Search results for "snail"
showing 10 items of 133 documents
About the finding of the invasive geomitrid Xerolenta obvia (Menke, 1828) (Mollusca, Stylommatophora) in Andorra.
2022
An invasive snail population of Xerolenta obvia was discovered at the end of 2021 in Sant Julià de Lòria (Principat d'Andorra). This location, the first occurrence of this species for this country, is intermediate between the few locations in the south of France and the only known location in Spain. For its taxonomical determination, morpho-anatomical studies of the shell and the reproductive system have been carried out, and it has been compared with other species of geomitrids that are more similar based on the shell, such as Cernuella neglecta or Helicella itala and even, for less expert people, with Xerosecta cespitum arigonis, also present in Andorra. X. obvia is an i…
Ecological divergence of closely related Diplostomum (Trematoda) parasites.
2006
Parasite life-cycles present intriguing model systems to study divergence in resource use and ecology between parasite taxa. In ecologically similar taxa, consistent selective forces may lead to convergence of life-history traits, but resource overlap and similarity of life-cycles may also promote divergence between the taxa in (1) use of host species or (2) specific niche within a host. We studied the life-history characteristics of 2 sympatric species of Diplostomum parasites, D. spathaceum and D. gasterostei, concentrating particularly on differences in intermediate host use and characteristics of the infective stages between the species. This group of trematodes is a notoriously difficu…
Model predictions of the ionic mechanisms underlying the beating and bursting pacemaker characteristics of molluscan neurons
1976
The general properties of the excitable membrane on molluscan pacemaker neurons can be described on the basis of a fair amount of experimental evidence available in the literature. The neuronal membrane exhibits under voltage clamp an initial inward current carried by both Na+ and Ca2+ ions, the time- and voltage-dependent characteristics of which are similar to that of other excitable structures. The conductance mechanism for the two ion species and the transport kinetics appear to be closely similar. The time course and amplitude of the delayed outward current carried by K+ ions shows a marked dependence on the membrane potential. Characteristic for the molluscan neurons is the existence …
Iberian Distribution of the Freshwater Snail Genus Bithynia Leach, 1818 (Mollusca: Truncatelloidea), Vector of Opisthorchiasis and Metorchiasis
2021
Background: Opisthorchis felineus and Metorchis bilis are trematodes that cause opisthorchiasis and metorchiasis, respectively. The freshwater snails Bithynia hispanica and B. tentaculata are the respective intermediate hosts for these parasites in the Iberian Peninsula, where both parasites are present. Methods: To study the distribution of these snail species, an exhaustive literature review and revision of museum collections was performed. Results: A total of 370 localities were compiled and mapped. B. tentaculata were found throughout the Iberian Peninsula, both in Spain and Portugal, while B. hispanica was found only in the Mediterranean coast of Spain. Conclusion: Knowing the distribu…
Patterns of cercarial production from Diplostomum spathaceum: terminal investment or bet hedging?
2004
In the production of the infective cercariae of trematodes, the terminal investment hypothesis of life-history theory predicts that the rate of host exploitation and cercarial production should increase during the period of cercarial shedding since the reproductive value of the parasite decreases during this period. In contrast, a bet hedging hypothesis that focuses on the success of transmission when host contact rate is variable predicts that cercarial production should decrease in an attempt to keep the host alive for longer and thus would increase the probability of successful transmission. We examined these two hypotheses under laboratory conditions and recorded the production ofDiplos…
Immunohistochemical study of correlation between histologic subtype and expression of epithelial-mesenchymal transition-related proteins in synovial …
2011
Context.—Synovial sarcomas are mesenchymal tumors with epithelial nature and comprise biphasic and monophasic fibrous subtypes. However, factors determining epithelial or spindle cell differentiation are still unexplored. Aberrant epithelial-mesenchymal transition has been implicated in the pathogenesis of diverse human malignancies.Objective.—To analyze the correlation between cellular phenotype and expression of proteins associated with different epithelial-mesenchymal transition-related pathways.Design.—Immunohistochemical analysis of E-cadherin, Snail, Slug, and dysadherin, components of the Wnt/wingless and PI3K/Akt pathways, was performed on 14 biphasic and 27 monophasic fibrous tumor…
Estimating trematode prevalence in snail hosts using a single-step duplex PCR: how badly does cercarial shedding underestimate infection rates?
2014
Background: Trematode communities often consist of different species exploiting the same host population, with two or more trematodes sometimes co-occuring in the same host. A commonly used diagnostic method to detect larval trematode infections in snails has been based on cercarial shedding, though it is often criticized as inaccurate. In the present study we compare infection prevalences determined by cercarial emission with those determined, for the first time, by molecular methods, allowing us to quantify the underestimation of single and double infections based on cercarial emission. We thus developed a duplex PCR for two host-parasite systems, to specifically differentiate between sin…
Metabolism of phenol in the terrestrial snail Cepaea nemoralis L
1992
1. The metabolism of phenol in the terrestrial snail Cepaea nemoralis was studied after injection into the haemocoel of the dorsolateral foot region. 2. Excreted metabolites, and metabolites extracted from the body, were analysed by h.p.l.c. In addition to phenyl beta-D-glucoside, arbutine (quinol beta-D-glucoside), a new conjugate of phenol, was detected.
Land Snails as a Diet Diversification Proxy during the Early Upper Palaeolithic in Europe
2014
Despite the ubiquity of terrestrial gastropods in the Late Pleistocene and Holocene archaeological record, it is still unknown when and how this type of invertebrate resource was incorporated into human diets. In this paper, we report the oldest evidence of land snail exploitation as a food resource in Europe dated to 31.3-26.9 ka yr cal BP from the recently discovered site of Cova de la Barriada (eastern Iberian Peninsula). Mono-specific accumulations of large Iberus alonensis land snails (Ferussac 1821) were found in three different archaeological levels in association with combustion structures, along with lithic and faunal assemblages. Using a new analytical protocol based on taphonomic…
GENETIC VARIABILITY AND DRIFT LOAD IN POPULATIONS OF AN AQUATIC SNAIL
2004
Population genetic theory predicts that in small populations, random genetic drift will fix and accumulate slightly deleterious mutations, resulting in reduced reproductive output. This genetic load due to random drift (i.e., drift load) can increase the extinction risk of small populations. We studied the relationship between genetic variability (indicator of past population size) and reproductive output in eight isolated, natural populations of the hermaphroditic snail Lymnaea stagnalis. In a common laboratory environment, snails from populations with the lowest genetic variability mature slower and have lower fecundity than snails from genetically more variable populations. This result s…