The Applesnails of Florida

The applesnails belong to the subclass Prosobranchia of the Gastropoda which are 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 The operculum is a cover used to close the aperture when the snails are withdrawn into their shells. Applesnails 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. The operculum (which detaches after death) is corneous with concentric growth rings. Applesnails lay grape-like clusters of pink to red eggs on solid objects above the water which provides the fastest way to determine if applesnails are present. There are three species in Florida. One is native and the others are introduced. The Florida applesnail, Pomacea paludosa, occurs throughout peninsular Florida (Thompson 1984). It is the principal food of the Everglades Kite (Rostrhamus sociabilis plumbeus Ridgway) and thus should be considered beneficial. The spiketopped applesnail, Pomacea bridgesi, was introduced many years ago into South Florida. However, it is the third species of Pomacea, P. canaliculata, that has caused recent concern to agriculture. This species grows nearly twice the size as the other two species and has become a serious rice pest in many countries.