> Pomacea canaliculata (Lamarck 1822)

> Habitat & Distribution
A native of South America, the invasive pest P. canaliculata has spread throughout Florida and portions of Texas and California, as well as east Asia and the Pacific islands (Carlson et al. 2004, Joshi & Sebastian 2006, Rawlings et al. 2007).  It was first reported from Georgia in 2005, appearing in the Alabaha River near Blackshear, Pierce County (See Essay #2 below).  By the summer of 2007, reliable reports had reached us of Pomacea introductions in the towns of St. Marys and Alma (Bacon Co.), as well as on St. Simons Island.  In May of 2008 the first population was documented in South Carolina (See Essays #4 & #5 below).  

Pomacea inhabits ponds, ditches, freshwater marshes, and similar aquatic environments with low flow and large standing crops of aquatic macrophytes.

> Ecology & Life history
Pomacea canaliculata is a voracious consumer of almost any aquatic vegetation, including crops such as rice and taro (Estebenet 1995).  The snails can survive months of dewatering by burrowing and enclosing their shells tightly.  Large eggs are laid in pink clusters on emergent vegetation and other solid surfaces above the water line.  Maturity can be reached in as little as three months or may require two years, depending on the environment, with iteroparous reproduction thereafter (Andrews 1964, Albrecht et al. 1999, Martin & Estebenet 2002).  Estebenet & Cazzaniga (1992) estimated r = 0.09 and R = 20.1 for a laboratory population in Argentina.  Sex determination appears to be oligogenic (Yusa 2004b, 2006, see also Essay #1 below).

Pomacea was spread through Asia at least partly as a conscious effort by farmers hoping to harvest the snails for food.  Many of the Asian populations are albinistic, with unpigmented bodies and yellow shells, and are often referred to as "golden apple snails" (Yusa 2004a).  Here in the United States most of the populations are pigmented, and their spread seems to have been accidental, perhaps via aquarium hobbyists.  Additional information on the consequences of P. canaliculata introduction is available from Howells (2005a & b) and the Invasive Species Specialist Group. 

> Taxonomy & Systematics
The systematics of the Ampullariidae in general, and of P. canaliculata in particular, are currently an active area of research (Cowie et al. 2006).  The Georgia populations have been referred to Pomacea insularum by Rawlings et al. (2007) on the basis of mtDNA sequence data.  Although the morphological distinction between adult canaliculata and insularum seems to be negligible, there are some rather suggestive differences in egg mass morphology (Florida Fish & Wildlife Commission).  Controlled breeding experiments to confirm reproductive isolation between the two nominal species would be a welcome addition to the research program.

> Essay #1
I reviewed Yoichi Yusa's oligogenic model of sex determination in Ampullariids on 11Aug05, and offered some thoughts regarding the ongoing systematic work of Cowie and Hayes.
 
> Essay #2
I posted the newspaper article reporting the initial discovery of P. canaliculata in Georgia on 17Sept05.  The essay includes links to a variety of online references and contributions from Bob Howells in Texas.

> Essay #3
See my post of 24May07 for a review of the large book by Joshi & Sebastian, "Global Advances in Ecology and Management of Golden Apple Snails."

> Essay #4
Reports of the spread of Pomacea to the Myrtle Beach area of South Carolina reached us in May, 2008.  This post also includes a couple fresh figures of adults and eggs.

> Essay #5
I updated the situation with the Myrtle Beach introduction in August, 2008.  This post includes links to an SC DNR flier, distribution map, newspaper articles, photos, and more.

> References
Albrecht, E. A., Carreno, N.B.  & Castro-Vazquez, A. (1999)  A quantitative study of environmental factors influencing the seasonal onset of reproductive behaviour in the south American apple-snail Pomacea canaliculata (Gastropoda: Ampullariidae).  J. Molluscan Stud. 65: 241-250.  Andrews, E. B.  (1964)  The functional anatomy of the mantle cavity, kidney and blood system of some pilid gastropods.  J. Zool. 146: 70 - 94.  Andrews, E. B. (1965)  The functional anatomy and histology of the reproductive system of some pilid gastropod  molluscs.  Proc. Malac. Soc. Lond. 36: 121 -140.  Carlsson, N. O. L., Broenmark, C & Hansson, L-A  (2004)  Invading Herbivory: The Golden Apple Snail Alters Ecosystem Functioning in Asian Wetlands.  Ecology 85: 1575-1580.  Cowie, R. H., K. A. Hayes, & S. C. Thiengo (2006)  What are apple snails? Confused taxonomy and some preliminary resolution.  pp 3 - 23 in R. C. Joshi & L. S. Sebastian (eds.), Global advances in ecology and management of golden apple snails.  Philippine Rice Research Institute, Nueva Ecija.  Estebenet, A. L. (1995) Food and feeding in Pomacea canaliculata (Gastropoda: Ampullariidae).  Veliger 38: 277-283.  Estebenet, A. L. & N. Cazzaniga (1992)  Growth and demography of Pomacea canaliculata under laboratory conditions.  Malac. Rev. 25: 1-12.   Florida Fish and Wildlife Conservation Commission.   "Non-native applesnails in Florida (PDF)."  University of Florida Institute of Food and Agricultural Sciences.  "Applesnails of Florida."   Frank, Bill.  "The Channeled Applesnail in Northeast Florida."  www.jaxshells.org.  Ghesquiere, S.  "Pomacea canaliculata"  www.applesnail.net.  Howells, R. G. (2005a)  Exotic Applesnails in Texas Waters (PDF).  Howells, R. G. (2005b)  Invasive applesnails in Texas: Status of these harmful snails through spring 2005 (PDF).    Invasive Species Specialist Group, IUCN Species Survival Commission.  "Pomacaea canaliculata."  Global Invasive Species Database.   Joshi, R. C. & L. S. Sebastian (2006)  Global advances in ecology and management of golden apple snails.  Philippine Rice Research Institute, Nueva Ecija.  600 pp.  Martin, P. R. & Estebenet, A. L.  (2002)  Interpopulation variation in life-history traits of Pomacea canaliculata (Gastropoda: Ampullariidae) in southwestern Buenos Aires Province, Argentina.  Malacologia 44: 153-163.   Rawlings, T. A., Hayes, K. A., Cowie, R. H. & Collins, T. M. (2007)  The identity, distribution, and impacts of non-native apple snails in the continental United States.  BMC Evolutionary Biology 7: 97.    Yusa, Y.  (2004a)  Inheritance of color polymorphism and the pattern of sperm competition in the apple snail Pomacea canaliculata.  J. Moll. Stud.  70: 43 - 48.  Yusa, Y.  (2004b)  Brood sex ratio in the apple snail Pomacea canaliculata is determined genetically and not by environmental factors.  J. Moll. Stud.  70: 269 - 275.  Yusa, Y. (2006)  Genetics of sex-ratio variation inferred from parent-offspring regressions and sib correlations in the apple snail Pomacea canaliculata.  Heredity 96: 100-105.