• Reduce text

    Reduce text
  • Restore text size

    Restore text size
  • Increase the text

    Increase the text
  • Print

Earthworms (L. terrestris) have dug tunnels through yellow earth and subsequently deposited casts in the top litter layer, thus mixing minerals and plant debris. Photo taken of a laboratory terrarium. © INRA, FAYOLLE Léon

Soil ecotoxicology and agroecology: partners in progress

Using the right earthworms when evaluating pesticides

Researchers at the INRA center of Versailles-Grignon have shown that certain earthworm species commonly found in cultivated soils, namely Aporrectodea caliginosa and Lumbricus terrestris, are more sensitive to pesticides than the earthworm species currently used in pesticide approval protocols, Eisenia fetida. As a result, these species could be better suited to pesticide evaluation processes.

By Catherine Foucaud-Scheunemann, translated by Jessica Pearce
Updated on 07/31/2014
Published on 07/03/2014

Earthworm eggs.. © INRA, BOULOUX G. / EXTERIEUR
Earthworm eggs. © INRA, BOULOUX G. / EXTERIEUR

Agricultural pesticides can contaminate the air, water, and soil and thus present ecotoxicological risks to the organisms living therein. Evaluating these risks is a crucial part of the approval process that a pesticide must undergo before being released on the market; the goal is to prevent environmental contamination. This process is defined by EU regulations (Directive 91/414 CEE) and includes tests whose aim is to measure the effects of pesticides on earthworms. In Europe, there are many earthworm species but just one of them, Eisenia fetida, is currently used to evaluate the impacts of chemical products aimed at protecting crops.

Quantifying how sensitive different earthworm species are to pesticides

Researchers at the INRA center of Versailles-Grignon compared the sensitivity of different earthworm species to pesticides. To accomplish this task, they combed through 1,800 scientific publications and identified 15 that seemed particularly relevant to their goal. They then built a database that included several variables mentioned in these publications. One of these variables was the median lethal dose, or LD50. This is the dose of a substance that causes 50% of a study population to die, given controlled experimental conditions. In this context, it can be used to gauge the sensitivity of an earthworm species to a given pesticide.

Thanks to this approach, in which they statistically analyzed a series of studies (known as a meta-analysis), the researchers were able to discover that two earthworm species, Lumbricus terrestris and Aporrectodea caliginosa, are more sensitive to pesticides than is E. fetida. L. terrestris and A. caliginosa are denizens of agricultural soils, on which pesticides are frequently used, while E. fetida more commonly occurs in decomposing organic matter. Therefore, it is frequently found in manure or compost, which are “habitats” in which pesticides are rarely used.

Choosing the appropriate test species

Given these results, it seems that the use of E. fetida in pesticide approval protocols should be reconsidered. Indeed, A. caliginosa may be a more appropriate choice; it is easier to raise than L. terrestris.

Altogether, this research underscores that meta-analyses can be highly useful to ecotoxicologists seeking to compare the sensitivity of different earthworm species to pesticides. This approach can also be used to examine the relative utility of other organisms commonly exploited in pesticide approval protocols and that of other ecotoxicological tests. More importantly, this work shows that new approval protocols employing A. caliginosa should probably be developed. Although pesticides have resulted in substantially greater agricultural yields and have allowed tremendous progress to be made in meeting nutritional needs, their toxic effects on humans and the environment remain a major concern.


Well-known inhabitants of our soils, earthworms belong to many species that are spread across different soil layers:

  • Epigeic earthworms live in the dead leaves and plant debris that is deposited on the soils of forests and prairies, constituting what is known as the litter. They are small in size and reddish brown in color. Characteristic species are Eisenia fetida, Lumbricus castaneus, L. rubellus, and Satchellius mammalis;
  • Endogeic earthworms live permanently below the soil surface, where they dig horizontal tunnels. They are small in size. They can be pink, gray, or green in color, but they are generally unpigmented. Characteristic species are Aporrectodea caliginosa, A. icterica, Octolasium cyaneum, and Allolobophora chlorotica;
  • Anecic earthworms live deep underground and dig vertical tunnels. They are large (up to 1 m) and red, brown, or blackish in color. Characteristic species include Lumbricus terrestris, Aporrectodea giardi, and A. longa.

Earthworms, depending on the species, have a greater or lesser impact on the structure, maintenance, and fertility of the soils found in agricultural fields, forests, and prairies.


Pelosi C. et al. 2013. Searching for a more sensitive earthworm species to be used in pesticide homologation tests – A meta-analysis. Chemosphere 90: 895.