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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: giant applesnail

Synonyms and Other Names: Ampullaria insularum, Ampullaria gigas, Pomacea insularum, Pomacea gigas, island applesnail (Burks et al. 2017)

Identification: This snail has a large, dextral (right-side opening), round, globular shell with 3-4 whorls and a short spire with indented sutures (see image below, C. Morningstar, USGS). The aperture is very wide and tear-drop shaped, and the operculum is also tear-drop shaped, thin, and brown. It’s coloration varies, particularly in populations introduced from selective aquarium breeding but is often tan-brown to yellow and black with striped patterns (Bernatis 2014, Hayes et al. 2012). In their overlapping range, immature P. maculata can be differentiated from the smaller congener Florida applesnail, P. paludosa, by its indented (“channeled”) sutures, where P. paludosa sutures are flush with each shell whorl and whorls are short and bluntly rounded (Thompson 1999).

 

Egg clutches are bright pink and can contain 1500-2100 eggs (Burks et al. 2017) compared to the congener channeled applesnail, Pomacea canaliculata, with only 200-300 eggs per clutch. Egg masses serve as a character to differentiate these two species (see: image below, Rawlings et al. 2007), which are morphologically difficult to distinguish from one another (Burks et al. 2017; Hayes et al. 2012). Egg masses of P. paludosa contain fewer, large, white eggs, as illustrated in the image by Rawlings et al. 2007. It should be noted that the eggs masses of P. maculata turn from pink to white and become ashy as they hatch (Barnes et al. 2008).

 

 

"Egg masses of introduced and native Pomacea in the continental U.S. a. P. haustrum, b. P. diffusa, c. P. canaliculata, d. P. paludosa, e. P. insularum. Scale Bar:5 cm." Caption and image by Rawlings et al. 2007, Creative Commons Attribution 2.0 Generic

Size: Can reach 155 mm in shell height (Pain, 1960)

Native Range: Throughout much of tropical and subtropical South America (Hayes et al., 2012); Brazil (Amazon basin), Paraguay, Uruguay, and northern Argentina (Rio de la Plata basin) (Joshi et al. 2017).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: This large snail is found in a variety of freshwater systems, including lakes, rivers, streams, ponds, and ditches, and can be abundant in slow-moving wetland habitats (Rawlings et al. 2007). The giant applesnail can tolerate a salinity of up to 8 PSU (practical salinity units; Underwood et al., 2019). This species is not cold tolerant and will burry themselves in sediment to overwinter in temperate climates where they are introduced (Matsukura et al. 2016). Pomacea maculata, like all applesnails (Ampullridae), have an operculum, which they can use to seal their shells (Hayes et al 2012; Thompson 1999).

This species is dioecious (has separate sexes) and fertilization is internal (Andrews, 1964). Copulation is lengthy and may take up to 36 hours (Andrews, 1964). Bright pink egg masses are laid at dawn or dusk on emergent vegetation or manmade structures above the water (Rawlings et al. 2007; Barnes et al. 2008). Masses contain 1500-2000 eggs on average (but have been recorded to have more than 4500 eggs), with each egg measuring approximately 1.94 mm in diameter and eggs hatching 10-14 days after being deposited (Barnes et al., 2008, Burks et al. 2017).

Sexual maturity has been documented at around three months of age (Bernatis 2014), and it is thought to live up to three years, although average lifespan has not been confirmed (Arnold et al. 2014). Given the number of eggs produced by one female and their potentially long lifespan, it is estimated that one female could lay up to 56,00 eggs throughout its life (Burks et al. 2017).

This species feeds mainly on vegetation but has been shown to be an opportunistic omnivore in laboratory settings (Carter, unpublished in Burks et al. 2017). A variety of animals use this invader as a food source. Racoons, Procyon lotor, have been observed feeding on P. maculata (Carter et al. 2017), as well as a variety of birds, including Limpkin, Aramus guarauna, (pers com C. Morningstar: photo voucher, and the Everglades snail kite, Rostrhamus sociabilis, (pers com C. Morningstar: here and here). Pomacea maculata has been credited with the northern range expansion of both aforementioned bird species (Dobbs 2019, Poli et al. 2020), as well as an increase in bill size in Everglades snail kite populations (Cattau et al. 2017). In its native range, the red swamp crawfish, Procambarus clarkii, has been shown to feed on hatchlings of Pomacea maculata (Joshi et al. 2017).

Means of Introduction: Although the mechanisms of introduction are not certain, the species was likely introduced via the aquarium trade (Karatayev et al. 2009), and the source of the southeastern U.S. populations was genetically traced back to populations native to Argentina and Brazil (Rawlings et al. 2007). The timeline of introduction of this species in the southeastern U.S. is unclear due to the initial misidentification of the species as P. canaliculata (Rawlings et al. 2007). However, the earliest record in the NAS database is an egg clutch deposited in the University of Florida museum in 1989 by Fred Thompson as P. canaliculata, though it is now known this specimen is likely P. maculata (UF 142245). There is evidence that the snail can be transported by flood waters (Advocate staff report 2018). In addition, Pomacea maculata have been found hitchiking in shipments of farmed crayfish from Louisiana (Zellers, R. 2024).

Status: Established in the U.S. in most southeastern states as well as Puerto Rico, and much of Asia including China (Yang and Yu, 2019), Borneo, Cambodia, Singapore, South Korea, Taiwan, Thailand, and Vietnam (Hayes et al. 2008).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health	Other

Applesnails are known agricultural pests, feeding on rice crops and causing great economic damage (Cowie, 2002; Hayes et al., 2008). The parasite rat lungworm, Angiostrongylus cantonensis, a nematode that can cause eosinophilic meningitis in humans, has been detected in populations of P. maculata in New Orleans (Teem et al. 2013). In 2018, an Acadia Parish, Louisiana, farmer shut down his crawfish harvest due to applesnails that had entered his rice fields when it was flooded with water from a bayou that flows into the Mermentau River (Advocate staff report 2018). As applesnails have been found hitchiking in farmed crayfish shipments from Louisiana, increased regulations are now necessary to prevent contaniment (Zellers, R. 2024)

Introduction has also had ecological effects on predator prey relationships. For instance, Cattau et al. (2017) found that a predator of P. maculata, Everglades snail kite, Rostrhamus sociabilis, has increased bill size in response to the larger prey size when compared to the native applesnail.

 

 

Image of an Everglades Snail Kite (Rostrhamus sociabilis) holding a large P. maculata in its talons. Photographed in Paynes Prairie State Park at Alachua Sink in 2022 by C.R. Morningstar, USGS.

Remarks: Initially P. insularum had been identified as P. canaliculata in Florida, Georgia, and Texas. Genetic testing confirmed that specimens collected in Florida, Georgia, and Texas were P. insularum (Rawlings et al. 2007). Since then, P. insularum (common name “island applesnail”) has been synonymized with P. maculata (Hayes et al., 2012; Rawlings et al. 2007). Pomacea maculata and P. canaliculata are known to hybridize, and laboratory experiments showed that hybrid offspring were more cold tolerant that nonhybrid parents (Matsukura et al 2016).

Research by Savaya-Alkalay et al. (2018) suggests that the development of all-male prawn populations of Macrobrachium rosenbergii has potential as a biocontrol agent for hatchling and adult apple snails (Pomacea spp.). Medium-sized and large prawns (10–30 g) efficiently preyed on snails up to15 mm, while small prawns (up to 4 g) effectively consumed snail hatchlings.

References: (click for full references)

Advocate staff report. 2018. Invasive snail found in Acadiana crawfish pond; pest also poses threat to rice plants. The Acadiana Advocate. Baton Rouge, LA. http://www.theadvocate.com/acadiana/news/article_a44e0de0-1039-11e8-ab97-efed1305c5da.html. Created on 02/12/2018. Accessed on 02/13/2018.

Andrews, E.B. 1964. The functional anatomy and histology of the reproductive system of some Pilid gastropod molluscs. Journal of Molluscan Studies 36(2):121-140.

Arnold, T.E., Brenner, M., Curtis, J.H., Dutton, A., Baker, S.M., Escobar, J.H. & Ortega, C.A. 2014. Application of stable isotopes (δ18O) to determine growth patterns of theinvasive gastropod Pomacea maculata in Florida Lakes. The Florida Scientist 77:126-143

Barnes, M.A., R.K. Fordham, R.L. Burks, and J.J. Hand. 2008. Fecundity of the exotic applesnail, Pomacea insularum. Journal of the North American Benthological Society 27(3):738-745.

Bernatis, J.L. 2014. Morphology, ecophysiology, and impacts of nonindigenous Pomacea in Florida. Unpublished Ph.D. dissertation. University of Florida, Gainesville, Florida.

Burks, R.L., Bernatis, J., Byers, J.E., Carter, J., Martin, C.W., McDowell, W.G. and Van Dyke, J., 2017. Identity, reproductive potential, distribution, ecology and management of invasive Pomacea maculata in the southern United States. Biology and Management of Invasive Apple Snails. Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, 3119, pp.293-333.

Carter, J., S. Merino, D. Prejean, and G. LaFleur, Jr. 2017. Observations of raccoon (Procyon lotor) predation on the invasive Maculata apple snail (Pomacea maculata) in southern Louisiana. Southeastern Naturalist 16(3):N14-N18.

Cattau, C.E., R.J. Fletcher, Jr., R.T. Kimball, C.W. Miller, and W.M. Kitchens. 2017. Rapid morphological change of a top predator with invasion of a novel prey. Ecology and Evolution DOI:10.1038/s41559-017-0378-1, 10 pp.

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

Dobbs, R.C. 2019. Limpkin, Aramus guarauna (L., 1766) (Gruiformes, Aramidae), extralimital breeding in Louisiana is associated with availability of the invasive Giant Apple Snail, Pomacea maculata Perry, 1810 (Caenogastropoda, Ampullariidae). Check List 15(3):497-507. https://doi.org/10.15560/15.3.497.

Grana, F. Personal communication. Puerto Rico Department of Natural and Environmental Resources.

Hayes, K.A., R.H. Cowie, S.C. Thiengo, and E.E. Strong. 2012. Comparing apples with apples: clarifying the identities of two highly invasive Neotropical Ampullaridae (Caenogastropoda). Zoological Journal of the Linnean Society 166(4):723-753.

Hayes, K.A., R.C. Joshi, S.C. Thiengo, and R.H. Cowie. 2008. Out of South America: multiple origins of non-native apple snails in Asia. Diversity and Distributions 14(4):701-712.

Howells, R. G. 2001. History and status of applesnail (Pomacea spp.) introductions in Texas. Texas Parks and Wildlife Department, Management Data Series No. 183.

Joshi R.C., Cowie R.H., and Sebastian L.S. (eds). 2017. Biology and management of invasive apple snails. Philippine Rice Research Institute (PhilRice), Maligaya, Science City of Muñoz, Nueva Ecija 3119.

Karatayev, A.Y., Burlakova, L.E., Karatayev, V.A. and Padilla, D.K., 2009. Introduction, distribution, spread, and impacts of exotic freshwater gastropods in Texas. Hydrobiologia, 619, pp.181-194.

Pain, T. 1960. Pomacea (Ampullariidae) of the Amazon River system. Journal of Conchology 24: 421-432.

Poli, C.L., Dudek, S.J., Jeffrey, B.M., Robertson, E.P. and Fletcher Jr, R.J., 2020. Recent breeding range expansion of the endangered Snail Kite (Rostrhamus sociabilis) in Florida. The Wilson Journal of Ornithology, 132(1), pp.183-188.

Rawlings, T. A., K. A. Hayes, R. H. Cowie, and T. M. Collins. 2007. The identity, distribution, and impacts on non-native apple snails in the continental United States. BMC Evolutionary Biology, http://www.biomedcentral.com/1471-2148/7/97.

Savaya-Alkalay, A., Ovadia, O., Barki, A., and A. Sagi. 2018. Size-selective predation by all-male prawns: implications for sustainable biocontrol of snail invasions. Biological Invasions 20:137–149.

Teem, J.L., Qvarnstrom, Y., Bishop, H.S., da Silva, A.J., Carter, J., White-McLean, J. and Smith, T., 2013. The occurrence of the rat lungworm, Angiostrongylus cantonensis, in nonindigenous snails in the Gulf of Mexico region of the United States. Hawai'i Journal of Medicine & Public Health, 72(6 Suppl 2), p.11.

Thompson, F.G. 1999. An identification manual for the freshwater snails of Florida. https://www.floridamuseum.ufl.edu/iz/resources/florida-snails/. Created on 07/08/2019. Accessed on 07/08/2019.

Matsukura, K., Y. Izumi, K. Yoshida, and T. Wada. 2016. Cold tolerance of invasive freshwater snails, Pomacea canaliculata, P. maculata, and their hybrids helps explain their different distributions. Freshwater Biology 61:80-87. https://doi.org/10.1111/fwb.12681.

Underwood, E.B., T.L. Darden, D.M. Knott, and P.R. Kinsley-Smith. 2019. "Determining the salinity tolerance of invasive island apple snail Pomacea maculata (Perry, 1810) hatchlings to assess the invasion probability in estuarine habitats in South Carolina, USA." Journal of Shellfish Research 38.1: 177-182.

Yang, Q.Q. and Yu, X.P., 2019. A new species of apple snail in the genus Pomacea (Gastropoda: Caenogastropoda: Ampullariidae). Zoological Studies, 58.

Zellers, R. 2024. AGFC discovers invasive apple snails in live crawfish shipments. Arkansas Game and Fish Commission. Little Rock, AR. https://www.agfc.com/news/agfc-discovers-invasive-apple-snails-in-live-crawfish-shipments/. Created on 04/09/2024. Accessed on 04/15/2024.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Pomacea maculata

Author: Morningstar, C.R., A. Jordon, and L.D. Stratton

Peer Review Date: 9/28/2023

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.