Freshwater Pulmonate Snail Research Articles

Extracellular application of cobalt: a fast and simple method for delineating invertebrate neurosecretory pathways

The extracellular cobalt backfilling technique was shown to be an excellent method to obtain cobalt backfills of invertebrate neurosecretory cells (NSCs). Aqueous cobalt was placed in an extracellular suction electrode into which a portion of a neurohaemal (NH) region containing the axons and/or terminals of NSCs was drawn. Spontaneously discharging extracellular action potentials were recorded as the cobalt was applied to the NH region, and the greater the electrical activity, the more extensive the cobalt backfilling. The greatest success occurred with 0.5 M cobalt chloride dissolved in physiological saline. No backfills were obtained in the absence of electrical activity. This technique was shown to backfill NSCs terminating in NH regions of the insect, Rhodnius prolixus, the isopod crustacean, Oniscus asellus, and the freshwater pulmonate snail, Helisoma. Combined with a light insensitive silver intensification method, this paper describes a relatively fast and simple method for delineating invertebrate neurosecretory pathways.

The impairment of mobility and development in freshwater snails ( Physa fontinalis and Lymnaea stagnalis caused by herbicides

1. 1. The pulmonate freshwater snails Physa and Lymnaea and the earthworms Eisenia and Lumbricus can take up and concentrate a carbamate herbicide (chlorpropham). 2. 2. The mobility of freshwater snails was diminished in the presence of the herbicides chlorpropham (carbamate), cycloate (thiocarbamate), pentanochlor (amide) and chloroxurone (urea derivate). 3. 3. The egg-assemblies of Lymnaea stagnalis turned out to be suitable objects for testing the influences of herbicides upon embryonic development. 4. 4. In the presence of chlorpropham, chloroxurone, cycloate, propanil, simazine and terbutryne, all applied in concentrations lower than in practical use, the period of egg-maturing was delayed and the total number of dead embryos increased. 5. 5. Developing snail eggs were very sensitive towards triazine herbicides (simazine, terbutryne) reflecting in an ed 50-value lower than 10 −7M. 6. 6. Similar herbicidal-induced effects suggested that the developing stages of snail embryos may be suitable models for the ecologically more important but experimentally less accessible earthworms.

The Effects of Isolation, Grouping and Population Density on Fecundity ofBulinus truncatus

Summary Bulinus truncatus is the intermediate host of Schistosoma haematobium, a trematode parasite causing bladder bilharziasis in man. In the struggle against this disease, control of snail populations is an important goal and expansion of our knowledge of the reproductive activity of Bulinus is relevant in this regard. In this study the effects of various factors on the fecundity of Bulinus were investigated in specimens kept under continuous water refreshment conditions. The results are considered to be more indicative of the natural situation than results obtained under the current use of discontinuous water refreshment. Isolated snails produce considerably higher numbers of egg masses and eggs than grouped snails. The effect of grouping on isolated snails, and the reverse situation, is very rapid, being fully effective within one week. The increase in fecundity of isolated snails is most probably caused by the absence of copulatory activity, since transfer of semen is known to curtail egg laying in freshwater pulmonate snails. Egg mass production was shown to decrease with increasing population density. This may be caused either by the difference in space available or by the possible difference in copulatory activity. Isolated snails showed a faster body growth than grouped snails. The possible role of hormones involved in establishing the above effects and the consequences of the results for snail control programs are discussed.

Copper toxicity to the fresh water snail,Lymnaea luteola

Haemocyanins are found in arthropoda and mollusca and show a copper content characteristic for each phylum. Heavy metal accumulation by mollusks is widely reported. Approximately one third of the enzymes either required addition of a metal ion as a cofactor in order to exhibit maximum activity or contained a slightly bound metal ion which appeared to be involved in the catalytic process. Copper is the only metal which has been detected in significant amounts in amino oxidase. The present study is designed to evaluate the influence of such copper, which is of such common occurrence in biological material, on some of the lipolytic enzymes of fresh water pulmonate snail, Lymnaea luteola when added to ambient medium. The present study also highlights the possible detoxification mechanism prevailing in this fresh water mollusk.

An evaluation of the interactions between freshwater pulmonate snail hosts of human schistosomes and macrophytes.

An account is given of a laboratory investigation designed to evaluate the extent to which the freshwater pulmonate snail Biomphalaria glabrata (Say) can utilize various species of aquatic plants, mainly macrophytes, when presented in the following forms over different time scales: normal plants; dried plant material; homogenized plant material in calcium alginate matrices; water-soluble filtrates of plant homogenates in the medium. The following propositions, derived from the theory of phased coevolution of components of the module consisting of the epiphytic bacteria, algae, snails and macrophytes, are evaluated on the basis of the present results and others including those obtained in this laboratory. That as the snails had become specialized to exploit surface communities of epiphytic algae, decaying plant material and dissolved organic matter (DOM) early in their evolutionary history they would continue to exploit these resources when they later become associated with aquatic macrophytes. That pulmonate snails would tend to be feeding generalists capable of adapting to food of varying chemical composition, given sufficient time, provided it was sufficiently small or flaccid. That although macrophytes and snails show a strong positive relationship, the living macrophyte tissue would be little used by the snails. That the hard outer envelope, inherited from their terrestrial ancestors, would remain as the major defence mechanism of aquatic macrophytes against attack by snails and other aquatic invertebrates. That aquatic macrophytes would invest little in the nutrient deficiency strategy to reduce attack by invertebrates such as snails. That truly aquatic submerged macrophytes would not possess secondary plant compounds (SPC) that would be molluscicidal. Emergent parts of subaquatic or aquatic plants might be expected to be better sources of SPC with molluscicidal factors than submerged aquatic plants. Species of epiphytic or planktonic algae might be better sources of SPC with molluscicidal effects than aquatic macrophytes. That the strategies developed by pulmonate snails for obtaining their energy supplies would not be conducive to rapid speciation. The analysis of the present and other related results supports these propositions. Predictions based on the theory of mutualism involving the snails, macrophytes and other components of the module also receive some support from an analysis of the present results. The additional empirical work that could be undertaken to test this theory is briefly discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Histopathology of larval trematode infections in the freshwater pulmonate snail, Helisoma anceps

A histological examination of Diplostomulum scheuringi and Halipegus occidualis infections in the pulmonate snail, Helisoma anceps, revealted extensive damage caused by the parasites. Sporocysts of D. scheuringi were found in the digestive gland and gonad of infected snails. Several extensive encapsulation responses were noted in the digestive gland. These foci are believed to have been elicited around both sporocysts and migrating cercariae. The castration of snails infected by D. scheuringi is believed to be chemically mediated. Rediae of H. occidualis caused significant mechanical damage to both hepatopancreatic and gonadal tissue of H. anceps. Castration was almost always found to be the result of infection by this paratsite species. The damage was primarily mechanically mediated, through direct ingestion of tissue by the rediae.

Relationships between apparent net H + excretion and Na +, Ca 2+ and Cl − uptake in the pulmonate freshwater snail Lymnaea stagnalis

1. 1. Lymnaea stagnalis was able to take up Na + from Cl −-free (1 mM Na +) and Cl − from Na +-free (1 mM Cl −) media. The respective uptake rates, however, were smaller than those from 1 mM NaCl. 2. 2. Under Cl −-free conditions Na + uptake coincided with almost equivalent apparent net H + excretion. 3. 3. Cl − uptake under Na +-free conditions did not coincide with negative apparent net H + excretion, but with equivalent net Ca 2+ uptake. 4. 4. Under NaCl-free conditions the snails continuously absorbed Ca 2+ associated with equivalent apparent net H + excretion. 5. 5. The model for the mechanisms of Na + and Cl − uptake in L. stagnalis, by Na +/H + and Cl −/HCO 3 − exchange, have to be extended with Ca 2+/2H + exchange and/or Ca 2+ −2HCO 3 − cotransport.

Neurohormonal control of Na + and Cl − metabolism in the pulmonate freshwater snail Lymnaea stagnalis

In Lymnaea stagnalis, extirpation of the cerebral ganglia resulted in a significant decrease of the Na + and Cl − concentrations in the haemolymph. In intact snails, injection of an extract of the cerebral ganglia stimulated the Na + influx from the external medium in a dose-dependent way. No effect on the Cl − influx was found. Extract injections did not affect the Na + efflux. The Na + influx stimulating activity, in relatively high concentrations, was also present in extracts of the median lip nerve (an important neurohaemal area, originating from the cerebral ganglia). The influx-stimulating activity was heat-stable and destroyed by Pronase treatment. It is suggested that in L. stagnalis, Na + uptake from the medium is controlled by a neurohormone produced by the cerebral ganglia.

The feeding strategies of juvenile and adult Biomphalaria glabrata (Say) under simulated natural conditions and their relevance to ecological theory and snail control

Aspects of the feeding biology of the freshwater pulmonate snail Biomphalaria glabrata were studied under simulated natural conditions in the laboratory by examining crop and rectal contents, the mouth parts of the snail and its method of feeding when presented with a variety of potential food items. The results confirm the generalization that freshwater pulmonate snails, such as B . glabrata , subsist mainly by selecting decaying macrophyte tissue, colonial diatoms and smaller green algae in preference to living macrophyte tissue, filamentous green algae, or small adpressed forms of epiphytic diatoms and epiphytic bacteria. The generalist feeding strategy adopted by B . glabrata can be related to the morphology of the mouth parts and to its feeding behaviour. The adult snail has a total of about 4425 radula teeth (in 75 transverse rows each with 59 teeth) whose dimensions are of the same order of magnitude as diatoms, with narrow gaps in between, thus making the radula an ideal system for scraping the larger, colonial diatoms from the surface of freshwater macrophytes, but not the smaller adpressed diatoms or bacteria. The snails show considerable flexibility in the use of the mouth parts. Thus, the extent of the area grazed by the radula can be regulated by changes in the direction or velocity of the head movements. The latter may be either straight or pendular while the number of bites per sweep can be varied from two to nine. The dorsal mandible may also be used independently for scraping epiphytic algae. Living macrophyte tissue is cut by the backwardly directed power stroke of the radula, sometimes acting in opposition to the dorsal mandible, whereas the flaccid decaying macrophyte tissue can be ingested by a pumping action with minimal use of the radula. The costs and benefits of the various strategies are discussed. There are marked differences between the feeding niches of juvenile and adult B . glabrata as the former eat less living macrophyte tissue and fewer species of large diatoms but much larger quantities of decaying plant material than their adult conspecifics. These ontogenetic changes can be related to variations in the relative growth rate of the odontophore and their chemoreception niches. The ratio of the abundance of food items in the crop to the rectum indicate that macrophyte tissue is probably used almost completely but that the green algae Scenedesmus and Rhizoclonium may pass through the gut undigested. Many of the diatom species are also resistant to digestion. The sizes of particles ingested vary from 0.026 to 0.78 mm 2 the latter being the largest the snails are capable of swallowing. As the snails prefer flaccid material it is suggested that controlled release formulations, designed to kill target snails selectively, should be of this consistency and the above size range. The results are discussed within the context of the hypothesis that the snails, the macrophytes, their epiphytic algae and the bacteria involved in decomposition are components of a module with six subsets (Paine 1980). Evidence is given that the linkage between each of the subsets are strongly mutualistic, and that they involve the release and use of dissolved organic matter. It is argued that these positive interactions must be taken into account when constructing models to explain stability and complexity of communities.

The hyperglycemic factor of the CNS of the freshwater snail Lymnaea stagnalis: Interaction with glucose stimulation of glycogen synthesis and evidence for its release during anaerobiosis

In the freshwater pulmonate snail Lymnaea stagnalis glycogen synthesis in the glycogen storage cells (GC) is stimulated by increasing external glucose concentrations. On the other hand, a hyperglycemic factor from the CNS inhibits glycogen synthesis and stimulates glycogen breakdown in these cells. This CNS factor may be involved in the physiological control of glycogen mobilization. In the present study the interaction between the inhibiting effect of the CNS factor and the stimulating effect of increasing glucose concentrations on glycogen synthesis in isolated GC was investigated. The results, analyzed by determination of the Michaelis-Menten parameters for saturation kinetics, suggest that the CNS factor increases the glucose concentration required for half-maximal stimulation of glycogen synthesis, but does not influence the maximum rate of synthesis (competitive type of inhibition). The role of the hyperglycemic factor during conditions of glycogen breakdown was investigated by extirpation of the cerebral ganglia (-CG), which contain the main release sites of the factor. Extirpation did not affect the hemolymph glucose concentration or the glycogen levels in the GC during starvation. However, -CG animals showed reduced levels of the hyperglycemia normally associated with exposure to anaerobic conditions.

Predation and the distribution and abundance of a pulmonate pond snail.

The abundances of a freshwater pulmonate snail, Lymnaea elodes were studied in a temporary pond and a permanent, more productive pond in northeastern Indiana, USA. When snails from both populations were reared in each of the ponds in containers excluding predators, snails grew to be 1.3 to 2 times as large in the more productive pond, and laid 9 times as many eggs. However, field sampling data showed adults to be more abundant in the temporary pond. The only obvious difference between the two ponds was the presence of the molluscivorous central mudminnow (Umbra limi) in the permanent pond. These fish fed upon L. elodes when eggs and juvenile snails were abundant. In an experiment in the temporary pond, addition of mudminnows lowered egg and juvenile snail survival in pens where snail abundances had been increased. We suggest that vertebrate predators like the mudminnow can be significant sources of mortality for thin shelled species like L. elodes, possibly excluding them from habitats like lakes and rivers.

Direct effects of the hyperglycemic factor of the freshwater snail Lymnaea stagnalis on isolated glycogen cells

In the freshwater pulmonate snail Lymnaea stagnalis special cells, the glycogen cells (GC) are present for the storage of glycogen reserves. These cells occur in large numbers in the anterior mantle region. In a previous paper in vitro experiments with intact anterior mantle tissue indicated that a hyperglycemic factor is released from the central nervous system (CNS) which stimulates glycogen mobilization in mantle tissue ( M. A. Hemminga, J. J. Maaskant, W. Koomen, and J. Joosse (1985). Neuroendocrine control of glycogen mobilization in the freshwater snail Lymnaea stagnalis. Gen. Comp. Endocrinol. 57, 117–123). In the present study the question of whether this factor affects glycogen metabolism of GC isolated from mantle tissue was investigated. It is reported that in high-K + Ringers the CNS is stimulated to release a factor which, in a dose-dependent way, inhibits glycogen synthesis in isolated GC (measured as a decreased incorporation of [ 14C]glucose into glycogen). Simultaneous with this glycogen synthesis-inhibiting effect, stimulation of glycogen degradation is found (measured as a decreased retention of prelabeled glycogen). It is concluded that (1) the factor released by the CNS having these effects on isolated GC is the same as the hyperglycemic factor which was reported to stimulate glycogen mobilization in intact mantle tissue, and (2) GC after isolation from mantle tissue have retained their ability to respond to this factor. High-K + bathing Ringers of the cerebral/buccal ganglia have a stronger inhibiting effect on glycogen synthesis in isolated GC than bathing Ringers of the remainder part of the CNS, indicating that in this part of the brain the major release sites of the hyperglycemic factor are located. Dorsal body hormone, ovulation hormone, or growth hormone of L. stagnalis probably are not identical with the hyperglycemic factor, as homogenates of parts of the cerebral ganglia which are known to contain these respective hormones do not influence glycogen synthesis in isolated GC.

Effects of photoperiod and temperature on the glycogen stores in the mantle and the head-foot muscles of the freshwater pulmonate snail Lymnaea stagnalis

Abstract 1. 1. The effects of various combinations of photoperiod (LD: 16L-8D; SD: 8L-16D) and temperatures (8 and 20°C) on the glycogen content of the anterior mantle region, which contains large numbers of glycogen storage cells, and of the head-foot muscles of the freshwater pulmonate snail Lymnaea stagnalis were investigated. 2. 2. At 20°C, but not at 8°C, SD photoperiods favour accumulation of glycogen in both tissues. In contrast, LD photoperiods, at 20°C, induce depletion of the glycogen reserves. 3. 3. The changes of the glycogen contents presumably result from a reorientated metabolism linked to photoperiodically induced changes of ovipository activity, as is discussed.

The effect of temperature on spontaneous, and ovulation hormone-induced female reproduction in Lymnaea stagnalis

Spontaneous oviposition of the freshwater pulmonate snail Lymnaea stagnalis stopped after transfer from 20° to low temperatures (8 and 4°). This was due to a reduction in the activities of the neurosecretory caudodorsal cells (CDC), which produce the ovulation hormone (CDCH). Oviposition latencies (time interval between CDCH-injection and start of oviposition) increased with decreasing temperature. The ovotestis and the female accessory sex organs of snails placed at 8° became less sensitive, and those at 4° became completely insensitive to injected CDCH. This was probably caused by a reduction in activities of the endocrine dorsal bodies (DB), which control vitellogenesis and the activities of the female accessory sex organs. After a change from 4 to 20°, CDCH injections rapidly became effective in inducing egg mass production, and spontaneous oviposition also restarted quickly, suggesting a rapid increase in DB and CDC activities.

Uptake and assimilation of short chain carboxylic acids by Biomphalaria glabrata (Say), the freshwater pulmonate snail host of Schistosoma mansoni (Sambon)

The use of radiolabelling and high performance liquid chromatography (h. p. l. c. ) has shown that the freshwater pulmonate snail Biomphalaria glabrata can achieve a net uptake of short chain carboxylic acid (C 2 -C 4 ) from the medium, and also metabolize them. This appears to be the first time that this phenomenon has been reported for a freshwater invertebrate. The uptake characteristics for acetate and butanoate conform to the Michaelis-Menten model. The transport constants,V max (in micromole equivalents per gram of wet mass per hour) and K s (in micromoles per litre) for acetate (1005 and 2.29 respectively) and butanoate (129 and 1.29 respectively) are similar to those obtained by other workers for marine, detritivorous, polychaete worms. Evidence is given that the carboxylic acids are transported through the body wall, and not taken up to any significant extent by microorganisms or absorbed on the surface mucus. The acids are metabolized by the snail after accumulation, as shown by the appearance of label in respiratory CO 2 and the decline in the mass-specific accumulation rates (m. s. a. r. ), in micromole equivalents per gram of mass per hour, to an asymptote during the course of a 4 h incubation period. Differences in m.s.a.r. values for [1- 14 C]- and [2- 14 C]acetate probably reflect the different fates of the two carbons during metabolism. The m. s. a. r. values are influenced by the metabolic state of the snails. Thus they increase in response to food deprivation and decrease under anoxic conditions. However, as snails continue to accumulate acetate from the medium, even when well fed, or ‘preloaded ’ with acetate, it is clear that this acid is not being used solely as a food supplement. Estimates of the contributions that C 2 and C 4 acids might make to the basal metabolism of the snails have been made using the following param eters: (i) the range of concentrations of these acids in microhabitats, such as the interstitial waters in surface sediments, and an experimentally decayed macrophyte, Lemna paucicostata (ii) transport constants of the carboxylic acids taken up by the snails; (iii) the respiration rates of the snails. It was calculated that the acetate in interstitial waters can contribute only a negligible amount (less than 6%) of the snail’s basal metabolic rate (b. m. r. ). However, if the snails encountered the concentrations of 2250 μm and 400 μm of acetate and butanoate respectively found in supernatant from laboratory decaying Lemna , then each acid could provide more than 50% of the snails’ b. m. r. The significance of these results to the behavioural and chemical ecology of the snails is discussed.

Ovulation hormone, nutritive state, and female reproductive activity in Lymnaea stagnalis

A study of the relation between nutritive state and female reproductive activity as affected by the ovulation hormone (CDCH) has been made in the freshwater pulmonate snail Lymnaea stagnalis. CDCH is produced by the neuroendocrine caudodorsal cells (CDC) in the cerebral ganglia. Spontaneous oviposition ceased within 6 days of the beginning of a starvation period. This is most probably partially due to a reduction in the CDC activities because (1) quantitative electron microscopy showed a nearly 80% decrease in the number of release phenomena in the CDC-axon terminals in the neurohemal area in the intercerebral commissure, and (2) a bioassay showed a considerable reduction in the amount of CDCH in this area. During starvation the ovotestis and the female accessory sex organs became progressively less sensitive and, after 25 days, were completely insensitive to injected CDCH. This was indicated by a decrease in the responses to CDCH injection and, correspondingly, by a gradual increase in the CDCH thresholds for ovulation and egg formation. It is argued that the insensitivity may be caused by a reduction in the activities of the endocrine dorsal bodies. During refeeding, CDCH injections again become effective in inducing egg mass production, followed by resumption of spontaneous oviposition. This suggests a rapid restoration of DB and CDC activities following refeeding.

Vertical movement and time allocation of a freshwater pulmonate snail

The paper presents an analysis of locomotion and location in a vertical water column of 10Biomphalaria glabrata, under constant conditions of light, temperature, and food availability. Individual snails varied in distance traveled, and in the percentage of time spent in different areas of the water column. Distance covered ranged from 53 cm to 100 cm h−1 . Approximately 21% of locomotion was observed to be passive (floating up or sinking down). Snails spent approximately 58% of the time in the bottom section, 35% in the top section and only 7% in the middle region. The study provides baseline data that can be used to compare further studies ofBiomphalaria glabrata as various conditions are altered.

Overwinter Tissue Degrowth in Natural Populations of Freshwater Pulmonate Snails (Helisoma Trivolvis and Lymnaea Palustris)

When populations of aquatic invertebrates including molluscs) are subjected to seasonal periods of starvation, many individuals survive by major shifts in metabolic budgeting. These shifts can result in degrowth, defined as decrease in individual biomass, in some cases involving loss of structural proteins. Snails after degrowth can be recognized in natural populations because their "oversize" shells provide evidence of former larger tissue biomass. Fall and spring samples were taken from four selected populations of Helisoma trivolvis and four of Lymnaea palustris in upstate New York. Both are freshwater pulmonate snails, with a widespread and relatively euryoecic distribution. Shell : tissue ratios were calculated, and overwinter changes are significant (P <.001) for six of the populations. Overwinter tissue degrowth is demonstrated in three populations of Helisoma and one of Lymnaea, with overwinter growth occurring in one population of Hlisoma and two of Lymnaea. The actual dry—mass values of tissues found in spring individuals can be compared with values predicted from their individual shell masses in spring (using regressions for the same populations in fall). Surviving individuals of Helisoma in the three populations with degrowth can have tissues at 19—116% of the predicted mass (with 56 out of 59 below 100%) and, in the population of Lymnaea showing degrowth individual values ranging from 58 to 169% (with 19 out of 22 below 100%). Mean values for the three Helisoma populations are 75.3, 71.7, and 58.7% and for the degrowth Lymnaea populations, 85.3%. This field demonstration of degrowth is discussed in relation to other laboratory studies of starvation in molluscs and in relation to actuarial bioenergetics of natural populations. Capacity for true degrowth can be claimed to confer adaptive advantages in certain environments and is of considerable ecological and evolutionary significance.

Urine composition and kidney function in the pulmonate freshwater snail Lymnaea stagnalis

1. 1. Final urine is intermittently released from the pneumostome of the pulmonate freshwater snail Lymnaea slagnalis. A technique is described to sample this fluid. 2. 2. The ionic composition of final urine greatly differs from that of haemolymph; Na + and Cl − are reabsorbed to a considerable degree. In lettuce fed snails K + is excreted. 3. 3. The urine Na + and Cl − concentrations are about 38 and 31 mM lower, respectively, than the haemolymph concentrations, also when the latter concentrations vary.

Behavioural responses of Biomphalaria glabrata(Say) to chemical factors from aquatic macrophytes including decaying Lemna paucicostata(Hegelm ex Engelm)

SUMMARY. 1. The behavioural responses of the freshwater pulmonate snail Biomphalaria glabrata to homogenates of various aquatic macrophytes were investigated with the aid of diffusion olfactometers.2. Of the eleven species studied, three lacked any attractants or arrestants, two contained weak arrestants, and three induced strong repellent effects. Only two, Apium nodiflorum and Lemna paucicostata, induced significant attractant and arrestant effects comparable to those obtained with lettuce (Lactuca sativa) controls.3. Decaying Lemna paucicostata homogenate proved to be a significantly stronger attractant and arrestant than fresh homogenate. Evidence is given that these effects are mainly due to low molecular weight compounds (<1000 mol. wt) of which the major end products of microbial decomposition, short chain carboxylic acids (C2‐C5), are likely to be the most important. However, as carboxylic acids account for only a fraction of the total response, other low and high molecular weight compounds are also implicated.4. The ecological relevance of these results is discussed with particular reference to the hypothesis that the relationship between the snails and macrophytes is essentially mutualistic.