Practical information to identify and manage non-native, invasive plants and animals
The Quiet Invasion:A Guide to Invasive Species of the Galveston Bay Area
Pomacea insularum
| ITIS TSN: | 70342 |
| Presence: | Current Invaders |
| Habitat: | Aquatic |
| Native Range: | South America |
Human Health
Apple snails are an intermediate host to the rat lungworm (Angiostrongylus cantonesis), a parasitic worm of rats. People can become infected by this parasite by eating raw or undercooked snails or by eating raw produce contaminated by rat lungworm larvae. People with mild infections usually recover fully. However, severe infections of the parasite can cause eosinophilic meningitis. Rat lungworm has been found in apple snails collected from New Orleans, Louisiana (Teem and Gutierrez 2008).Prohibited Lists
This species (and all other snail species from the family Ampullariidae except for the spiketop applesnail, P. bridgesii) are legally classified in Texas as exotic, harmful, or potentially harmful. No person may import, possess, sell, or place this species into state waters except as authorized by a rule or permit issued by the TPWD.Introduction Pathways
Escape or release from plant or animal aquaculture operations and the aquarium/pet trade (Rawlings et al. 2007).Geographic Distribution
P. insularum is found in the southern U.S.in eight states, including Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, and North Carolina (Benson 2010). This species is present in the Lower Galveston Bay watershed in Brazoria, Chambers, Galveston, and Harris counties as well as in three additional Texas counties (Austin, Fort Bend, and Waller) (Karatayev et al. 2009).Specific Primary Habitats
Apple snails are found in shallow, freshwater habitats including streams, bayous, ponds, irrigation canals and rice fields. Apple snails tolerate salinities up to 7 parts per thousand (ppt) well and can survive in salinities up to 14 ppt (Ramakrishnan 2007). Temperature tolerances of this species were determined by Ramakrishnan (2007) to be 15-36�C and may limit distribution of the species in the U.S. Under conditions of hypoxia apple snails can switch to air breathing by using their mantle cavity as an aerial lung. Texas populations have been found to maintain low low population densities (<2 per m2) in permanent, stable freshwater systems (ponds and streams). Much higher population densities (>130 per m2) have been found in ephemeral agricultural environments (e.g. rice fields) in southeast Texas (Burlakova et al. 2010).Ecological, Economic, or Social Impact
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 (Karatayev et al. 2009). Economic losses can include damage to rice crops as has been evidenced in invasions of apple snails documented in Asia (Burlakova et al. 2009). 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 (Burlakova et al. 2010).Physical Description
Apple snails are typically globular or spherical in shape. They may be banded, brown, black, or yellowish-tan with color patterns being variable. Albino and gold color variations also exist (Benson 2010).Reproduction Characteristics
Unlike most snails which are hermaphroditic, apple snails have separate male and female sexes. They lay their egg clusters on solid objects (e.g. plant stems, tree trunks, rocks, stormwater outfalls, or docks) just above the water line. Each egg cluster can contain thousands of eggs that are initially bright pink or reddish in color. Over time, the eggs fade to a light pink or white color. The presence of egg masses is a good indicator of snail presence/absence in a water body. P. insularum not only has high fecundity, but reproduces over a long period of time (March to early November in southeast Texas), thus this species is able to take advantage of unpredictable environments, like floodplains (Burlakova et al. 2010).Feeding
The apple snail diet consists primarily of rooted aquatic vegetation. Burlakova et al. (2009) found that apple snails will feed on native plant species such as coon's tail, spider lily, widgeongrass, and lanceleaf arrowhead. Apple snails may also feed on Spartina alterniflora, California bulrush, water cana, and common cattail, but will only do so when shoot dryness is low. Apple snails are also known to feed on invasive plants such as elephant ear, alligatorweed, and common water hyacinth.Control
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 snake, and notify the TPWD.Lists
This species belongs to the following lists:
Images
To view a larger version of an image, click on the thumbnail. Closeup of island applesnail (P. insularum) found in Brazoria County in 2006. Photo courtesy of Lyubov E. Burlakova, Buffalo State College. |
 Island applesnail (P. insularum) found in Brazoria County in 2006. Photo courtesy of Lyubov E. Burlakova, Buffalo State College. |
 Island applesnails (P. insularum) found in an irrigation canal in Brazoria County in 2006. Photo courtesy of Lyubov E. Burlakova, Buffalo State College. |