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The diploid chromosome set of Arion vulgaris Moquin-Tandon consists of 52 chromosomes, with the karyotype formula: 2n = 44m+6sm+2st=52; FN = 104. The chromosome number (n = 26, 2n = 52) of A. vulgaris is identical to that of A. subfuscus sensu lato, A. ater (L.) and A. rufus (L.) which may suggest their close relationship.
Spray forms of various chemical compounds including compounds of plant origin, molluscicides, and insecticides were tested in order to investigate their possibilities for reducing damage to young rape plants caused by the slug Arion lusitanicus Mabille, 1868. Among them, abamectin (0.2%), methiocarb (0.5%) and metaldehyde (1.0%) reduced damage to the plants, although metaldehyde remained active for only nine days. These three chemical compounds were not phytotoxic to rape plants, and none of them proved lethal to the slugs at the concentration used. The reduction in rape plant damage was obtained as a result of their deterrent and/or antifeedant action. The results indicate that abamectin has high potential usefulness in protecting winter rape seedlings from slugs.
W 2000 roku stwierdzono nowe stanowisko występowania ślimaka Arion lusitanicus Mabille. Było ono zlokalizowane w Poznachowicach Górnych (UTM DA 43) w siedlisku upraw rolniczych. Ślimak bardzo dobrze zaadoptował się w nowym siedlisku i jest groźnym szkodnikiem roślin uprawnych.
Studies on the daily activity of A. lusitanicus were conducted under field and laboratory conditions. Two main phases - the activity phase and the phase of resting- have been distinguished in the daily cycle of the slug. The observed activity was of different types, such as crawling, feeding and the state of semiactivity. lt has been found that slug activity is determined by various atmospheric factors, mainly by light intensity, rainfalls and presence of dew. Slug activity is strongly influenced by their physiological 24 hr. life rhythm. Full activity was exhibited by all individuals after sunset and after the appearance of dew. They return to their shelters about three hours after sunrise. Feeding of A. lusitanicus, including periods of resting, lasts throughout the whole night, since their emergence from shelters until early morning hours. Most of the slugs start intensive feeding 2-3 hours after sunset.
The experiments were carried out in Rzeszów, a region of the Arion lusitanicus mass occurrence, and also in Poznań. The studies were performed under field conditions, in isolators dug inio the ground. It was found that the slug began egg laying by the end of the first decade of August. The period of egg laying, depending on meteorological conditions, lasted for 2-3.5 months. The eggs were laid in clutches, each containing from 5 to 193 eggs. Most of eggs laid in August hatched before winter. For the eggs laid in mid-August the period of hatching was shorter than those laid at the turn of August/September, and the percentage of hatched eggs was lower. Eggs deposited at later dates (in September-November) did not hatch before winter.
In the years 1997-1999, studies on the intensity of the slug Arion lusitanicus occurring in different microhabitats were carried out on the territory of Podkarpackie province. Observations were performed in the environments of vegetable gardens, arable fields and non-crop areas. The intensity of the slug occurrence varied greatly in arable crops of different plant species and in other microhabitats. Vegetable crops and areas adjacent to them were inhabited by the slug most numerously. Considerably less slugs occurred in agricultural plant crops.
Within the last decades the slug Arion lusitanicus has expanded its range over wide areas of Europe, in most of them it is now a serious pest. Poland has been invaded relatively recently (since the late 1980s). Considering the ecological importance of the slug, very little is known yet about the mechanism of invasion, establishment of new populations and influence on the native fauna and flora. The analysis of nucleotide sequences of mitochondrial cytochrome oxidase subunit 1 gene (cox1) revealed a great inter- and intrapopulation variation in the Polish populations of A. lusitanicus. The differentiation of all the studied Polish populations of A. lusitanicus is 0.2–2.2%, while two analysed Belgian populations are monomorphic and moderately genetically diverse at 0.8%. This indicates a heterogeneous origin of the Polish populations, probably resulting from multiple independent introduction events. The genotype found in the first four Polish populations (S. Poland) suggests that their origin is different from the remaining populations.
Population studies on Arion lusitanicus, a slug species introduced into Poland, were carried out over the last decade. The slug occurs commonly in some areas and spreads out relatively quickly. It has an annual life cycle with eggs, and immature individuals overwinter. In the end of July A. lusitanicus begins copulation and three weeks later it lays eggs from which the first offspring hatch within a month. The copulation process and egg laying last until late fall. One A. lusitanicus can lay over 400 eggs. During the growing season there are two peaks of population density. This species feeds on plant material such as leaves, stems, bulbs, but also consumes animal material. The basic plant material are arable crops particularly vegetables and some species of agricultural crops, some fruit trees, ornamental plants, herbs and weeds. A. lusitanicus displays apparent food specialization and prefers certain cultivated and wild growing plants. A. lusitanicus shows large reproduction potential, wide food and ecologic tolerance, and is regarded as a serious pests occurring in home gardens.
All previously known former Yugoslavian terrestrial slugs of the families Arionidae, Milacidae, Limacidae and Agriolimacidae have been discussed in this paper. The author conducted his research in the former Yugoslavia's territory in 1982-1983. He has also examined material from museums and private collections. The taxa, from the family to the species, are provided with full synonymy, more important references, descriptions of the external appearance and systematically useful anatomical characters, information on ecology and distribution in the world, list of new and already known localities, and comments, which - e.g. - help to distinguish a particular taxon from other ones. There are also keys to all the families and species, characteristics of the former Yugoslavia's slug fauna figures of all the species (nearly all made by the author himself) and distribution maps on a simplified UTM grid. The occurrence of 48 species has been established. Six other, in the author's opinion, were erroneously recorded in literature and should not be reckoned among the fauna of this area. Besides, 11 species mentioned by former authors still have a completely unclear status. Two species new to science have been described, i.e. Tandonia rara and Deroceras maasseni, and 20 names synonymized.
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