Antifungal Activity of Earthworm Coelomic Fluid Obtained from Eisenia andrei, Dendrobaena veneta and Allolobophora chlorotica on Six Species of Phytopathogenic Fungi

The functioning of soil ecosystems greatly depends on the interactions occurring between soil biota communities. It is well known that earthworms are an important soil component that substantially affects its function, including their meaningful impact on the development of different phytopathogenic soil fungi. Phytopathogenic fungi are responsible for crop disease and cause great economic damage. It has previously been established that earthworms’ coelomic fluid can suppress the growth of phytopathogenic fungi, but the exact molecular mechanism is unknown. The present study aimed at broadening the proof of this observed phenomenon by investigating the effects of the coelomic fluid extract of three different earthworm species (Eisenia andrei, Dendrobaena veneta and Allolobophora chlorotica) on the growth of six different phytopathogenic fungi species (Berkeleyomyces basicola, Fusarium culmorum, Globisporangium irregulare, Rhizoctonia solani, Macrophomina phaseolina, and Sclerotinia sclerotiorum). Coelomic fluid extract was obtained by electrostimulation or usage of extraction buffer (only in case of A. chlorotica) and prepared in three different concentrations by diluting the obtained coelomic fluid with physiological saline. The coelomic fluid extract of the three investigated earthworm species had an inhibitory effect on the growth of all six phytopathogenic fungi species. The greatest inhibitory effect was achieved with the E. andrei coelomic fluid extract reducing the growth of R. solani fungi. The findings of this research confirm the antifungal activity of coelomic fluid obtained from earthworm species belonging to different ecological categories and may be of potential use in crop protection against phytopathogenic fungi.

Photoautotrophic microorganisms as a carbon source for temperate soil invertebrates

We tested experimentally if photoautotrophic microorganisms are a carbon source for invertebrates in temperate soils. We exposed forest or arable soils to a 13 CO 2 -enriched atmosphere and quantified 13 C assimilation by three common animal groups: earthworms (Oligochaeta), springtails (Hexapoda) and slugs (Gastropoda). Endogeic earthworms ( Allolobophora chlorotica ) and hemiedaphic springtails ( Ceratophysella denticulata ) were highly 13 C enriched when incubated under light, deriving up to 3.0 and 17.0%, respectively, of their body carbon from the microbial source in 7 days. Earthworms assimilated more 13 C in undisturbed soil than when the microbial material was mixed into the soil, presumably reflecting selective surface grazing. By contrast, neither adult nor newly hatched terrestrial slugs ( Deroceras reticulatum ) grazed on algal mats. Non-photosynthetic 13 CO 2 fixation in the dark was negligible. We conclude from these preliminary laboratory experiments that, in addition to litter and root-derived carbon from vascular plants, photoautotrophic soil surface microorganisms (cyanobacteria, algae) may be an ecologically important carbon input route for temperate soil animals that are traditionally assigned to the decomposer channel in soil food web models and carbon cycling studies.

Assessment of biosolids in earthworm choice tests with different species and soils

Earthworm avoidance response is a new tool for rapid and efficient screening of potentially toxic substances added to soil environments. This technique was used to determine if five common, ecologically different earthworm species (Allolobophora chlorotica, Aporrectodea longa, Aporrectodea caliginosa, Eisenia fetida and Lumbricus terrestris) avoid soils amended with six biosolids (treated sewage sludge) applied at rates equivalent to realistic field rates of 0, 2, 5, 10 and 20 t ha-1. The results showed that A. chlorotica, E. fetida and L. terrestris were attracted by low concentrations of biosolids (2 t ha-1), whereas they avoided the highest concentration (20 t ha-1). The other species did not show any preferences. An additional treatment comparing the behaviour of E. fetida in natural and artificial soil suggested that the type of soil can alter the preference of earthworms. Comparisons of behavioural and actual toxicity data for the same six biosolids suggest that avoidance responses by earthworms are sensitive enough to reflect different toxicities of biosolids. It is concluded that earthworm avoidance behaviour offers an ecologically relevant tool for screening the deleterious rate-effect of biosolid amended soils.