Slug Arion Research Articles

Daily activity of the pest slug Arion lusitanicus under laboratory conditions

SummaryThe daily activity of the slug Arion lusitanicus was studied using time‐lapse video analysis in the laboratory. Under constant temperature (18°C) and 16–h photoperiod, the activity of slugs was measured in half‐hourly periods as locomotor activity, feeding or resting. Track lengths were determined using image analysis. Locomotion of A. lusitanicus was greatest at 5:30, 1.5 h after sunrise, and at 20:30, 1 h after sunset; least locomotor activity occurred between 13:00 and 14:00. The mean distance travelled by A. lusitanicus in 24 h was 10.8 m. The largest slug was the most active and the smallest the least. Slugs spent 68% of 24 hours resting, mainly under artificial shelter traps, 27% in locomotion and 4% feeding. Feeding occurred mainly during the hours of dakness (76%). All categories of behaviour investigated varied greatly between individuals and also between times of day. Homing to artificial shelters and other roost sites was regularly observed within 24 h (41%), but decreased considerably thereafter.The behavioural patterns proved to be in agreement with those found in a previous field investigation and are therefore also discussed with a view to their importance in pest control.

Evaluation of an Alternative Mucosal Irritation Test Using Slugs

The objective of this study was to evaluate an alternative mucosal irritation test using the slug Arion lusitanicus as test organism. The effect of 28 reference substances on the mucosal tissue of the slugs was determined by the amount of mucus produced, the reduction in body weight, and the release of proteins from the body wall. The data of the mucosal irritation test were compared with the available in vivo Draize scores for eye irritation (MMAS). The amount of mucus produced and the reduction in body weight caused by a 60-min contact period were significantly correlated ( r = 0.73) with the MMAS score for eye irritation. However, the mucus production was the best endpoint to classify the chemicals into the three categories corresponding the EU classification (NI, R36, and R41). Since irritating alcohols did not induce an increased mucus production and therefore the irritation potential of these molecules was underestimated, two prediction models were developed. For nonalcohols a 60-min contact period with the chemicals was sufficient and the molecules were classified according to the amount of mucus produced. A concordance, specificity, and sensitivity of 65, 100 and 83%, respectively, was obtained. For the alcohols a second 60-min contact period was necessary and the molecules were classified using the protein release as endpoint. Ninety-one percent of the alcohols were correctly classified with a sensitivity and specificity of 100%. We can conclude that the mucosal irritation test using slugs seems to be a reliable and promising method for the evaluation of the irritation potential of drugs instead of diverse tests using different animal models to estimate the irritation on human mucosal tissues.

Isoelectric focusing as a tool to evaluate carabid beetles as predatory agents of the pest slug Arion lusitanicus

Isoelectric focusing was investigated to detect esterases of the pest slug Arion lusitanicus in the crop contents of predatory carabid beetles. The method is exceptionally well suited for field studies, as it is fast, cheap, easy to apply, and almost species-specific. The identification of A. lusitanicus was enabled by four characteristic, stable esterase electromorphs. The profile clearly differed from the band patterns of the digestive enzymes of the carabid beetles, from esterases of other potential prey species and even from the enzymes of early developmental stages of the slug. To test the heaviest stained isoenzyme for its decay under controlled conditions, three carabid species were fed on a fixed amount of slug hepatopancreas. In Carabus cancellatus and Pterostichus melanarius the enzyme lost 35% of its activity after 16 h, fitting a logarithmic curve, whereas in Carabus granulatus the same decay status was already reached after 8 h following a linear regression. Both, the similarities and differences between beetle species might be due to their mode of extra- versus intraintestinal digestion and the amount of hepatopancreas fed. The temperature during digestion was also influential, as the regression slopes of esterase activity between the two temperature regimes tested in C. granulatus were significantly different. The volume of crop contents decreased during digestion in both Carabus species, corresponding to the decline in esterase. In contrast, the crop volume of P. melanarius reached its maximum almost 4 h after ingestion. This was interpreted as an effect of its mode of ingestion and time-elapsed enzyme production.

Field tests with a molluscicide containing iron phosphate

The effect of slug pellets containing iron phosphate was evaluated in field trials. In comparison with untreated controls, iron phosphate reduced leaf loss of lettuce, increased the number of marketable lettuce heads and reduced numbers of the slug Arion lusitanicus. The reference treatment metaldehyde was more effective in preventing slug damage and reduced numbers of all slug species present ( A. lusitanicus, A. hortensis and Deroceras reticulatum). In rape, iron phosphate reduced the percentage of seedlings with slug damage, but did not affect the total number of seedlings per unit area. Iron phosphate seems promising for organic agriculture, where other chemical molluscicides cannot be used.

Sialic acids in gastropods

The occurrence of N-acetylneuraminic acid and N-glycolylneuraminic acid residues in preparations of the slug Arion lusitanicus (Gastropoda) was determined by sodium dodecyl sulphate electrophoresis of the proteins followed by lectin blots stained with the sialic acid specific lectin from Maackia amurensis, by the sensitivity of this binding to sialidase from Clostridium perfringens, by specific fluorescent labelling of sialic acids with 1,2-diamino-4,5-methylenedioxybenzene, by the determination of the sensitivity to sialate-pyruvate-lyase, by co-migration with standards on high performance anion exchange chromatography with pulsed amperometric detection and by identification of the typical masses in the fragmentation patterns of the trimethylsilyl derivatives after gas chromatography. It is the first time sialic acids are identified in gastropods.

Spermatophore formation and transfer in Arion lusitanicus Mabille, 1868 (Gastropoda: Pulmonata: Arionidae)

1. Reconciling comparative anatomy and mitochondrial phylogenetics in revising species limits in the Australian semislug Helicarion Férussac, 1821 (Gastropoda: Stylommatophora) Isabel Hyman, Frank Köhler Zoological Journal of the Linnean Society CrossRef

Spatial distribution and home-range of the pest slug Arion lusitanicus (Mollusca: Pulmonata)

Abstract The density and distribution of egg-batches, juveniles and adult Arion lusitanicus , as well as individual home-ranges, were investigated over two seasons. The study was performed on grassland which was mown twice a year and received no herbicides or pesticides, with neighbouring field and stream-side vegetation. Female-mature slugs preferred restricted areas closely neighbouring the taller vegetation of the stream-side vegetation and field, but less-favourable parts of the site were also inhabited in the second year when population densities increased and weather conditions were more favourable. It was postulated that slugs could have home-ranges, as homing behaviour is a well-known phenomenon. The application of a long-lasting individual marking technique enabled calculations of home-ranges (convex polygons) for slugs for the first time. Home-range size averaged 45.4 m 2 when the population density was low in 1995, and was found to be negatively correlated with density, as it decreased to 12.4 m 2 in 1996, when population density was high. Mating sites were found to be distinctly closer to the geometric centres of activity than the sites used for egg-deposition. Egg-batches were aggregated under the shelter traps (50 × 50 cm squares of hardboard covered with polystyrene) and the pattern of distribution of egg-batches persisted in the young hatchlings. A number of foreign A. lusitanicus were introduced into the unfavourable centre of the site, and by two to four weeks after release their distribution exactly resembled that of the local ones. In all the various aspects of behaviour investigated, large individual differences were found, suggesting a great plasticity in this generalist species. The importance of the species‘ dispersal capacity in relation to general ecological and applied aspects of control is discussed in the context of the present findings.

Parametric intensity and the spatial arrangement of the terrestrial mollusc herbivores Deroceras reticulatum and Arion intermedius

Summary 1. Parametric intensity and spatial arrangement analyses were used to investigate the spatial pattern of the slugs Arion intermedius and Deroceras reticulatum. 2. The spatial lag of sampling (distance between sampling points) was shown to be unimportant in the intensity analyses. Rather, the 0·25 m grain scale was imposed on the whole sampling. The observed slope of the variance to mean relationships was common to both species, possibly determined by egg laying in batches at 0·25 m. However, the variance of the sample, for a given mean, was lower in summer. This corresponded with a reduction in the proportion of zero counts, which could be due to slug movement, possibly increased by predator activity, acting at the 0·25 m scale. 3. By contrast with the intensity analyses, the lag scale was important for spatial arrangement. At 0·25 m, in March 1997, the A. intermedius and D. reticulatum juveniles were aggregated, presumably about where egg batches were laid. At higher scales, the arrangements of D. reticulatum became spatially random, and A. intermedius resolved to a patch arrangement at the 16 m scale. 4. Over time, the D. reticulatum spatial arrangements remained random and independent of the previous sampling date. From March to July 1997, the A. intermedius patch persisted. A crash in abundance of both species, between July and October 1997, appeared to destroy the patch, but subsequent association suggested that the patch persisted until March 1998. The arrangements of the species were independent of one another on all sampling dates. 5. These species‐specific spatial arrangements were independent of all measured environmental factors and consistent with differences in the local reproduction, survival and migration of A. intermedius and D. reticulatum. 6. This comparative study indicates that the terms aggregated, random and regular should have separate definitions for parametric intensity and spatial arrangement. Furthermore, spatial scale has different meaning in intensity and arrangement analyses. Spatial arrangements are not described by parametric intensity. Spatial arrangements change with spatial scale. Temporal changes in intensity need not manifest as changes in spatial arrangement.

Is there a geographical pattern in the breeding system of a complex of hermaphroditic slugs (Mollusca: Gastropoda: Carinarion)?

Allozyme analyses of the hermaphroditic slugs Arion (Carinarion) fasciatus, A. (C.) circumscriptus and A. (C.) silvaticus have suggested that the three species in North America and north-west Europe predominantly reproduce uniparentally, most probably by selfing. We used allozyme electrophoresis to investigate the population genetic structure of these species throughout a larger part of their native European distribution. Our results show that the previously reported "species" specific allozyme markers are no longer valid if populations from central Europe are investigated, and A. fasciatus and A. silvaticus appear to be "paraphyletic" taxa. In contrast to the general belief that selfing organisms show low gene diversities, the high selfing rates in N-NE European Carinarion do not necessarily result in low gene diversities. Moreover, our data suggest a geographical pattern in the prevalence of outcrossing, at least in A. fasciatus, with selfing in N-NE Europe and a mixed breeding system (i.e. selfing and outcrossing) in central Europe. Possible scenarios for the disjunct distribution of breeding systems in Carinarion are discussed.

Daily activity of the pest slug Arion lusitanicus Mabille

Daily activity of the pest slug Arion lusitanicus Mabille

Effects of plant extracts on the feeding behaviour of the slug Arion lusitanicus

SummaryMethanol extracts of the plants Geranium robertianum, Lepidium sativum, Origanum vulgare, Salvia officinalis, Salvia pratensis, Saponaha officinalis, Thymus vulgaris, Trifolium repens and Valerianella locusta were produced and applied to cotyledons of 6–8 days old rape seedlings to investigate whether they can influence the feeding of the slug Arion lusitanicus on young rape. All plant extracts appeared to reduce slug feeding on rape to some extent, but only the extracts of Saponaria officinalis and V. locusta significantly deterred A. lusitanicus from feeding. The small effects of some extracts may be due to a poor extraction efficiency or an insufficient feeding inhibition capacity of these extracts.

Preference for Acyanogenic White Clover (Trifolium repens) in the Vole Arvicola terrestris: I. Experiments with Two Varieties

We report experimental results showing that, under both laboratory conditions as well as in outdoor enclosures, the fossorial vole Arvicola terrestris preferentially feeds on acyanogenic white clover (Trifolium repens) when offered the choice between two varieties (Ladino and Aran) differing highly in their content in cyanogenic glycosides. We also observed that the voles adapted their diet and reduced their relative consumption of the cyanogenic variety during experiments conducted for two to three weeks in outdoor enclosures as compared to shorter tests conducted for 48 hr in laboratory cages. In addition, we report a similar preference for the acyanogenic Ladino variety for the slugs Arion ater and A. subfuscus.

The palatability of 78 wildflower strip plants to the slug Arion lusitanicus

Summary.AsArion lusitanicushas been observed in high densities in wildflower strips, the palatability of the foliage of 78 species of sown and naturally occurring plants found in such strips was investigated. In the laboratory, the slugs were offered a surplus of fresh, mature leaves and, after 16 h, a consumption index was calculated to rank the plants according to their palatability to the slugs.Arion lusitanicusshowed clear preferences for particular plant species, but more than two thirds of all plants investigated were scarcely eaten.Brassica napuswas most eaten, followed byPapaver rhoeas, Capsella bursa‐pastorisandLamium purpureum.Overall,A. lusitanicuspreferred sown species to naturally occurring ones and preferred annuals to perennials.

Allozyme diversity in slugs of the Carinarion complex (Mollusca, Pulmonata)

Previous allozyme analyses of the hermaphroditic terrestrial slugs Arion fasciatus, A. circumscriptus and A. silvaticus (subgenus Carinarion) have suggested that in North America these species are each single monomorphic strains. However, new data on 18 putative enzyme loci show that in western Europe the three taxa, respectively, consist of at least three, two and 12 homozygous multilocus genotypes (strains), which regularly co-occur. The current opinion that American and European Carinarion populations are similarly structured, and that colonization events did not affect the population genetics of North American Carinarion, should therefore be readdressed. The present data also provide the first indication of heterozygosity and possible outcrossing in Carinarion. Nevertheless, uniparental reproduction is confirmed as the main breeding system in West European Carinarion, although the high incidence of multistrain populations in A. silvaticus and A. fasciatus appears at variance with the current model of population genetic structuring in selfing terrestrial pulmonates. Finally, the systematic status of the three Carinarion spp. is tentatively questioned.

Allozyme diversity in slugs of the Carinarion complex (Mollusca, Pulmonata)

Previous allozyme analyses of the hermaphroditic terrestrial slugs Arion fasciatus, A. circumscriptus and A. silvaticus (subgenus Carinarion) have suggested that in North America these species are each single monomorphic strains. However, new data on 18 putative enzyme loci show that in western Europe the three taxa, respectively, consist of at least three, two and 12 homozygous multilocus genotypes (strains), which regularly co-occur. The current opinion that American and European Carinarion populations are similarly structured, and that colonization events did not affect the population genetics of North American Carinarion, should therefore be readdressed. The present data also provide the first indication of heterozygosity and possible outcrossing in Carinarion. Nevertheless, uniparental reproduction is confirmed as the main breeding system in West European Carinarion, although the high incidence of multistrain populations in A. silvaticus and A. fasciatus appears at variance with the current model of population genetic structuring in selfing terrestrial pulmonates. Finally, the systematic status of the three Carinarion spp. is tentatively questioned.

The influence of slug (Arion rufus) mucus and cast material addition on microbial biomass, respiration, and nutrient cycling in beech leaf litter

The influence of slug (Arion rufus) mucus and cast material addition on microbial biomass, respiration, and nutrient cycling in beech leaf litter

Successional changes in microbial biomass, activity and nutrient status in faecal material of the slug Arion rufus (gastropoda) deposited after feeding on different plant materials

Microbial biomass and activity in casts of the slug Arion rufus L. of different ages (0 to 160 days) deposited after feeding on beech leaf litter ( Fagus sylvatica L.) and fresh leaves of Allium ursinum L. and Mercurialis perennis L. were investigated. The following parameters were determined: basal respiration (O 2-consumption), microbial biomass (SIR, substrate-induced respiration method), microbial growth ability after C (glucose), CN, CP and CNP amendment, specific respiration ( qO 2), lag time (time between CNP addition and start of exponential increase in respiration rates) and decomposition time (time required to achieve the maximum respiration rate following CNP addition). Basal respiration and microbial biomass initially increased but then decreased in ageing cast materials. The increase in basal respiration usually predated that in microbial biomass. Basal respiration in cast materials of beech leaf litter, A. ursinum leaves and M. perennis leaves was at a maximum at day 5 (521 μl O 2 g −1 dry wt h −1), day 1 (1420 μl O 2 g −1 h −1) and days 1, 2 and 5 (average 1270 μl O 2 g −1 dry wt h −1), respectively. Microbial biomass (C mic) for the respective materials was at a maximum at day 5 (29.9 mg C mic g −1 dry wt), day 2 (64.4 mg C mic g −1) and day 1 (83.1 mg C mic g −1). Specific respiration of cast materials deposited after feeding on beech leaf litter was exceptionally high at day 1 (43.4 μl O 2 mg −1 C mic h −1) and decreased with age. Specific respiration of cast materials deposited after feeding on A. ursinum leaves also significantly decreased with age but no significant trend occurred in cast materials of M. perennis leaves. In cast materials of beech leaf litter of an age of 1 and 2 days C was the primarily limiting element and N and P were available for microbial growth. Between days 5 and 20, C-amended microorganisms were limited by N and CN-amended microorganisms were limited by P. Following day 40 P was mobilized in ageing cast materials of beech leaf litter. In cast materials deposited after feeding on A. ursinum and M. perennis leaves, microbial growth usually was limited by C. Requirement for P by microorganisms in 4- and 12-h-old C-amended cast materials was high. This P requirement decreased in ageing cast materials indicating P mobilization. In later successional stages sufficient P supply but a strong N demand by microorganisms occurred, which presumably was caused by immobilization of N in ageing cast materials. Decomposition time in cast materials deposited after feeding on beech leaf litter was shorter than in intact leaf litter. Lag time and decomposition time increased with age of casts produced after feeding on each of the food materials but remained almost constant in ageing beech leaf litter. The increase was more pronounced in A. ursinum and M. perennis casts than in casts deposited after feeding on beech leaf litter. Considering Piankas r K -concept the prolongation of the lag and decomposition times in ageing casts and the decline in specific respiration in casts deposited after feeding on beech leaf litter and leaves of A. ursinum with age indicate successional replacement of r-strategists by K-strategists in ageing casts. According to Grime's theory of life strategies, the short lag and decomposition times in early successional stages in casts indicate dominance of ruderal populations.

Fine structure of the germinating cells during the spermiogenesis ofArion rufus (Mollusca, Pulmonate Gastropoda)

Changes in spermatozoan ultrastructure have been studied during spermiogenesis of the slug Arion rufus (Gastropoda, Pulmonata, Stylommatophora). The ovotestis was investigated during the male stage, definite by the presence of spermatozoa. Some peculiar characteristics are shown by early spermatids: Around the nucleus, the nuclear envelope presents two thick layers located on opposite sides, the apical and basal plates, that will determine the antero-posterior axis of the spermatid. The chromatin, first dispersed throughout the nucleoplasm gives later on thick filaments which become attached over the inner surface of these plates. The chromatin filaments are then arranged parallel to the anteroposterior axis as the nucleus elongates. The position of the plates determines the antero-posterior axis of the spermatid. In the mature spermatozoa, the chromatin is more condensed and the nucleus presents an helical organization. The acrosome and flagellum are respectively attached externally to the center of the apical and basal plates. The acrosome consists of a membrane-bound vesicle and forms a column of homogeneous material. In the middle piece, the mitochondria have been transformed into a mitochondrial derivate by the way of a complicated metamorphosis. The axoneme is surrounded by three mitochondrial helices but only one of them contains glycogene granules.

Fine structure of the germinating cells during the spermiogenesis of Arion rufus (Mollusca, Pulmonate Gastropoda).

Changes in spermatozoan ultrastructure have been studied during spermiogenesis of the slug Arion rufus (Gastropoda, Pulmonata, Stylommatophora). The ovotestis was investigated during the male stage, definite by the presence of spermatozoa. Some peculiar characteristics are shown by early spermatids: Around the nucleus, the nuclear envelope presents two thick layers located on opposite sides, the apical and basal plates, that will determine the antero-posterior axis of the spermatid. The chromatin, first dispersed throughout the nucleoplasm gives later on thick filaments which become attached over the inner surface of these plates. The chromatin filaments are then arranged parallel to the anteroposterior axis as the nucleus elongates. The position of the plates determines the antero-posterior axis of the spermatid. In the mature spermatozoa, the chromatin is more condensed and the nucleus presents an helical organization. The acrosome and flagellum are respectively attached externally to the center of the apical and basal plates. The acrosome consists of a membrane-bound vesicle and forms a column of homogeneous material. In the middle piece, the mitochondria have been transformed into a mitochondrial derivate by the way of a complicated metamorphosis. The axoneme is surrounded by three mitochondrial helices but only one of them contains glycogene granules.

Selective Grazing of Hairless Silene dioica Plants by Land Gastropods

Silene dioica (Caryophyllaceae) has evolved different morphotypes that vary in hairiness in different habitats in the Swedish mountains. A hairy form, var. serpentinicola and a hairless (glabrous) form, var. smithii grow on serpentine, i.e. a dry soil rich in heavy metals. Var. lapponica is a densely hairy morphotype on subalpine meadows. Crosses between these varieties showed that glabrousness has a simple Mendelian inheritance and that glabrousness is determined by a recessive allele. The crosses further suggested that the recessive allele has been present in the original population that invaded the mountain area. Glabrous plants have, however, never been found on subalpine meadows, even though an earlier study has shown that gene flow is relatively common among serpentine and nearby meadow populations. In addition to the genetic background of glabrousness, we studied the grazing on glabrous smithii and hairy serpentinicola and lapponica plants by the slugs Arion fasciatus and Arion subfuscus and the snail Arianta arbustorum in greenhouse and in nature. Arion slugs, abundant on subalpine meadows, preferred glabrous plants and, in particular, A. fasciatus consumed high amounts of S. dioica. Arianta snails, however, consumed irrespective of morphotype. The selective behaviour was seen both at the seedling stage and the adult plant stage. Arion slugs were more choosy when they were given a choice of glabrous smithii and densely hairy lapponica plants then when they were served smithii and the less hairy variety serpentinicola. This study implies that the Arion slugs are important agents of selection on subalpine meadows. The selective grazing seems to counteract the flow of the recessive allele that determines glabrousness, from serpentine into meadow populations. Gastropods are rare in the dry serpentine habitat. The evolution of a distinct glabrous morphotype on serpentine is therefore rather due to relaxation of selection than to adaptation to serpentine stress.