Snail Size Research Articles

Density and Distribution Pattern of Lola Snail (Trocus niloticus) in the Coastal Waters of Malaku Village, Central Maluku

The lola snail (Trochus niloticus) is a species of sea snail that has important economic value. This research aims to determine the density and distribution patterns of lola snails in the coastal waters of Malaku Village, Central Maluku. Sampling used a stratified random sampling method with line transects, the research location was divided into 3 stations. Stations I and III have plank coral substrates and dead coral fragments, while station II has rocky substrates and coral flats. The results of the research found that the total number of lola snail individuals found at the research location was 110 individuals spread across 3 research stations. The maximum size of lola snails found was 99.41 mm in diameter and the minimum size found was 47.18 mm in diameter. The highest density of Lola snails at each research station was 0.08 ind/m2 and the lowest was 0.05 ind/m2. The distribution pattern of Lola snails at the research location is a clustered pattern.

МЕТАЦЕРКАРИИ ТРЕМАТОД В МОЛЛЮСКЕ VIVIPARUS CONTECTUS (MILLET, 1813) ИЗ РЫБИНСКОГО ВОДОХРАНИЛИЩА

Examination of 102 snails of Viviparus contectus from Rybinsk Reservoir in July–August 2023 revealed the presence of trematodes metacercariae of three families: Echinostomatidae, Cyathocotylidae and Leucochloridiomorphidae. Neoacanthoparyphium echinatoides was the species with the highest prevalence and intensity of infection (98.5%, 41.7, 1–192), followed by the Linstowiella viviparae (86%, 17.2, 3–45). Unencysted metacercariae Leucochloridiomorpha constantiae had a low prevalence and intensity of infection (13.7%, 0.51, 1–16). L. constantiae larvae parasitized only male snails. In contrast, the closely related species Leucochloridiomorpha lutea had high infestation rates (89.2%, 5.7, 1–20). L. lutea larvae equally infected of both the sexes of the snail. The sizes of cysts and metacercariae of all species are given. For metacercariae Neoacanthoparyphium echinatoides and Leucochloridiomorpha lutea, the infection intensity as a function of snail size was shown.

Effects of temperature on the life history traits of intermediate host snails of fascioliasis: A systematic review.

The impact of climate change has led to variations in various biological processes, leading to altered transmission dynamics of infectious diseases, including snail-borne diseases (SBDs). Fascioliasis is one of the neglected zoonotic tropical snail-borne diseases caused by the trematode of the genus Fasciola. This review focused on laboratory experimental and model studies that evaluate the potential effect of temperature change on the ecology and biology of the intermediate host snails (IHS) of Fasciola. A literature search was conducted on Google Scholar, EBSCOhost, and PubMed databases using predefined medical subject heading terms, Boolean operators, and truncation symbols in combination with direct keywords: Fasciolosis AND Temperature, Lymnaea OR Austropeplea OR Radix OR Galba OR Fossaria OR Pseudosuccinea AND growth, fecundity, AND survival at the global scale. Other search terms used were (Fascioliasis AND Temperature), (Lymnaea AND Temperature), (Austropeplea AND Temperature), (Fossaria AND Temperature), (Galba AND Temperature), (Pseudosuccinea AND Temperature), and (Radix AND Temperature). The final synthesis included thirty-five published articles. The studies reviewed indicated that temperature rise may alter the distribution, and optimal conditions for breeding, growth, and survival of IHS, ultimately resulting in changing the transmission dynamics of fascioliasis. The literature also confirmed that the life history traits of IHS and their interaction with the liver fluke parasites are driven by temperature, and hence climate change may have profound outcomes on the population size of snails, parasite density, and disease epidemiology. We concluded that understanding the impact of temperature on the growth, fecundity, and survival of IHS may broaden our knowledge of the possible effects of climate change and hence inform fascioliasis control programs.

Molluscicidal activity of Nicotiana tabacum extracts on the invasive snail Pomacea canaliculata

Botanical molluscicides for controlling the invasive snail Pomacea canaliculata have attracted worldwide attention because of their cost and environmental friendliness. Aqueous extracts from discarded tobacco leaf (Nicotiana tobacum) were evaluated for molluscicidal activity against different-sized P. canaliculata under laboratory conditions. The results showed that over 90% of the snails died in 1 g/L tobacco extract within 4 days, and the survival of P. canaliculata was inversely proportional to the snail size, tobacco extract concentration and length of exposure time. Adult males were more susceptible to tobacco extract than females. The snails had few chances to feed or mate in 0.5 g/L tobacco extract, and reproduction was greatly limited in 0.2 g/L. The growth of juvenile snails was inhibited in 0.2 g/L tobacco extract, but adults were unaffected. The antioxidant capacity of P. canaliculata in response to tobacco extract can be size- and sex-dependent, and the activities of superoxide dismutase, catalase, and acetylcholinesterase and the contents of glutathione and malondialdehyde were increased in adult males. These results suggest that discarded tobacco leaves can be useful as a molluscicide for controlling the invasive snail P. canaliculata based on its effects on survival, behaviour, food intake, growth performance and antioxidant capacity.

Production of juveniles of the freshwater, egg-laying lymnaeid snail Radix plicatula as prey for the juveniles of Whitman leech (Whitmania pigra)

ABSTRACT The leech Whitmania pigra is well known in traditional Chinese medicine for promoting human blood circulation and alleviating blood stasis. To evaluate its suitability as bait for this neonate leech, we investigate the reproductive efficiency of the snail Radix plicatula under laboratory conditions. Furthermore, the effects of the size of R. plicatula on the growth of newborn W. pigra were evaluated. Wild snails laid eggs in mid-March with body weight >0.223 g and peaked at the beginning of April to early May. The accumulated number of eggs was 1489.70 ± 895.98 and 2145.67 ± 694.47 separately for individual and paired snails (P = 0.083). The time elapsed up to the hatching of the first egg in the four collected egg masses ranged from 12 to 18 days, and the hatching percentage ranged from 97-% to 100-% . The predation rate of the newborn W. pigra was significantly higher when feeding on small snails than on medium and large snails (P < 0.01). Furthermore, increased snail size resulted in decreased leech growth and survival rates. The investigations demonstrated that the snail R. plicatula could serve as a suitable living bait in the rearing of W. pigra to help alleviate the scarcity of leech on the market.

Shell shape as a potential predictor of age class in the invasive snailLissachatina fulica

ABSTRACTUnderstanding the life-history traits of invasive species can increase the effectiveness of eradication efforts and decrease costs. In the giant African snail Lissachatina fulica, one of the 100 worst invasive species on the planet, age structure can be an important indicator of invasiveness. Here, we associated variation in snail size with variation in weight and shell shape, in an effort to better understand the growth pattern in this species. Our study involved two components: we estimated the allometric relationship between weight and length in a natural population and monitored developmental variation in snail shape, weight, length and nutritional condition (condition factor) in a lab population. The weight and length growth patterns of the lab population were estimated independently using exponential regressions based on weekly measurements; shell shape was quantified using geometric morphometrics. In both populations, we found negative allometry between weight and length, suggesting that snail shells tend to elongate during growth. Geometric morphometrics confirmed this pattern and revealed that the change from a rounded to an elongated shell shape does not occur at a constant pace but during a specific growth interval (i.e. at a shell length of 55–65 mm), which is described in the literature as the size when the animal becomes hermaphroditic. Future studies should test whether the shape change reported here corresponds to the transition to the hermaphrodite age class, and with this in mind, we provide two simple morphological indexes that allow us to characterize shell shape as rounded or elongated. If shell size and shape are indicative of the transition to the hermaphroditism, then our findings can help to place individuals of L. fulica into appropriate age classes, and this will represent a useful baseline for development of eradication policies.

Multi-strain compatibility polymorphism between a parasite and its snail host, a neglected vector of schistosomiasis in Africa

Interactions between Schistosoma mansoni and its snail host are understood primarily through experimental work with one South American vector species, Biomphalaria glabrata. However, 90% of schistosomiasis transmission occurs in Africa, where a diversity of Biomphalaria species may serve as vectors. With the long-term goal of determining the genetic and ecological determinants of infection in African snail hosts, we developed genetic models of Biomphalaria sudanica, a principal vector in the African Great Lakes. We determined laboratory infection dynamics of two S. mansoni lines in four B. sudanica lines. We measured the effects of the following variables on infection success and the number of cercariae produced (infection intensity): (i) the combination of parasite and snail line; (ii) the dose of parasites; and (iii) the size of snail at time of exposure. We found one snail line to be almost completely incompatible with both parasite lines, while other snail lines showed a polymorphism in compatibility: compatible with one parasite line while incompatible with another. Interestingly, these patterns were opposite in some of the snail lines. The parasite-snail combination had no significant effect on the number of cercariae produced in a successful infection. Miracidia dose had a strong effect on infection status, in that higher doses led to a greater proportion of infected snails, but had no effect on infection intensity. In one of the snail-schistosome combinations, snail size at the time of exposure affected both infection status and cercarial production in that the smallest size class of snails (1.5–2.9 mm) had the highest infection rates, and produced the greatest number of cercariae, suggesting that immunity increases with age and development. The strongest predictor of the infection intensity was the size of snail at the time of shedding: 1 ​mm of snail growth equated to a 19% increase in cercarial production. These results strongly suggest that infection status is determined in part by the interaction between snail and schistosome genetic lines, consistent with a gene-for-gene or matching allele model. This foundational work provides rationale for determining the genetic interactions between African snails and schistosomes, which may be applied to control strategies.

Population Density and Reproductive Seasonality of Tryonia cheatumi (Gastropoda: Cochliopidae), the Phantom Tryonia

We studied population density, population size, and reproductive seasonality of the Phantom Tryonia, Tryonia cheatumi (Pilsbry, 1935). This endangered freshwater snail is found only in the San Solomon Spring system, a cienega, or karst-based, arid-land freshwater spring system, in western Texas, USA. We sampled populations at seven locations in the system seasonally over a 2-yr period. San Solomon Spring, the system's largest spring and modified into a swimming pool, had the largest population of T. cheatumi, with an estimated 49 million individuals and a mean density as high as 23,626 ± 39,030 (individuals/m2 ± SD). There were seasonal differences in mean density (up to 25-fold) and median snail size at all sites, but consistent seasonal patterns of mean density or size were not observed. Median snail size among samples was not related to water temperature, and juveniles were present in most samples in all seasons. These results support continuous, aseasonal reproduction, as expected in thermally stable habitats, but differences in median size and mean density among seasons and sites suggest that other factors affect reproduction and seasonal variation in population size of T. cheatumi.

Research on the molluscicidal activity and molecular mechanisms of arecoline against Pomacea canaliculata

Pomacea canaliculata, as an invasive snail in China, can adversely affect agricultural crop yields, ecological environment, and human health. In this paper, we studied the molluscicidal activity and mechanisms of arecoline against P. canaliculata. The molluscicidal activity tests showed that arecoline exhibits strong toxicity against P. canaliculata, and the LC50 value (72 h) was 1.05 mg/L (15 ± 2 mm shell diameter). Additionally, Molluscicidal toxicity were negatively correlated with the size of snails. Snails (25 ± 2 mm shell diameter) were choosed for mechanisms research and the result of microstructure and biochemistry showed that arecoline (4 mg/L, 20 ℃) had strong toxic effect on the gill, and the main signs were the loss of cilia in the gill filaments. Moreover, arecoline significantly decreased the oxygen consumption rate, ammonia excretion rate and inhibited acetylcholinesterase (AChE). Then, the changes in protein expression were studied by iTRAQ, and 526 downregulated proteins were found. Among these, cilia and flagella-associated 157-like (PcCFP) and rootletin-like (PcRoo) were selected as candidate target proteins through bioinformatics analysis, and then RNA interference (RNAi) was adopted to verify the function of PcCFP and PcRoo. The results showed that after arecoline treated, the mortality and the cilia shedding rate of PcRoo RNAi treated group was significantly lower than control group. The above results indicate that arecoline can bind well with protein PcRoo, and then leads to the drop of gill cilia, affect respiratory metabolism, accelerate its entry into hemolymph, inhibit AChE and finally leads to the death of P. canaliculata.

SEASONAL OCCURRENCE OF NEOECHINORHYNCHUS EMYDIS (PHYLUM: ACANTHOCEPHALA) IN THE FRESHWATER SNAIL, PLANORBELLA CF. P. TRIVOLVIS, FROM OKLAHOMA.

The acanthocephalan Neoechinorhynchus emydis has a complex life cycle and infects turtle, ostracod, and snail hosts. However, little information is available on the seasonal distribution or the effects of N. emydis on freshwater snail hosts. To address this, we examined the seasonal distribution and melanization of acanthocephalans in Planorbella cf. Planorbella trivolvis snails from a single location in north-central Oklahoma. Seasonally, prevalence of N. emydis was 0% during the winter, increased to 50% during the summer, and declined to 17% in the fall. Mean abundance exhibited more variation but generally followed a similar pattern as prevalence. More important, all acanthocephalans located within the head/foot region of snail hosts contained melaninlike pigment surrounding each worm, suggesting that snails were mounting an immunological reaction to infections with N. emydis. Snail shell diameter was greatest during the fall and decreased during the winter, indicating that larger or older snails were dying during the winter. However, because field-collected snails were commonly infected with trematodes, and snail size varied significantly with season, it was unclear whether the observed seasonal dynamics of acanthocephalan infections were a result of snail mortality resulting from snail age, parasitic infections, or a combination of factors. To control for these factors, we exposed laboratory-reared Planorbella cf. P. trivolvis snails to naturally infected ostracods in field cages for 5-wk intervals during the winter, spring, and summer. Data from snail-cage infections were consistent with the seasonal field survey such that N. emydis infections were highest in the summer (20%) and lowest (0%) in the winter, suggesting that snails were not ingesting infected ostracods during the winter. However, fewer of our laboratory-reared snails survived in field cages during winter than during spring and summer, suggesting that snails may die more often during harsh winter conditions. Finally, we conducted a laboratory survival experiment by testing the life span and egg production of field-collected snails of various sizes that were naturally infected with acanthocephalans or trematodes or both. Our snail-survival experiment indicated that snail size but not infection status with acanthocephalans or trematodes affected snail survival, with larger snails surviving a shorter amount of time than smaller snails. In addition, snails infected with trematodes laid significantly fewer eggs compared with uninfected snails or snails infected with acanthocephalans. However, we found no significant difference in the number of eggs laid by acanthocephalan-infected and uninfected snails. Although other abiotic factors still need evaluation, we suggest that the occurrence of acanthocephalans in snails throughout the year may be partially influenced by the abundance of infected ostracods that snails may be ingesting and snail population fluctuations during the year.

Study of the behavior of snails intermediate hosts of Schistosoma spp. under different maintenance conditions and their resistance to salinity in an african laboratory environment

BackgroundThe control of snails intermediate hosts remains an effective strategy to limit schistosomiasis transmission despite the widespread mass de-worming campaign based on praziquantel. Therefore, the study of snail biology could help to improve snails control strategies. This study evaluated the development of Biomphalaria pfeifferi, Bulinus senegalensis and Bulinus truncatus in various water sources and their resistance to salinity. MethodsFive day-old juveniles individuals issued from adult snails non-shedding Schistosoma spp cercariae were breed in distilled water, commercial mineral water, ground pump water and well water. Snail’s survival rate and size were measured over a period of 40 days. These two parameters were also measured over 30 days in increasing saline solutions (1 g/l, 3.5 g/l and 4 g/l) made of well water to which sodium chloride was added. ResultsB. truncatus growth was not hampered by any water sources with a survival rate between 68% and 84% (log rank X2 = 1.86, df = 3, p = 0.60). Despite a poor survival rate (8%) in distilled water, B. pfeifferi, has adapted to other water sources with a survival fraction between 88% and 96% (log rank X2 = 61.94, df = 3, p < 0.0001). B. senegalensis development was very delicate with low survival rate of 4% in distilled water, 20% in well water and 24% in commercial mineral water and ground pump water (log rank X2 = 13.24, df = 3, p = 0,004). For each species, even if the difference is not significant, the size of snails is larger with well water and pump water compared to distilled and commercial mineral water.B. pfeifferi survival rate was at 45% in both three saline solutions at day 30. B. senegalensis population collapsed at day 10 in 4 g/l saline solution and persisted until day 30 in both 1.5 g/l and 3.5 g/l solution. B. truncatus also persisted with a survival rate at 20% in 1.5 g/l but collapsed at day 5 and 15 in 4 g/l and 3.5 g/l solution, respectively. ConclusionThe differences in adaptation between snails species show the need to take into account the water sources for snail breeding in the laboratory. Further studies could help to determine the optimal water quality for each snail species in order to standardize breeding conditions. This study could contribute to the understanding of the dynamics and distribution of snails in natural conditions.

Effects of prey size on predatory behaviour of leech ( Whitmania pigra ) feeding on snails ( Cipangopaludina cathayensis )

Rapid development of medicine has led to increased use of leech (Whitmania pigra). The suitable feeding technology is the key factor for successful breeding leeches. However, there is little information available to concern the effect of prey size on predatory behaviour of the leeches. In this study, we conducted predation trials by two sizes of W. pigra preying on three sizes of snails (Cipangopaludina cathayensis), and then analysed predation rate, feeding rate, searching time and handling time. Our results demonstrated that there were higher predation rate of small-size W. pigra preying on small-size snails compared with medium or large ones, and the predation rates gradually decreased with prolongation of the predation time. In addition, the small-size W. pigra had higher feeding rates than larger size among three treatments. However, snail sizes did no have significant effects on the feeding rates of the leeches. Furthermore, we found that it took longer time of small-size leeches to search snails than large-size leeches, while the handling time of two sizes of W. pigra increased with the snail size. This study suggests that farmers should take smaller amount and more frequent feeding approach for leech larva in the artificial breeding processes. On the other hand, adult leeches should be provided with enough feeding in one time. Due to the size-specific feeding characteristics of the leeches, we suggest that leeches should be raised based on size.

Asymmetric density-dependent competition does not contribute to the maintenance of sex in a mixed population ofsexual and asexual Potamopyrgus antipodarum.

Asexual reproduction is expected to have a twofold reproductive advantage over sexual reproduction, owing to the cost of producing males in sexual subpopulations. The persistence of sexual females, thus, requires an advantage to sexual reproduction, at least periodically. Here, we tested the hypothesis that asexual females are more sensitive to limited resources. Under this idea, fluctuations in the availability of resources (per capita) could periodically favour sexual females when resources become limited. We combined sexual and asexual freshwater snails (Potamopyrgus antipodarum) together in nylon mesh enclosures at three different densities in an outdoor mesocosm. After 1 month, we counted the brood size of fertile female snails. We found that fecundity declined significantly with increasing density. However, sexual females did not produce more offspring than asexual females at any of the experimental densities. Our results, thus, suggest that the cost of sexual reproduction in P.antipodarum is not ameliorated by periods of intense resource competition.

Sexual dimorphism in shell size of the land snail Leptopoma perlucidum (Caenogastropoda: Cyclophoridae).

Sexual dimorphism in the shell size and shape of land snails has been less explored compared to that of other marine and freshwater snail taxa. This study examined the differences in shell size and shape across both sexes of Leptopoma perlucidum land snails. We collected 84 land snails of both sexes from two isolated populations on two islands off Borneo. A total of five shell size variables were measured: (1) shell height, (2) shell width, (3) shell spire height, (4) aperture height, and (5) aperture width. We performed frequentist and Bayesian t-tests to determine if there was a significant difference between the two sexes of L. perlucidum on each of the five shell measurements. Additionally, the shell shape was quantified based on nine landmark points using the geometric morphometric approach. We used generalised Procrustes and principal component analyses to test the effects of sex and location on shell shape. The results showed that female shells were larger than male shells across all five measurements (all with p-values < 0.05), but particularly in regards to shell height and shell width. Future taxonomic studies looking to resolve the Leptopoma species’ status should consider the variability of shell size caused by sexual dimorphism.

Spatial variation of life-history traits in Bulinus truncatus, the intermediate host of schistosomes, in the context of field application of niclosamide in C\xf4te d\u2019Ivoire

BackgroundControl of intermediate host snails using molluscicides for the control and/or elimination of schistosomiasis is a strategy in line with WHO recommendations. Niclosamide is the main chemical molluscicide recommended by WHO. However, except the immediate killing of the snail, the extent of the impact of the molluscicide application on the evolution of snail life-history traits, in relation to recolonization of treated sites is not well known. This study aimed to characterize the spatial variation of life-history traits of populations of the freshwater snail Bulinus truncatus, in relation to niclosamide spraying in the field.From 2016 to 2018, we conducted a trial, using niclosamide to control the intermediate host snails for interrupting the seasonal transmission of urinary schistosomiasis in northern and central Côte d’Ivoire. Five villages (sites) were considered, including three test and two control villages. In the test villages, the molluscicide was sprayed in habitats harboring B. truncatus snails three times a year (November, February–March and June). We sampled six B. truncatus populations: two populations from the control villages without any treatment; one collected before treatment and three sampled 2–3 months after treatment of the site with niclosamide. The snail populations were monitored for several life-history traits, including survival, growth, fecundity and hatchability, under laboratory conditions, over one generation (G1). We tested the population, region (North/Centre) and treatment status (treated/untreated) effects on the variation of the measured life-history traits and correlations between pairs of traits were estimated.ResultsOn the whole, the traits varied among populations. The risk of death was lower in northern populations compared to central ones. The age at first reproduction was reached earlier with a smaller size of snails in northern populations. Values of first reproduction features (size and fecundity) were lower in treated snail populations. The overall growth of untreated populations was higher than that of treated ones. The late fecundity and egg hatching were higher in northern than in central snails. At first reproduction, age was negatively correlated with some fecundity parameters. However, growth was positively associated with fecundity.ConclusionsOur study showed a spatial variation of life-history traits in B. truncatus snails. The mollusciciding seems to have led to the depression of some life-history traits in the snail populations. However, investigations should be carried out over several generations of snails to better clarify the impact of niclosamide on the evolution of the life-history traits.

Plant diets of land snail community members are similar in composition but differ in richness

ABSTRACTHerbivore diets are often generalistic, and communities of herbivores tend to share much of their diets. In the tropical lowlands of Malaysian Borneo, tens of different noncarnivorous land snail species are able to coexist in communities on limestone outcrops. We tried to answer the question whether diet differentiation plays a role in their coexistence. We show, with a large metabarcoding study of the plant diet from gut contents of 658 individual snails (from 26 species, with a focus on three of the most common species in the region), that the different snail species indeed share much of their plant diet, but that mean diet richness varies strongly among species (up to 15.3×). These differences are mostly explained by snail size, with larger snails having wider diets. Furthermore, phylogenetic analyses of the plant diet by individual snails showed signs of clustering in c. 28% of the individuals, possibly suggesting phylogenetic specialization, although such clustering was weak when diets were considered by species. We discuss how observed trends in diet richness and diet clustering could also be explained by random feeding, with larger species simply eating more or less specifically, and by other, noncompetitive interactions, such as snails avoiding desiccation. Our study shows how to efficiently put the power of metabarcoding to work in unravelling the complex community processes commonly encountered in tropical ecosystems and is thus of substantial relevance to both community ecologists and conservationists.

Freshwater disease hotspots: Drivers of fine‐scale spatial heterogeneity in trematode parasitism in streams

AbstractPopulations of stream organisms often show large heterogeneity in space, which can substantially influence community dynamics and ecosystem functioning. However, few studies have examined spatial heterogeneity of parasites in lotic ecosystems, especially at fine spatial scales (e.g., within stream reaches).We quantified parasite infections in 3,255 host snails (Juga plicifera) at 1‐m intervals along three second‐order stream reaches to examine relationships between trematode parasite infections, fine‐scale heterogeneity in host characteristics (density and size), and the stream environment (depth, allochthonous materials, flow velocity, and substrate rugosity). We then conducted a field experiment to specifically test the effect of resource heterogeneity in the form of leaf litter on trematode densities (i.e., infected snails per unit area), which represents a measure of local disease risk to secondary hosts. We hypothesised that variation in bottom‐up effects of host resources to snail hosts to parasites would drive spatial heterogeneity in trematode density.In the field surveys, trematode density ranged from 0 to 80 infected snails/m2 and showed spatial autocorrelation within two of three stream reaches. Trematode density increased with snail density, which was positively related with the amount of allochthonous materials but negatively related to steam depth. Individual host infection probability increased with snail size, which was positively related to both allochthonous materials and stream depth.In the experiment, host snail and trematode densities increased by 3‐fold and 4‐fold, respectively, in the leaf addition treatments relative to controls. The experiment therefore provided mechanistic understanding of patterns from the surveys by demonstrating a bottom‐up effect from high quality resources to host space use to trematode density.Our results demonstrate a strong role of within‐reach variation in allochthonous resources and habitat (depth) in driving spatial heterogeneity of stream parasites, which probably creates fine‐scale hotspots of disease transmission to downstream hosts. More broadly, our findings help integrate parasites into our understanding of how environmental heterogeneity influences community structure and ecosystem processes (e.g., disease risk) in streams.

The Danubian cryptic invader Theodoxus fluviatilis (Gastropoda: Neritidae) in the River Rhine: a potential indicator for metal pollution?

Metal pollution poses a major threat to aquatic systems especially in anthropogenic influenced areas, in as much as metals are persistent in the environment. The freshwater snail Theodoxus fluviatilis has often been used as an indicator species for the ecological status in river monitoring. In the River Rhine, the native Northern-European form of T. fluviatilis is nowadays extinct, whilst the Danubian form is spreading along the river. The aim of our study was to investigate if the cryptic invader is affected by metal exposure present in the River Rhine and to discuss its potential as an indicator for metal pollution. Several environmental abiotic (14 water environmental variables plus five common metal concentrations in water and biofilm) and biotic parameters (biofilm mass) were measured across 23 sites along the River Rhine. Five population and six histopathological parameters were evaluated on snails collected at all 23 sites. Aqueous chromium concentration was positively correlated to the damage of male reproductive organs of T. fluviatilis, and higher ammonium concentration was correlated to a decrease in snail size and an increase in the proportion of juveniles. None of the analysed snail parameters was negatively correlated to concentrations of other metals measured, like copper and zinc. Therefore, based on the parameters evaluated, our results indicate that the Danubian form of T. fluviatilis is only restrictedly suitable as an indicator for metal pollution in the River Rhine system. Further field and laboratory investigations including other stressors are necessary to evaluate the indicator potential of the cryptic invader holistically.

Tracking coastal acidification from erosion of gastropod shells: spatial sensitivity and organism size effect.

The rapidly changing marine environmental chemistry associated with growing industrialisation, urban population expansion, and the unabated rise in atmospheric CO2 necessitates monitoring. Traditional approaches using metres, dataloggers, and buoys to monitor marine acidification have limited application in coastal oceans and intertidal zones subjected to direct wave action. The present study trialled a system to biomonitor coastal acidification (carbonate ion and pH) based on the dissolution of living gastropod shells. We extended on an approach that ranked shell erosion (SER) in Nerita chamaeleon (Nc) in environments where such erosion was found to correlate with exposure to acidified water. We assessed the spatial scale at which the Nc-SER marker could detect change in acidification along rocky shores, and whether snail body size affected this marker. We found that proportional and unique Nc-SERs not only varied between acidified and non-acidified reference shores at a coarse spatial scale (10km), but also in predictable ways at fine scales (metres), vertically and horizontally within a shore. Differences between acidified and reference shores in the relationship for snail size and Nc-SER were accentuated by less weathered shells at reference localities, highlighting the value of including small, juvenile snails in monitoring protocols. Gastropod shells are shown to be useful for assessing point sources of acidification and the spatial area of affected coastal zones. This cost-effective and easy-to-use approach (potentially even by citizen-scientists) offers an early warning system of acidification of rocky shore ecosystems, where the deployment of instruments is precluded.

Growth and Reproduction of Planorbarius corneus (Linnaeus, 1758) in Laboratory Conditions

Abstract This study presents the results of observation on growth and reproduction of Planorbarius corneus (Linnaeus, 1758) (Gastropoda, Pulmonata) over the course of several years of continuous rearing in the laboratory in order to use them as test organisms for toxicity testing of chemicals. Some growth and reproduction features (shell diameter increase, fecundity, hatching time and rate, age at first reproduction, juvenile survival), which could provide more information for culturing P. corneus in the laboratory, are presented. The quantitative results of growth and reproduction in laboratory conditions were obtained: heterogenous growth varied between 0.1 mm and 5.3 mm in individual snails, production of 0.6 egg masses per snail/day and 11 eggs per snail/day. A statistically significant negative correlation between initial snail size and growth was noticed. In the second part of the experiment, the reproductive output of 4 isolated snails was compared to that of permanently grouped snails. As a result, 2-fold decreased growth and 4-fold decreased reproductive output in the progeny of isolated animals was noticed.