common name: applesnails of Florida
scientific name: Pomacea spp. (Gastropoda: Ampullariidae)

Introduction - Species Found in Florida - Identification of Applesnails of Florida - Economic Importance of Invasive Species - Management - Selected References

Introduction

Applesnails are larger than most freshwater snails and can be separated from other freshwater species by their oval shell which has the umbilicus (the axially aligned, hollow, cone-shaped space within the whorls of a coiled mollusc shell) of the shell perforated or broadly open. There are four species of Pomacea in Florida, one of which is native and considered beneficial (Capinera and White 2011).

Species Found in Florida

Of the four species of applesnails in Florida, only the Florida applesnail is a native species, while the other three species are introduced. All are tropical/subtropical species in the genus Pomacea, and are not known to withstand water temperatures below 10°C (FFWCC 2006).

Identification of Applesnails of Florida

Identification based on shell shape is very difficult. 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.

In applesnails, the spire of the shell can be conspicuous, but is much less than the height of the aperture. Applesnails 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 applesnails are present.

Economic Importance of Invasive Species

The introduced island applesnail primarily eats rooted aquatic vegetation, while the native Florida applesnail feeds heavily on periphyton, a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus attached to submerged surfaces in most aquatic ecosystems.

Mating and egg laying for both island and Florida applesnails start in March, and can continue through October. The females emerge from the water, usually at night, to lay white or bright pink egg masses on stable substrates such as tree trunks, pilings, seawalls, or even plant stems. If adverse conditions occur, applesnails can burrow into sediments, seal the entrance to their shells with the operculum, and remain in this condition for several months. The other applesnails found in Florida seem not to be spreading or causing injury.

Florida applesnails showing operculum

However, it is the channeled applesnail, P. canaliculata (Lamarck, 1828), that causes concern to agriculturists. The channeled applesnail has caused significant damage to rice and taro crops in the Pacific islands and in southeast Asia. Fortunately, this species has not been documented from Florida. It has been reported from California and Hawaii (USGS 2010). Although, the USGS map (2010) shows it in northeastern Florida, recent molecular data proved that this population was not P. canaliculata (Capinera and White 2011).

Both the island and channeled applesnails are potential threats to Florida's aquatic ecosystems. It is not known whether these two species have similar feeding preferences (FFWCC 2006).

channeled applesnail

closeup of channeled applesnail

Management

While elimination of applesnails by chemical means has been attempted, no effective chemical recommendation has been developed. The most effective management methods are hand or mechanical removal of snails and egg masses. In Florida, some of the natural predators of applesnails include limpkins, Everglades (snail) kites, raccoons, turtles and alligators. It is also believed that redear sunfish and certain ducks will consume smaller immature snails (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 applesnail and should be left undisturbed, as they do not pose a threat and are the principal food of the Everglades kite. Never release applesnails from aquaria into the wild (FFWCC 2006).

Pomacea eggs by species

Effective 5 April 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 applesnail, P. diffusa (FFWCC 2006). To ship any of these species without a permit is a violation of U.S. federal law.

Selected References

Authors: Thomas R. Fasulo, University of Florida
Photographs: Bill Frank, http://www.jacksonvilleshells.org; Jeffrey Lotz, FDACS-DPI; Barbara Claiborne; Luis Ruiz Berti; Rawlings et al. BMC Evolutionary Biology 2007 7:97 doi:10.1186/1471-2148-7-97, used with permission
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-323
Publication Date: March 2004. Latest revision: July 2011.
Copyright 2004-2011 University of Florida

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