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PubMed2002

Fasciola gigantica: the growth and larval productivity of redial generations in the snail Lymnaea truncatula.

Bimiracidial infections of French Lymnaea truncatula with a Madagascan isolate of Fasciola gigantica were carried out under laboratory conditions to study the growth of rediae and their larval productivity in relation to the different redial generations. The total numbers of rediae and their mean lengths significantly increased with the duration of infection until day 49 post-exposure (p.e.). Significant differences in the lengths between the different redial generations were noted. At day 49 p.e. (at 20 degrees C), the cercariae were produced by the first redial generation, while the productivity of other redial groups was delayed. This last finding shows a slow larval development of this Madagascan isolate of F. gigantica in this French population of L. truncatula.

Animals↗
PubMed2004

Morphology of the rediae of Echinostoma paraensei (Trematoda: Echinostomatidae) from its intermediate host Lymnaea columella (Mollusca, Gastropoda).

The morphology of the rediae of Echinostoma paraensei obtained from Lymnaea columella was studied using light, scanning and transmission electron microscopy. The measurements of the mature rediae differ from those described originally, and the taxonomic importance of the ambulatory buds and papilliform process is discussed. Uniciliated papillae were observed in the mouth region. The birth papilla is a bulb-like structure, well defined at the anterior end of the body of the rediae, which opens through a split. There are no microvilli in the tegument surface of the larvae, but numerous tegumental folds, varying according to the contraction of the body of the rediae. The outer syncytial layer is located on a thick basal lamina below which the circular and the longitudinal muscle fiber layers are located.

Animals↗
PubMed2004

Presence of Trichobilharzia szidati in Lymnaea stagnalis and T. franki in Radix auricularia in northeastern France: molecular evidence.

A molecular approach was used to analyse a focus of cercarial dermatitis in northeastern France (Lake Der-Chantecoq), including both cercariae and snails,by sequencing the internal transcribed spacers (ITS1 for ocellate furcocercariae and ITS2 for snails). Lymnaea stagnalis were found infected with the furcocercariae of Trichobilharzia szidati, and T. franki furcocercariae were found in Radix auricularia. The record of these two visceral parasites of birds in northern France confirms strong host-parasite relationships. The use of these standardised markers will be of the highest significance for our understanding of the epidemiology of cercarial dermatitis in this recreational lake.

Adult↗
PubMed2005

Seasonal transmission of Fasciola hepatica in cattle and Lymnaea (Fossaria) humilis snails in central Mexico.

A 19-month study on the prevalence of fasciolosis in 30 naturally infected cows, the presence of infected and non-infected Lymnaea (Fossaria) humilis snails, and variation in soil temperature and humidity is reported. The prevalence of fasciolosis in cattle declined from around 50% in March to 30% in July, then, it increased from August, reaching a plateau of 100% in November-January, before gradually declining thereafter. A rise in soil humidity and temperature in June and July, respectively, which peaked between August and November was observed. In July, L. (F.) humilis snails appeared, but the infection could only be found in these in August and November. The number of infected snails did not reflect the infestation rate in cows, even though the infestation kinetics in both hosts behaved as predicted from the life cycle of the parasite.

Animals↗
PubMed2005

Do larvae of Trichobilharzia szidati and Echinostoma revolutum generate behavioral fever in Lymnaea stagnalis individuals?

The objective of this study was to determine whether individuals of Lymnaea stagnalis naturally parasitized with Trichobilharzia szidati and Echinostoma revolutum can generate the behavioral fever against larvae of those parasites. Thermal preferences of each snail were examined in an oblong thermal gradient during 48 h observation. Uninfected animals under study chose higher temperatures than those releasing cercariae of parasites. Infected snails kept in constant temperature lived shorter than uninfected ones. At high temperature, they released more cercariae per day than at low temperature. Temperature had a great influence on the longevity of emerged cercariae. The thermal behavior of infected snails is not a symptom of behavioral fever but probably can play a therapeutic role in the host.

Animals↗
PubMed2006

Infestation of Lymnaea stagnalis by digenean flukes in the Jeziorak Lake.

The low number of articles on naturally trematode-infected snails results from the difficulty to obtain the quantitatively representative material. The main aim of our study was to check which age (size) groups of snails are the most susceptible to trematode invasion. Furthermore, we examined in which season the parasite prevalence is the highest. We collected Lymnaea stagnalis individuals in a nearshore zone of the Jeziorak Lake (the longest Polish lake located in northern Poland). The shell height of the snails was measured and the infestation by trematode larvae was determined. The logistic regression has shown that parasite prevalence increased significantly with the snail size (with the individuals >30 mm being the most infected), the distance from the beginning of the year (i.e., month) and the vicinity of summer.

Animals↗
PubMed2000

Variability of Fasciola hepatica infection in Lymnaea ovata in relation to snail population and snail age.

Bimiracidial infections of Lymnaea ovata with Fasciola hepatica were performed under laboratory conditions to determine the susceptibility of snails from six French populations to trematode infection. In five populations of L. ovata the prevalence of infection in the 1-mm groups ranged between 2.7% and 43.7% at day 35 postexposure; it decreased in the 2-mm snails and was zero in larger groups. In the snails from Thenay (periodically polluted brook) the prevalence of F. hepatica infection decreased from the 1-mm group to the 8-mm group (from 23.9% to 1.0%) and was zero in the 10-mm L. ovata. The total number of cercariae shed per snail was 18.3 in the 1-mm group, increasing to 117 in the 8-mm group. The latter findings could be interpreted as a consequence of periodic pollution in the brook of Thenay; pollution might disrupt the defense system of L. ovata and facilitate the subsequent larval development of F. hepatica.

Aging↗
PubMed1996

Paramphistomum daubneyi and Fasciola hepatica: the redial burden and cercarial shedding in Lymnaea truncatula subjected to successive unimiracidial cross-exposures.

The development of redial burden and cercarial shedding were studied in two groups of Lymnaea truncatula subjected to successive cross-exposures to one miracidium of Paramphistomum daubneyi and one of Fasciola hepatica per snail, or vice versa. The results were compared with those obtained in controls subjected to two unimiracidial exposures to the same trematode species. The infection rate was 61% in the group cross-exposed to P. daubneyi/F. hepatica and 37% in that cross-exposed to F. hepatica/P. daubneyi; it was 37% in the control group exposed to F. hepatica and 21% in that exposed to P. doubneyi. Snails harboring larval forms of both trematodes were few in number in cross-exposed groups and the redial burden was low, with one trematode dominating over the other. Free cercariae of F. hepatica and those of P. daubneyi were significantly more numerous at day 35 in the group cross-exposed to P. daubneyi/F. hepatica than in the controls or the other cross-exposed group. Mixed cercarial sheddings were obtained from 40% of snails with emission in the group cross-exposed to P. daubneyi/F. hepatica and from 21% of those in the F. hepatica/P. daubneyi group. The numbers of P. daubneyi metacercariae were significantly greater in the group cross-exposed to P. daubneyi/F. hepatica than in the other cross-exposed group, whereas no significant difference in mean numbers was noted for the F. hepatica cysts. Repartition of metacercariae over the patent period was clearly more irregular for P. daubneyi than for the other trematode.

Animals↗
PubMed1997

Paramphistomum daubneyi: the development of redial generations in the snail Lymnaea truncatula.

Rediae of Paramphistomum daubneyi were counted and measured in Lymnaea truncatula to elucidate the variability in the numbers of free rediae and cercariae occurring between naturally infected snails and experimental single-miracidium infections. Experiments were performed using one miracidium per snail and snail raising was carried out at 20 degrees C. Two redial generations succeeded each other in the snail until day 49. A mean of 8-10 rediae differentiated in the sporocyst at days 7 and 14; the remaining germ balls and redial embryos decreased in number after day 21. First-generation rediae became free in the snail's body starting at day 14 and their number increased to a mean of 7.5 at day 49, with a maximum of 10 rediae being detected in 1 snail. They produced second-generation rediae, which exited from the body starting at day 28, and then cercariae, which exited from day 42 onward. The count of second-generation rediae was 6-6.2/snail at day 49, with a maximum of 12 being detected in 1 snail; they produced only cercariae.

Animals↗
PubMed1999

Oviposition of Lymnaea truncatula infected by Fasciola hepatica under experimental conditions.

Experimental infections of Lymnaea truncatula by Fasciola hepatica (one, two, or three miracidia per snail) were carried out under laboratory conditions to analyze the oviposition of infected snails and determine the characteristics of their egg masses. In the infected snails from the three groups, egg-laying steadily decreased until week 4 postexposure and stopped afterward until the end of the experiment, except for the cercaria-shedding snails from the one-miracidium group, for which low numbers of egg masses were noted between weeks 9 and 12. In uninfected snails the number of egg masses decreased until week 4 and remained low during subsequent weeks. At weeks 11 and 12 postexposure the natality rate was 98.9% in controls, 56% in the cercaria-shedding snails from the one-miracidium group, and 59.2-68.5% in uninfected snails. In the cercaria-shedding snails from the one-miracidium group the restoration of reproduction activity after week 8 may be explained by a lower parasite burden in these snails than in those from the two- and three-miracidium groups.

Animals↗
PubMed1999

Paramphistomum daubneyi and Fasciola hepatica: influence of temperature changes on the shedding of cercariae from dually infected Lymnaea truncatula.

Dual infections of Lymnaea truncatula with Paramphistomum daubneyi and Fasciola hepatica were performed to determine whether temperature changes in snails (daily water change with spring water at 6 degrees-8 degrees C, which subsequently increased to room temperature at 20 degrees C) would influence snail infection and the production of cercariae by both trematodes. At day 30 post-exposure the surviving snails were individually placed in petri dishes to constitute two groups. Snails from the first group were maintained at a temperature of 20 degrees C, and the water in the petri dishes was changed daily. The protocol was identical for the second group of snails except that the water temperature was 6 degrees-8 degrees C when changed. The interval between exposure and the first shedding of cercariae in snails immersed in cold water for a short period was longer (67-69 days instead of 48-50 days in the 20 degrees C group). In both groups, snails infected only with F. hepatica or P. daubneyi or with both trematodes were detected. In snails infected only with F. hepatica the frequency of cercaria-shedding snails and the total number of metacercariae were significantly greater in the 20 degrees C group. Inversely, in snails infected only with P. daubneyi the frequency of cercaria-shedding snails and the number of metacercariae were significantly greater in the 6 degrees-8 degrees C group. In snails harboring both trematode larval forms, no significant difference in the frequencies of cercaria-shedding snails between the two groups was noted. Metacercariae of both trematodes were obtained from these snails. In the 20 degrees C group, F. hepatica metacercariae were more numerous, whereas in the 6 degrees-8 degrees C group the number of P. daubneyi metacercariae was greater. From these results it appears that greater activity of P. daubneyi cercariae occurs in snails subjected to daily temperature changes (from 6 degrees to 20 degrees C).

Animals↗
PubMed2001

Cercarial productivity of Fasciola hepatica in Lymnaea truncatula during usual and unusual development of redial generations.

Single-miracidium infections of Lymnaea truncatula by Fasciola hepatica were carried out to determine the cercarial productivity of each redial generation when the first-appearing mother redia (R1a redia) normally developed (usual development of redial generations) or quickly died (unusual development). In both developmental patterns of infection, the number of morulae was significantly higher in the second-appearing mother rediae (R1b group) than in either the daughter rediae from R1a rediae (R2a group) or the rediae from subsequent groups (R2b/R3a). The live R1a group did not produce cercariae. The percentages of cercariae produced by the R1b, R2a, and R2b/R3a groups were 28.2%, 62.8%, and 8.9% when the development of redial generations was usual. In contrast, in an unusual development, they were 69.3%, 20.3%, and 10.2%, respectively. Cercarial production until day 63 post-exposure was essentially provided by the R2a rediae, when the development of redial generations was usual, and by the R1b rediae when it was unusual.

Animals↗
PubMed2001

Prevalence of cercariae from Lymnaea stagnalis snails in a pond system in Southern Germany.

Lymnaea stagnalis snails were collected from 174 individual ponds of an extensive pond system in South Germany; 43,441 snails collected during 1980 2000 were examined for shedding cercariae. The species richness (at least 18 species of cercariae) and the high cercarial prevalence (at least 44.9%) may result from the high abundance and diversity of vertebrate and invertebrate hosts in the area. The mean prevalence (% +/- SEM) of most cercarial species increased from May-June to August-October, e.g. in Diplostomum spathaceum from 4.1% to 18.6%, in all echinostomatids from 5.6% to 18.0%, in Pseudechinoparyphium echinatum from 3.0% to 11.2%, in Xiphidiocercariae from 2.2% to 13.4%, and the overall prevalence shifted from 13.7% to 53.5%. There was no change in the prevalence of the different cercarial species over the last 20 years. The agents of cercarial dermatitis showed a constant low prevalence, 0.17% in Trichobilharzia ocellata (43,441 L. stagnalis examined) and 0.24% in other Trichobilharzia species (4,245 Radix examined). Such low prevalences seem to be normal in areas where cercarial dermatitis occurs in humans.

Animals↗
PubMed2001

More efficient allopatric combinations of Fasciola hepatica and Lymnaea truncatula due to modification of redial development?

Experimental infections of two susceptible French populations of Lymnaea truncatula (Courcelles and Saint Ours) with an allopatric (Fès, Morocco) or a semi-sympatric (Limoges, France) isolate of Fasciola hepatica miracidia were performed to determine the effect of allopatric miracidia on redial and cercarial production. In both populations, cercarial release was significantly greater in allopatric than in semi-sympatric snails. Compared to semi-sympatric snails, the examination of allopatric snails killed from day 14 to day 35 post-exposure demonstrated (1) a significant decrease after day 28 in the number of daughter rediae (R2a group) exiting from the first-appearing mother redia (R1a redia), and (2) the differentiation of numerous daughter rediae (R2b group) in the body of second-appearing mother rediae (R1b group). These experiments demonstrated that the exposure of L. truncatula to an allopatric isolate of miracidia disturbed the usual developmental pattern of redial generations and caused the formation of numerous R2b rediae. The authors hypothesized that the increase in cercarial release noted in allopatric snails would be assured by the rediae from the R2b group after their emergence from the body of R1b mother rediae.

Animals↗
PubMed2006

Increase in intracellular Ca2+ concentration is not the only cause of lidocaine-induced cell damage in the cultured neurons of Lymnaea stagnalis.

PURPOSE: To determine whether the increase in intracellular Ca2+ concentration induced by lidocaine produces neurotoxicity, we compared morphological changes and Ca2+ concentrations, using fura-2 imaging, in the cultured neurons of Lymnaea stagnalis. METHODS: We used BAPTA-AM, a Ca2+ chelator, to prevent the increase in the intracellular Ca2+ concentration, and Calcimycin A23187, a Ca2+ ionophore, to identify the relationship between increased intracellular Ca(2+) concentrations and neuronal damage without lidocaine. Morphological changes were confirmed using trypan blue to stain the cells. RESULTS: Increasing the dose of lidocaine increased the intracellular Ca2+ concentration; however, there was no morphological damage to the cells in lidocaine at 3 x 10(-3) M. Lidocaine at 3 x 10(-2) M increased the intracellular Ca2+ concentration in both saline (from 238 +/- 63 to 1038 +/- 156 nM) and Ca2+-free medium (from 211 +/- 97 to 1046 +/- 169 nM) and produced morphological damage and shrinkage, with the formation of a rugged surface. With the addition of BAPTA-AM, lidocaine at 3 x 10(-2) M moderately increased the intracellular Ca2+ concentration (from 150 +/- 97 to 428 +/- 246 nM) and produced morphological damage. These morphologically changed cells were stained dark blue with trypan blue dye. The Ca2+ ionophore increased the intracellular Ca2+ concentration (from 277 +/- 191 to 1323 +/- 67 nM) and decreased it to 186 +/- 109 nM at 60 min. Morphological damage was not observed during the 60 min, but became apparent a few hours later. CONCLUSION: These results indicated that the increase in intracellular Ca2+ concentration is not the only cause of lidocaine-induced cell damage.

Anesthetics, Local↗
PubMed2002

Lead toxicity, locomotion and feeding in the freshwater snail, Lymnaea stagnalis (L.).

The effects of lead (5 or 10 ppm) on the survival of the freshwater snail Lymnaea stagnalis (L.) collected from lead contaminated or uncontaminated environments were evaluated under controlled laboratory conditions. The animals from the contaminated environment had significantly greater survivability than those from the unpolluted environment to subsequent acute (up to 24 days) exposure to lead. Acute (72 h) exposure to lead inhibited several behavioural activities including locomotion, feeding, tentacle extension and emergence from the shell. Lead bioaccumulated in the snail tissues, especially the buccal mass and stomach. The freshwater snail provides a valuable system for studying the bioaccumulation and development of tolerance to environmental lead.

Animals↗
PubMed2006

Leaf mechanical properties modulate feeding movements and ingestive success of the pond snail, Lymnaea stagnalis.

We examined the mechanical properties of Butterhead and Iceberg lettuce leaves, and the rate at which they were eaten by the pond snail Lymnaea stagnalis. The outer part of Butterhead leaves were less robust than either the inner Butterhead or outer Iceberg leaves (Young's modulus 2.8, 5.2, 7.7 MPa respectively; ultimate tensile stress 0.18, 0.34 0.51 MPa) which were also thicker. Snails ingested inner Butterhead and Iceberg strips more slowly (36 and 32%) than outer Butterhead. This was not due to differences in latency to first bite or biting rate. Rather, the drop was due to a decrease in the proportion of successful bites (inner Butterhead 84%; Iceberg 86%), to a shorter length ingested per bite (inner Butterhead 55%; Iceberg 45%) and to increased handling time (inner Butterhead 30%). We conclude that sensory input from the mechanically more robust lettuce slows the buccal central pattern generator.

Animals↗
PubMed2006

Effects of self-fertilization, environmental stress and exposure to xenobiotics on fitness-related traits of the freshwater snail Lymnaea stagnalis.

Genetic and ecological factors may interact in their effects on fitness. Such interactions are thus to be expected between inbreeding and exposure of a population to a toxicant. The magnitude of inbreeding depression is thought to increase in stressful environments. To test this hypothesis, we investigated the combined effects of environmental conditions and inbreeding on fitness in the self-fertile snail Lymnaea stagnalis, using a stress gradient (0-2) applied to a 100 isolated and paired lineages: laboratory control (0), outdoor microcosm control (1) and pesticide exposure under outdoor microcosm conditions (2). Outdoor stress conditions were maintained for 28 days prior to measurements of fitness traits (fecundity, hatching success, and size at hatching) under laboratory conditions, so that delayed environmental effects could be estimated. Under laboratory control conditions, we found significant initial family level heterogeneity for most measured traits, including physiological performances as assessed through energetic biomarkers. Whatever the environmental conditions, inbreeding depression was very low for progeny performances. Negative values of self-fertilization depression (SFD) were obtained. Unexpectedly, SFD showed a negative relationship with the assumed stress intensity, reflecting a higher sensitivity under pairing than under selfing, mostly due to parental fecundity. This suggests that stressful conditions may favour selfing. Stress intensity increased the distribution limits of both depression indices, suggesting that changes in fitness are less predictable in a population under stress. Implications of such findings for environmental risk assessment of pesticides are discussed.

Animals↗