 26(4):1143-1150.

McClary, A. 1964. Surface inspiration and ciliary feeding in Pomacea paludosa (Prosobranchia: Mesogastropoda: Ampullariidae). Malacologia 2:87-104.

Odum, H.T. 1957. Trophic structure and productivity of Silver Springs, Florida. Ecological Monographs 27:55-112.

Perry, M.C. 1974. Ecological studies of the apple snail at Lake Woodruff National Wildlife Refuge. Florida Scientist 36:22-30.

Sharfstein, B. and A.D. Steinman. 2001. Growth and survival of the Florida apple snail (Pomacea paludosa) fed 3 naturally occurring macrophyte assemblages. Journal of the North American Benthological Society 20(1):84-95.

Shuford, R.B.E., P.V. McCormick, and J. Magson. 2005. Habitat related growth of juvenile Florida applesnails (Pomacea paludosa). Florida Scientist 68:11-19.

Thompson, F.G. 1984. The freshwater snails of Florida: a manual for identification. Univeristy of Florida Press, Gainesville, FL. 94pp.

Turner, R.L. 1996. Use of stems of emergent plants for oviposition by the Florida apple snail, Pomacea paludosa, and implications for marsh management. Florida Scientist 59(1):34-49.

Turner, R. L., and P. M. Mikkelsen. 2004. Annotated Bibliography of the Florida applesnail, Pomacea paludosa (SAY) (Gastropoda: Ampullariidae) From 1824 to 1999. Nemouria 48:1-188.