Freshwater Pond Snail Research Articles

Ichnofossil morphology as a response to resource distribution: Insights from modern invertebrate foraging

A number of surficial horizontal ichnofossils have non-random, simple geometric morphologies such as spirals or meanders. These paths may result from an organism's interactive response to the perceived spatial distribution of resources on the seafloor. This hypothesis was tested by examining the movements of foraging invertebrates in response to the location, shape and internal density gradient of food patches in a controlled laboratory environment. Freshwater pond snails ( Planorbis planorbis), marine intertidal crabs ( Hemigrapsus nudus) and microscopic soil nematodes ( Caenorhabditis elegans) were placed in experimental arenas free of competitors and containing food patches of varying shapes and density distributions, and allowed to move and forage freely. Their movements were recorded at 1-minute intervals, and any visible tracks and trails were photographed. Pathways were digitally reconstructed using the recorded movement data, and along with the photographs were digitally analyzed. The total path length, path tortuosity, polygon area, step number, average step length and average turning radius within the resource patches were compared to the values for movement outside the resource patches. All three invertebrates engaged in area-restricted searching when within patches, consisting of a larger step number, higher path tortuosity, larger polygon area, greater turning radius, and a shorter step length. The behavior of these three invertebrate species suggests that resource distribution, in terms of patch morphology, acts as a strong control on forager movement and path morphology. Area-restricted searching as a distinct movement style may have evolved in response to the appearance of patchy resource distributions on the seafloor during the Cambrian substrate revolution.

Expression of exogenous fluorescent proteins in early freshwater pond snail embryos

We have for the first time succeeded in expressing in vitro-synthesized mRNAs in both the sinistral and the dextral Lymnaea stagnalis early embryos by microinjecting the mRNAs into the eggs before the first polar body stage. Translation of exogenous mRNA in developing embryos was confirmed by expressing various fluorescent proteins; mCherry, DsRed-Express, and enhanced green fluorescent protein. We have found that the protein expression derived from the introduced exogenous mRNA largely depends on the elapsed time after the microinjection and not on the developmental stage of injection, and also on the amount of injected mRNA. Developmental abnormalities were hardly observed. The first notable fluorescent signal was detected within 2-3 h after the injection while the embryos were still in uncleaved stage. Fluorescence gradually increased until 8-9 h and was stable up to 24 h. From these results, it is suggested that there is enough translation machinery necessary for early development and the translation of injected mRNA proceeds immediately and constantly in the early embryos. This is true for both the sinistral and dextral L. stagnalis embryos. Application of the developed method to other freshwater pond snails, dextral Lymnaea peregra, sinistral Physa acuta, and sinistral Indoplanorbis exustus revealed that their early expression mechanisms to be similar to that of L. stagnalis. Thus, in vitro-synthesized mRNA expression is expected to be important for the understanding of evolutional process and the molecular mechanism underlining the handedness determination in these freshwater snail embryos.

Hypoxia-induced modulation of the respiratory CPG

Despite recent advances in our understanding of the neural control of breathing, the precise cellular, synaptic, and molecular mechanisms underlying the generation and modulation of respiratory rhythm remain largely unknown. This lack of fundamental knowledge in the field of neural control of respiration is likely due to the complexity of the mammalian brain where synaptic connectivity between central respiratory neurons, motor neurons and their peripheral counterparts cannot be mapped reliably. We have therefore developed an invertebrate model system wherein the essential elements of the central pattern generator (CPG), the motor neurons and the peripheral chemosensory cells involved in respiratory control have been worked out both in vivo and in vitro. We discuss our recent identification of peripheral, hypoxia sensitive chemoreceptor elements in a sensory organ of the pulmonate freshwater pond snail Lymnaea stagnalis, which provide an excitatory drive to the respiratory CPG neuron RPeD1 via direct chemical synaptic connections. Further studies using this unique invertebrate model system may reveal highly conserved principles of CPG neuromodulation that will remain relevant to more complex mammalian systems.

Memory from one-trial training is resistant to extinction in Lymnaea Stagnaliss

Background: Memories that follow a traumatic event or extreme stress have been shown in some cases, to be particularly resistant to therapies meant to reduce their impact on patients. Two methods shown to decrease memories in laboratory tests are disruption after reactivation and extinction training. Newly formed memories undergo a period of stabilization, during which they are susceptible to amnesia treatments. Over a period of time memories become stabilized and can no longer be disrupted. However memories that are retrieved are returned to a labile state that must undergo a process of ‘reconsolidation’. Also, many memories can be occluded by ‘extinction training’, which consists of withholding the training stimulus in the training environment resulting in a new memory that overshadows the original training. 
 Methods and Results: Using the Lymnaea stagnalis model system we show that memories following an extreme aversive stimulus demonstrate resistance to manipulation by these methods. Lymnaea stagnalis are fresh-water pond snails that can breathe either cutaneously or aerially through an orifice (pneumostome). Snails can form a long-term memory (LTM) to suppress pneumostome opening after operant conditioning consisting of either multiple sessions of repeated tactile stimulation to the orifice area each time the snail attempts to open its pneumostome or a single applications of 25mM KCl stimulus contingent with pneumostome opening (one-trial training; 1TT). The LTM formed following one-trial training has many of the same characteristics as memory formed following repetitive tactile training. Specifically, both are dependent on new mRNA synthesis in the circuit that controls aerial respiration and both can be blocked by cooling immediately after training. However, we show that memories in Lymnaea that form after a single, highly aversive stimulus, unlike LTM after repetitive training, aren’t disrupted after reactivation. We also attempted to extinguish the 1TT memory by placing the snails in the training beaker and not applying the KCl stimulus when they opened their pneumostome. When repetitive training was employed, extinction sessions such as these resulted in naïve levels of aerial respiration i.e. occlusion of the operantly trained memory. 
 Conclusions: Therefore, memory after 1TT is more resistant to suppression by extinction training than memories formed after less aversive stimuli. Further research will attempt to determine the cellular mechanism that causes the memory to be particularly resilient.

Role of chemical signalling in release of motor programs during embryogenesis of freshwater snails Lymnaea stagnalis and Helisoma trivolvis

We have earlier found that freshwater pond snails Helisoma trivolvis and Lymnaea stagnalis, when reared under conditions of starvation, release chemical signals that reversibly suppress larval development of conspecific embryos. Here, we report that (i) these signals are not strictly conspecific and affect also embryos of a closely related species, which occupies a similar environmental niche; (ii) besides the development of embryos, the signals also affect the release of main motor programs, such as locomotion, feeding, and cardiac activity; (iii) action of the signals is bidirectional: they retard the development and release of motor programs at the early larval stages (trochophore to veliger) and accelerate them at later stages (late veliger to hatching). A possible adaptive significance of the described phenomena is discussed.

The Political Economy of Asian Transition from Communism. Suijian Guo

Previous articleNext article No AccessReviewsThe Political Economy of Asian Transition from Communism. Suijian Guo Le-Yin ZhangLe-Yin Zhang Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The China Journal Volume 57Jan., 2007 Published on behalf of the Australian Centre on China in the World at the Australian National University Article DOIhttps://doi.org/10.1086/tcj.57.20066249 Views: 4Total views on this site Citations: 10Citations are reported from Crossref Copyright The China JournalPDF download Crossref reports the following articles citing this article:Shaofeng Xu, Lingyue Zhang, Kaizong Lin, Miao Bai, Yue Wang, Mengyao Xu, Minglu Zhang, Can Zhang, Yun Shi, He Zhou Effects of light and water disturbance on the growth of Microcystis aeruginosa and the release of algal toxins, Water Environment Research 93, no.1212 (Oct 2021): 2958–2970.https://doi.org/10.1002/wer.1644Gülüzar Atli How metals directly affect the antioxidant status in the liver and kidney of Oreochromis niloticus? An in vitro study, Journal of Trace Elements in Medicine and Biology 62 (Dec 2020): 126567.https://doi.org/10.1016/j.jtemb.2020.126567Min Shen, Yanting Cui, Renjie Wang, Tiantian Dong, Haibin Ye, Shusheng Wang, Ranghui Fu, Yuquan Li Acute response of Pacific white shrimp Litopenaeus vannamei to high-salinity reductions in osmosis-, metabolism-, and immune-related enzyme activities, Aquaculture International 28, no.11 (Aug 2019): 31–39.https://doi.org/10.1007/s10499-019-00441-yZhihua Ren, Yu Fan, Zhuo Zhang, Chaoxi Chen, Changhao Chen, Xuemei Wang, Junliang Deng, Guangneng Peng, Yanchun Hu, Suizhong Cao, Shumin Yu, Xiaoping Ma, Liuhong Shen, Zhijun Zhong, Ziyao Zhou, Zhiwen Xu, Zhicai Zuo Sodium selenite inhibits deoxynivalenol-induced injury in GPX1-knockdown porcine splenic lymphocytes in culture, Scientific Reports 8, no.11 (Dec 2018).https://doi.org/10.1038/s41598-018-36149-xGülüzar Atli, Martin Grosell Characterization and response of antioxidant systems in the tissues of the freshwater pond snail (Lymnaea stagnalis) during acute copper exposure, Aquatic Toxicology 176 (Jul 2016): 38–44.https://doi.org/10.1016/j.aquatox.2016.04.007Sachin O. Khairnar, Xiangli Tian, Shuanglin Dong, Ziheng Fang, Bhavesh V. Solanki, Holeyappa A. Shanthanagouda Effects of the amplitude and frequency of salinity fluctuations on antioxidant responses in juvenile tongue sole, Cynoglossus semilaevis, Spanish Journal of Agricultural Research 14, no.22 (Jun 2016): e0503.https://doi.org/10.5424/sjar/2016142-8691Guo-Di Liu, Zhang Sheng, You-Fa Wang, Ying-Li Han, Yang Zhou, Jun-Quan Zhu Glutathione peroxidase 1 expression, malondialdehyde levels and histological alterations in the liver of Acrossocheilus fasciatus exposed to cadmium chloride, Gene 578, no.22 (Mar 2016): 210–218.https://doi.org/10.1016/j.gene.2015.12.034E. Baysoy, G. Atli, C.Ö. Gürler, Z. Dogan, A. Eroglu, K. Kocalar, M. Canli The effects of increased freshwater salinity in the biodisponibility of metals (Cr, Pb) and effects on antioxidant systems of Oreochromis niloticus, Ecotoxicology and Environmental Safety 84 (Oct 2012): 249–253.https://doi.org/10.1016/j.ecoenv.2012.07.017Fei Yin, Baojun Tang, Dong Zhang, Xiong Zou Lipid Metabolic Response, Peroxidation, and Antioxidant Defence Status of Juvenile Lined Seahorse, Hippocampus erectus , Fed with Highly Unsaturated Fatty Acids Enriched Artemia Nauplii, Journal of the World Aquaculture Society 43, no.55 (Oct 2012): 716–726.https://doi.org/10.1111/j.1749-7345.2012.00598.xFei Yin, Shiming Peng, Peng Sun, Zhaohong Shi Effects of low salinity on antioxidant enzymes activities in kidney and muscle of juvenile silver pomfret Pampus argenteus, Acta Ecologica Sinica 31, no.11 (Feb 2011): 55–60.https://doi.org/10.1016/j.chnaes.2010.11.009

Apical sensory neurones mediate developmental retardation induced by conspecific environmental stimuli in freshwater pulmonate snails.

Freshwater pond snails Helisoma trivolvis and Lymnaea stagnalis undergo larval development and metamorphosis inside egg capsules. We report that their development is permanently under slight tonic inhibitory influence of the anterior sensory monoaminergic neurones, which are the remnants of the apical sensory organ. Conspecific juvenile snails, when reared under conditions of starvation and crowding, release chemical signals that are detected by these neurones in encapsulated larvae and reversibly suppress larval development, thus providing a link between environmental signals and developmental regulation. Induced retardation starts from the trochophore stage and results in up to twofold prolongation of the larval lifespan. Upon stimulation with the signal, the neurones increase synthesis and release of monoamines [serotonin (5-HT) in Helisoma and dopamine in Lymnaea] that inhibit larval development acting via ergometrine-sensitive internal receptors. Thus, the novel regulatory mechanism in larval development of molluscs is suggested and compared with the phenomenon of dauer larvae formation in the nematode Caenorhabditis elegans.

Partial characterisation of high-molecular weight glycoconjugates in the trail mucus of the freshwater pond snail Lymnaea stagnalis

We have studied the glycoconjugates in trail mucus of the pond snail Lymnaea stagnalis. The mucus was dissolved with 6 M guanidinium hydrochloride (GuHCl) and the major component was comprised of very high- M r glycoconjugates that were eluted in the void volume of a Sepharose CL-4B gel-filtration column. This high- M r material was pooled and thereafter subjected to density gradient centrifugation first in 4 M GuHCl/CsCl and subsequently 0.2 M GuHCl/CsCl to further remove non-glycosylated proteins and DNA. The harvested glycoconjugate pool chromatographed in the void volume of Sepharose CL-2B. However, reduction of disulfide bonds lowered the molecular size of approximately 80% of the void material yielding a major fragment and some minor smaller fragments in gel chromatography. The reduced glycoconjugates were digested with papain and yielded high molecular weight, proteinase-resistant glycopeptides. This fragmentation pattern is similar to that found for oligomeric gel-forming mucins in mammals and the amino acid composition (60% Ser/Thr) and sugar analysis of the glycopeptides is consistent with mucin-like molecules, there being no significant amounts of xylose or uronic acids. The residual 20% of the preparation, which apparently resisted reduction and protease digestion, had a similar amino acid composition to the bulk, but was somewhat different in sugar composition, containing some xylose and a significant amount of glucuronic acid. The two groups of molecules had very different morphologies in the electron microscope. Taken together, these data suggest that trail mucus is a complex mixture of at least two families of protein-glycoconjugate molecules based upon the gel-forming mucin and proteoglycan families, though we cannot rule out that polysaccharides may also be present.

Regulation of seasonal reproduction in mollusks.

Understanding the physiological basis of environmental regulation of reproduction at the cellular level has been difficult or unfeasible in vertebrate species because of the highly complex and diffuse nature of vertebrate neuroendocrine systems. This is not the case with the simple nervous system of mollusks in which reproductive neuroendocrine cells are often readily identifiable in living tissue. Given that there are mollusks that are seasonal breeders, that the neuroendocrine cells controlling reproduction have been identified in several molluskan species, that these neurons are conducive to cell physiological analysis, and that basic features of cell biology have been highly conserved between mammals and mollusks, it seems that the mollusk would provide an excellent model system to investigate cell-physiological events that mediate effects of environmental signals on reproduction. The purpose of this review is to explore this idea in three species in which the topic of the neural basis of seasonal reproduction has been studied: the giant garden slug Limax maximus, the freshwater pond snail Lymnaea stagnalis, and the marine snail Aplysia californica.

Foraging trade‐offs and resource patchiness: theory and experiments with a freshwater snail community

Empirical results concerning a freshwater snail community are interpreted using a two‐species consumer model that incorporates resource structure. Behavioural‐scale measurements on a guild of five species of freshwater pond snails (Mollusca: Pulmonata) indicate a trade‐off between the ability to utilize a patch’s resource and the ability to quickly find new resource patches. Community‐level experiments demonstrate that both species richness and composition are affected by the patchiness of the environment. In particular, treatments with low patchiness are dominated by species best at exploiting local resources (diggers) whereas treatments with high patchiness are dominated by species best at finding new patches (grazers). Results from a controlled mesocosm experiment with two of the most common of these species, Helisoma trivolvis (a relative digger) and Physella gyrina (Physidae) (a relative grazer) show that the patchiness of the environment strongly influences the outcomes of interspecific competition among these two species: the digger performed much better in less patchy habitats, whereas the grazer performed better in more patchy habitats. A two‐species model of diggers and grazers modified to incorporate behavioural aspects of patchiness produces this same pattern of competitive outcomes.

Identification of a putative mechanosensory neuron in Lymnaea: characterization of its synaptic and functional connections with the whole-body withdrawal interneuron.

1. In this study, we identified a putative mechanosensory neuron in the freshwater pond snail Lymnaea stagnalis. This sensory neuron, termed right parietal dorsal 3 (RPD3), mediates part of the whole-body withdrawal behavior via the activation of a withdrawal interneuron. 2. RPD3 is located in the central ring ganglia, where its soma is situated on the dorsal surface of the right parietal ganglion. Intracellular injection of the dye Lucifer yellow revealed that RPD3 has both central and peripheral axonal projections. 3. In isolated-CNS preparations, RPD3 was quiescent. In semi-intact preparations, however, a gentle/moderate mechanical touch (by a pair of blunt forceps) to the mantle cavity or columellar musculature elicited action potentials in RPD3 in the absence of prepotential activity. Furthermore, mechanical stimulus-induced action potentials in RPD3 persisted in the presence of zero Ca2+/ high Mg2+ and high Ca2+/high Mg2+ salines. Together, these data suggest that RPD3 is most likely to be a primary sensory neuron. 4. In both isolated-CNS and semi-intact preparations, intracellular depolarization of RPD3 excited the whole-body withdrawal interneuron right pedal dorsal 11 (RPeD11). This synaptic connection persisted in the presence of high Ca2+ and high Mg2+ saline, suggesting that it is likely to be monosynaptic. Moreover, when stimulated electrically, the interneuron RPeD11 induced an hyperpolarizing response in RPD3. The possibility of this connection being monosynaptic was not tested, however, in the present study. Together, these data demonstrate that RPD3 excites RPeD11, which in turn may inhibit RPD3 activity. 5. In the semi-intact preparation, a mechanical touch to the mantle edge excited RPD3, which in turn generated action potentials in RPeD11. Zero Ca2+ saline blocked this synaptic connection between RPD3 and RPeD11, suggesting that it is chemical. 6. To demonstrate that RPD3 was sufficient to induce the withdrawal response and that the withdrawal behavior was mediated indirectly via RPeD11, we made simultaneous intracellular recordings from these two neurons while monitoring muscle contractions via a tension transducer. Intracellular depolarization of RPD3 elicited action potentials in RPeD11, followed by the contraction of the columellar muscle. Similar stimulation of RPD3 failed to excite a simultaneously hyperpolarized RPeD11 and as a result, no contraction of the columellar muscle occurred. Direct intracellular depolarization of RPeD11, however, induced the contraction of the columellar muscle. These data suggest that RPD3-induced withdrawal behavior is mediated in part via RPeD11.

Effect of aluminium and lead on activity in the freshwater pond snail Lymnaea stagnalis

Time-lapse video was used to examine the effect of short- (19 h) and long-term (1 year) exposure to Al or Pb at neutral pH in static water conditions on the total distance moved by the freshwater snail Lymnaea stagnalis. Aluminium at 100, 200, 500, or 1000 μg∙L−1 normally depressed and Pb at 50 and 200 μg∙L−1 often increased activity over the first 19 h of exposure. Smaller (younger) snails generally showed greater sensitivity to Al. Exposure to 100 or 500 μg Al∙L−1 for up to 30 days caused hyperactivity, but thereafter and 1 year later, activity was similar to controls, suggesting that the snails had become tolerant. Lead (200 μg∙L−1) caused continued hyperactivity for up to 50 days, although movement was significantly reduced after 1 year, suggesting that acclimation had occurred. The effect of Al is interesting given the supposed limited bioavailability of this metal at neutral pH.

DIFFERENTIAL TRACER COUPLING BETWEEN PAIRS OF IDENTIFIED NEURONES OF THE MOLLUSC LYMNAEA STAGNALIS

Electrical coupling is a common means of cell-to-cell communication in both neuronal and non-neuronal tissues (Lowenstein, 1985). Within the nervous system, many electrically coupled neurones exhibit dye coupling (Bennett, 1973; Stewart, 1978; Glantz and Kirk, 1980; Spencer and Satterlie, 1980; Fraser and Heitler, 1993); however, some electrically coupled cells do not dye-couple (Audesirk et al. 1982; Murphy et al. 1983; Berdan, 1987; Robinson et al. 1993; Veenstra et al. 1993). Electrical coupling and dye coupling, often considered in parallel, are in fact two different parameters that can vary independently (e.g. Audesirk et al. 1982; Perez-Armendariz et al. 1991). The giant identified neurones of pulmonate and opisthobranch molluscs have frequently been used for studies of neuronal communication and its plasticity (Winlow and McCrohan, 1987; Bulloch, 1989). In the present study, we explored the relationship between electrical and tracer coupling in both strongly and weakly coupled pairs of molluscan neurones. Specifically, we examined electrically coupled, identified neurones in a freshwater pond snail, Lymnaea stagnalis L., and tested for tracer coupling with Lucifer Yellow CH and biocytin. The cells examined were the strongly electrically coupled neurones, visceral dorsal 1 (VD1) and right parietal dorsal 2 (RPD2) (Boer et al. 1979; Benjamin and Pilkington, 1986), and the weakly coupled neurones, left buccal 1 (LB1) and right buccal 1 (RB1) (Benjamin and Rose, 1979). The use of these particular neurones made it possible to compare electrical coupling with tracer coupling in the molluscan central nervous system (CNS). All experiments were performed on laboratory-bred Lymnaea stagnalis (Mollusca, Pulmonata), maintained as previously described (Ridgway et al. 1991). The CNS was dissected from mature animals (16­18 mm shell length) and pinned to the silicone rubber (RTV 616 GE) base of a recording dish in normal saline (51.3 mmol l-1 NaCl, 1.7 mmol l-1 KCl, 4.1 mmol l-1 CaCl2, 1.5 mmol l-1 MgCl2 and 5 mmol l-1 Hepes, pH 7.9). Following removal of the outer connective tissue sheath, a small Pronase crystal (Sigma, type XIV, P-5147), held by forceps, was carefully applied to specific ganglia; this treatment softened the inner sheath and facilitated microelectrode penetration. The CNS was then rinsed several times at 5 °C in normal saline.

Trematode Prevalence and the Population Dynamics of Freshwater Pond Snails

-We performed a 4-yr study of prevalence of larval trematodes in three populations of two snail species in three Indiana ponds and also recorded the relative abundance of cercarial types in these species (Lymnaea elodes and Physa gyrina), as well as a third species, Helisoma trivolvis. Yearly variation in L. elodes was considerable, but prevalence was greatest in the least productive pond (24% of snails for both L. elodes and P. gyrina) because longer generation times increased the frequency of older snails in samples, and prevalence increased with age. In dry seasons, prevalence averaged only 7.9% in vernal ponds, but increased to 25.6% in wet years. Prevalence actually increased in dry years in a permanent pond. These changes were due perhaps to alteration of final host visitation of ponds, indicating the importance of habitat predictability (e.g., time pond remains full). Over all ponds and years, 17% of Lymnaea elodes collected were infected, and prevalence increased with shell size (and age). The dominant cercarial type in L. elodes was an echinostome, in P. gyrina, a notocotylid, and in H. trivolvis, a spirorchid. Life tables constructed here for the first time for Lymnaea elodes using these age-specific prevalences, along with field survivorship and fecundity data, indicate that parasites can lower replacement rates of snail populations by approximately 10 to 20%. Manipulatory experiments in field situations are necessary to determine if this loss of reproduction can regulate host populations.

Sensitivity of freshwater pulmonate snails, Lymnaea luteola L., to heavy metals.

The current alarm of the impacts of metal pollution on living organisms has received much attention with the tragedy of Minimata and later Niigata, in Japan. Although there has been a great deal of the concern about the acute and chronic toxicities of heavy metals to freshwater fishes and crustaceans but little information is available on the effects of heavy metals to freshwater snails, which are widely distributed in the aquatic environment. The present study was undertaken to determine the acute toxicities of selected heavy metals to a freshwater pond snail Lymnaea luteolo Lamarck; a locally abundant species and play an important role in the aquatic food chain(s). Static bioassays were conducted with the salts of cadmium, copper, chromium, mercury, nickel, silver and zinc in hard water.

Zinc sensitivity of a freshwater snail, Lymnaea luteola L., in relation to seasonal variations in temperature.

The aquatic environment has numerous physical and chemical parameters that may influence the physiology and chemical toxicity to freshwater organisms. Temperature is one of the these factors having a marked influence on heavy metal toxicity to fishes and macroinvertebrates. There is a limited and scattered information available on temperature induced changes in acute toxicity of zinc compounds to freshwater pond snails. This information is essential because there are large temperature differences with season and latitudes and the aquatic organisms are subjected to seasonal temperature changes of 20-25/sup 0/C or even more. It is proposed to study the effect of seasonal changes in temperature on zinc toxicity to a freshwater pond snail, Lymnaea luteola (Lamarck), which form an important link in aquatic food chain(s) and are widely distributed in lakes, ponds and rivers of India.

Histopathological Changes Induced by Pentachlorophenol and Sodium Pentachlorophenate in the Mantle of the Freshwater Snail Viviparus bengalensis (L.)

AbstractThe freshwater pondsnail Viviparus bengalensis (LINNAEUS) was exposed to sublethal concentrations of pentachlorophenol (1.561 mg/l) and sodium pentachlorophenate (0.991 mg/l). Both the chemicals caused considerable damage in the mantle of the snail. Their toxic effects included shrinkage and elongation of epithelial cells, the cells losing contact with each other, resulting in the formation of intercellular spaces, enlargement of nuclei, shrinkage of the basement layer and loss of shape of polygonal cells of connective tissue.

Evidence for genetic influences on neurotransmitter content of identified neurones of lymnaea stagnalis

1. Neurotransmitter content was measured in two identified giant neurones in isogenic and wild-type populations of the freshwater pond snail Lymnaea stagnalis. 2. The paired serotonergic cerebral giant neurones (LCl and RCl) have higher transmitter levels and less variability in inbred animals than in wild-type animals. 3. The transmitter content of the unpaired dopaminergic right pedal giant neurone (RPeDl) does not differ between inbred and wild-type animals in either level or variability. 4. It is proposed that serotonin content of the cerebral giant neurones is under partial genetic control, and that animals of the wild-type population may possess a number of different alleles for the genes influencing serotonin levels. 5. Inbreeding resulted in fixation of an allele promoting high serotonin levels. 6. This particular wild-type population is probably already isogenic for genes influencing dopamine content in the right pedal giant neurone.

Amine-containing neurons in the brain of Lymnaea stagnalis: Distribution and effects of precursors

1. 1. Glyoxylic acid-induced fluorescence in whole-brain preparations of the central nervous system of the freshwater pond snail, Lymnaea stagnalis, was used to map the distribution of serotonin and dopamine-containing neurons. Serotonin and dopamine were easily distinguishable by differences in color of fluorescence. 2. 2. Serotonin-containing neurons were consistently found in the cerebral, pedal, right parietal and visceral ganglia. Dopamine-containing neurons were found in the pedal, and buccal ganglia. 3. 3. Prior incubation of brains in 5-hydroxytryptophan (5-HTP), the immediate precursor to serotonin, produced serotonin-like fluoresence in neurons which do not normally fluoresce. These neurons thus probably possess specific uptake mechanisms for 5-HTP. Since 5-HTP itself fluoresces yellow, the glyoxylic arid technique cannot determine if these neurons contain the enzyme aromatic amino acid decarboxylase, which converts 5-HTP to serotonin, or merely fluoresce because of the 5-HTP taken into the cells.

The temperature dependence of the acute toxicity of copper to a freshwater pond snail, Viviparus bengalensis L.

Static bioassays with copper (as CuSO4 · 5H2O) were conducted in laboratory with a freshwater pond snailViviparus bengalensis, at different environmental temperatures. The 96 hr LC50 values in ppm of Cu were 0.060 at 32.5 °C; 0.066 at 24 °C; 0.09 at 27.3 °C and 0.39 at 20.3 °C. In higher copper concentrations some behavioural changes such as secretion of mucus, discharge of eggs and embryos were noted. The results indicate that toxicity to copper increases with temperature increase.