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  • Author: Maciej Ligaszewski x
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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)

Abstract

Observations were made concerning active species protection of the Roman snail. Samples were collected from three natural plots in which 3,000 marked hatchlings of farmed origin, aged 1+ (three individuals per m2), were placed in mid-May 2011. The hatchlings originated from breeding snails of the park, or ‘source’ plot. The other plots were a forest, or ‘inhabited’ plot, occupied by a foreign population and a cultivated ‘empty’ plot, which had been emptied of its natural population. By the end of June 2012, the introduced snails were aged 2+, when snails of this species reach maturity. During this period, as part of the analysis of collected samples, the snails in their final maturation period in this age group were divided into mature and immature groups. After thirteen months of observations, a greater density was observed for the farm-originated, naturalised population in the ‘empty’ plot than in the total populations for the other two plots. In the ‘empty’ plot the percentage of somatic and sexually mature farmed snails aged 2+ was significantly higher than in the same snail groups from the other two research plots. There were no statistically significant differences between the shell diameters of the mature farmed snails in all the research plots. The Roman snails of farmed origin considerably extended their territorial range, maintaining their high percentage share in the local natural populations.