Synonym(s): applesnail, apple snail
The shell of the island applesnail (Pomacea insularum) varies from 1.5 - 2.3 inches wide and 1.75 - 3 inches high (about the size of a baseball or human fist). Patterning on the shell can be wildly variable, but shell is usually banded brown, yellow-tan, or even blackish. The shell opening, or aperture is large and oval or round. Body color of applesnails vary from yellow to brownish black, with or without dark spiral bands. Their presence is often first noted by observation of their bright pink egg masses.
Ecological Threat: Negative ecological effects of this herbivorous snail species include impacts on wetlands and wetland restoration activities, competition with native snails, and the introduction of exotic parasites. Economic losses can include damage to rice crops as has been evidenced in invasions of applesnails documented in Asia. Yet, in Texas, there is no documented agricultural damage from P. insularum at present. However, rice farmers experience increased maintenance costs for levees in fields with large populations of P. insularum due to the constant burrowing by snails.
Biology: Invasive Island applesnails can spread rapidly from agricultural areas into wetlands and other natural freshwater systems where it may have a serious impact. Like all invasive species, Island applesnails have the potential to compete with native species for limited resources. This snail species feed on all types of aquatic plants, which could alter the natural balance of a water system. Additionally, their rapid and profuse reproduction coupled with their lack of predators in the United States could make their populations explode causing further issues. It has already threatened the major rice-crops of Texas and California.
In addition Island Applesnails are an intermediate host to the rat lungworm, Angiostrongylus cantonesis, a parasitic worm of rats. Humans can become infected by this parasite by eating raw or undercooked snails or by eating raw produce contaminated by rat lungworm larvae. Humans with mild infections usually recover fully. However, severe infections of the parasite can cause eosinophilic meningitis. Rat lungworm has been found in applesnails collected from New Orleans, Louisiana.
History: The island applesnail, Pomacea insularum, which is native to South America, has historically been confused with the channeled applesnail, P. canaliculata, in the United States. The two species are nearly identical in appearance. However, DNA testing can confirm species identification. Invasive island applesnails have been documented in Florida, Georgia, Alabama, Texas, and Louisiana.
Island Applesnail introductions are assumed to be very similar to the channeled applesnail. That is, the main method of introduction appears to be dumping of aquaria into native freshwater systems.
U.S. Habitat: Applesnails are found in shallow, freshwater habitats including streams, bayous, ponds, irrigation canals and rice fields. Applesnails tolerate salinities up to 7 parts per thousand (ppt) well and can survive in salinities up to 14 ppt. Temperature tolerances of this species were determined to be 15-36C and may limit distribution of the species in the U.S.
Native Origin: South America
U.S. Present: Invasive island applesnails have been documented in Florida, Georgia, Alabama, Texas, and Louisiana.
Applesnails with channeled shells are now established in six counties in southeastern Texas. There is still some debate whether all of the individuals are Island applesnails (P. insularum) rather than their close relative the Channeled applesnails (P. canaliculata).
May be confused with any of the Applesnails of the genus Pomacea, probably for its almost visually-identical relative, the Channeled applesnail, P. canaliculata.
Since early detection is key to preventing the spread and establishment of this species, regional/local monitoring or surveillance is essential. Nonnative species should not be released. If found, note the capture location, kill and freeze the snail, and notify the TPWD.
Burlakova1, Lyubov, Alexander KarataBurlakova1yev, and Dianna Padilla, et. al. "Wetland Restoration and Invasive Species: Apple snail (Pomacea insularum) Feeding on Native and Invasive Aquatic Plants." Restoration Ecology. 17.3 (2009): 433-440.
Carlsson, N. O. L., and J. O. Lacoursière. 2005. Herbivory on aquatic vascular plants by the introduced golden apple snail (Pomacea canaliculata) in Lao PDR. Biological Invasions 7:233–241.
Cowie, R. H. 2002. Apple snails as agricultural pests: the biology, impacts, and management. Pages 1–28 in G. M.Barker, editor. Molluscs as crop pests. CABI, Wallingford, Connecticut.
Estebenet, A. L., and P. R. Martín. 2002. Pomacea canaliculata (Gastropoda: Ampullariidae): life-history traits and their plasticity. Biocell 26:83–89.