Investigation of the population genetic structure, salinity tolerance, and occurrence of a parasite in the island apple snail, Pomacea maculata, in South Carolina, USA
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Underwood, Elizabeth
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Abstract
The island apple snail, Pomacea maculata (Gastropoda:Ampullariidae), is an invasive freshwater gastropod native to South America that is currently established in several southeastern states, including South Carolina. It is considered invasive due to the negative impacts associated with intense grazing, high fecundity, an ability to out-compete native species, and the potential to serve as a host for the rat lungworm nematode parasite (Angiostrongylus cantonensis), which can cause eosinophilic meningitis in humans. The first aim of this study was to determine the population genetic structure and genetic diversity of this species in South Carolina and Georgia using microsatellite markers. The second aim was to determine the frequency of occurrence of A. cantonensis in P. maculata in South Carolina using a quantitative real-time PCR assay. The third aim was to determine the salinity tolerance of P. maculata hatchlings exposed to constant salinity treatments (0, 4, 8, 12, 16 psu). Overall, genetic diversity was low at all locations and significant genetic structure was observed among all sampling locations, with the exception of the two sites in Kingsland, GA. These results indicate that the populations in South Carolina and Georgia were likely the result of separate introductions and that these populations are genetically isolated. The low genetic diversity observed could indicate these populations may be susceptible to eradication efforts and/or environmental changes. No positive detections of A. cantonensis were found in any P. maculata, indicating the absence of this parasite in P. maculata in South Carolina. 100% hatchling survival was observed at 0 psu, and 0% survival was observed at both 12 and 16 psu. Survival probabilities at 4 psu and 8 psu were 0.925 and 0.156, respectively. These results demonstrate the ability of P. maculata to survive salinities as high as 8 psu, a salinity that is representative of upstream estuarine habitats in coastal South Carolina.