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Изучение врожденного иммунитета моллюсков необходимо для понимания эволюции иммунной системы и разработки стратегии борьбы с их паразитами. В данной работе впервые получен и проанализирован транскриптом гемоцитов моллюсков Planorbarius corneus, зараженных в естественных условиях трематодой Bilharziella polonica (Schistosomatidae). В сборках обнаружены транскрипты, кодирующие все основные группы факторов врождённого иммунитета. Наиболее многочисленной группой оказались молекулы распознавания патогенов. На основе нуклеотидных последовательностей транскриптов предсказана доменная структура кодируемых ими белков. Проанализирована структура доменов лектинов, толл-подобных рецепторов, молекул адгезии и токсинов. Показано большое разнообразие патоген-распознающих молекул гемоцитов P. corneus. Полученные данные расширяют знания об иммунных реакциях легочных моллюсков на трематодную инвазию и дают возможность рассматривать роговую катушку как новый модельный организм для изучения их защитных реакций.

We found two functional populations of hemocytes in the hemolymph of the pulmonate snail Planorbarius corneus: hyalinocytes and granulocytes. The hyalinocytes were much more numerous than granulocytes. Each population was subdivided into subpopulations based on morphological and functional characteristics. The hyalinocyte population was represented by two subpopulations differing in size, granularity, and ability to form pseudopodia. In snails infected with the trematodes Plagiorchis sp., the cellular composition of the hemolymph changes, with hemocytes being mostly represented by granulocytes. This phenomenon is associated with the fact that granulocytes form a hemocytic paletot on the surface of sporocysts of Plagiorchis sp. It is suggested that pulmonate molluscs have one lineage of hemolymph cells. Hematopoietic stem cells can divide, ensuring multiplication of prohemocytes. The latter differentiate into hyalinocytes, which, in turn, differentiate into granulocytes. [ABSTRACT FROM AUTHOR]

A toxicological study is performed to analyze the in vivo effect of zinc chloride in different concentrations on the pulmonary and cutaneous respiration of Planorbarius corneus (L., 1758). At 0.5 MPC Zn2+ in an environment containing the experimental mollusks, there are no statistically significant changes in parameters in either of the studied respiration mechanism when compared to the control. The increasing concentration of the toxicant to 2 MPC is accompanied by a sharp increase in respiration parameters (p < 0.01). At 5 and 10 MPC of zinc ions in the environment, an increasing (from a lower concentration to a higher one) decrease in the values of pulmonary and cutaneous respiration (p < 0.01) is observed. The main reason for the changes in the respiratory function of that mollusk is the damage effect of the toxicant on the pulmonary and cutaneous respiratory epithelium. This effect results in a highly intensified production of mucus and the formation of a thick layer of coagulation mucus, which completely blocks the oxygen intake by cutaneous epithelium and induces cell death in the respiratory epithelium. [ABSTRACT FROM AUTHOR]

As part of surveillance of snail-borne trematodiasis in Knowsley Safari (KS), Prescot, United Kingdom, a collection was made in July 2021 of various planorbid (n = 173) and lymnaeid (n = 218) snails. These were taken from 15 purposely selected freshwater habitats. In the laboratory emergent trematode cercariae, often from single snails, were identified by morphology with a sub-set, of those most accessible, later characterized by cytochrome oxidase subunit 1 (cox1) DNA barcoding. Two schistosomatid cercariae were of special note in the context of human cercarial dermatitis (HCD), Bilharziella polonica emergent from Planorbarius corneus and Trichobilharzia spp. emergent from Ampullacaena balthica. The former schistosomatid was last reported in the United Kingdom over 50 years ago. From cox1 analyses, the latter likely consisted of two taxa, Trichobilharzia anseri, a first report in the United Kingdom, and a hitherto unnamed genetic lineage having some affiliation with Trichobilharzia longicauda. The chronobiology of emergent cercariae from P. corneus was assessed, with the vertical swimming rate of B. polonica measured. We provide a brief risk appraisal of HCD for public activities typically undertaken within KS educational and recreational programmes. [ABSTRACT FROM AUTHOR]

Larvae of Tylodelphys Diesing, 1950 are major digenean pathogens of fish and amphibians. Tylodelphys spp. may induce mass mortality of fish and increase their susceptibility to predation. Even though Tylodelphys spp. cause substantial damage to aquaculture systems, surprisingly little is known regarding the taxonomy of this commercially important genus with a limited number of visible autapomorphic identification features. The authors obtained the DNA sequences and analyzed the molecular phylogenetics of Tylodelphys spp. adults isolated from bird hosts of Czech origin and provide comparative measurements of the analyzed species. They identified a previously unknown species complex that is subject to cryptic speciation and was previously morphologically identified as Tylodelphys excavata (Rudolphi, 1803) sensu lato. This species complex consists of three morphologically similar but genetically well-separated species. Tylodelphys excavata sensu stricto remains the dominant Tylodelphys isolated from Ciconia ciconia, which also serves as a satellite host of Tylodelphys circibuteonis Odening, 1962, which is the resurrected species for which birds of prey serve as core hosts. The authors describe Tylodelphys nigriciconis sp. n. Heneberg & Sitko as a new species identified in Ciconia nigra. By providing the first sequences of Tylodelphys podicipina Kozicka and Niewiadomska, 1960, they also show that Tylodelphys immer Dubois, 1961 is a junior synonym of T. podicipina. Further research is needed to match the provided molecular data with the DNA of larval Tylodelphys from outbreaks in commercially exploited fish species. [ABSTRACT FROM AUTHOR]

The spread of freshwater invasive species through aquarium trade poses a threat to the ecosystem, economy and human health. The availability of the exotic freshwater gastropod mollusc, Planorbarius corneus (Linnaeus, 1758) (Gastropoda: Planorbidae), in pet shops in Kolkata, West Bengal, India, raises concern for its potential establishment as an invasive species. Assuming the role of the native predators as a potential biotic barrier for invasion, observations on the predation pattern of the malacophagous leech, Glossiphonia weberi (Blanchard, 1897) (Clitellata: Glossiphoniidae) against P. corneus was made in single as well as in combination with the native snail Indoplanorbis exustus (Deshayes, 1834) (Gastropoda: Planorbidae). Using varying size classes and densities of P. corneus, the predation potential of G. weberi was estimated after a 24 hour period. In another set of experiments, the predation of G. weberi against the snail P. corneus was observed in the presence of I. exustus under four different habitat conditions. The purpose was to justify - (1) the effect of conspecific and heterospecific conditions of the prey availability and (2) the effect of habitat complexity on the predatory efficacy of G. weberi. The results indicated that G. weberi consumed varied numbers of P. corneus, depending on the size and the densities of the prey and predator. Although the prey heterogeneity and complex habitats caused significant reduction of predation on both of the prey species, G. weberi significantly preferred P. corneus over I. exustus in open (P < 0.0001), macrophyte (P = 0.002) and pebbles and macrophyte containing habitats (P < 0.0001). Apparently, G. weberi preferred the exotic snail P. corneus in presence of alternative prey snail I. exustus, under different habitat conditions. Therefore, G. weberi may act as a significant biotic resistance against the colonization and establishment of P. corneus in the Indian context. However, further studies including the multiple prey and predators are required to ascertain the food web level impact of the exotic snail P. corneus in invaded freshwater ecosystems.

Оцінено особливості сумісного впливу різної тривалості умов десикації (10, 20, 30, 40, 50, 60 діб) й інвазії материнськими та дочірніми редіями Notocotylus thienemanni й спороцистами Cercaria psеudogracilis на вміст гемоглобіну (Hb) у гемолімфі Planorbarius corneus та активну реакцію (рН) останньої. З’ясовано, що на умови десикації ці молюски відповідають зростанням концентрації Hb у їх гемолімфі. Цей дихальний пігмент відзначається потужними буферними властивостями, що дає змогу незараженим гельмінтами особинам постійно підтримувати активну реакцію їх гемолімфи на слабколужному рівні. Трематодна ж інвазія для P. corneus є обтяжувальним чинником, який значно вповільнює процес зростання вмісту Hb їх у гемолімфі, що супроводжується її підкисленням.

Two endogenous biorhythms of mass specific rate of oxygen consumption with periods of 10.8 and 4.7 weeks were detected in the late postlarval ontogenesis of freshwater gastropod mollusks Planorbarius corneus using a singular spectral analysis. The local extreme points of both biorhythms in different individuals fall at the same ages. Periods of both biorhythms are approximately the same in all the animals studied and remain unchanged throughout the individual development. Both biorhythms are fading and have a similar amplitude, which decreases from approximately 1.1 μL O2/(h g) up to 20 weeks to 0.26 μL O2/(h g) at the time of death. Thus, new, previously undescribed endogenous biorhythms associated with metabolic rate have been identified. [ABSTRACT FROM AUTHOR]

The changes of the intracellular potentials by the action of sevoflurane were studied for the diagnostic intact neurons of the isolated cerebrospinal axis of the Planorbarius corneus using intracellular electrodes. There observed a two-phase reaction of the neurons de- and hyperpolarization. The sevoflurane concentration of 2 mM depolarized the neurons (to 5 mV), the depolarization was interchanged with the mild hyperpolarization (at 2-5 mV). The impulse activity rate (IA) increased under depolarization, while decreased under hyperpolarization, the parameters of the action potentials (AP) changed slightly. The inversive hyperpolarization occurred for 5-10 minutes upon the anesthetic elimination. There occurred the short-term and inversive depolarization of the neurons at the sevoflurane concentration of 5 mM to 9,4 ± 2,2% of the reference, while the IA rate increased, the amplitude of the action potentials decreased with their duration increase, and sometimes the AP generation was completely abrogated. On action of sevoflurane concentration of 5 mM there developed the inversive hyperpolarization of the neurons to 18,1 ± 16,9% of the reference, that lasted 15-20 minutes thereafter. The repeated neuron exposure with the same anesthetic is always reproduced followed by the florid hyperpolarization. The modulation of the electrical activity with sevoflurane (the hyperpolarization of the neurons and the decrease/termination of AP generation that evidenced the "improvement" of their functional status) may be the basis for the preconditioning, neuro- and cardioprotection.

Intercellular potentials changes of identifiable intact neurons ini solated CNS of great ramshorn (Planorbarius corneus) have been investigated with the help of intercellular microelectrodes and ion currents of isolated neurons of great ramshorns and pond snails (Lymnaea stagnalis) with the fixation of potential influenced by desflurane in concentrations of 1 and 10 mM (1.2 и 12 MAC) and sevoflurane in concentrations of 1 and 5 mM (2.27 and 11.36 MAC). In 3-5 minutes after the start of anesthetics' action some neurons developed insignificant hyperpolarization (for 2-5 mV), and some other developed depolarization (up to 10 mV). When anesthetics were being washed out for 5-10 minutes the reversible depolarization appeared. Changes in ion currents under the influence of anesthetics were more homogeneous compared to changes in biopotentials. Desflurane and sevoflurane in 1 mM concentrations suppressed amplitudes of sodium, calcium and potassium currents by 40%, and inactivation of potassium low currents was speed up. Anesthetics in the concentration of 5-10 mM suppressed currents by 70-80%. It developed fast (for 20-30 seconds) and after this action the amplitudes restored slowly (for 5-15 minutes) and it failed to reach the initial values in all the times. Intercellular activity of sevoflurane did not suppress ion currents, i.e. it was ineffective.

The change in the rate and mass-specific rate of oxygen consumption was studied during individual ontogenesis of nine Planorbarius corneus individuals starting from 3 weeks after hatching until the death of animals. It is shown that, at the initial stages of development, the mass-specific rate of oxygen consumption increases, reaching a maximum at 3–7 weeks after hatching. The rate of oxygen consumption then permanently increases, and the mass-specific rate of oxygen consumption permanently decreases. The dependences of mass-specific rate of oxygen consumption (q) on the age (t) for individual P. corneus can be described by the equation qst/(1 – exp(–k (t + t0))). The values ​​of the coefficients of this equation for different specimens do not differ significantly and are, on average, k = 0.134 ± 0.016 weeks–1; qst = 0.117 ± 0.006 mL O2/(h g). The dependence of the rate of oxygen consumption (Q, mL O2/h) on body weight (M, g) in individual development is well described by allometric equations, the power coefficients of which vary from 0.647 to 0.944 and significantly differ from each other (p < 0.001). Nevertheless, the data for all mollusks can be described by the united equation Q = 0.061 M0.795. The power coefficient of this equation does not significantly differ from the Hemmingsen constant 0.75. [ABSTRACT FROM AUTHOR]

Bird schistosomes are commonly established as the causative agent of swimmer's itch − a hyper-sensitive skin reaction to the penetration of their infective larvae. The aim of the present study was to investigate the prevalence of the genus Bilharziella in comparison to other bird schistosome species from Lake Drawsko − one of the largest recreational lakes in Poland, struggling with the huge problem of swimmer's itch. In total, 317 specimens of pulmonate snails were collected and examined. The overall digenean infection was 35.33%. The highest bird schistosome prevalence was observed for Bilharziella sp. (4.63%) in Planorbarius corneus, followed by Trichobilharzia szidati (3.23%) in Lymnaea stagnalis and Trichobilharzia sp. (1.3%) in Stagnicola palustris. The location of Bilharziella sp. on the presented phylogeny showed that it is with high probability a different species than known so far B. polonica. Our finding complements the confirmed occurrence of bird schistosomes in European water bodies. Overall, presented research reveals the special importance of P. corneus as a source of the bird schistosome cercariae. This study suggests that the health threat connected with the blood flukes need to be further investigated by constant monitoring of their occurrence in intermediate hosts.

Abstract: Individual growth of 15 great ramshorn snail Planorbarius corneus individuals was studied in aquaculture at 20°С starting from 2 weeks after hatching until the death of the animals. It was demonstrated that the weight of mollusks increases throughout the study period by an S-type curve. The linear growth (shell diameter) follows a parabolic (convex) curve. Both weight and linear growth on a specified age range is well approximated by the Bertalanffy equation, while the interdependence between the shell weight and diameter by an allometric equation. The value of Bertalanffy equation coefficients is different in different individuals. The mean values of the growth constants in these equations for the weight and linear growth do not differ. Their value is 0.041 ± 0.004 weeks-1. The species lifespan, which is determined by a product of the growth constant into maximal lifespan, is ≈4.5. [ABSTRACT FROM AUTHOR]

Carbamate insecticides such as carbaryl and organophosphates such as azinphos-methyl share the ability to inhibit the activity of B-esterases. This study aimed to (1) assess the inhibitory effects of carbaryl on B-esterase activity in soft tissues and hemolymph of Planorbarius corneus ; (2) establish whether binary mixtures of carbaryl and azinphos-methyl depart or not from a model of concentration addition on the inhibition of cholinesterase activity; (3) determine the bioconcentration and elimination of the pesticides. The results showed that exposure of gastropods to increasing concentrations of carbaryl (0.1–5 mg L −1 ) for 48 h inhibited cholinesterase activity in a concentration-dependent manner, with an EC 50 of 1.4 ± 0.3 mg L −1 and 1.2 ± 0.1 mg L −1 for soft tissue and hemolymph, respectively. Carboxylesterase activity, measured with the substrates p-nitrophenyl butyrate and p-nitrophenyl acetate, was between 2.3 and 25 times more sensitive to carbaryl inhibition than cholinesterase activity. Binary mixtures corresponding to 0.5 EC 50 carbaryl + 0.5 EC 50 azinphos-methyl and 0.75 EC 50 carbaryl + 0.75 EC 50 azinphos-methyl produced inhibitions of cholinesterase activity similar to those of individual pesticides, following a model of concentration addition. Bioconcentration was analyzed using a one-compartment model. The absorption kinetics ( k 1 ) for both pesticides alone (1.4 mg L −1 of carbaryl or 1.8 mg L −1 of azinphos-methyl) or mixed (1.4 mg L −1 of carbaryl + 1.8 mg L −1 of azinphos-methyl) were similar. The elimination kinetics ratio ( k 2 ) estimated for the pesticides alone or in the mixtures showed that carbaryl was eliminated 3.5 times faster than azinphos-methyl. These results suggest that exposure of Planorbarius corneus to binary mixtures of carbaryl and azinphos-methyl for 48 h follow a concentration addition model on inhibition of cholinesterase activity and that the pesticide mixtures do not change the toxicokinetic parameters of the parent compounds. [ABSTRACT FROM AUTHOR]

The discovery that mammalian neutrophils generate extracellular chromatin fibers that entrap/kill bacteria supported a new paradigm for innate immunity in animals. Similar findings in other models across diverse taxa have led to the hypothesis that the phenomenon is ancient and evolutionary conserved. Here, using a variety of synthetic (e.g. peptidoglycan) and biological (e.g. trematode larvae) components to investigate extracellular trap-like (ET-like) fiber production in vitro by haemocytes of Lymnaea stagnalis , Radix lagotis and Planorbarius corneus snails, ET-like fibers were rarely observed. We suggest, therefore, that ET-like fibers play a marginal role in defence of these snail species and thus the fiber production may not be a critical process underpinning immunity in all invertebrate species. [ABSTRACT FROM AUTHOR]

After numerous reports the local press about the 'stinging water' in created on the Dzierżęcinka River-Water Valley reservoir and recognizing in bathers the symptoms of swimmers' itch, environmental study on the presence of bird schistosome larvae in snail hosts was conducted. Snails belonging to Lymnaeidae and Planorbidae were collected at two sites: (i) part of anthropogenic reservoir (192 individuals) and (ii) the river part (37 individuals). Higher prevalence of Digenea was observed in snail populations living in Water Valley (29.8 %) compared to Dzierżęcinka River (21.3 %). The larvae of bird schistosomes were recorded in both localities in 1.8 % of collected snails. The prevalence of bird schistosomes reached 2.9 % in Planorbarius corneus, 2.8 % in Radix auricularia, and 5.9 % in Radix balthica/labiata. Laboratory tests have shown that at 19 °C the number of bird schistosome cercariae released from snail hosts significantly exceeded the number of cercariae of other identified Digenea species. It is worth underlining that despite the low prevalence of bird schistosomes, the high number of released cercariae was sufficient to create a real threat of swimmers' itch in bathers. As indicated by the example presented, anthropogenic reservoirs create excellent conditions for Digenea species including bird schistosomes. In view of the real risk of people using the waters, tests on presence of the parasites in snail hosts should be included to the standard procedure of security control in bathing places. [ABSTRACT FROM AUTHOR]

Nucleotide sequences of internal transcribed spacers (ITS1 and ITS2) of rDNA have been obtained and analyzed in natural populations of Planorbarius corneus snails from the Leningrad and Kaliningrad oblasts. The close similarity between ITS1 and ITS2 of the snails from different areas proves that Planorbarius corneus is a polymorphic but uniform species. [ABSTRACT FROM AUTHOR]

Abstract: Exogenous pyrogens, isolated from viruses, bacteria and fungi, are widely used in research on fever in endotherms. The present study investigates the use of viral pyrogen poly (I:C) for inducing the symptoms of so-called behavioral fever in ectothermic animals Planorbarius corneus (Mollusca: Gastropoda). The observations of thermoregulatory behavior of the snails placed in the temperature gradient showed that the snails which were injected with 750ngg−1 polyinosinic-polycytidylic acid-poly (I:C), after remaining latent for more than 24h, moved to warmer areas (with the temperature around 30°C) and stayed there until the end of the experiment. Transferred to the culture, they lived for a period similar to that of the control snails. Our observations indicate that P. corneus snails can exhibit a symptoms of fever response to poly (I:C) and could be used as model animals in the research on behavioral fever in invertebrates. [Copyright &y& Elsevier]

Abstract: Chlorpyrifos is an organophosphate insecticide used for pest control on a number of food crops in many parts of the world. In recent years, there has been an important decrease in the number of organisms of Planorbarius corneus. Since the presence of pesticides in the water can be one of the reasons for this decrease, it is very important to study the effect of subchronic exposure to environmental concentrations of pesticides on these organisms. The aim of the present work was to investigate different effects of the subchronic exposure to low concentrations of the organophosphate chlorpyrifos in P. corneus and the possibility to use these as biomarkers. To this end, we have exposed the organisms to 0.4 and 5μgL−1 of chlorpyrifos for 14 days and recorded the number of egg masses, the number of eggs per mass, the number of eggs without embryo, the time for hatching, and the % of hatching and survival. We have also determined the activities of cholinesterases, carboxylesterases and glutathione S-transferase in whole organism soft tissue and in the gonads. A 14 days exposure to 0.4μgL−1 caused an increase in the number of egg masses without eggs and a decrease in carboxylesterases measured with p-nitrophenyl butyrate. However the exposure to 5μgL−1 also caused an increase in the time for hatching, a decrease in the % of hatching and survival and also inhibition of cholinesterases and carboxylesterases with p-nitrophenyl acetate and butyrate. In contrast, the glutathione S-transferase has not been modified with the tested concentrations. We concluded that when P. corneus exposed to chlorpyrifos for 14 days, the CES determined with p-nitrophenyl butyrate proved to be the most sensitive biomarker. However, exposure to environmental concentrations showed a decrease in the reproduction ability which could cause a decrease in the number of organisms of this species. [Copyright &y& Elsevier]

Abstract: Fever is regarded as a physiological response to infection both in endothermic and ectothermic animals. In ectotherms, fevers are achieved only behaviorally, and has been described in many vertebrates’ and few invertebrates’ groups. In snails only symptoms of reverse fever as a response to trematode invasion were found. Present work reports on the effects of two different pyrogens – lipopolysaccharide extracted from Escherichia coli (LPS), and zymosan – from Saccharomyces cerevisiae on the thermal behavior of wintering (studied during a winter season) specimens of the Planorbarius corneus (L.). Using the thermal gradient protocol we demonstrate that the individuals of this snail species responded with behavioral fevers to dosages of pyrogens. LPS injection to the surface of the snail’s foot at a dose of 10μg/g resulted in a significant increase in preferred temperature at 5h after injection. Similarly zymosan at a dose of 0.5 and 1.0μg/g – caused fever at 8h and 9h respectively. Average temperature chosen by feverish animals after latency period reached 28.7±0.41°C (LPS), 28.1±0.43°C (zymosan 1.0μg/g) or 25.5±0.33°C (zymosan 0.5μg/g). We conclude, therefore, that snails are capable of reacting with fever to selected pathogen associated factors, and P. corneus can be used as a model to study a behavioral fever phenomenon in invertebrate animals. [Copyright &y& Elsevier]

Abstract: The subject of the research was the thermal preferences of Planorbarius corneus individuals infected by larvae of digenetic trematodes. Snails were obtained over two consecutive years, 2009 and 2010, from 10 water bodies located in central Poland. The relationship between the seasons and the occurrence of patent invasions in hosts found in the shore-zone of lakes was observed. Behavioural experiments conducted on P. corneus individuals placed in a thermal gradient demonstrated that parasite infection had an impact on the thermal preferences of the snails. Individuals that shed cercariae of Bilharziella polonica, Cotylurus sp., Notocotylus ephemera, Rubenstrema exasperatum/Neoglyphe locellus, Rubenstrema opisthovitellinum, or Tylodelphys excavata displayed symptoms of behavioural anapyrexia, similarly to experimentally injured snails. This response increased the survival of infected individuals while simultaneously prolonging the period of shedding of dispersive forms of parasites. This point of view was upheld by the observation that infected snails bred at 19°C lived longer than at 26°C and the shedding rate of cercariae at a lower temperature was lower than at a higher one. [Copyright &y& Elsevier]

Abstract: Whilst the effects of oestrogenic contaminants in the aquatic environment are well documented in fish, effects in invertebrate species has been subject to debate, possibly due to differences in experimental conditions (temperature, timing and duration of exposure) between studies. It has been suggested that molluscs are only susceptible to oestrogens in periods either following the main spawning or leading up to the maturation of gametes. To investigate this possibility, two temperate, seasonally reproducing gastropods (Planorbarius corneus and Viviparus viviparus) were exposed to two concentrations of 17β-oestradiol (E2; 10ng/l and 100ng/l nominal) in an outdoor mesocosm (subject to natural seasons). In addition, P. corneus was also exposed to E2 (1, 10 and 100ng/l) in the laboratory at temperatures and photoperiods to simulate summer and autumn. In the mesocosm, both snail species produced similar numbers of eggs/embryos as reference groups in the summer, but the groups exposed to 10ngE2/l (nominal) had significantly higher productivities after the onset of autumn, when entering their quiescent phase, whilst the snails exposed to a higher concentration (100ng/l, nominal) had an increased rate of mortality, and did not experience increased reproduction. In the laboratory, the rate of egg laying in P. corneus was unaffected in simulated summer (20°C, 16h photoperiod), but snails exposed to 10 and 100ng/l (nominal) in simulated autumn (15°C, 12h photoperiod) showed a concentration-dependent inhibition of the natural decline in egg laying observed in the control snails. Overall, rather than an increase in reproductive rate, the response of this species was a perpetuation of summer reproductive rates into autumn. We conclude that exposure to E2 can affect reproduction in the freshwater gastropods studied, but in P. corneus at least, this is dependent on the seasonal conditions (temperature and photoperiod) at which exposures are made. [ABSTRACT FROM AUTHOR]

Abstract: The Great Ramshorn (Planorbarius corneus L.) is a frequent inhabitat of central European wetlands and floodplains. The dispersal capacity of P. corneus, as a key factor to survival, was analysed using different computer model approaches: a general equation-based model and an individual-based model. Both models came to different conclusions on the maximum covered distances of P. corneus-individuals. The parametrisation of the models were based on detailed laboratory measurements and field experiments performed with specimen of the fen wetland system of Rhin-Havelluch (Brandenburg, North-East Germany). Based on the results of the statistical analysis, the dispersal behaviour could be depicted in the equation-based model as a random walk which implied a relatively regular resource utilisation in long-term simulations. Depicting the dispersal qualities of P. corneus with a highly resolved individual-based model showed distinct local aggregations clusters of the snail-individuals. As a consequence, the resource utilisation was less regularly in the long-term simulations for the individual-based model than it was in the equation-based model. Another characteristic of the individual-based representation was that in the case of several consecutive move steps and based on the autocorrelation of the data the P. corneus-individuals could use a wider area of space. The data from the empirical measurements of short-term dispersal observations of single individuals were integrated within the different model extrapolations. This made it possible to discuss the long-term consequences, like the large dispersal range of the individuals and the spatial distribution of the population in the plane, for the persistence of P. corneus in a real landscape. [Copyright &y& Elsevier]

The aim of the present study was to investigate the involvement of nitric oxide (NO) as a messenger molecule in neuron–microglia communication in the central nervous system (CNS) of the freshwater snail Planorbarius corneus. The presence of both neuronal (nNOS) and inducible nitric oxide synthase (iNOS) was studied using NADPH-diaphorase (NADPH-d) histochemistry and NOS immunocytochemistry. The experiments were performed on whole ganglia and cultured microglial cells after different activation modalities, such as treatment with lipopolysaccharide and adenosine triphosphate and/or maintaining ganglia in culture medium till 7 days. In sections, nNOS immunoreactivity was found only in neurons and nNOS-positive elements were less numerous than NADPH-d-positive ones, with which they partially overlapped. The iNOS immunoreactivity was observed only after activation, in both nerve and microglial cells. We also found that the number of iNOS-immunoreactive neurons and microglia varied, depending on the activation modalities. In microglial cell cultures, iNOS was expressed in the first generation of cells only after activation, whereas a second generation, proliferated after ganglia activation, expressed iNOS even in the unstimulated condition. [Copyright &y& Elsevier]