Christopher Nathan Lowe

Influence of food particle size on inter- and intra-specific interactions of Allolobophora chlorotica (Savigny) and Lumbricus terrestris

The inverse relationship between the particle size of food resources and earthworm growth rate is widely recognised. The aim was to determine the effects of the particle size of food on interactions between combinations of adult and hatchling A. chlorotica and L. terrestris under laboratory conditions. Treatments were set up in 1 litre mesocosms, maintained in darkness at 15 ′ 1 °C. Separated cattle solids (SCS) were used as food either unmilled or milled to < 1 mm. The latter led to a 185 and 54 % increase in the mass of A. chlorotica and L. terrestris respectively, compared with unmilled SCS. Intra-specific competition in A. chlorotica was detected in adult and hatchling pairings. A positive inter-specific interaction was recorded with hatchling A. chlorotica and mature L. terrestris fed unmilled SCS with growth of the former significantly greater (P<0.01) than in conspecific monoculture. Clitellate A. chlorotica were only recorded in unmilled SCS treatments when paired with L. terrestris (week 18). In milled treatments, 100% maturation was achieved in monoculture and in pairings with hatchling and mature L. terrestris by week 14. The final mass of initially hatchling L. terrestris (3.23 g) fed milled SCS in monoculture was significantly greater (P<0.01) than in pairings with hatchling A. chlorotica and mature conspecifics. With unmilled SCS, lowest initially hatchling L. terrestris mean mass (1.04 g) was recorded when paired with mature conspecifics. Growth of both species was significantly enhanced by decreased food particle size and this effect was size specific. The intensity of competitive interactions was influenced by food particle size and stage of earthworm development. Results suggested a positive association between the two species and mechanisms for this are proposed.

As-resistance in laboratory-reared F1, F2 and F3 generation offspring of the earthworm Lumbricus rubellus inhabiting an As-contaminated mine soil

Previous studies provided no unequivocal evidence demonstrating that field populations of Lumbricus rubellus Hoffmeister (1843), exhibit genetically inherited resistance to As-toxicity. In this study F1, F2 and F3 generation offspring derived from adults inhabiting As-contaminated field soil were resistant when exposed to 2000 mg kg(-1) sodium arsenate. The offspring of uncontaminated adults were not As-resistant. Cocoon viability was 80% for F1 and 82% for F2 offspring from As-contaminated adults and 59% in the F1 control population. High energy synchrotron analysis was used to determine whether ligand complexation of As differed in samples of: resistant mine-site adults, the resistant F1 and F2 offspring of the mine-site earthworms exposed to the LC(25) sodium arsenate (700 mg kg(-1)) of the F1 parental generation; and adult L. rubellus from an uncontaminated site exposed to LC(25) concentrations of sodium arsenate (50 mg kg(-1)). XANES and EXAFS indicated that As was present as a sulfur-coordinated species.

Is tagging with visual implant elastomer a reliable technique for marking earthworms

Visual implant elastomer (VIE) has recently been employed to investigate different aspects of earthworm ecology. However, a number of fundamental questions relating to the detection and positioning of the tag, its persistence and potential effects on earthworms remain unknown. Seven earthworm species belonging to three ecological groupings, with different pigmentation and burrowing behaviour, were tagged using different coloured VIE. External inspection after two days, one week and 1, 10 and 27 months were followed by preservation, dissection and internal inspection. Tags could be seen in living specimens to 27 months, and dissection revealed that in most cases they were lodged in the coelomic cavity, held in place by septa. However, over longer time periods (more than two years), the chlorogogenous tissue tended to bind to the tags and made external observation increasingly diffi cult. Migration of the VIE material towards the posterior of the earthworm and potential loss of the tag were only observed on rare occasions, and a recovery rate in excess of 98% was recorded. By introducing a reasonable amount of VIE into segments, just after the clitellum, this technique can become a valuable tool in earthworm ecology and life history studies, particularly in short-medium term laboratory and fi eld experiments.

Interactions of juvenile Lumbricus terrestris with adults and their burrow systems in a two-dimensional microcosm

Abstract – The objective of this work was to evaluate interactions of Lumbricus terrestris juveniles with adults and with inherited burrow systems. An experiment was set up using a two dimensional Evans’ boxes microcosm. Adult L. terrestris were added to 16 boxes (one individual per box) and kept in darkness at 17°C along with eight unoccupied boxes for two months. The adult L. terrestris were removed from eight randomly selected boxes, and L. terrestris juveniles were added (one juvenile per box), composing three treatments with eight replicates: 1, with an adult in an inherited burrow (ABJ); 2, alone in an inherited burrow (BJ); and 3, alone in a previously uninhabited box (J). The proportion of juveniles occupying adult burrows observed was signifi cantly different in treatments ABJ (48%) and BJ (75%). The mean mass of juveniles at experimental termination differed signifi cantly among treatments and was greater in treatment J (4.04±0.39 g) in comparison to the BJ (3.09±0.93 g) and ABJ treatments (2.13±0.64 g). Results suggest a negative infl uence of both the presence of an adult and its burrow system on juvenile growth. Intraspecifi c competition partially explained this, but further investigation is required to examine how an inherited environment (i.e. burrow) could negatively affect the growth of juveniles.Index terms: anecic, earthworm, intraspecifi c interactions.

Assessment of avoidance behaviour by earthworms (Lumbricus rubellus and Octolasion cyaneum) in linear pollution gradients.

Avoidance behaviour by earthworms is recognised as a valuable endpoint in soil quality assessment and has resulted in the development of a standardised test (ISO 17512-1, 2008) providing epigeic earthworms with a choice between test and control soils. This study sought to develop and evaluate an avoidance test utilising soil-dwelling earthworms in linear pollution gradients with Visible Implant Elastomer (VIE) tags used to identify individual organisms. Sequential experiments were established in laboratory-based mesocosms (0.6m×0.13m×0.1m) that determined the relative sensitivities (in terms of associated avoidance behaviour) of Octolasion cyaneum and Lumbricus rubellus at varying levels of polluted soil and also assessed the influence of introduction point on recorded movement within gradients. In an initial gradient (0%, 25%, 50%, 75%, 100% polluted soil), both species exhibited a clear avoidance response with all surviving earthworms retrieved (after 7 days) from the unpolluted soil. In a less polluted gradient (0%, 6.25%, 12.5%, 18.75%, 25%) L. rubellus were retrieved throughout the gradient while O. cyaneum were located within the 0% and 6.25% divisions, suggesting a species-specific response to polluted soil. Results also showed that the use of a linear pollution gradient system has the potential to assess earthworm avoidance behaviour and could provide a more ecologically relevant alternative to the ISO 17512: 2008 avoidance test. However, further work is required to establish the effectiveness of this procedure, specifically in initial chemical screening and assessment of single contaminant bioavailability, where uptake of pollutants by earthworms could be measured and directly related to the point of introduction and retrieval.

Development of earthworm communities in translocated grasslands at Manchester Airport, UK

The aim of this work was to assess density, biomass and species composition of earthworm communities within four translocated grasslands at Runway 2, Manchester Airport. Results from this study also evaluated the availability of earthworms as a food source for displaced, protected vertebrate species. The sites studied differed in topography and method/type of soil/turf transfer. Earthworms were extracted by digging and hand sorting of soil from replicated 0.1 m2 plots, followed by vermifuge application. Monitoring from 1998‐2001 produced nine species of earthworm representing all three ecological groupings. Throughout, areas supplied with turf contained significantly (P<0.05) more earthworms with greater mass than adjacent areas supplied with soil only. Areas of hummocks and adjacent wet hollows, both covered with the same translocated turf, differed in species composition. Data are presented for mean earthworm community density and mass over the sampling period. Across all sites, figures for density and mass (in 2001), ranged from 50‐427 m ‐2 and 12‐128 g m ‐2 respectively. In all sampled areas, density and mass of earthworms has either increased or remained relatively stable, suggesting each translocation method to be successful after 4 years.

Effects of silver nanoparticles on survival, biomass change and avoidance behaviour of the endogeic earthworm Allolobophora chlorotica

Increasing commercial application of silver nanoparticles (Ag NP) and subsequent presence in wastewater and sewage sludge has raised concerns regarding their effects in the aquatic and terrestrial environment. Several studies have employed standardised acute and chronic earthworm-based tests to establish the toxicological effects of Ag NP within soil. These studies have relied heavily on the use of epigiec earthworm species which may have limited ecological relevance in mineral soil. This study assessed the influence of Ag NP (uncoated 80nm powder) and AgNO3 on survival, change in biomass and avoidance behaviour in a soil dwelling (endogiec) species, Allolobophora chlorotica. Earthworms were exposed for 14 days to soils spiked with Ag NP or AgNO3 at 0, 12.5, 25, 50 and 100mgkg-1 either separately for survival and biomass measurement, or combined within a linear gradient to assess avoidance. Avoidance behaviour was shown to provide the most sensitive endpoint with an observable effect at an Ag NP/AgNO3 concentration of 12.5mgkg-1 compared with 50mgkg-1 for biomass change and 100mgkg-1 for survival. Greater mortality was observed in AgNO3 (66.7%) compared with Ag NP-spiked soils (12.5%) at 100mgkg-1, attributed to increased presence of silver ions. Although comparison of results with studies employing Eisenia fetida and Eisenia andrei suggest that the A. chlorotica response to Ag NP is more sensitive, further research employing both epigeic and endogeic earthworms under similar experimental conditions is required to confirm this observation.

Controlled Cultivation of Endogeic and Anecic Earthworms

Cultivation of epigeic earthworms is relatively simple as these species live within the same organic-rich substrate that they utilise as a food source. Endogeic and anecic species which require a substrate containing a high proportion of mineral soil are seemingly less easily produced. However, these species are potentially of value in a range of ecological contexts. Basic information of the life history of a given species may be collected through controlled cultivation. The natural activities of soil dwelling species can be an asset in soil restoration where earthworms are present in low numbers or totally absent for anthropogenic reasons. Production of stock to act as potential reference sources for DNA-related studies and other applied (e.g. ecotoxicological) research. In the future, mass production of endogeic and anecic earthworm species might also benefit wider ecosystem rehabilitation.

Assessing the contribution of arboriculture operations to anthropogenic greenhouse gas emissions: A case study of a UK tree surgery company

The arboriculture industry relies heavily on fossil fuel-powered equipment to maintain trees in urban areas; removing carbon sinks (trees) and emitting carbon dioxide (CO2) during management practices. It has been suggested that the arboriculture industry may make a disproportionately large contribution to greenhouse gas (GHG) emissions. The aim of this study was to identify the contribution of arboriculture to GHG emissions and provide recommendations for reduction. A case study of a tree surgery company (Down to Earth Trees Ltd) was used to assess indicative industry emissions. Direct emissions from sources owned or controlled by the company were 101.2 t of CO2e per year, with 5.2 t of CO2e per year of indirect emissions from energy use and 98.9 t of CO2e per year of indirect emissions from sources owned or controlled by other organisations. Results suggested that the arboriculture industry releases seven times more CO2e emissions per year than other similar-sized industries in the service sector. This was mainly attributed to the use of machinery and heavy-duty vehicles and removal of carbon storing biomass. Changing current practices could reduce GHG emissions from arboriculture by between 12% and 18%. Furthermore, by providing a renewable feedstock for generation of electricity, it is suggested that the arboriculture industry may achieve carbon positive status.

Experimental woodland establishment on brick clays in southern England

A series of long-term field experiments examining a range of reclamation options for the establish-ment of woodland on Oxford Clay soil-forming materials restored after landfilling is described. Hostile soil physical and nutritional characteristics prevent normal tree survival and growth, but the experi-ments show that there are limited options to alleviate these conditions. The combined results show that tree species of alder, poplar and willow planted on loose-tipped mounds are most suited to the soil conditions, although growth is slow. Application of organic fertilizers has mixed effects.