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We have sequenced, assembled, and analyzed the nuclear and mitochondrial genomes and transcriptomes of Potamopyrgus estuarinus and Potamopyrgus kaitunuparaoa , two prosobranch snail species native to New Zealand that together span the continuum from estuary to freshwater. These two species are the closest known relatives of the freshwater species Potamopyrgus antipodarum— a model for studying the evolution of sex, host–parasite coevolution, and biological invasiveness—and thus provide key evolutionary context for understanding its unusual biology. The P. estuarinus and P. kaitunuparaoa genomes are very similar in size and overall gene content. Comparative analyses of genome content indicate that these two species harbor a near-identical set of genes involved in meiosis and sperm functions, including seven genes with meiosis-specific functions. These results are consistent with obligate sexual reproduction in these two species and provide a framework for future analyses of P. antipodarum— a species comprising both obligately sexual and obligately asexual lineages, each separately derived from a sexual ancestor. Genome-wide multigene phylogenetic analyses indicate that P. kaitunuparaoa is likely the closest relative to P. antipodarum. We nevertheless show that there has been considerable introgression between P. estuarinus and P. kaitunuparaoa. That introgression does not extend to the mitochondrial genome, which appears to serve as a barrier to hybridization between P. estuarinus and P. kaitunuparaoa. Nuclear-encoded genes whose products function in joint mitochondrial-nuclear enzyme complexes exhibit similar patterns of nonintrogression, indicating that incompatibilities between the mitochondrial and the nuclear genome may have prevented more extensive gene flow between these two species. [ABSTRACT FROM AUTHOR]

Municipal wastewater treatment plants (WWTPs) discharge micropollutants like pharmaceuticals, pesticides, personal care products or endocrine disrupting chemicals but also nutrients. Both can adversely influence the freshwater ecosystem and may finally affect the ecological conditions. Many studies focus on the potential impact of large WWTPs even if smaller ones are more common, often less efficient and discharge into small creeks or the upper reaches of rivers. As a result, the receiving waters are characterized by relatively high shares of treated wastewater. Thus, the primary objective of this study was to investigate the ecotoxicological effects of a small WWTP on freshwater amphipods and mollusks in a small creek using an active and passive monitoring approach, accompanied by laboratory experiments (LE). In vitro assays with recombinant yeasts and the microtox assay with Aliivibrio fischeri were performed in parallel to determine the endocrine potential and the baseline toxicity. The evaluation of the effects of the analysed WWTP was possible due to its shutdown during our study and the application of the same in vivo and in vitro assays before and after the shutdown. During the operation of the WWTP the discharge of treated wastewater caused significantly higher mortalities and lower reproduction of the anaylsed invertebrates in the active and passive montoring as well as in the LEs. Furthermore, the amphipod species assemblage in the creek was affected downstream of the WWTP effluent. Besides, the endocrine activity and baseline toxicity were significantly higher downstream of the effluent. After the shutdown of the WWTP, the in vitro activity levels and adverse in vivo effects in the receiving water recovered quickly with no significant differences downstream of the former WWTP effluent compared to the upstream station. Furthermore, the previously disturbed amphipod species assemblage recovered significantly with a shift in favor of Gammarus fossarum downstream of the effluent. These biological results are consistent with a marked decline by 81.5% for the detected micropollutants in the receiving creek after the shutdown which points to a prominent role of micropollutants for the observed effects. [ABSTRACT FROM AUTHOR]

Inducible defences against parasites that are only activated when needed can mitigate the cost of immune or behavioural evasion of parasites. Priming of the immune system and activation of behavioural defences can follow exposure to cues associated with imminent infection risk. In contrast, prior infection can cause immune depression or leave the host with less energy to defend itself against further infections. We investigate the priming of anti-parasite defences and the effect of prior infections in the amphipod Paracalliope fluviatilis, the second intermediate host of the trematode Coitocaecum parvum. During experimental infections, amphipods that had been primed by exposure to chemical cues (from first intermediate snail hosts infected by C. parvum) of infection risk were not better at avoiding further infection than control amphipods. All amphipods showed the same swimming behaviour, whether or not they had been primed by chemical cues from infected snails, or whether or not they were in the presence of live infective stages. In contrast, regardless of whether or not they had been exposed to control water or chemical cues from infected snails, amphipods harbouring prior infections acquired in nature were significantly more likely to acquire new parasites under controlled conditions. These results suggest that the induction of defences via external cues associated with the threat of infection do not play a role in the amphipod’s anti-parasite strategy. However, prior infections may pre-dispose a host to acquire further parasites, with consequences for the distribution of parasites among host individuals and the regulation of the host population. [ABSTRACT FROM AUTHOR]

Abstract: Harmful mutations are ubiquitous and inevitable, and the rate at which these mutations are removed from populations is a critical determinant of evolutionary fate. Closely related sexual and asexual taxa provide a particularly powerful setting to study deleterious mutation elimination because sexual reproduction should facilitate mutational clearance by reducing selective interference between sites and by allowing the production of offspring with different mutational complements than their parents. Here, we compared the rate of removal of conservative (i.e., similar biochemical properties) and radical (i.e., distinct biochemical properties) nonsynonymous mutations from mitochondrial genomes of sexual versus asexual Potamopyrgus antipodarum, a New Zealand freshwater snail characterized by coexisting and ecologically similar sexual and asexual lineages. Our analyses revealed that radical nonsynonymous mutations are cleared at higher rates than conservative changes and that sexual lineages eliminate radical changes more rapidly than asexual counterparts. These results are consistent with reduced efficacy of purifying selection in asexual lineages allowing harmful mutations to remain polymorphic longer than in sexual lineages. Together, these data illuminate some of the population‐level processes contributing to mitochondrial mutation accumulation and suggest that mutation accumulation could influence the outcome of competition between sexual and asexual lineages. [ABSTRACT FROM AUTHOR]

Background. To date, numerous studies of the impact of snail Potamopyrgus antipodarum (Gray, 1843) on invaded ecosystems have been conducted. However, the majority of such studies intended to assess changes induced in macroinvertebrate assemblages, while the possible effects of P. antipodarum on higher trophic levels have not hitherto been studied. Of particular interest from the point of view of fisheries management is the elucidation of how this invasive snail can alter the energy flow towards higher trophic levels. When abundant, P. antipodarum consumes a substantial part of the primary production, but it is poorly consumed by native fishes. Consequently, part of its assimilated energy may become locked in lower trophic levels and fail to reach higher levels directly. Therefore, invasion of this snail may decrease fish production. Materials and methods. Several years after establishment of P. antipodarum in a temperate mesotrophic Lake Dusia, we assessed: (1) changes in the biomass of littoral macroinvertebrates (proxy to secondary production), (2) assimilation of P. antipodarum by benthivorous fish (energy flow), and (3) changes in growth and catches of littoral benthivorous fish (fish production). All the analyses were based on a merger of "grey" literature and original data during the pre- and post-invasion periods. Results. There was an evident increase in the biomass of littoral macroinvertebrates, and the assemblage changed from crustacean- to gastropod-dominated due to over-domination of P. antipodarum. However, P. antipodarum did not replace the native prey of fish. Moreover, a marked decrease was recorded in littoral fish growth and catches after the invasion of P. antipodarum. Conclusion. Dense populations of P. antipodarum may reduce the channelling of primary production towards higher trophic levels and, consequently, the invasion may threaten fisheries of temperate mesotrophic lakes. [ABSTRACT FROM AUTHOR]

Predator detection and avoidance can be important factors determining the success of an introduced species. The New Zealand mud snail (Potamopyrgus antipodarum) exhibits avoidance behaviors when chemically detecting native piscine predators in New Zealand, and these behaviors appear specific to sympatric fish populations. Here we utilized three different introduced clonal populations of the New Zealand mud snail from North America, and various clones from New Zealand lakes, to examine the effect of a novel piscine predator, the blacknose dace (Rhinichthys atratulus), on behavior. Two of the introduced clones in North America are invasive (US1 and US2) while a third clone (US3) has not exhibited invasive tendencies. In a laboratory setting, we examined geotactic (vertical movement in response to gravity), photokinetic (differential speeds in response to light), and emergence behaviors of each clonal population in the presence and absence of a predator chemical cue. Geotaxis was measured by determining the vertical distance traveled in two minutes. Photokinesis was measured by quantifying the horizontal distance travelled in two minutes in light and dark conditions. Emergence time was determined by removing individuals from the water for five seconds and then replacing them in water and measuring the time to emerge from the shell. We found that the two invasive populations of the New Zealand mud snail (US1 and US2) detected and behaviorally responded to the novel predator utilizing positive photokinesis. The US1 population also showed some evidence of geotactically responding to fish odor. The introduced but likely non-invasive US3 population did not exhibit a detectable response to the odor of fish. Some evidence of photokinetic behavioral responses to the North American fish odor was also found in New Zealand native populations. Fish odor did not appear to influence the time it took for any population of snails to emerge from their shells. These results suggest that the ability to detect and respond to novel predators may be an important trait in the invasion success of New Zealand mud snails by potentially allowing snails to avoid novel predato. [ABSTRACT FROM AUTHOR]

The globally successful invasive snail, Potamopyrgus antipodarum (Tateidae), is rarely parasitized except in its native New Zealand where it is infected as first intermediate host by at least 20 species of trematode parasitic castrators. In France and Poland, only one trematode parasitic castrator, belonging to the Aporocotylidae (the blood flukes of fishes), is known to infect P. antipodarum, and its origin remains a mystery. We investigated the genetic identities, taxonomic relationships, and prevalences of this parasite and other aporocotylids infecting P. antipodarum and closely related snails in a French stream, and throughout New Zealand and southeast Australia. ITS2 DNA sequences of the French parasite matched with Aporocotylid sp. I (sensu Hechinger, 2012) from P. antipodarum in New Zealand. Hence, the aporocotylid parasite in Europe most likely originated from the native range of the introduced host. Aporocotylid sp. I was rare in both native and invasive ranges, infecting overall less than 1 out of 1,000 snails. The parasite and its host have a persistent relationship in France, as they both were repeatedly encountered over a period of 14 years. Our molecular phylogeny also reveals that this parasite is part of a diverse and poorly known group of aporocotylids in New Zealand and southeastern Australia. [ABSTRACT FROM AUTHOR]

Aquatic insects that oviposit on rocks may evolve strategies to mitigate loss of eggs to opportunistic predation by common native grazers, but such strategies may be ineffective against non-native grazers. We tested whether the eggs of common New Zealand caddisfly families (Hydrobiosidae and Hydropsychidae) that oviposit on rocks were more susceptible to predation by native or non-native snails. The native snailPotamopyrgus antipodarum(Grey, 1843) and non-native snailsPhysa acutaDraparnaud, 1805 andPseudosuccinea columella(Say, 1817) were presented with caddisfly egg masses and the number of individual eggs consumed was recorded after 24 and 48 hours. The largerPseudosuccineareadily consumed the eggs, especially spumaline-encapsulated Hydrobiosidae eggs.Physaconsumed very few Hydrobiosidae eggs and no Hydropsychidae eggs, whereasPotamopyrgusdid not consume eggs of either family. The trichopteran egg masses tested did not succumb to predation by the nativePotamopyrgusbut are highly vulnerable to predation by a larger non-native snail. [ABSTRACT FROM AUTHOR]

Conventional acute tests are not suited to assess the effects of toxicants, because they do not use the concentrations that are usually found in natural ecosystems. By contrast, nonlethal realistic concentrations may cause deleterious effects on animal fitness as a consequence of behaviour impairment. Behaviour is a good integrative variable of complex biochemical and physiological processes. Therefore, bioassays based on behaviour are a useful tool in ecotoxicology. In this study, two bioassays were conducted: (1) acute bioassay (48 h) of acetone on the aquatic snail Potamopyrgus antipodarum, and (2) video-recording behavioural bioassay with pulse exposures to acetone to assess its effects on feeding behaviour. In the latter, animals were exposed to three pulses of acetone (24 h each) with 6 days of postexposure after each pulse. This design allowed us to assess the degree of feeding behaviour recovery after exposure and the effects of repeated pulses. Our results show that postexposure periods have an important effect on the recovery of normal feeding behaviour and that this developed bioassay is an ecotoxicological tool with a relatively low-cost and a short-time consuming. The application of this new tool to different ecotoxicological requirements is discussed. [ABSTRACT FROM AUTHOR]

Most freshwater ecosystems are subject to multiple anthropogenic stressors, which commonly reduce biodiversity across all levels. Existing freshwater bioassessment programmes aim at identifying responses of aquatic biota to stressors. For practical reasons, higher-level taxonomic groups (e.g. genus or family) are often used in these programmes. This approach, however, may bias assessment results as different species can differ substantially in their biological traits, thus emphasising the need for species-level data. DNA barcoding can reliably generate species-level data for animals by sequencing a fragment of the mitochondrial cytochrome c oxidase subunit I gene ( COI ). This allows investigating species-specific responses to environmental stressors. In this study, we sampled 43 stream sites in southern New Zealand spanning wide gradients of agricultural stressors (fine sediment and nutrient levels). We first used conventional morphological assessment to determine stream invertebrate responses to the stressors, focusing on two important indicator taxa, the mayfly Deleatidium and the snail Potamopyrgus . We then tested for the presence of cryptic species in Deleatidium and Potamopyrgus using DNA barcoding of the COI gene for 520 and 305 specimens, respectively. While all Potamopyrgus specimens belonged to a single species, Deleatidium consisted of 12 distinct molecularly identified clades that likely represent distinct species. Finally, we compared stressor responses assessed at genus and species level. While overall Deleatidium abundance was unrelated to stressor levels, some of the individual clades differed clearly in the magnitude and direction of their responses to nutrient and sediment stress. While the most abundant cryptic Deleatidium clade (clade 1) showed no relationship to sediment or nutrient levels, clades 2 and 3 responded negatively to nutrient or sediment increases, respectively. These contrasting patterns indicate that individual freshwater invertebrate species, often merged to a higher taxonomic level for biomonitoring purposes, can differ substantially in their tolerance to stressors and respond in more complex ways than observed at genus level. Overall, our results highlight the considerable potential and importance of including DNA barcoding into freshwater ecosystem assessment and biomonitoring programmes. [ABSTRACT FROM AUTHOR]

The prosobranch gastropod Potamopyrgus antipodarum (Gray, 1843) is poorly understood as a parasite host outside its native New Zealand, including in Europe. Our aim was to ascertain whether non-native P. antipodarum could acquire aspidogastrids or digeneans in habitats where these parasites are found in native hosts. We examined 2400 P. antipodarum individuals from Sosno Lake (Poland). The majority of snails were adult females. No males were found. We found five P. antipodarum individuals with Aspidogaster conchicola and 39 snails with metacercariae of Echinoparyphium aconiatum Dietz 1909 or E. recurvatum (Linstow, 1873). Snails with metacercariae and unparasitized snails, but not snails with A. conchicola , produced embryos. Ours is the first record of an Aspidogastrea – P. antipodarum association. [ABSTRACT FROM AUTHOR]

Abstract: This study highlights the usefulness of gastropods for water quality monitoring. Gastropods were caged upstream and downstream of an effluent discharge. Exposure was assessed by measurement of organic contaminants in water. Contamination of the Potamopyrgus antipodarum mudsnail was also measured using innovative techniques at the end of the 42 days of exposure. Biological effects were measured at the individual level (growth, reproduction) and subindividual level (energy reserves, vitellin-like proteins, steroid levels, expression of genes involved in estrogen signaling pathways), thus providing a better understanding of reprotoxic effects. The effluent was mainly contaminated by pharmaceutical compounds, as was the mudsnail. The highest concentrations were measured for oxazepam and were higher than 2 mg/kg downstream of the effluent discharge. Alkylphenols, bisphenol A, and vertebrate-like sex-steroid hormones were also bioaccumulated by the mudsnail downstream of the effluent. The combined use of water and snail contamination provided a complete exposure assessment. Exposure was further linked to biological effects. The mudsnail was shown to be a better adapted species for in situ exposures than Valvata piscinalis. Reproduction was sharply decreased after 6 weeks of exposure in the mudsnail. Feeding issues were excluded, confirming the toxic origin. These effects were related to estrogen signaling pathways using genomic analysis. Genes coding for proteins involved in nongenomic signaling pathways were inhibited, and those of genomic pathway repressors were induced. These results suggest that the chemical contamination due to the effluent discharge altered steroid control of reproduction and blocked the transition between oocyte and unshelled embryo, resulting in a drastic decrease of embryo production, while survival was not affected. [Copyright &y& Elsevier]

Invertebrate drift is a fundamental process in streams and rivers. Studies from laboratory experiments and small streams have identified numerous extrinsic (e.g. discharge, light intensity, water quality) and intrinsic factors (invertebrate life stage, benthic density, behaviour) that govern invertebrate drift concentrations (# m−3), but the factors that govern invertebrate drift in larger rivers remain poorly understood. For example, while large increases or decreases in discharge can lead to large increases in invertebrate drift, the role of smaller, incremental changes in discharge is poorly described. In addition, while we might expect invertebrate drift concentrations to be proportional to benthic densities (# m−2), the benthic-drift relation has not been rigorously evaluated., Here, we develop a framework for modelling invertebrate drift that is derived from sediment transport studies. We use this framework to guide the analysis of high-resolution data sets of benthic density and drift concentration for four important invertebrate taxa from the Colorado River downstream of Glen Canyon Dam (mean daily discharge 325 m3 s−1) that were collected over 18 months and include multiple observations within days. Ramping of regulated flows on this river segment provides an experimental treatment that is repeated daily and allowed us to describe the functional relations between invertebrate drift and two primary controls, discharge and benthic densities., Twofold daily variation in discharge resulted in a >10-fold increase in drift concentrations of benthic invertebrates associated with pools and detritus (i.e. Gammarus lacustris and Potamopyrgus antipodarum). In contrast, drift concentrations of sessile blackfly larvae ( Simuliium arcticum), which are associated with high-velocity cobble microhabitats, decreased by over 80% as discharge doubled. Drift concentrations of Chironomidae increased proportional to discharge., Drift of all four taxa was positively related to benthic density. Drift concentrations of Gammarus, Potamopyrgus and Chironomidae were proportional to benthic density. Drift concentrations of Simulium were positively related to benthic density, but the benthic-drift relation was less than proportional (i.e. a doubling of benthic density only led to a 40% increase in drift concentrations)., Our study demonstrates that invertebrate drift concentrations in the Colorado River are jointly controlled by discharge and benthic densities, but these controls operate at different timescales. Twofold daily variation in discharge associated with hydropeaking was the primary control on within-day variation in invertebrate drift concentrations. In contrast, benthic density, which varied 10- to 1000-fold among sampling dates, depending on the taxa, was the primary control on invertebrate drift concentrations over longer timescales (weeks to months). [ABSTRACT FROM AUTHOR]

Potamopyrgus antipodarum from 13 locations in central and western Japan were investigated for mitochondrial DNA haplotypes. Two haplotypes (JA and JB) were found based on an analysis of a 343-bp sequence of the cytochrome c oxidase subunit I gene. The JB type comprised two subhaplotypes (JB-I and JB-II), which were distinguishable by an additional sequence of 289 bp. Eleven populations were likely monomorphic in the mtDNA haplotype, while two populations, which were supposed to have been established recently, were polymorphic, encompassing JA and JB haplotypes. This result suggests that different haplotypes invaded Japan via different routes and that polymorphic populations were formed by colonization from more than one source population. [ABSTRACT FROM AUTHOR]

One of the main objectives of ecological risk assessment is to evaluate the effects of toxicants on ecologically relevant biological systems such as populations or communities. However, the effects of toxicants are commonly measured on selected subindividual or individual endpoints due to their specificity against chemical stressors. Introducing these effects into population models is a promising way to predict impacts on populations. The models currently employed are very simplistic, and their environmental relevance needs to be improved to establish the ecological relevance of hazard assessment. The present study with the gastropod Potamopyrgus antipodarum combines a field experimental approach with a modeling framework. It clarifies the role played by seasonal variability of life-history traits in the population's vulnerability to the alteration of individual performance, potentially due to toxic stress. The present study comprised 3 steps: 1) characterization of the seasonal variability in life-history traits of a local population over 1 yr by using in situ experiments on caged snails, coupled with a demographic follow-up; 2) development of a periodic matrix population model that visualizes the monthly variability of population dynamics; and 3) simulation of the demographic consequences of an alteration in life-history traits (i.e., fertility, juvenile, and adult survival). The results revealed that demographic impacts strongly depend on the season when alterations of individual performance occur. Model analysis showed that this seasonal variability in population vulnerability is strongly related to the phenology of the population. The authors emphasize that improving the realism of population models is a major objective for ecological risk assessment, and that taking into account species phenology in modeling approaches should be a priority. Environ Toxicol Chem 2013;32:1727-1736. © 2013 SETAC [ABSTRACT FROM AUTHOR]

Spreading throughout a new ecosystem is the last step of an exotic species to become invasive. In the case of invasive aquatic molluscs, tolerance to air exposure is one of the main mechanisms allowing overland translocation and spreading. he mudsnail Potamopyrgus antipodarum (Hydrobiidae, Mollusca) is native to New Zealand but it has spread worldwide, invading ecosystems in Europe, Australia, America and Asia. he aim of our study is to assess mudsnail tolerance to air exposure, which may contribute to the successful overland translocation of this species. We conducted a laboratory experiment with four levels of air exposure (9, 18, 24 and 36 hours in a controlled climatic chamber). Snails were placed for 60 seconds in a laboratory paper filter to remove surface snail water. Then they were placed back in empty vessels during the four periods of air exposure, except the control group, which was immediately returned to water. At the end of each period of air exposure all vessels were filled with water and the cumulative mortality was monitored after 24, 96, 168 and 264 hours of rehydration. The calculated Lethal Times (i.e. the time of air exposure (in hours) necessary to cause the death of 50% (LT50) or 99% (LT99) of the population) and their 95% confidence limits at 24, 96, 168 and 264 hours were 28.1 (25.2-31.9), 26.9 (24.2-30.1), 25.9 (23.4-28.9) and 25.9 (23.4-28.9) hours, respectively for LT50, and 49.6 (42.7-63.3), 45.6 (39.9-56.5), 43.2 (38.0-53.0) and 43.2 (38.0-53.0) hours, respectively for LT99. Therefore an air exposure time over 43 hours caused the death of all studied individuals during all monitoring periods. Extending the monitoring period beyond 24 hours did not significantly change lethal times. Therefore, we recommend exposing fishing tools or boats at open air during at least 53 hours as a low cost measure to control mudsnail spread in early stages of invasion. [ABSTRACT FROM AUTHOR]

Biological invasions represent a relevant ecological and economic problem of our globalized world. While a few species have been classified as invasive due to their ecological and economic impacts on the invaded ecosystems (e.g., zebra mussel), others show contrasting invasive potential, depending on the invaded ecosystem and/or the traits of the exotic species. This paper reviews the worldwide distribution, ecological impacts and the reasons that explain the invasive success of the aquatic mud snail Potamopyrgus antipodarum Gray (Hydrobiidae, Mollusca), which is native to New Zealand. This review shows that most studies on P. antipodarum distribution have been conducted in Europe, North America and Australia, and few studies in Asia. The distribution of this snail is still unknown in other parts of the world (e.g., Africa, South and Central America). The range of invaded aquatic ecosystems varies from fresh to salt water and from lentic to lotic ecosystems. The ecological impact of this species is due to the fast population growth rate and to the extremely high densities that it can reach, leading to altered C and N cycles in invaded ecosystems. However, at low densities mud snails have been shown to enhance secondary production. Additionally, P. antipodarum has been found to overcome the negative effects of predators and parasites (e.g., it survives the pass through the digestive tracts of fish). This review contributes to assess the magnitude and ecological risk of P. antipodarum invasion throughout the world. [ABSTRACT FROM AUTHOR]

We used a non-destructive method to identify important definitive host species in the complex life cycles for two groups of digenetic trematodes (Microphallus sp. and Notocotylus spp.). Specifically, we exposed experimental populations of the intermediate snail host Potamopyrgus antipodarum to faeces collected from New Zealand waterfowl. We found that most infections were produced when the snails were exposed to faeces from Mallard (Anas platyrhynchos), Grey Duck (A. superciliosa), Mallard-Grey duck hybrids, or New Zealand Scaup (Aythya novaeseelandiae). In addition, the parasite communities clustered into three distinct groups in multivariate space: (1) control populations and snail populations that were exposed to faeces collected from Paradise Shelduck Tadoma varigata and Black Swan (Cygnus atratus), (2) snail populations that developed mostly Microphallus sp. infections and that were exposed to scaup, Mallard, or Grey Duck faeces, and (3) snail populations exposed to scaup faeces, which developed mostly Notocotylus spp. infections. These results suggest that Mallard, Grey Duck, and scaup are functionally relevant to the life cycles of both Microphallus sp. and Notocotylus spp. [ABSTRACT FROM AUTHOR]

In situ experiments are an important tool within ecotoxicological research but there is a lack of suitable methodologies especially for freshwater invertebrate species. Within this study, a novel in situ methodology with Potamopyrgus antipodarum was developed. Snails were inserted into cages, made of Plexiglas measuring 7×9×7cm3 and fixed with stainless steel pins into the sediment at the relevant sampling sites. During the experiment physico-chemical properties of the water and concentrations of metals, PAHs and PCBs were measured in the sediment. The growth and survival of the snails was not affected, but the reproduction increased significantly at one of the most polluted sites. The increase in reproduction was neither correlated with physico-chemical parameters, nor with the concentrations of the different compounds, but maybe related to certain groups of estrogenic compounds. The study demonstrates the excellent applicability of this novel in situ test. [Copyright &y& Elsevier]

The New Zealand mud snail (NZMS) Potamopyrgus antipodarum, a normative species recently introduced into North America, has been shown to negatively influence ecosystem function. Methods to careful or eliminate NZMS are needed. Twenty four-hour treatments with 2 mg of potassium permanganate (KMnO4) per liter of water were evaluated against NZMS held for 24 h in artificial stream sections that contained refuge areas. The snails did not seek refuge when placed into an area that contained KmnO4 and also had neutral preference when provided the opportunity to select between artificial stream sections with and without KMnO4. In a separate series of experiments, NZMS and rainbow trout Oncorhynchus mykiss were placed into hatchery raceway sections that were treated with a 2 mg/L KMnO4 solution for 2 h/d over a period of 14 consecutive days. Mortality of NZMS and rainbow trout was not elevated in these raceways relative to nontreated control raceways. There was evidence, however, that the presence of the KMnO4 depressed fish growth (i.e., Fulton's condition factor). The KMnO4 treatment did not cause significant gill damage in rainbow trout. Our results show that KMnO4 at 2 mg/L is not effective in controlling or eliminating NZMS populations. [ABSTRACT FROM AUTHOR]

We used microsatellites to assess genetic diversity and spatial structuring of the invasive apomictic New Zealand mudsnail ( Potamopyrgus antipodarum) in the initial focal area of its recent North American invasion, a portion of the upper Snake River basin (Idaho) that is segmented by a series of hydropower dams. Thirty-four samples (812 total snails) from a 368 km reach of this drainage were genotyped for six loci. Sixty-five distinct clones were detected and grouped into four divergent clusters based on chord distances. Genetic structuring of populations was generally low. Our results indicate that the founding population(s) of this invasion was composed of a small number of putative clonal lineages which spread rapidly within this fragmented watershed owing to the enhanced dispersal ability of these parthenogens. The substantial genetic variation documented in this study suggests that caution should be used in the application of biological control measures for this pest species. [ABSTRACT FROM AUTHOR]

Outside its native range, the invasive New Zealand mud snail (NZMS), Potamopyrgus antipodarum, is rarely reported to harbor parasites. To test this observation, 7 sites along the Snake River and Polecat Creek in the Grand Teton National Park/John D Rockefeller Memorial Parkway area (Wyoming) were surveyed for native aquatic snails, NZMS, and associated digenean trematodes, in July 2005. At 6 sites, native snails harbored patent digenean infections; within 2 hr, ≤10% of lymnaeid snails shed furcocercariae or xiphidiocercariae, and ≤42% of physid snails released furcocercariae or echinostome cercariae. Partial 18S rDNA sequences were recovered from several furcocercariae. Potamopyrgus antipodarum was present at, and collected from, 5 sites. Polymerase chain reaction assays targeting digenean rDNA sequences in DNA extracted from pools of 150 NZMS snails did not detect parasites. The examination of 960 NZMS by overnight shedding yielded 1 occurrence of (surface-encysted) metacercariae of an unclassified notocotylid (based on 18S and 28S rDNA sequences). The dissection of 150 ethanol-fixed NZMS (30/site) revealed 2 types of digenean metacercariae encysted in tissues of 5 snails from Polecat Creek. Thus, invasive NZMS may serve as first and second intermediate host for digenean parasites. [ABSTRACT FROM AUTHOR]

The article presents a study on how sediment size and current velocity affect epi- and endobenthic spatial variability of the hydrobiid snail, Potamopyrgus antipodarum, in New Zealand's South Island. The species' densities were lowest on gravel and highest on cobbles, and that densities on stones and sand were comparable, based on a multi-stream survey conducted. A colonization experiment revealed that more P. antipodarum use subsurface sediments than surface sediments, and that frequency of subsurface may be habitat-mediated. The results suggest that the large portion of snails occupying sediment subsurfaces must be accounted for in an accurate population census.

Granular activated carbon (GAC) adsorbers are often the penultimate stage of surface water treatment and provide ideal habitats for invertebrates. Proliferation of chlorine-resistant invertebrates in GAC adsorbers may lead to their efflux into distribution systems, possibly resulting in contamination of customers’ tap water. GAC adsorber sampling and laboratory experiments were undertaken to determine the effects of routine backwashing on GAC adsorber populations of the chlorine-resistant snail Potamopyrgus jenkinsi at a water treatment works. GAC adsorber sampling results suggested that routine backwashing altered the spatial distribution of snails, but not their overall abundance. In small-scale glass columns 40–50% of the smallest (0.3–0.6mm shell height) juvenile snails were removed by a GAC backwash bed expansion of 30–40%; however, bed expansions of greater than 20% were not possible in the GAC adsorbers. [Copyright &y& Elsevier]

The article presents a study that forecasts the potential distribution of Potamopyrgus antipodarum, an invasive freshwater New Zealand mudsnail, in Australia and North America using the ecological niche modeling program Genetic Algorithm for Rule-set Production (GARP). Under the study, the strength of predictions made by study models built with data from the snail's native range in New Zealand, and models built with data obtained from Australia and North America were compared to make better predictions about the species' potential distribution. The findings show a large expansion in the range of P. antipodarum in both locations invaded by the species.

Introduced species provide an opportunity to examine responses to novel ecological conditions, in particular to the absence of co-evolved enemies. Introduced populations could evolve lower investment in resistance or could down-regulate their immune system as a plastic response to enemy absence. The response might have consequences for the success of introduced species. Assuming a trade-off between resistance and traits related to demographic success, an evolved change or reallocation from resistance could increase the chances of invasions. On the other hand, introduced populations could have increased resistance as a correlate of greater vigour and competitive ability among successful invaders [Sampling Bias hypothesis (SBH)]. These hypotheses make different predictions about investment in resistance in introduced populations. Using a New Zealand clonal snail ( Potamopyrgus antipodarum), we examined the resistance of three introduced genotypes (one from the US and two from Europe) to several populations of a native range parasite ( Microphallus sp.). One genotype (Euro A) was resistant to all native range parasite populations, consistent with the SBH. However, two remaining genotypes (Euro C and US 1) were less susceptible to parasite populations that were allopatric to their source populations. Furthermore, resistance of one genotype (US 1) collected from the introduced range was indistinguishable from its resistance when collected from the range of the parasite. Hence, there was no evidence for decreased resistance in the absence of native enemies, which is inconsistent with hypotheses that envision reduced allocation to resistance or a trade-off between competitive ability and resistance. [ABSTRACT FROM AUTHOR]

The article examines the dominance of invertebrate secondary production of invasive New Zealand mudsnails in Gibbon River, Firehole River, and Polecat Creek in the Greater Yellowstone Area in Wyoming. The researchers measured the secondary production of mudsnails and native invertebrates to determine what specie has high degree of dominance and invasiveness in the vicinity of the three mentioned rivers. Mudsnail production was approximated by measuring in situ growth rate and multiplying by monthly biomass, while native invertebrate was estimated using instantaneous growth and size frequency methods. Their findings revealed that mudsnails were more productive than the native specie. They suggested that mudsnail invasion altered food web function within the habitat.

Stimuli associated with copulatory behavior are often needed to maximize reproductive output in internally fertilized sexual taxa. Although non-pseudogamous parthenogenetic females have no need for sperm, parthenogens descended from sexual ancestors may still require copulatory stimuli to reach their full reproductive potential. Retention of physiological dependence on copulation in parthenogens could facilitate the maintenance of sexual reproduction in species where sexual and parthenogenetic individuals coexist if parthenogens do not receive enough copulatory stimuli to achieve maximal daughter production. A laboratory experiment was conducted to determine whether embryo production in parthenogenetic female snails ( Potamopyrgus antipodarum) is dependent on male presence. Rather than male presence, this experiment showed that embryo production is affected by the number of coexisting parthenogens. Specifically, parthenogens housed with fewer other parthenogens produced significantly more embryos than parthenogens housed with a greater number of other parthenogens, regardless of male presence and total population size. This result indicates that copulatory dependence is not likely to contribute to the maintenance of sex in P. antipodarum. Instead, it demonstrates that females of P. antipodarum negatively affect each other's reproduction, and suggests that females of P. antipodarum may exert a larger competitive influence than males of P. antipodarum. Moreover, this finding raises the possibility that highly parthenogenetic and consequently female-dense populations of P. antipodarum may experience decreased reproductive output when population size is large and resources are limiting. [ABSTRACT FROM AUTHOR]

Patch selection for cobbles covered by different food types, with and without deposited sediment, by two common New Zealand stream invertebrates, the snail Potamopyrgus antipodarum (Hydrobiidae) and the mayfly Deleatidium sp. (Leptophlebiidae), was quantified. Each taxa was exposed to cobbles covered by (1) filamentous green algae (FGA) or diatoms, and (2) diatoms or heterotrophic biofilms. Two cobbles of each food type were used in each trial, one of which was contaminated by deposited sediment. All cobbles were embedded in plaster in small basins to prevent animals hiding under them, and a known number of animals placed into each basin. The location of each animal was recorded over time, with some observations being made during darkness to see whether this influenced animal movement. More Potamopyrgus were found on cobbles covered by FGA than cobbles covered by diatoms. Sediment-contaminated cobbles covered with FGA also supported more snails than uncontaminated cobbles covered with diatoms. More Potamopyrgus were found on cobbles covered by diatoms than biofilms, and sediment reduced their preference for both these foods. More Deleatidium nymphs were found on diatom-covered cobbles than FGA-covered cobbles. Sediment reduced the preference of Deleatidium for diatoms, but more animals were found on cobbles with sediment-contaminated diatoms than uncontaminated FGA. Patch selection was similar between cobbles covered by either diatoms or biofilms, but sediment reduced the preference of both these foods to Deleatidium. More Deleatidium were recorded on bare plaster during darkness, suggesting they were more mobile at night and searching for new habitats. These results help explain the common occurrence of Potamopyrgus in streams draining developed catchments where FGA blooms and deposited sediment are common, and of Deleatidium in streams draining less developed catchments where FGA and deposited sediment are uncommon. [ABSTRACT FROM AUTHOR]

Although parental care occurs in most phyla encompassing a wide array of forms, little is known about its evolution in invertebrates. Two types of egg capsules have been known among ovoviviparous New Zealand hydrobiid gastropods, elastic capsules and simple membranes. Based on a phylogenetic analysis using two mtDNA sequence fragments, I asked whether the second state was derived from the first or whether brooding had multiple origins. The evolution of ovoviviparity was also investigated in the context of habitat transition between brackish and freshwater. Maximum parsimony and Markov chain models of character state transformations in a maximum likelihood framework suggested that hydrobiids have invaded freshwater three times independently. Two of these invasions were followed by the evolution of ovoviviparity, probably in adaptation to changing water levels during periods of irregular precipitation. The syntopy of two congeneric species, one oviparous and the other one brooding, indicated that the transition between reproductive modes must have occurred rapidly. [ABSTRACT FROM AUTHOR]

The small aquatic snail Potamopyrgus antipodarum is an important invading species in Europe, Australia and North America. European populations are generally believed to derive from accidental introductions from New Zealand, probably dating back to the mid-19th century. We have employed mitochondrial DNA sequences to test the proposed New Zealand origin of European Potamopyrgus, and to learn more about its genealogical history. Using a 481-bp region of the 16S ribosomal RNA gene, we identified 17 distinct haplotypes among 65 snails from New Zealand. In marked contrast, only two haplotypes were found across all European samples, which cover a large geographical area. Importantly, these two haplotypes are shared with snails from the North Island of New Zealand. Due to sampling limitations we cannot rule out a South Island origin for one of the haplotypes, but our results clearly demonstrate the New Zealand origin of European populations. The marked divergence among the two European haplotypes implies the successful colonization by two distinct mitochondrial lineages, which is consistent with previous data based on nuclear markers. [ABSTRACT FROM AUTHOR]

SUMMARY 1. Disturbance and anthropogenic land use changes are usually considered to be key factors facilitating biological invasions. However, specific comparisons of invasion success between sites affected to different degrees by these factors are rare. 2. In this study we related the large-scale distribution of the invading New Zealand mud snail (Potamopyrgus antipodarum ) in southern Victorian streams, Australia, to anthropogenic land use, flow variability, water quality and distance from the site to the sea along the stream channel. 3. The presence of P. antipodarum was positively related to an index of flow-driven disturbance, the coefficient of variability of mean daily flows for the year prior to the study. 4. Furthermore, we found that the invader was more likely to occur at sites with multiple land uses in the catchment, in the forms of grazing, forestry and anthropogenic developments (e.g. towns and dams), compared with sites with low-impact activities in the catchment. However, this relationship was confounded by a higher likelihood of finding this snail in lowland sites close to the sea. 5. We conclude that P. antipodarum could potentially be found worldwide at sites with similar ecological characteristics. We hypothesise that its success as an invader may be related to an ability to quickly re-colonise denuded areas and that population abundances may respond to increased food resources. Disturbances could facilitate this invader by creating spaces for colonisation (e.g. a possible consequence of floods) or changing resource levels (e.g. increased nutrient levels in streams with intense human land use in their catchments). [ABSTRACT FROM AUTHOR]

The structure of gastropod communities was examined from January to June 1999 in four sites of the streams of Mont Saint-Michel Bay along a gradient of salinity, and the occurrence of larval trematodes infecting snails was studied. Abundance and species richness of gastropods increased from polyhaline (95 snails, 1 species) to oligohaline waters (6672 snails, 6 species). Whatever the salinity, the most abundant species was Potamopyrgus antipodarum, an invasive non-indigenous species that represented 80% of the gastropods. Only one male was found in P. antipodarum populations suggesting a predominantly parthenogenetic mode of reproduction. Among 7218 gastropods collected, 1.2% were infected by larval trematodes: 5 species in Lymnaea peregra (4.4%), 4 species in Planorbis planorbis (12.0%), one echinostome in Physa acuta (0.2%), and a new species of Sanguinicola in P. antipodarum (0.5%). This is the first record of infected P. antipodarum in Europe. No parasites were found in polyhaline waters. The prevalence per host population varied from 0 to 100% depending on time of collection, salinity and host species. In the lowest-salinity site, abundance of gastropods and prevalence of trematodes were negatively correlated. The dominance of P. antipodarum in the gastropod communities is discussed in relation with euryhalinity, parthenogenesis and weak rate of parasitism. [ABSTRACT FROM AUTHOR]

The lethal responses of three European clones—A, B, and C—of the prosobranch snail Potamopyrgus antipodarum to acute cadmium exposure were examined by the use of a conventional LC50 test and a delayed toxicity test. The questions addressed were: (1) Are there differences in susceptibility (LC50 values and uniformity of response) among the three European clones of P. antipodarum? (2) Are the patterns of differences in susceptibility among clones observed in the LC50 test also observed for the delayed toxicity test? (3) Is there concordance in the ranking of susceptibility among clones under acute cadmium exposure and under chronic cadmium exposure? The results showed that the widths of the tolerance distribution differed among clones. Clones A and B had a steeper slope than clone C (for clone A the difference was marginally significant), which indicates that individuals from clones A and B showed a more uniform response to acute lethal cadmium stress than individuals from clone C. On the basis of the measured differences in LC50 values, clone A individuals showed the highest tolerance to acute cadmium (LC50 value: 1.92 mg Cd L-1) followed by clone B (LC50 value: 1.29 mg Cd L-1) and clone C (LC50 value: 0.56 mg Cd L-1). Clone C was significantly less tolerant than clones A and B. The delayed toxicity test showed a similar pattern to the LC50 test with regard to tolerance differences among clones; however, mortality continued following transfer to clean water, indicating that cadmium was lethal at much lower concentrations than indicated by the conventional LC50 test. Results of the LC50 test and the delayed toxicity test in the present study were in general agreement with results from chronic cadmium exposure experiments (Jensen et al.[2000]Ecol Appl[submitted]), i.e., the least susceptible clone A in the acute cadmium exposure test was also the least susceptible clone in the chronic cadmium exposure test. Based on the dramatic differences between the LC50 and the cadmium exposure concentrations causing delayed toxicity, we suggest that the potential for delayed toxicity should be given greater consideration in ecotoxicity testing. [ABSTRACT FROM AUTHOR]

The level of host exploitation is expected, under theory, to be selected to maximise (subject to constraints) the lifetime reproductive success of the parasite. Here we studied the effect of two castrating trematode species on their intermediate snail host, Potamopyrgus antipodarum. One of the trematode species, Microphallus sp., encysts in the snail host and the encysted larvae “hatch” following ingestion of infected snails by birds. The other species, Notocotylus gippyensis, by contrast, releases swimming larvae; ingestion of the snail host is not required for, and does not aid, transmission to the final host. We isolated field-collected snails for 3 months in the laboratory, and followed the survival of infected and uninfected snails under two conditions: not fed and fed ad libitum. Mortality of the infected hosts was higher than mortality of the uninfected ones, but the response to starvation treatment was parasite species specific. N. gippyensis induced significantly higher mortality in starved snails than did Microphallus. Based on these results, we suggest that host exploitation by different species of trematodes may depend on the type of transmission. Encysting in the snail host may select for a reduced rate of host exploitation so as to increase the probability of transmission to the final host. [ABSTRACT FROM AUTHOR]

1. Females of the rare lagoonal mudsnail Hydrobia neglecta respond to increasing population density by a lowered output of eggs. The effect is even more marked when the widespread and abundant congener H. ulvae comprises part of a joint population. Thus, increasing the density by 50% from 18 000 H. neglecta per square metre decreases egg production by 30%, but when H. ulvae comprises 33% of the higher mudsnail density the decrease is 63%. 2. Mortality of both male and female H. neglecta is also greater in the presence of H. ulvae than in its absence, whilst mortality of H. ulvae in mixed populations is minor. 3. Since an allopatric female H. neglecta produces only 11–14 eggs during her expected reproductive lifetime, such a reduction of fecundity in the presence of moderate numbers of H. ulvae could prove disastrous for populations of H. neglecta closed to intraspecific immigration but open to invasion by H. ulvae. Such is the position in several areas, including the semi-isolated, landlocked lagoons that are the habitat of H. neglecta outside the Baltic Sea. 4. This probably partly explains why H. ulvae and H. neglecta are rarely sympatric in such lagoons, and why H. neglecta is only common in Britain where H. ulvae is absent from the adjacent intertidal zone and unable to be washed into lagoons by overtopping. This has important repercussions on attempts to conserve this rare hydrobiid, and probably on other rare and legally-protected lagoonal species. © 1998 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The toxicity and environmental risk of chemicals, such as the antiepileptic drug carbamazepine (CBZ), is commonly assessed using standardized laboratory tests and laboratory-to-field extrapolation. To investigate the toxicity of CBZ to aquatic key organisms in a more complex and environmentally relevant scenario, we conducted a 32-day multiple-stress experiment in artificial indoor streams. We exposed the non-biting midge Chironomus riparius , the blackworm Lumbriculus variegatus , and the New Zealand mud snail Potamopyrgus antipodarum to 80 and 400 μg CBZ/L in six artificial indoor streams. In addition to hydraulic stress, species' interaction, and low organic content in the sediment, organisms were co-exposed to the herbicide terbutryn (TBY) as a second chemical stressor at a concentration of 6 μg/L. The exposure to CBZ under multiple stress conditions resulted in a 10- to more than 25-fold higher toxicity in C. riparius and P. antipodarum when compared to a previous, standardized laboratory experiment. The co-exposure to TBY enhanced the adverse effects of CBZ on snails (reduced production of embryos). This effect was additive as the single exposure to TBY also reduced the reproduction of snails, most likely through the reduction of biofilm biomass. The emergence of C. riparius declined at a CBZ concentration of 400 μg/L (without the co-exposure to TBY) and at 80 μg/L in combination with TBY. The difference in sensitivity between laboratory and indoor stream experiments is indicative of a potential underestimation of risk when toxicity data are extrapolated to field conditions. The present results suggest the inclusion of non-chemical and chemical stressors in environmental hazard and risk assessments. • Multiple-stressor experiment in artificial indoor streams. • Higher toxicity of carbamazepine compared to the laboratory. • Reduced biofilm biomass caused by carbamazepine and terbutryn exposure. • Protective hazard assessments should address multiple-stressor effects. [ABSTRACT FROM AUTHOR]