Earthworm ecology

The effects of earthworms Eisenia spp. on microorganisms of three different habitat soil, compost, and
vermiculture were studied. Microbial communities of gut and fresh faeces of earthworms and substrates,
the worms were collected from, were analysed. Microbial biomass and composition of the total microbial
community were examined using phospholipid fatty acid (PLFA) biomarkers. Archaeal and bacterial
communities were studied by polymerase chain reaction-denaturing gradient gel electrophoresis
(DGGE). The culturing methods were used for assessment of counts, species richness and growth strategy
of bacteria.
In comparison with the substrates, the viable microbial biomass and the group of non-ester-linked
PLFAs indicative of anaerobes were higher in both the gut and faeces of all earthworm populations.
The prokaryotic community evaluated using DGGE revealed that archaeal community structure in the gut
and faeces of earthworms from populations differed from that in substrates, whereas the passage
through the gut had less influence on the bacterial community structure, particularly in compost and
vermiculture.
The counts of culturable bacteria increased due to gut passage only in forest and vermiculture populations.
The fast-growing bacteria increased due to gut passage only in forest soil population. Actinobacteria
(Arthrobacter, Microbacterium, Lechevalieria and Nesterenkonia) and Firmicutes (Bacillus and
Paenibacillus) were generally favoured in substrates and their species richness decreased with gut passage,
whereas Gammaproteobacteria (Aeromonas, Enterobacter, Pseudomonas and Salmonella) dominated
in gut contents. The impact of earthworm activity on the microbial community was higher in nutrientpoor
forest soil than in nutrient-rich compost and vermiculture substrates.

Herbicide use is increasing worldwide both in agriculture and private gardens. However, our knowledge of potential side-effects on non-target soil organisms, even on such eminent ones as earthworms, is still very scarce. In a greenhouse experiment, we assessed the impact of the most widely used glyphosate-based herbicide Roundup on two earthworm species with different feeding strategies. We demonstrate, that the surface casting activity of vertically burrowing earthworms (Lumbricus terrestris) almost ceased three weeks after herbicide application, while the activity of soil dwelling earthworms (Aporrectodea caliginosa) was not affected. Reproduction of the soil dwellers was reduced by 56% within three months after herbicide application. Herbicide application led to increased soil concentrations of nitrate by 1592% and phosphate by 127%, pointing to potential risks for nutrient leaching into streams, lakes, or groundwater aquifers. These sizeable herbicide-induced impacts on agroecosystems are particularly worrisome because these herbicides have been globally used for decades.

Background
Many biominerals are formed from amorphous calcium carbonate (ACC), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete calcium carbonate granules which are predominantly calcite but can contain highly stable ACC. To investigate the likely controls on the stability of ACC we analysed the milky fluid from which the granules form and solid granules for their amino acid and functional group compositions by liquid chromatography and Fourier transform infrared (FTIR) spectroscopy respectively. Additionally the granules were analysed for their elemental composition using inductively coupled plasma optical emission spectroscopy (ICP-OES) and electron microprobe analysis (EMPA). We quantified the mass of ACC present in solid granules using FTIR and compared this to the elemental and amino acid composition of the granules. Bulk analysis of granules was carried out on powdered bulk material. Spatially resolved analysis was carried out on thin sections of single granules using synchrotron-based -FTIR and EMPA electron microprobe analysis.

Results
The milky fluid from which the granules form is rich in amino acids (up to 136  3 nmol mg-1 (n = 3;  std dev) for individual amino acids). The CaCO3 phase present in the fluid is ACC. Even four years after their production, granules contain ACC. There is no correlation between mass of ACC present and elemental composition of granules. Concentrations of amino acids in granules generally correlate well with ACC content (r > 0.7, p < 0.05) consistent with a role for the amino acids (or the proteins that they make up) in the stabilisation of the ACC. Intra-granule variation in both ACC (RSD = 16%) and amino acid concentration (RSD = 22 – 35%) was high for granules produced by the same earthworm. Maps of ACC distribution were produced using synchrotron-based -FTIR mapping of thin sections of granules. Maps based on the relative intensity of the 2: 4 peak ratio, cluster analysis and component regression using ACC and calcite standards showed similar spatial distributions of likely ACC-rich and calcite-rich areas. We were unable to identify organic peaks in the -FTIR spectra and thus could not determine whether ACC-rich domains also had relatively high amino acid concentrations. There was no correlation between the distribution of ACC and elemental concentrations determined by electron microprobe analysis.

Conclusions
The ACC present in earthworm CaCO3 granules is highly stable. Our results suggest a role for amino acids (or proteins) in this stability. We see no evidence for stabilisation of ACC by the incorporation of inorganic components.

The genus Moniligaster Perrier, 1872 is restricted to the Western Ghats mountain regions of the southern Peninsular India. A new species, Moniligaster julkai Narayanan & Paliwal, sp. nov., is described and illustrated using samples found in the Kerala districts of Kottayam and Pathanamthitta. Apart from that, the status of Moniligaster deshayesi minor Michaelsen, 1913 is critically reviewed, and it is upgraded to species rank as Moniligaster minor Michaelsen, 1913, based on a collection made near its type locality. Furthermore, new distributional records for other Moniligaster species are provided. With this discovery, the genus Moniligaster now has a total of 14 recognised species.

1. There is little consensus on how agriculture will meet future food demands sustainably. Soils and their biota play a crucial role by mediating ecosystem services that support agricultural productivity. However, a multitude of site-specific environmental factors and management practices interact to affect the ability of soil biota to perform vital functions, confounding the interpretation of results from experimental approaches. Insights can be gained through models which integrate the physiological, biological and ecological mechanisms underpinning soil functions.
2. We present a powerful modelling approach for predicting how agricultural management practices (pesticide applications and tillage practices) affect soil functioning through earthworm populations. By combining energy budgets and individual-based simulation models, and integrating key behavioural and ecological drivers, we accurately predict population responses to pesticide applications in different climatic conditions.
3. We use the model to analyse the ecological consequences of different weed management practices. Our results demonstrate that an important link between agricultural management (herbicide applications and zero, reduced and conventional tillage) and earthworms is the maintenance of soil organic matter (SOM).
4. We show how zero and reduced tillage practices can increase crop yields while preserving natural ecosystem functions. This demonstrates how management practices which aim to sustain agricultural productivity should account for their effects on earthworm populations, as their proliferation stimulates agricultural productivity.
5. Synthesis and Applications.  Our results indicate that weed management that relies on tillage has longer term effects on soil biota than pesticide control, if the herbicides have short dissipation times. If pesticides known to be toxic to earthworms are applied, the risk of exposure will be reduced if irrigation is stopped around application time or if application is carried out during dry periods. Similarly, if the organic content of the soil is increased the recovery rate of earthworm populations can be increased. However, effects are not necessarily additive and the impact of different growing practices on earthworms will depend on their timing and the environmental conditions. Our model can be used to estimate the overall impact of different combinations of crop management activities in different regions to explore how earthworm populations respond.  If our models are linked to crop yield models the costs and benefits of different crop solutions for both yields and biota could be estimated and aid optimisation of the trade-off between different ecosystem services.

Cattle treading accompanied by a high input of organic matter was previously found to favour methanogenesis
in soils at a site used as winter pasture in outdoor cattle husbandry. In this current study, the
phylogenetic microarray AnaeroChip revealed high methanogenic diversity in a cattle-impacted soil with
predominance of Methanosarcina, and presence of Methanoculleus, Methanobacterium, Methanocalculus,
Methanobrevibacter, Methanosaeta, Methanothermobacter, Methanogenium, Methanohalobium, and Methanolobus.
The bioturbation effects of an epigeic earthworm, Eisenia andrei, on the methanogenic
microbial community in cattle-impacted soil were studied in a 6-month laboratory microcosm experiment.
The microarray showed that the methanogenic community was changed by addition of earthworms
to the soil. The abundance of 16S rRNA Methanosarcina gene copies decreased two fold in soil
with worms compared to soil without worms after 2 months of incubation and decreased three fold after
4 and 6 months of incubation. The biomass of anaerobic microorganisms, as determined by unsubstituted
non-ester-linked phospholipid fatty acid analysis, decreased in soil incubated for 4 and 6 months
with worms. The abundance of the methyl-coenzyme M reductase (mcrA) gene, which is involved in CH4
production and is present in all methanogens, was not, however, changed by worms, and addition of
worms even increased the rate of methane production. This study provides the first data concerning
interactions between earthworms and methanogens in cattle-impacted pasture soil. The results of this
laboratory microcosm experiment indicate that E. andrei changes the composition of the soil methanogenic
community but does not reduce the total abundance of the methanogenic community and
methane production rate.