Observations on Growth Rates and Maturity in an Introduced Population of the Roman Snail (Helix pomatiaLinnaeus, 1758) at a Semi-Natural Site with no Natural Population (original) (raw)
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Folia Malacologica, 2015
The Roman snail (Helix pomatia L.) has been exploited for food to the point where it has been subject to legal restrictions on its collection, and steps have been taken to monitor its distribution and abundance. There are, however, few cases where monitoring has involved the precise re-examination of accurately located populations, and these have confirmed persistence over periods of up to six years. Using a standard methodology, ten populations of H. pomatia near the town of Września (central Poland) first surveyed in 1999 were re-sampled in 2014. In all cases the snail populations had persisted, and the habitats had not altered significantly. These results indicate that in the absence of over-exploitation or habitat change populations of this species persist.
Folia Malacologica, 2010
Populations of Helix pomatia L. in Poland have been commercially exploited since 1951; the snails are mostly exported. The growing interest in the Roman snail on the European market has resulted in its increased exploitation, in some areas leading to a considerable decrease in its abundance. Introducing export quota in 1964 did not prevent overexploitation. Precise assessment of abundance and distribution of the Roman snail populations in areas where it is exploited is necessary. In 2009 the team from the Faculty of Biology, Adam Mickiewicz University in Poznañ, conducted a preliminary assessment and mapping of the abundance and distribution of the Roman snail populations in Kujawsko-Pomorskie voivodeship. Most populations showed a low density. From scientific point of view the most reasonable solution would be to suspend exploitation in 2010 and continue monitoring, while decisions to issue permits for limited exploitation should be postponed till 2011. It would enable a more detailed estimation of the non-exploited populations and an assessment of losses resulting from exploitation of controlled reference populations. In this way acceptable limits of annual commercial collecting could be set for particular parts of the voivodeship.
Biodiversity and Conservation, 2006
Helix pomatia L., the Roman snail, is a species faced with growing commercial interest in Moldova. Its life history characteristics (slow maturation and recruitment, high mortality among juveniles and low fecundity) along with its strong spatial aggregation, makes it especially vulnerable to exploitation. In this study, differences in density, shell size and age distribution were assessed in 7 unexploited and 10 exploited sites in the northern and central parts of Moldova. A significant impact of exploitation on snail population densities, shell size of adult snails and age distribution was revealed. Exploited sites had much lower densities than unexploited ones and in two places no live snails were found. This may suggest that exploitation is currently carried out at an unsustainable level, but additional information on the demography of populations and intensity of exploitation is required in order to make inferences regarding sustainability and long-term population management. There was a higher proportion of adult snails in exploited sites than in non-exploited, because of the collection strategies: not only adults, but also all other age groups are gathered. Bigger adult shell size in exploited sites may be related to lower population density, but further study is required to confirm this. Establishing of well-organized population monitoring systems and development of snail breeding enterprises are proposed in order to conserve the species in Moldova.
Annals of Animal Science, 2014
Results of ReseaRch on the active species pRotection of the Roman snail (Helix pomatia, linnaeus, 1758) using faRmed snails in the second yeaR of life. fiRst season of the study* * abstract the effect of three forms of active species protection in the Roman snail were studied. on the "source plot" the natural population was supported by introducing hatchlings of farmed Roman snails aged 1+, bred from adult specimens of this population. these hatchlings (age 1+) from "source plot" population were also introduced to the following two natural plots: to the "empty plot", where the population was formed by introduction of farmed Roman snails in the second year of life (1+) into a selected area which had been emptied of the natural population; to the "inhabited plot", where farmed Roman snails aged 1+, originating from breeding snails of the foreign population from a "source plot", were introduced to the local natural population. it was established that introducing Roman snails aged 1+ and bred under farm conditions has a clearly positive influence on the age structure of the natural population in the studied plots. the rate of growth of these snails adjusted to the rate of growth of the specimens in the same age group belonging to the natural population. the farmed Roman snails grew most rapidly in the "empty plot" sown with fodder vegetation, more slowly in the "source plot" with access to appropriate herbaceous vegetation, and most slowly in the "inhabited plot". the attempt to create a naturalized population in a specially adapted "empty plot" without the natural population was successful. this was determined not only by a large number of hiding places from calcareous stones available to the Roman snails but above all by the species structure of the herb flora, which met their nutritional requirements as it contained high proportions of plants such as Brassica rapa × Brassica rapa subsp. chinensis, white clover (trifolium repens), red clover (trifolium pratense) and the hybrid of lucerne (medicago × varia martyn).
The release of captive bred snails (Partula taeniata) into a semi-natural environment
1995
A population of zoo bred Partula taeniata was released into a patch of native Polynesian plants in the Palm House at the Royal Botanic Gardens, Kew, London, UK. The released snails were from a colony established from wild-caught snails in 1982, which had been in captive conditions for up to six generations. Monitoring of the snails was continuous and intensive for the first 2 weeks, and at decreasing frequency over the next 1.5 months. There was high survivorship early on in the release, but once the intensive monitoring ended survivorship became hard to determine due to difficulties in locating snails in the large and complex habitat. However, snails are known to have persisted for at least 15 months, and new individuals have been noted maturing into all developmental stages. The snails exhibited patterns of feeding and microhabitat choice similar to those observed in the wild, despite being reared in a highly artificial environment. The methods and results provide some guidelines for future release trials for this highly endangered group of snails.
Notes on the activity of the Roman snail (Helix Pomatia L.)
Folia Malacologica, 2016
A study of Roman snail (Helix pomatia L.) populations in Wrocław shows that even in the active season and under favourable conditions the proportion of snails active or resting on the surface rather than buried in the soil is usually much less than 50%. This confirms earlier studies on this and other species. Variation in the proportion found on the surface was not related to weather conditions at the time, nor were troughs and peaks correlated among sites.
Brooding in a temperate zone land snail: seasonal and regional patterns
Contributions to Zoology, 2013
The goal of this study is to assess if the reproductive strategy of a brooding land snail shifts along a climatic gradient. We focused on the following traits: timing and length of the reproductive season, brood size, ontogenetic dynamics of embryos, and reproductive mode (viviparity versus egg-laying). We dissected the central European door snail Alinda biplicata, collected monthly from eight populations covering the oceaniccontinental climatic gradient within the species’ distribution range. Forty percent of the 1706 dissected individuals were brooding. The species displayed a spring-summer reproductive activity pattern: intrauterine brooding was recorded between March and September; first embryos of a developmental stage that equals that of live-born neonates appeared in late April. Brooding started approximately when the mean daily temperature of a month exceeds ca. 5°C, thus the ontogenetic development of embryos is advancing earlier in populations under the influence of mild o...
2016
The goal of this study is to assess if the reproductive strategy of a brooding land snail shifts along a climatic gradient. We focused on the following traits: timing and length of the repro-ductive season, brood size, ontogenetic dynamics of embryos, and reproductive mode (viviparity versus egg-laying). We dis-sected the central European door snail Alinda biplicata, col-lected monthly from eight populations covering the oceanic-continental climatic gradient within the species ’ distribution range. Forty percent of the 1706 dissected individuals were brooding. The species displayed a spring-summer reproductive activity pattern: intrauterine brooding was recorded between March and September; first embryos of a developmental stage that equals that of live-born neonates appeared in late April. Brooding started approximately when the mean daily tempera-
Laboratory rearing conditions for improved growth of juvenile Helix aspersa Müller snails
Laboratory Animals, 2006
A laboratory rearing system in semi-controlled conditions is proposed to facilitate the behavioural rhythms of the edible snail (Helix aspersa) and to produce a high growth rate with low variability. The growth data were used to construct a model for weight estimation based on age. The animals' live weights showed low variability (o17%) and normal distribution. The best model for estimating weight from age is the logistic model, with a high corelation coefficient (>90%), and a high level of significance for the coefficient (Po0.0001).