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The compensatory growth potential of a grazed fungal biomass was mathematically expressed as a function of patchiness in its distribution and demonstrated in an experiment using the fungivorous collembolan Onychiurus armatus and the soil fungi Verticillium bulbillosum and Penicillium spinulosum. The model addresses the regrowth potential in relation to patch fragmentation, travelling time and consumption rate of the collembolan and the mean relative growth rate of the fungus. It suggests that the mean relative growth rate required for regrowth decreases with patch fragmentation and increases with the mean growth rate of the fungus. The experiments were performed with a system of soil-filled vials provided with fungi and collembolans. The size of the vials and the length of the tubes connecting them were varied to give different patch sizes and travelling times. The respiratory activity of fungi after grazing increased as a unit of mycelium was distributed into smaller connected vials. The slow growing species V. bulbillosum showed a greater but delayed response to grazing in comparison with the fast growing P. spinulosum. An increased travelling time delayed the growth response in both species.

The influence of seasonal temperature variations and liming and acidification of the soil on lead uptake in juveniles and adults of the earthworm species Lumbricus terrestris L. was studied by enclosing specimens for up to five months in net bags provided with lead-contaminated, sandy soil. Lead concentrations were analyzed in the pharynx, gizzard, muscles, seminal vesicles and cerebral ganglion. Lead distribution in whole animals was assessed after an injection of 203Pb. The lead concentrations of the tissues were mostly linearly correlated with the soil concentrations, which ranged from

The olfactorial response of the fungivorous soil collembolanOnychiurus armatus was examined in a bioassay covering volatile compounds identified in the odor blends of two of its preferred fungal speciesMonierella isabellina andVerticillium bulbillosum. The odor of the fungi was trapped using activated carbon filters, extracted with diethyl ether, and subjected to GC-MS analysis. About 50% of the compounds resolved by GC were identified by a combination of electron impact and chemical ionization mass spectrometry. In a Y-shaped olfactometer the collembolans were attracted to a variety of common odors, such as CO2 and 2-methyl-1-propanol, and a species-specific odor, such as 1-heptene, and arrested by, for example, decanal and 2-octene. The response was not improved by pairwise combinations of common and specific odors. An amount of 0.5 ng of ethyl acetate or 3 pg of 1-pentanol was sufficient to attract the collembolans. The specific compounds ofV. bulbillosum, 1-heptene and 1-octen-3-ol, may be key stimuli explaining whyO. armatus prefersV. bulbillosum.

1. Resource partitioning of two sympatric species of collembolans, Orchesella cincta and Tomocerus flavescens, was explored from differences in their food odour perception. 2. Preferences of the collembolans of odours from four fungal species and a green alga were tested in a Y-tube olfactometer. The collembolans were separated by only one dif- ference in odour preference; Cladosporium herbarum was significantly more attrac- tive to 0. cincta than the other food sources, whereas T flavescens was most attracted to Mortierella isabellina. 3. Fungal odours were trapped in an activated carbon filter, extracted with diethylether and subjected to GC-MS analysis. The analysis revealed a number of dif- ferences in the odour composition of the two fungal species but the odour of C. herbarum could not be distinguished from that of C. cladosporioides, which was lower ranked by 0. cincta. 4. Nine fungal odour compounds were used in an electroantennogram (EAG) assay. There were differences in antennal responses between the collembolan species to 2- methyl- l-propanol, dipentene, 1 -octanol and camphor. The identity of the compounds responsible for attracting 0. cincta to C. herbarum and T flavescens to M. isabellina could not be resolved. A cluster analysis of the EAG responses emphasized the physi- ological origin of the differences in food preferences between the two collembolan species and suggested that P. cincta was more variable in its odour perception than T flavescens. (Less)

A discrete probability model was developed to describe the distributions of dispersal distances of two soil-living collembolan species, Folsomia fimetarioides and Isotomiella minor, in an experimental gradient with metal polluted soil. The model assumes that animals move stepwise between adjacent habitats with a probability that is influenced by soil metal concentration, metal induced mortality and resistance, interspecific competition and the capability of individuals to perceive concentration differences. Theoretical and observed distributions were compared to determine the contribution of each factor to the dispersal pattern. Mor soils from a contaminated area were used to construct gradients consisting of three connected 20-cm3 PVC rings filled with soil of different zinc and copper concentrations. Adult collembolans were added to each ring, and survivors and newly hatched juveniles were counted after 2 and 10 weeks of incubation. The probability that individuals remained in the soil where they were released was generally < 0.5. They responded to increasing metal concentrations by an exponentially decreasing probability to settle. The model suggested that dispersal distances of F fimetarioides were largely affected by resistance to metals, which was supported by independent observations of enhanced reproduction by individuals collected in the polluted field soil compared with individuals from an unpolluted soil in the same area. Both species preferred to settle in the unpolluted part of the gradient, but E fimetarioides was slower due to a poorer dispersal ability or a slower response to high metal concentrations. Significantly more F fimetarioides remained in the most polluted soil during the first 2 weeks of incubation when L minor was also present in the gradient, but the contribution of competition to the model description of dispersal distances was weak. The closest fit to the experimental data was attained when individuals were assumed to perceive differences in metal concentrations as they moved from one soil to another.

1. Dispersal in a fungivore species of Collembola, Onychiurus armatus, in a homo- geneous soil was theoretically approached as a deterministic compartmental process, in which the movement of animals between discrete patches could be described by a series of differential equations or by the discrete geometric probability distribution, assuming a constant probability to move from one patch to the next. 2. Experiments were designed for a release of collembolans in two types of soil in a physical arrangement of distinct patches represented by vials connected by tubings to cover a distance of 40 cm. Dispersal distances of individuals were determined, and theoretical and observed distributions compared. 3. Dispersal rates, estimated from transfer rate constants, ranged from 0 020 to 1 42 day-1, suggesting that an average 0. armatus moved less than 10 cm day -1. The probability to leave a patch varied between 0 10 and 0 50. 4. Dispersal was dependent on population density, soil type and length of fungal mycelium; it was almost twice as high at a high than at a low density (90 000 and 30000 individuals m-2) in a mor soil and four times as high in a sandy compared with a mor soil. Dispersal rate decreased as the mycelial length increased, especially in a sandy soil. 5. Collembolans in a feeding phase had a higher tendency to disperse than those that were moulting. 6. Enriching the soil patch at 40 cm distance from the release point with a favoured food item, the fungal species Mortierella isabellina, increased dispersal rate by more than four times in a mor soil, suggesting that fungal odour can attract collembolans from a large distance and enhance their rate of movement more than a three-fold increase of their population density does. (Less)

The occurrence of a number of soil intertebrate species in severely polluted soils raises the question whether they have evolved resistance, e.g. by adaptation or acclimatization. This was examined in experiments on the earthworm Dendrobaena octaedra (Sav.) using specimens from sites polluted by a brass industry. One site, exposed since the 17th century, was situated close to an old mill, another was near a modern mill that has been operating for the last two decades, and the third was a non-polluted reference site. Adults and juveniles of D. octaedra from each site were reared in each of the three different soils. Growth (increase of body weight), survival, and cocoon production of the populations were followed over 225 d

Mysz zaroślowa Apodemus sylvaticus (Linnaeus, 1758) jest znacznie wieksza w Islandii niz np. w Europie Środkowej. Średni ciezar aktywnych plciowo samcow waha sie pomiedzy 32,4 a 34,5 g w 1973 roku i 29,9-33,5 g w 1974 roku.

The sensitivity towards metal pollution of some population and community characteristics in Collembola was demonstrated based on observations at eight field sites along a transect from a brass mill. Samples were collected in coniferous forest soils at Gusum, southeastern Sweden, where a local brass mill has created a metal gradient in the surrounding area, with Cu and Zn concentrations in the mor (Oa + Oe) layer close to the mill at levels 50 times above background. Cu concentrations in whole animals increased exponentially in the vicinity of the smelter, but accumulation in body tissues was only observed at background sites. Neither species number, density, nor species diversity were linearly correlated with metal concentrations but instead showed a bell-shaped distribution. The vertical distribution of Collembola was clearly dependent on soil metal concentrations, and their densities at 2 – 10 cm depth were positively correlated with metal concentrations at 0–2 cm depth. The most pertinent information was gained from observations on the species composition. Tullbergia spp. and Onychiurus armatus (Tullberg) became more abundant in the polluted soils, whereas Folsomia quadrioculata (Tullberg) and Frisea mirabilis (Tullberg) generally disappeared. Folsomia fimetarioides (Axelson) became the dominant species in the polluted soil and seemed to have a distribution that was inversely related to that of Isotomiella minor (Schäffer). The general persistence of a high abundance of Collembola in the polluted soils and the more specific changes in species abundances may be due to quantitative and qualitative changes in food supply, low bioavailability of the metals, and efficient avoidance and detoxification capabilities in the animals.

Survival of adultDendrobaena rubida, cocoon production, cocoon viability, and growth of juveniles were examined in laboratory experiments when the worms were reared in acidified and metal polluted soils. Solutions of Cu, Cd and Pb were added to give total concentrations of 10, 100 and 500 μg g−1 in soils with a pH of 4.5, 5.5 and 6.5. Adult tissues, hatchlings and cocoons were analyzed for metals.

The effect of metal pollution on species composition, population density, and age structure of earthworms was studied in coniferous forests near a brass mill in SE Sweden. Samples were taken in two biotapes, dominated by Deschampsia flexuosa and Vaccinium myrtillus, respectively, from eight sites at varying distances (175–20 000 m) from the mill. pH and CEC were found to increase in the soil close to the mill. A decrease in the concentration of extractable metals (Zn, Cu, Pb) could be followed up to 1·2 km from the emission source. Copper and lead were analysed in pharynx, gizzard, muscles, clitellum, seminal vesicles and cerebral ganglion of different earthworm species. Generally, the concentration of copper in tissues was higher compared with lead and inversely proportional to the distance from the mill. A substantial metal uptake was found in the vital tissues, such as seminal vesicles and cerebral ganglion. Juveniles tended to have higher metal concentrations compared with adults. Density and biomass of earthworms was proportional to the distance from the mill, especially in the Deschampsia-dominated biotopes. Dendrobaena octaedra was the most abundant lumbricid species but was absent in soils within 1 km from the mill. Data indicate that the reduced density of earthworms near the mill was due to metal toxicity, but food deprivation could not be ruled out as a possible factor. Reasons for decreased density of earthworms at more remote sites are discussed and data on density and soil zinc concentrations are used to predict the density of earthworms at a metal polluted site.

Colonies of the fungus Mortierella isabellina (Oudem) were grazed by the collembolan Onychiurus armatus (Tullb.) for short periods interrupted by incubation without grazing in laboratory experiments. The grazed fungus had a lower respiration than ungrazed when Collembola were present on the mycelium. Fungal respiration was significantly increased with grazing when Collembola were periodically removed from the mycelium. Metal contamination of the substrate increased fungal respiration, regardless of grazing. Length of fungal mycelium was significantly greater in a natural soil in the presence of Collembola but reduced in a metal-polluted soil. Factors that may determine the impact of grazing on fungi are discussed.

Five-year-studies of two wood mouse populations (Apodemus sylvaticus L.) were carried out outside the village Vik. S. Iceland, and in a birch forest close to the lake Mývatn, N. Iceland. The population at Vik was studied on a 1.10 ha grid on a slope covered with Angelica archangelica L., the seeds of which constituted a major food resource for the mice. Altogether 948 individuals were caught, marked and followed during 1973–1978. No other free-living small mammals occur in Iceland, and predator pressure is low and considered non-existent on the Angelica slope. The population density was extremely high; highest autumn density recorded was 150 ind ha−1. Like other Apodemus populations, the one at Vik showed a typical seasonal pattern in numbers: a winter decrease, relatively stable numbers in late summer, and an autumn peak. Breeding started in late April or early May and ended in late September; no winter breeding was observed. Three or four litters were produced, and the last litter(s) of the season greatly contributed to the autumn increase. The output of young per reproductive female throughout the year was negatively correlated with spring density, and autumn peak density with the number of females in August. Also overwinter success and weight changes appeared to be associated with population density (and weather). Survival rates did not vary much between years and seasons and were consistently rather high. Autumn survival of juveniles was positively correlated with mean minimum temperatures. Juvenile survival was, at least at times, negatively affected by the presence of adult males. Trapping outside the main grid did not indicate any marked dispersal, though some immigration to the grid must have occurred, especially in spring and early summer. Among the factors governing the population density and dynamics of wood mouse at Vik we emphasize the absence of interspecific competition and predation, the rich and dependable food resources (mainly Angelica seeds), the mild (though moist and windy) climate, the shelter of dense Angelica stands, the abundance of crevices (e.g. nest-sites), and the social interactions. The birch forest in northern Iceland was low productive and the wood mouse population differed from the Vik population by exhibiting low density, short breeding season, and high vagility; characteristics we consider to be representative for most Apodemus populations in Iceland.

In Iceland Cepaea hortensis Mull. reaches its northern limit of distribution occurring in restricted areas along the south coast. Samples of snails collected along steep cliffs in two such restricted areas were effectively monomorphic for shell colour (yellow), but were polymorphic for banding pattern and revealed strong area effects. In both localities samples from sites facing east contained varying frequencies of unbanded snails whereas in ecologically similar sites facing south unbanded were absent. In an experimental population released at a south-facing site unbanded snails failed to become established whereas banded individuals survived and bred. It is suggested that the area effects are maintained through non-visual (most likely climatic) selection though other possibilities cannot be ruled out.

A soil-inhabiting species of Collembola, Onychiurs armatus (Tullb.), locates its food source, hyphomycetous fungi, by volatile compounds released from the mycelium. Attractivity was ranked based on the odour of the fungal species, represented by compounds in the range C 5 -C 18 and typically released in olfactometer experiments at a rate of 250 pg h −1 from a 175 mm 2 fungal patch representing about 400 μg mycelium. Among fungi grown in agar Verticillium bulbillosum was most attractive; the preference of O. armatus switched to other species, however, when these were cultured in soil.

The present occurrence of anthropochorous earthworm (Lumbricidae) species was used to trace former human settlements in the Faroe Islands. Densities of earthworms were higher in infields (both extant and abandoned) than in outfields and in infields densities were higher among houses (house remains in abandoned settlements) than in the hayfields. Also in shielings (abandoned at different times from the Viking age until the mediaeval age), densities were higher than in the surrounding outfields. Deep burrowing species ( Allolobophora rosea and Lumbricus terrestris ) were found both in shieling soils and around abandoned house remains (both in infields and outfields). Other anthropochorous species that occur mainly in the topsoil were found in present infields, in abandoned settlements and in shielings ( Lumbricus castaneus and Octolasium lacteum ). Both L. castaneus and O. lacteum were found in sites visibly indistinguishable from the surrounding outfields, but where shielings were said to have existed. Those two species do not occur in the outfields. We discuss the process of colonization of anthropochorous species during establishment of settlements and the subsequent extinction of those species when settlements are abandoned. Apparently, certain species maintain their foothold in enriched soils for considerable times after abandonment and can be used to trace former human occupation.

The Icelandic small mammal fauna is depauperated as is the associated ectoparasite fauna. Three small mammal species occur, viz. Apodemus sylvaticus L., Mus musculus L., and Rattus norvegicus Berk. (R. rattus is probably not a regular member). The mice supposedly came to the island by settlers from the 10th century and onwards. Apodemus and Mus from five localities altogether had seven ectoparasite species, five mites and two fleas. All species occurred on Apodemus whereas Mus was infested by four. Compared with the numbers of ectoparasite species recorded in similar studies in the Nordic countries, there are conspicuously few species in Iceland. Further, Apodemus had an overall higher infestation frequency than Mus (90% and 30%, respectively) and a higher total density of ectoparasites (3.3–20.3 and 0.5 inds/host, respectively). The density figures were high compared with those for mainland Apodemus. Especially the mite Laelaps agilis C. L. Koch and the flea Ctenophthalmus agyrtes (Heller) were common on Icelandic Apodemus. Reduced competition among parasites and/or low predator pressure on small mammals may explain the density figures obtained. The ectoparasite species compositions on small mammals in Scandinavia and Iceland have many features in common that renders it probable that Apodemus originate from Scandinavia.

The influence of food quantity and quality on growth and survival of Onychiurus armatus (Tullb.) in metal polluted environments has been investigated in laboratory experiments. The Collembola was reared on five species of fungi isolated from a metal polluted soil close to a brass mill in SE Sweden. Survival of O. armatus was improved when fungal biomass was continuously added in a polluted mor (1,300 ppm Zn and 200 ppm Cu), and when specimens were fed metal polluted fungi for 1, 3 and 7 days a week, only those that were starved had increased mortality. Allometric growth, on the other hand, was significantly reduced when Collembola was given surplus of metal polluted fungi, whereas growth losses caused by metals were offset by protein rich food. Hence, sufficient food quantities alone could overcome mortality losses but not growth retardation in a metal polluted environment. Feeding preference of O. armatus was not determined by the protein content of the fungi although this was beneficial for growth. Metals changed the relative palatability of fungal species, but one of the metal tolerant species, Paecilomyces farinosus, which was also protein rich, remained reasonably attractive for O. armatus also when it was metal polluted. The mechanisms by which growth and survival of O. armatus were promoted by a combination of protein and Zn/Cu rich fungi seemed to be crucial in understanding the fate of a population of this species in a metal polluted soil.

Une population dense de Apodemus sylvaticus vivant en l'absence de predateur et d'autres petits mammiferes competiteurs dans une region relativement isolee de la cote Sud de l'Islande a ete soumise a une reduction experimentale des ressources alimentaires.Les resultats montrent que la restriction de nourriture n'entraine pas de jeune,n'accroit pas le stress social ni la mortalite ou la dispersion mais affecte la structure de la population par une reduction marquee du recrutement des jeunes.La stabilite de l'environnement social favorise la survie et la reproduction de l'annee suivante.En conclusion les interactions sociales semblent importantes dans les mecanismes de regulation des populations

Small founder units (two or four individuals) of adult Allolobophora caliginosa (Sav.) and Lumbricus rubellus Hoffm. kept in netbags were introduced into a hayfield in NE Iceland. After 14 months 82% of the A. caliginosa units and 35% of the L. rubellus units still contained live adults, and the rates of individual survival were of the same magnitude. Differences in survival between units of A. caliginosa were presumably associated with position of the netbags in the field (exposure, etc.) and initial density of founders; thus, survival seemed to decrease with increasing density. A. caliginosa produced significantly more cocoons and newly hatched individuals than L. rubellus. Colonization success is discussed in relation to the experimental conditions and the difference between the two species in terms of differences in their ecology. It is suggested that A. caliginosa achieves a relatively high post-dispersal colonization success by having a relatively long life-span as adult rather than having a high birth rate.

The effects of uptake of copper and lead on the growth of Onychiurus armatus (Tullb.) (Collembola) were studied in laboratory experiments. Specimens were reared in petri dishes, supplied with a soil borne fungus Verticillium bulbillosum, (W. Gams and Malla), which was grown on a substrate contaminated with different amounts of metals. Growth of specimens of 0. armatus was measured in the F1 and F2 generations. Growth data were fitted to a growth model and the best estimates of growth rate and average maximum length were calculated and compared for different metal contaminations. The fungus accumulated metals efficiently, reaching levels of 1000 to 3500 ppm on substrates containing 15 to 300 ppm metals. 0. armatus concentrated metals during the first two weeks of its life cycle, and then excreted metals towards a steady state level. Copper concentration in the body was higher than lead concentration, and the metals behaved antagonistically when mixed. Neither metal was accumulated by Collembola, and equilibrium concentrations of copper varied from 150 to 600 ppm. Growth rate and average maximum lengths were higher at a moderate metal pollution, both in F1 and F2, and significantly reduced on substrate containing 90 ppm metal or more. The lowest concentration of copper and lead in specimens with significantly reduced growth rate was about 200 ppm. This concentration was also found in a field population in the vicinity of a brass mill. The consequences of reduced growth rate on survival and reproduction in a population are discussed.

The study was carried out on a permanent pasture and in a beech wood in southern Sweden in April and August 1967. Times and localities were chosen to obtain differences in soil physical properties and in associations, abundance and size classes of earthworms. Hand sorting was compared with extraction methods (formaldehyde and potassium permanganate solutions). The extraction methods were tested with and without added detergent. The formaldehyde method was as efficient as hand sorting when estimating populations of Lumbricus terrestris L. during periods of activity. Hand sorting was the best method for studying Allolobophora spp., whereas Dendrobaena spp. and L. rubellus Hoffm. can be studied using all the tested methods. There was a tendency for hand sorting to under-estimate small specimens. Detergent did not increase the efficiency of the extraction methods.

Various methods have been used for estimation of size and growth rate in earthworms. Lakhani and Satchell (1970) weighed individual specimens after drying them overnight at 105'C. Bouch6 (1966) determined the biovolume of soil macrofauna as well as of mesofauna by using a volumeter. In order to estimate growth rates in different populations of lumbricids based on a sample of approximately 25,000 individuals, the following biovolumetric method was developed and correlated to the dry weight method.