Search results for "Snails"
showing 10 items of 78 documents
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…
An evaluation of a model ecosystem with DDT
1980
The reproducibility, variability, and reliability of a simple aquatic-terrtestrial model ecosystem experiment was tested with p,p'-DDT. The variation among the model replicates as well as within the units was studied by using hierarchal analysis of variance. the complete budget of the chemical was calculated and a theoretical transport model was constructed. The degradation and accumulation of DDT was followed by gas chromatographic residue analysis, which showed good reproducibility of the experimental design. The degradation of DDT in the model was similar to that found in the field, but the determination of concentration factors was questionable. The material balance tables revealed that…
A global network for the control of snail-borne disease using satellite surveillance and geographic information systems
2001
Abstract At a team residency sponsored by the Rockefeller Foundation in Bellagio, Italy, 10-14 April 2000 an organizational plan was conceived to create a global network of collaborating health workers and earth scientists dedicated to the development of computer-based models that can be used for improved control programs for schistosomiasis and other snail-borne diseases of medical and veterinary importance. The models will be assembled using GIS methods, global climate model data, sensor data from earth observing satellites, disease prevalence data, the distribution and abundance of snail hosts, and digital maps of key environmental factors that affect development and propagation of snail…
Interactions related to non-host snails in the host-finding process of Euparyphium albuferensis and Echinostoma friedi (Trematoda: Echinostomatidae) …
2003
In order to determine whether the miracidia of Euparyphium albuferensis and Echinostoma friedi are sensitive to their host snail (HS) and capable of discriminating between HS and non-host snails (NHS), or whether these NHS can interfere and thus reduce the infection rates (decoy effect), a total of three experiments were conducted with HS, NHS and snail-conditioned water (SCW). Gyraulus chinensis is the HS for E. albuferensis miracidia, while Physa acuta, Radix peregra and Lymnaea fuscus are considered NHS. For E. friedi miracidia R. peregra, G. chinensis and L. fuscus are the HS, while P. acuta is the NHS. The NHS R. peregra produces the greatest decoy effect on Euparyphium albuferensis mi…
Miracidial infectivity of Hypoderaeum conoideum (Trematoda: Echinostomatidae): differential susceptibility of two lymnaeid species.
1999
A study was made of the infectivity of Hypoderaeum conoideum miracidia to a range of laboratory-reared specimens of freshwater snail species (Lymnaea peregra, L. corvus, Physella acuta, and Gyraulus chinensis) that coexist with the parasite in the same natural habitat. L. peregra and L. corvus were found to be equally susceptible to the parasite when specimens of each snail species were singly exposed to miracidia. However, when miracidia could choose either lymnaeid species, they showed a high degree of specificity toward L. peregra. The results obtained suggest that H. conoideum miracidia are capable of distinguishing among these lymnaeids in their orientation to the host. This indicates …
The life cycle ofBrachylaima ruminae n. sp. (Trematoda: Brachylaimidae), a parasite of rodents
1986
The life cycle of Brachylaima ruminae n.sp. (Trematoda: Brachylaimidae), a duodenal parasite of rodents on the Mediterranean island of Formentera (Spain) is elucidated. The new species follows a terrestrial triheteroxenous life cycle. Eggs passed in the faeces of the definitive host must be ingested by a specific first intermediate host, the land snail Rumina decollata. Branched cercariogenous sporocysts develop in the digestive gland. Microcercous cercariae come out through the terminal birth pores of the branches. Cercariae shed by the snail are terrestrial, crawling on humid substratum. They contact the second intermediate host, another land snail, principally the species R. decollata an…
Being successful in the world of narrow opportunities: transmission patterns of the trematode Ichthyocotylurus pileatus.
2009
SUMMARYParasites with complex life cycles face 2 major challenges for transmission in northern latitudes. They have to cope with the general unpredictability associated with the series of transmission events required for completion of the cycle, and transmission has to be completed within a narrow temporal window because of strong seasonality. Despite this, some parasites show high transmission success, suggesting the operation of effective transmission mechanisms. We explored the transmission of Ichthyocotylurus pileatus (Trematoda) from its snail (Valvata macrostoma) to fish (Perca fluviatilis) hosts by examining some key characteristics in the dynamics of the cercarial emergence from sna…
Characterizing a hybrid zone between a cryptic species pair of freshwater snails.
2015
Characterizing hybrid zones and their dynamics is a central goal in evolutionary biology, but this is particularly challenging for morphologically cryptic species. The lack of conspicuous divergence between parental types means intermediate hybrid forms often go undetected. We aimed to detect and characterize a suspected hybrid zone between a pair of morphologically cryptic lineages of the freshwater snail, Radix. We sampled Radix from across a contact zone between two mitochondrial lineages (Radix balthica and an undescribed lineage termed 'MOTU3') and detected admixture between two nuclear genotype clusters, which were significantly but not categorically associated with the mitochondrial …
Sympatric and allopatric experimental infections of the planorbid snail Gyraulus chinensis with miracidia of Euparyphium albuferensis (Trematoda: Ech…
2010
AbstractAn experimental infection with echinostomatid miracidia in sympatric or ‘local’ vs. allopatric or ‘away’ snail combinations, as a model to examine parasite compatibility, was carried out. We employedEuparyphium albuferensismiracidia to infectGyraulus chinensissnails, from three different natural parks: Albufera (Valencia, Spain); the Ebro Delta (Tarragona, Spain) and Coto de Doñana (Huelva, Spain). Insignificant differences between the three snail strains were noted for the infection rate and the rhythm of daily cercarial production. However, a significantly higher total cercarial production per snail, patent period and life span were observed in local snails. The different infectio…