Apple snails are larger than most freshwater snails and can be separated from other freshwater species by their oval shell which has the umbilicus of the shell perforated or broadly open. The spire of the shell can be conspicuous, but is much less than the height of the aperture. Apple snails lay grape-like clusters of either white, green, or pink to red eggs on solid objects above the water line, and this is the quickest way to determine if apple snails are present.
The apple snails belong to the subclass Prosobranchia of the Gastropoda. This subclass is distinguished from the other subclass, Pulmonata, by the presence of an operculum. The operculum is a cover used to close the aperture when the snails are withdrawn into their shells. The operculum (which detaches after death) is corneous with concentric growth rings.
The Florida apple snail, Pomacea paludosa (Say, 1829), occurs throughout peninsular Florida (Thompson 1984), as well as Cuba and Hispaniola (FFWCC 2006). Collections have been made in Georgia; Oahu, Hawaii; Louisiana; and Oklahoma (USGS 2006). It is the principal food of the Everglades kite, Rostrhamus sociabilis plumbeus Ridgway, and should be considered beneficial.
The spike-topped apple snail, P. diffusa Blume, 1957, was introduced many years ago into South Florida and is marketed as an aquarium species under the name "golden apple snail" (FFWCC 2006).
The titan apple snail, P. haustrum (Reeve, 1856), is rare in Florida (FFWCC 2006). The waters of the Loxahatchee National Wildlife Refuge waters in Palm Beach County, Florida, are the only known area where this species is established in the United States (USGS 2007).
The most common introduced species is the island apple snail, P. insularum (D'Orbigny, 1839), which was originally thought to be the channeled apple snail. This species was probably released in south Florida in the early 1980s by persons with the tropical pet industry, and rapidly expanded throughout the state. Pomacea insularumis now found, or introductions have occurred, in Alabama, Arizona, California, Georgia, Hawaii, North Carolina and Texas (FFWCC 2006).
However, it is the channeled apple snail, P. canaliculata (Lamarck, 1819), that causes concern to agriculturists. This species is a serious rice pest in many countries. Fortunately, this species has been documented from only one site in northern Florida (FFWCC 2006) near Jacksonville. It also has been reported from Mobile, Alabama; San Diego County, California; Yuma, Arizona; and numerous locations in Hawaii. It is considered established in California and Hawaii (USGS 2008).
The island and channeled apple snails are potential threats to Florida's aquatic ecosystems. The channeled apple snail has caused significant damage to rice and taro crops in the Pacific islands and in southeast Asia. It is not known whether these two species have similar feeding preferences (FFWCC 2006).
To help confirm the identity of any of these species, plus differentiate between the channeled and island apple snails, please see the color photos of the eggs of all five Florida species on the Florida Fish and Wildilfe Conservation Commission publication on Non-native Apple Snails in Florida.
A much more complete key for all the freshwater snails of Florida is available online through the Florida Museum of Natural History at http://www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm.
1. Apical spire of shell strongly rounded or arched, apical whorls bluntly rounded and not elevated (Fig. 3); adult shells about 40-70 mm high . . . . . Florida apple snail, Pomacea paludosa (Say, 1819)
This is a native snail that has existed in Florida since the Pliocene, based on fossil finds. It is also native to Cuba and Hispaniola. This species has been reported in Georgia; Oahu, Hawaii; Louisiana; and Oklahoma. It cannot survive low winter temperatures that occur in the northern tier of Florida counties and northward except where the water is artificially heated by industrial wastewater or in warm springs. It occurs as far west as the Choctawhatchee River. Easily distinguished from other apple snails in Florida by the low, rounded shell spike.
1'. Apical spire of shell step-like with nearly flat shoulders and deep sutures, apical whorls forming a point on top of spire (Figs. 1, 2) . . . . . 2 2. Shell with each whorl separated from one below by a deep groove or channel (Figs. 1, 4); adult shells 70-95 mm high; varying in color from olive brown to yellowish-brown, often with darker bands and blotches . . . . . channeled apple snail, Pomacea canaliculata (Lamarck, 1819)
closeup of channeled apple snail
This large apple snail (shell height up to 100 mm) was introduced into South Florida from the Paraguay River System at least as early as 1978. Like the giant African snail, this snail was purposely released into Hawaii, Philippines and Taiwan in the 1980s to be cultured for human consumption. However, there was little interest in eating these snails and the species spread rapidly from Indonesia to southern China and Japan. In contrast to the other Florida apple snails, this species feeds aggressively on many types of aquatic and terrestrial plants. In Hawaii, it feeds on taro and rice, whereas in southeastern Asia it has been a serious rice pest. It also can host the rat lung worm that can infect humans. Apparently this species can survive considerable time out of water and also can hibernate in the mud during cold weather which probably accounts for its presence in Japan. This species can survive up to 50 months (Estebenet and Cazzaniga 1992). In Florida, the species appears to be confined to a small location near Jacksonville. However, no threat to the small rice industry in Florida is foreseen since 98% of the rice grown in Florida is summer rice, rotated with sugar cane or vegetables. This is now the largest non-marine snail in Florida. It also can be distinguished by the deep groove or channel between whorls.
2'. Shell without deep groves separating whorls (Fig. 2); adult shells 40-60 mm high; coloration usually greenish with darker and lighter bands in nature . . . . . spike-topped apple snail, Pomacea diffusa Blume, 1957This is a Brazilian species that was introduced into south Florida, probably in the l950s. This species has a lower tolerance for cold water than the Florida apple snail and is established in Broward, Miami-Dade, Monroe and Palm Beach counties. However, commercial varieties have been bred for the aquarium trade, including the "albino mystery snail." These aquarium snails are sometimes dumped into isolated bodies of water and have been recovered as far north as Alachua County (Thompson 1984). They feed mostly on decaying vegetation.
Mating and egg laying for both the channeled and island apple snails start in March, and can continue through October. The females emerge from the water, usually at night, to lay bright pink egg masses on stable substrates such as tree trunks, pilings, seawalls, or even plant stems. If adverse conditions occur, the island apple snails can burrow into sediments, seal the entrance to their shells with the operculum, and remain in this condition for several months. Meanwhile, while adult channeled apple snails may survive dessication for up to one year, juveniles can only do so for up to 5 months (FFWCC 2006).
You can scrape off the egg masses and allow them to fall into the water since inundated eggs will not hatch. However, only pink egg masses should be scraped or removed. Egg masses with large, white eggs were laid by the native Florida apple snail and should be left undisturbed, as they do not pose a threat and are the principal food of the Everglades kite. Never replease apple snails from aquaria into the wild (FFWCC 2006).
Effective April 5, 2006, USDA APHIS requires permits for importation or interstate shipment of all marine and freshwater snails. Permits are not being issued for members of the genus Pomacea, with the exception of the spike-topped apple snail, P. diffusa (FFWCC 2006). Remember, to ship any of these species without a permit is a violation of federal law.
Author: Lionel A. Stange (retired), Department of Agriculture and Consumer Services, Division of Plant Industry; and Thomas R. Fasulo, University of Florida
Originally published as DPI Entomology Circular 388. Updated for this publication.
Photographs: Jeffrey Lotz, DPI; and Barbara Claiborne
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-323
Publication Date: March 2004. Latest revision: September 2008.
Copyright 2004-2008 University of Florida
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Florida apple snail
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channeled apple snail
spike-topped apple snail