Pomacea Maculata Research Articles

Climate and pH predict the potential range of the invasive apple snail (Pomacea insularum) in the southeastern United States.

Predicting the potential range of invasive species is essential for risk assessment, monitoring, and management, and it can also inform us about a species’ overall potential invasiveness. However, modeling the distribution of invasive species that have not reached their equilibrium distribution can be problematic for many predictive approaches. We apply the modeling approach of maximum entropy (MaxEnt) that is effective with incomplete, presence-only datasets to predict the distribution of the invasive island apple snail, Pomacea insularum. This freshwater snail is native to South America and has been spreading in the USA over the last decade from its initial introductions in Texas and Florida. It has now been documented throughout eight southeastern states. The snail’s extensive consumption of aquatic vegetation and ability to accumulate and transmit algal toxins through the food web heighten concerns about its spread. Our model shows that under current climate conditions the snail should remain mostly confined to the coastal plain of the southeastern USA where it is limited by minimum temperature in the coldest month and precipitation in the warmest quarter. Furthermore, low pH waters (pH <5.5) are detrimental to the snail’s survival and persistence. Of particular note are low-pH blackwater swamps, especially Okefenokee Swamp in southern Georgia (with a pH below 4 in many areas), which are predicted to preclude the snail’s establishment even though many of these areas are well matched climatically. Our results elucidate the factors that affect the regional distribution of P. insularum, while simultaneously presenting a spatial basis for the prediction of its future spread. Furthermore, the model for this species exemplifies that combining climatic and habitat variables is a powerful way to model distributions of invasive species.

Genetic exchange between two freshwater apple snails, Pomacea canaliculata and Pomacea maculata invading East and Southeast Asia

Two species of apple snails, Pomacea canaliculata and Pomacea maculata (formerly Pomacea insularum), have invaded many countries of East and Southeast Asia from their native range in South America. This study investigated the genetic structure of the two species invading these areas. Phylogenetic analysis based on sequences of the nuclear gene elongation factor 1-alpha (EF1α) detected two well-supported clades (Clade C and Clade M). Both P. canaliculata and P. maculata were represented in each clade. Some snails had both Clade C and Clade M EF1α sequences. These results suggest genetic exchange between snails of the two clades. A mating experiment between P. canaliculata with Clade C EF1α sequences and P. maculata with Clade M EF1α sequences resulted in viable F1 progeny under laboratory conditions. The genetic exchange was also inferred in some populations collected from Argentina, suggesting an existence of hybrid in the native range. Simple identification of EF1α types using a restriction enzyme, ApaLI, detected significant geographical structure of the EF1α variants in the invaded area. The divergent geographical structure could have resulted from either the founder effect or the bridgehead effect, although further genetic analysis is needed to clarify this. Average individual egg weight, which is an indicator of egg size, was higher in P. canaliculata than P. maculata in both field and laboratory reared samples, suggesting that some (probably most) P. canaliculata and P. maculata invading East and Southeast Asia still maintain species-specific populations.

Comparing apples with apples: clarifying the identities of two highly invasive Neotropical Ampullariidae (Caenogastropoda)

Ampullariidae comprises two lineages of freshwater gastropods: one Old World and one New World. Recent molecular work confirmed the monophyly of the family and began to clarify generic relationships, but current systematics remains unsatisfactory. With more than 300 available species group names for New World taxa alone, taxonomic confusion is rampant, as illustrated by two species that have been introduced widely and are difficult to differentiate conchologically, Pomacea maculata Perry, 1810 and Pomacea canaliculata (Lamarck, 1822). Misidentification hampers efforts to manage their spread and impacts as invasives, and prevents meaningful comparative analyses of their biology. Here we clarify the taxonomy, describe the morphological and genetic distinctiveness of the two species, and re-evaluate their biogeographic ranges. They differ most clearly genetically, with no shared haplotypes and a mean genetic distance of 0.135 at cytochrome c oxidase subunit I (COI). Differences in shell morphology are most obvious in recently hatched juveniles; the number of eggs per clutch is higher in P. maculata, and the individual eggs are smaller, so P. canaliculata hatchlings are nearly twice as large as those of P. maculata. Adult shells differ primarily in the angulation of the whorl shoulder and pigmentation of the inner pallial lip, with the latter a distinctive feature of P. maculata. They also differ in reproductive anatomy, most notably in P. canaliculata having two distinctive glandular tissues in the apical penial sheath gland, and P. maculata lacking a medial sheath gland but possessing a basal sheath gland. Pomacea canaliculata is restricted to a narrower southern range, whereas P. maculata ranges extensively throughout much of South America. Ampullaria gigas Spix, 1827 and Ampullaria insularum d'Orbigny, 1835 are herein synonymized with P. maculata. Neotypes are designated for P. maculata and A. gigas, and a lectotype is designated for A. insularum. A neotype is designated for P. canaliculata. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166, 723–753.

Impact of invasive apple snails on the functioning and services of natural and managed wetlands

At least 14 species of apple snail (Ampullariidae) have been released to water bodies outside their native ranges; however, less than half of these species have become widespread or caused appreciable impacts. We review evidence for the impact of apple snails on natural and managed wetlands focusing on those studies that have elucidated impact mechanisms. Significant changes in wetland ecosystems have been noted in regions where the snails are established: Two species in particular (Pomacea canaliculata and Pomacea maculata) have become major pests of aquatic crops, including rice, and caused enormous increases in molluscicide use. Invasive apple snails have also altered macrophyte community structure in natural and managed wetlands through selective herbivory and certain apple snail species can potentially shift the balance of freshwater ecosystems from clear water (macrophyte dominated) to turbid (plankton dominated) states by depleting densities of native aquatic plants. Furthermore, the introductions of some apple snail species have altered benthic community structure either directly, through predation, or indirectly, through exploitation competition or as a result of management actions. To date much of the evidence for these impacts has been based on correlations, with few manipulative field or mesocosm experiments. Greater attention to impact monitoring is required, and, for Asia in particular, a landscape approach to impact management that includes both natural and managed-rice wetlands is recommended.

Scientific Opinion on the evaluation of the pest risk analysis onPomacea insularum, the island apple snail, prepared by the Spanish Ministry of Environment and Rural and Marine Affairs

The Panel considers the Spanish pest risk analysis (PRA) to be clear and to provide appropriate supporting evidence. However, (i) the environmental impact assessment is incomplete and (ii) the estimates for the potentially endangered area are too limited. The Panel points out that large areas of the European Union have climatic conditions, that are very similar to those of the areas of native distribution of Pomacea spp. snails, and suitable host plants are available. The Panel agrees with the Spanish PRA on the following points with regard to the risk assessment area: (i) the potential consequences of the organism for rice crops are major; (ii) the probability for establishment of the organism is very likely and (iii) the probability of spread is estimated as likely. The Panel disagrees with the Spanish PRA on the following points and considers (i) the effects on the environment to be massive under suitable environmental conditions in the PRA area and (ii) the probability of entry of the organism to be high. Regarding risk reduction options the Panel agrees with the Spanish PRA that no single risk reduction method is sufficient to halt the introduction and spread of Pomacea spp. snails in the PRA area. However, a legislative ban on import of Pomacea spp. is the only risk reduction option identified that can reduce the probability of entry. The many other risk reduction options listed will help to reduce the probability of spread within the PRA area. The Panel considers that the risk reduction options should target the canaliculata complex, as Pomacea insularum and P. canaliculata, as well as other species from the complex, are almost indistinguishable. This is of particular importance for risk reduction options addressing both breeding and trade of the organism. © European Food Safety Authority, 2012

An Artificial Perch to Help Snail Kites Handle an Exotic Apple Snail

In the United States, the Snail Kite (Rostrhamus sociabilis plumbeus) is a federally endangered species and restricted to the wetlands of south-central Florida where the current population numbers less than 1,500. The Snail Kite is an extreme dietary specialist, previously feeding almost exclusively on one species of snail, the Florida Apple Snail (Pomacea paludosa). Within the past decade, an exotic species of apple snail, the Island Apple Snail (Pomacea insularum), has become established on lakes in central Florida. Island Apple Snails are larger than the native Florida Apple Snails, and Snail Kites handle the exotic snails less efficiently. Juvenile Snail Kites, in particular, have lower daily energy balances while feeding on Island Apple Snails. An inexpensive, easy-to-construct platform was developed that would provide Snail Kites with a flat, stable surface on which to extract snails. The platform has the potential to reduce the difficulties Snail Kites experience when handling exotic snails, and may benefit the Snail Kite population as a whole. Initial observations indicate that Snail Kites use the platforms frequently, and snails extracted at the platforms are larger than snails extracted at other perches.

Establishment of the Invasive Island Apple Snail Pomacea insularum (Gastropoda: Ampullaridae) and Eradication Efforts in Mobile, Alabama, USA

Species invasions are thought to be among the most detrimental of all anthropogenic disturbances. Invasive consumers severely impact native ecosystems through the consumption of and competition with native species. Worldwide, snails of the Family Ampullaridae have successfully colonized a wide range of habitats outside their native range. This is of great ecological concern because once established, these snails frequently exhibit rampant herbivory in the recipient ecosystem. Here, we chronicle the recent invasion of island apple snails (Pomacea insularum; d’Orbigny 1837) in a tributary of the Mobile–Tensaw Delta, Alabama, in order to establish a baseline against which future assessments of apple snail expansion can be measured. In addition, we discuss the current, albeit largely unsuccessful, efforts to eradicate these invaders post-invasion as well as the possible implications of the continued growth of this population should geographic expansion occur. We also provide the first genetic evidence, from the mitochondrial cytochrome c oxidase I (COI) sequence, positively identifying these snails as P. insularum. All individuals were identical for COI and genetically identical to invasive animals in Georgia and portions of Florida, as well as native animals near Buenos Aires, Argentina, indicating a possible secondary invasion from nearby invasive U.S. populations but, ultimately, an Argentinian origin. Based on our evidence, we suggest that the best control measures for apple snail invasions include increased proactive enforcement to prevent future invasions elsewhere in the southeastern United States (and similar areas), the adoption of research into new management strategies designed to prevent future invasions and slow the spread of established invasive populations, and rapid and overwhelming control and eradication efforts at the first sign of invasion.

Prime waterfront real estate: Apple snails choose wild taro for oviposition sites

Abstract While difficult to prevent introductions, scientific research can help guide control efforts of exotic, invasive species. South American island apple snails Pomacea insularum have quickly spread across the United States Gulf Coast and few control measures exist to delay their spread. Usually occupying cryptic benthic habitats, female apple snails crawl out of the water to deposit large, bright pink egg clutches on emergent objects. To help identify the most likely place to find and remove clutches, we conducted four lab experiments to investigate what specific object qualities (i.e. material; shape and height; plant species; natural and artificial) attracted P. insularum females to lay clutches. In our fourth experiment, we specifically examined the relationship between female size and reproductive output. To further understand reproductive output, we quantified experimental clutch characteristics (height above water, dimensions, mass, approximate volume, number of eggs, hatching efficiency). Pomacea insu-larum females laid more clutches on plant material, chose round over flat surfaces and failed to differentiate between tall and short structures. In comparison to a common native plant in the eastern US, Pontederia cordata, snails clearly preferred to lay clutches on a widely distributed exotic, invasive plant (wild taro, Colocasia esculenta). Unexpectedly, smaller snails showed higher overall total fecundity as well as more eggs per clutch than larger snails. Therefore, hand removal efforts of large females may not be enough to slow down clutch production. Collectively, our results indicate that conservationists and managers should search emergent plants for P. insularum clutches carefully to guard against established populations.

Quite the appetite: juvenile island apple snails (Pomacea insularum) survive consuming only exotic invasive plants

Most aquatic snails derive their energy by grazing periphyton. However, certain species, including the invasive island apple snail, Pomacea insularum, readily consume aquatic macrophytes. These snails often overlap in their distribution with other exotic, invasive plants. We sought to discover if juvenile P. insularum could survive and grow when fed only three reportedly less palatable food sources: Eurasian watermilfoil (Myriophyllum spicatum), wild taro (Colocasia esculenta) and water hyacinth (Eichhornia crassipes). Snails received nonrooted macrophytes simultaneously in a multiple-resource experiment. Using enclosures with compartments that separated plants but allowed snails full access, we housed individual early (10.7+ 0.9 mm operculum width; 0.56 –1.11 g blotted wet weight; mean+ 1 SD) or late (23+ 2 mm; 4.60– 14.82 g) juvenile P. insularum. We monitored snail survival and growth for 6 weeks. As controls, we placed standardized nonrooted macrophytes in enclosures without snails for 1 week. Replacing plants weekly, we calculated average daily consumption rates. Both size classes of snails grew substantially in terms of operculum width, shell height and blotted wet weight, with early juveniles exhibiting relatively larger gains in size over the 6-week period. No mortality occurred. Both size classes consumed significantly more watermilfoil than taro and more taro than water hyacinth. Collectively, these results translate into the potential for one single 10-g P. insularum (i.e. representative of the larger snails used in our experiment) to consume a combined 0.35 g of dried plant matter (or c. 3.5 g) of live macrophytes per day. Our study suggests that available resources offered by a community of exotic invasive plants may sustain snail survival.

An Aquatic Bal-Chatri for Trapping Snail Kites (Rostrhamus sociabilis)

The endangered Rostrhamus sociabilis plumbeus (Florida Snail Kite) has been the focus of several ecological studies emphasizing movements between and within wetland fragments. These studies have required the ability to trap and radiotag free-flying adults without significant risk of injury. We developed and tested a safe alternative to previous methods for trapping Snail Kites as part of a comparative study of VHF and satellite telemetry. The aquatic bal-chatri borrows from historical trap designs with modifications for trapping aquatic birds at the surface of the water. It consists of a square PVC frame with a series of parallel flourocarbon stringers and a mesh basket to restrain the lure species. Nooses are attached to the stringers and used to ensnare the toes of a predatory bird. The trap is held afloat by the PVC frame, with the mesh basket, stringers, and nooses positioned just beneath the surface of the water. After determining effective trap placement in relation to perched birds, we captured 11 kites in 13 days with native pomacea paludosa (Florida Apple Snail) and exotic Pomacea insularum (Island Apple Snail) as lures. Our results indicated that the aquatic bal-chatri can be used to target specific Snail Kites and recapture previously trapped individuals. This trap design is a safe, efficient, and low-cost alternative to methods previously used for capturing Snail Kites. Additionally, the aquatic bal-chatri is relatively easy to use and appears to have minimal impact on foraging behavior and breeding performance of Snail Kites.

Distribution of freshwater snails in family-based VAC ponds and associated waterbodies with special reference to intermediate hosts of fish-borne zoonotic trematodes in Nam Dinh Province, Vietnam

Fish-borne zoonotic trematodes, such as Clonorchis sinensis, heterophyids and others, constitute a public health concern in parts of northern Vietnam and infections with these trematodes are often thought to be linked to fish culture. One common fish culture system is the integrated fish-livestock (VAC) ponds where individual households have 1 or more ponds. Fish fry, mainly of various carp species, produced in hatcheries, not necessarily local, are introduced into nursery ponds and after approximately 6 weeks, juvenile fishes are transferred to household ponds, referred to as grow-out ponds. Grow-out ponds are usually fertilized with organic debris, including animal excreta, to stimulate algal growth and subsequently fish growth. This paper describes the distribution of freshwater snails and occurrence of trematode infections in these in VAC ponds and associated habitats as part of a major study on risk factors of FZT infections in cultured fish in two communes, Nghia Lac and Nghia Phu, Nghia Hung District, Nam Dinh Province. The area is under intense rice cultivation with an extensive canal network supplying fields and also household VAC ponds. A total of 16 snail species was found and four were widely distributed i.e. Angulyagra polyzonata, Melanoides tuberculata, Bithynia fuchsiana and Pomacea insularum. Snail diversity and counts were higher in nursery ponds than in grow-out ponds. Species of the families Thiaridae and Viviparidae were more abundant than other species in VAC ponds while species of the Bithyniidae, Stenothyridae and Planorbidae dominated in rice fields and small canals. Trematode infections were found in eight snail species and among these M. tuberculata had the highest overall prevalence of infection (13.28%). No trematode infections were found in species of the Viviparidae and Ampullaridae except for metacercariae. Parapleurolophocercous and pleurolophocercous cercariae constituted the most common type of cercariae recovered, contributing 40.6% of all infections followed by echinostome cercariae (35.0%) and xiphidiocercariae (17.3%). Bithynia fuschiana and M. tuberculata had the most diverse trematode fauna. C. sinensis was not recorded in this study. The VAC pond system in this area, is very important for transmission of minute intestinal trematodes while they play little role in transmission of C. sinensis as its intermediate hosts, bithynid snails, rarely occur in these ponds. From a public health perspective this is positive as the effects of infections with intestinal trematodes are considered mild. On the other hand it is possible that even such subtle effects could have importance in public health as transmission is very intense in the area. And this in combination with the aquaculture importance, reduced marketability of fishes with high metacercariae loads, warrants that control efforts against these trematodes are initiated to reduce transmission in this production system.

Pink eggs and snails: field oviposition patterns of an invasive snail, Pomacea insularum, indicate a preference for an invasive macrophyte

Oviposition of non-calcareous or thinly shelled eggs represents an important life stage of many insects, amphibians, and several gastropods. A recently identified invasive species of apple snail, Pomacea insularum, exhibits alarming invasive characteristics of high reproductive rates and generalist consumption patterns. This snail takes the opposite approach to egg laying compared to most aquatic insects as adult snails crawl out of the water to place clutches on emergent, or terrestrial, substrates. As fecundity best indicates invasive potential for mollusks, control or management efforts need to understand reproductive behavior in P. insularum to predict, and hopefully impede, its spread throughout the Gulf Coast of the United States. Specific characteristics of wetlands and shallow lakes may facilitate the invasion process of P. insularum by providing females with conditions that permit successful oviposition. In order to investigate this possibility, we studied P. insularum oviposition behavior in an invasive population at two times during the reproductive season in Texas, USA. Based on a subsequent survey (August 2009), plants comprised 78% of the available habitat. Wild taro (Colocasia esculenta) and alligator weed (Alternanthera philoxeroides) represented 48 and 43% of that proportion, respectively. During 2008–2009, no new concrete or metal structures appeared in our sampling reach and consistent amounts of plant stands and woody debris remained dominant. Given this distribution, P. insularum laid disproportionately more clutches on wild taro compared to its availability and less on alligator weed and bulrush (Schoenoplectus californicus) than expected. Owing to limited metal and concrete substrates, we found a higher proportion of clutches on these artificial substrates than expected in both May and August 2008. However, artificial substrates comprised less than 2% of available substrates in the bayou. Our results suggest that wetlands and shallow lakes surrounded by large emergent macrophytes, particularly wild taro, likely provide ideal oviposition sites for P. insularum, promote egg supply, and possibly facilitate invasion into new aquatic ecosystems.

Feeding rates of an introduced freshwater gastropod Pomacea insularum on native and nonindigenous aquatic plants in Florida

Pomacea insularum (Gastropoda: Ampullariidae) is a common, nonindigenous species in many parts of the world and an important consumer of aquatic macrophytes. We conducted laboratory trials to quantify the rates of consumption of native and nonindigenous aquatic plants in Florida, where this snail has been introduced. Twenty-two freshwater plant and alga species were presented to naïve P. insularum in laboratory trials, using single-snail replicates and simultaneous (no-snail) controls. Pomacea insularum damaged >50% of the replicate plants of 16 species; for 14 of these we calculated ash-free dry weight-specific feeding rates of P. insularum. The most heavily consumed plants were two native species: Limnobium spongia (0.744 g/g/d) and Chara sp. (0.478 g/g/d). Nonindigenous Panicum repens (0.306 g/g/d), Hydrilla verticillata (0.292 g/g/d) and Ceratophyllum demersum (0.254 g/g/d); and native Sagittaria latifolia (0.257 g/g/d), Najas guadalupensis (0.225 g/g/d) and Vallisneria americana (0.207 g/g/d) were also heavily consumed. Nonindigenous Eichhornia crassipes was consumed at a lower rate (0.053 g/g/d) while nonindigenous Colocasia esculenta and Pistia stratiotes were not consumed at detectable levels. Our results suggest that P. insularum cannot be relied upon as a biological control agent for nonindigenous plants and may heavily impact native macrophytes.

Effects of an exotic prey species on a native specialist: Example of the snail kite

Despite acknowledging that exotic species can exhibit tremendous influence over native populations, few case studies have clearly demonstrated the effects of exotic prey species on native predators. We examined the effects of the recently introduced island apple snail ( Pomacea insularum) on the foraging behavior and energetics of the endangered snail kite ( Rostrhamus sociabilis plumbeus) in Florida. We conducted time-activity budgets: (i) on kites foraging for native Florida apple snails ( Pomacea paludosa) in major wetland units within the kites’ range that had not been invaded by the exotic island apple snail and (ii) on kites foraging for exotic apple snails in Lake Tohopekaliga, the only major wetland utilized by the snail kite that had suffered a serious invasion of P. insularum. When foraging for P. insularum, snail kites dropped a greater proportion of snails, and they experienced increased handling times and decreased consumption rates; however, kites foraging for P. insularum also spent a smaller proportion of the day in flight. Estimates of net daily energy balances between kites feeding on P. insularum versus P. paludosa were comparable for adults, but juveniles experienced energetic deficiencies when feeding on the exotic snail. Due to this discrepancy, we hypothesize that wetlands invaded by P. insularum, such as Lake Tohopekaliga, may function as ecological traps for the snail kite in Florida by attracting breeding adults but simultaneously depressing juvenile survival. This study highlights the conservation implications and importance of elucidating the effects that exotic species have on native specialists, especially those that are endangered, because subtle influences on behavior may have significant population consequences.

Not a slow snail: Rapid rise of environmental awareness and ecological insights regarding invasive island apple snails (Pomacea insularum)

Abstract Background/Question/Methods Exotic invaders routinely move faster than scientific publication processes. Lacking aerial dispersal stages, snails generally match descriptions of slow colonizers. However, reminiscent of the pace with which zebra mussels gained notoriety, a growing sense of urgency has emerged from management communities regarding established populations of exotic, invasive island apple snails (Pomacea insularum). Recently separated by mitochondrial markers as a related, yet distinct, species, P. insularum sits poised to follow along the invasive trajectory of its better known relative, the golden apple snail (P. canaliculata). Literature studies examining mechanisms that promote invasiveness suggest family history of invasion serves as a sufficient enough warning sign. Furthermore, a paucity of natural history information exists on this larger (max wet weight 166-g), more fecund (2000 eggs as average clutch size) aquatic plant consumer. Without insights into basic life history, actions within management agencies often stall. In just the past five years, multiple introductions gave rise to established reproductive populations across the entire Gulf Coast, from Texas to Florida and even northward to South Carolina. Using a combination of empirical results from multiple experiments and recently compiled insights from researchers studying invasive apple snails (encapsulated as a blog: http://snailbusters.wordpress.com/), we explore three questions. First, what patterns in life history emerge for P. insularum? Second, what natural history aspects appear missing? And third, how can dissemination of new findings shape future studies? Results/Conclusions Synthesis of experiments and observations from Texas provide compelling (i.e. statistically significant) evidence that P. insularum preferentially chooses to deposit clutches on emergent plants. Snails favor plants with strong circular stems, particularly wild taro (Colocasia esculenta). Unfortunately, easy to measure clutch characteristics (e.g. length, width, depth, volume) fail to predict hatching success. Female P. insularum snails tend to oviposit clutches substantially higher on plant stems than smaller female P. canaliculata. Permanent inundation of newly laid clutches completely prevents hatching, although the impact of water stress on clutch hatching efficiency varies with stress intensity and frequency. Complimentary research also notes differences depending in clutch developmental stage. Among managers and researchers, agreement clearly exists that the egg stage represents our best chance at slowing down the invasion. Relatively few studies focus on interactions (i.e. competition, predation) with native organisms. In conclusion, because clear time-pressure exists to protect native biodiversity, rise in popularity of non-traditional formats (i.e. blogs) to speed research along and increase networking has started in the case of invasive apple snails.

Not a slow snail: Rapid rise of environmental awareness and ecological insights regarding invasive island apple snails (Pomacea insularum)

Exotic invaders routinely move faster than scientific publication processes. Lacking aerial dispersal stages, snails generally match descriptions of slow colonizers. However, reminiscent of the pace with which zebra mussels gained notoriety, a growing sense of urgency has emerged from management communities regarding established populations of exotic, invasive island apple snails (Pomacea insularum). Recently separated by mitochondrial markers as a related, yet distinct, species, P. insularum sits poised to follow along the invasive trajectory of its better known relative, the golden apple snail (P. canaliculata). Literature studies examining mechanisms that promote invasiveness suggest family history of invasion serves as a sufficient enough warning sign. Furthermore, a paucity of natural history information exists on this larger (max wet weight 166-g), more fecund (2000 eggs as average clutch size) aquatic plant consumer. Without insights into basic life history, actions within management agencies often stall. In just the past five years, multiple introductions gave rise to established reproductive populations across the entire Gulf Coast, from Texas to Florida and even northward to South Carolina. Using a combination of empirical results from multiple experiments and recently compiled insights from researchers studying invasive apple snails (encapsulated as a blog: http://snailbusters.wordpress.com/), we explore three questions. First, what patterns in life history emerge for P. insularum? Second, what natural history aspects appear missing? And third, how can dissemination of new findings shape future studies? Synthesis of experiments and observations from Texas provide compelling (i.e. statistically significant) evidence that P. insularum preferentially chooses to deposit clutches on emergent plants. Snails favor plants with strong circular stems, particularly wild taro (Colocasia esculenta). Unfortunately, easy to measure clutch characteristics (e.g. length, width, depth, volume) fail to predict hatching success. Female P. insularum snails tend to oviposit clutches substantially higher on plant stems than smaller female P. canaliculata. Permanent inundation of newly laid clutches completely prevents hatching, although the impact of water stress on clutch hatching efficiency varies with stress intensity and frequency. Complimentary research also notes differences depending in clutch developmental stage. Among managers and researchers, agreement clearly exists that the egg stage represents our best chance at slowing down the invasion. Relatively few studies focus on interactions (i.e. competition, predation) with native organisms. In conclusion, because clear time-pressure exists to protect native biodiversity, rise in popularity of non-traditional formats (i.e. blogs) to speed research along and increase networking has started in the case of invasive apple snails.

Wetland Restoration and Invasive Species: Apple snail (Pomacea insularum) Feeding on Native and Invasive Aquatic Plants

Abstract The apple snail Pomacea insularum is an aquatic invasive gastropod native to South America that has the potential to cause harm to aquatic ecosystems, wetland restoration, and agriculture. To predict the potential impact of this snail on aquatic ecosystems, we tested the feeding rate of P. insularum, under laboratory nonchoice experiments, for 3 species of invasive macrophytes and 13 species of native aquatic plants that are important for wetland restoration and health. High levels of consumption were recorded for four native species (Ceratophyllum demersum, Hymenocallis liriosme, Ruppia maritima, and Sagittaria lancifolia) and three invasive species (Colocasia esculenta, Alternanthera philoxeroides, and Eichhornia crassipes). In contrast, less than 10% of the biomass of Spartina alterniflora, Scirpus californicus, Thalia dealbata, and Typha latifolia was consumed by P. insularum over the test period. The palatability of macrophytes was negatively correlated with dry matter content, making our results generalizable to all regions where this invader may be present. Based on our results, wetland restoration in areas invaded by P. insularum should focus on emergent structural species with low palatability. Apple snails should not be considered as agents of biocontrol for invasive plants; although apple snails fed on invasive plants at a high rate, their consumption of many native species was even greater.

Distribution of heavy metal concentrations in the different soft tissues of the freshwater snail Pomacea insularum (D’Orbigny, 1839; Gastropoda), and sediments collected from polluted and unpolluted sites from Malaysia

Pomacea insularum were collected from polluted and unpolluted freshwater ecosystems in Malaysia. Besides the shells, the soft tissues were dissected and pooled into cephalic tentacle, foot, mantle, operculum, digestive tract, penial sac, lung sac, and remainder. These tissues were analyzed for the concentrations of Cu, Cd, Fe, Ni, and Zn. The present work resulted in three interesting findings. First, the concentrations of Cu, Cd, Fe, and Zn found in most of the different parts of P. insularum collected from the polluted Juru River were significantly (P < 0.05) higher than those found in the snails from the other four sites. Second, positive and significant correlation coefficients were found for sediment-lung sac for Cd, Fe, and Zn while sediment-digestive tract for Cu. These correlation results indicated that lung sacs could reflect the environmental concentrations of Cd, Fe, and Zn, while the digestive tract could do the same for Cu. Third, the different concentrations of heavy metals found in the different parts indicated different metal regulation and binding sites in these organs. The significant correlation coefficients between different tissues indicated that they might be caused by similar metal regulation and sequestration. Based on the above findings, P. insularum are a potential biomonitor of Cd, Cu, Fe, and Zn pollution in freshwater ecosystems.

Introduction, distribution, spread, and impacts of exotic freshwater gastropods in Texas

We examined the patterns of distribution, vectors of introduction, and potential ecological impacts of freshwater exotic species in Texas over the last 45 years. Currently, five species of exotic gastropods are established: channeled-type applesnail (Pomacea insularum), red-rim melania (Melanoides tuberculatus), quilted melania (Tarebia granifera), giant rams-horn snail (Marisa cornuarietis), and Chinese mysterysnail (Cipangopaludinachinensis). In contrast to the northern part of the US, where shipping appears to be the most important vector for the introduction of aquatic invasive species, aquarium and ornamental trade dominated among unintentional vectors of introduction of all freshwater exotics in Texas, resulting in different patterns of distribution, spread, and ecological impacts. The rate of spread of exotic gastropods in Texas varied from 39 waterbodies colonized over 18 years for P. insularum to only three waterbodies during last 45 years for C.chinensis. Four of five exotic gastropods were found in highly vulnerable aquifer-fed springs and rivers, which contain numerous endemic and endangered species. The fifth species, Pomacea insularum, is an agricultural pest. Potential negative ecological effects of exotic gastropods include impacts on wetlands and wetland restoration, competitive exclusion of native snails, and the introduction of exotic parasites, trematodes, which could infect fish and waterfowl, including federally protected species. Aquifer springs with stable temperature regimes are refuges for both cold and warm intolerant species.

Fecundity of the exotic applesnail,Pomacea insularum

International trade frequently moves mollusks around the globe, thereby increasing their opportunity to cause ecological and economic damage. Recent genetic studies have confirmed the identity of South American applesnails (Pomacea insularum) in the southeastern US, but limited literature exists on this species. Understanding fecundity provides direct insight into the invasive potential of mollusks. Our study documents P. insularum fecundity in Texas and offers comparisons with the closely related global invader P. canaliculata. We quantified P. insularum clutch and hatchling physical characteristics and examined field and laboratory hatching success. Clutches contained thousands of eggs (mean = 2064 eggs), and clutch size tended to increase over the reproductive season. Clutches exhibited average field and laboratory hatching efficiencies (number of hatchlings/total number of eggs) near 70 and 30%, respectively. Notably, several clutches hatched at 80% or higher in the field. Exotic P. insularum deposit more eggs/clutch than the related invader P. canaliculata, but we do not yet know how seasonal hatching efficiencies compare. However, even with a conservative estimate of 1 to 10% survival to adulthood, the average P. insularum clutch yields 14 to 144 new applesnails. The high fecundity of P. insularum translates into considerable ecological impact because adult females can contribute >1 clutch/wk over an extended growing season in the southeastern US. The need for research has increased with the emergence of P. insularum populations in the fragile Florida Everglades. We advocate life-history studies like ours to help understand the invasion potential of applesnails and other invasive mollusks.