Two distinct ecological behaviours within anecic earthworm species in temperate climates

Abstract

Earthworm species in temperate climates have usually been classified into three main ecological categories according to their morpho-anatomical, physiological and ecological traits: epigeic, endogeic and anecic. However, since these ecological categories were first defined, many studies on the ecological traits of widespread anecic species: Lumbricus centralis (Bouché, 1972), Lumbricus terrestris (Linnaeus, 1758), Aporrectodea longa longa (Ude, 1885) and Aporrectodea giardi (Ribaucourt, 1901) have revealed two distinct feeding behaviours, as well as differences in their growth rates and burrowing behaviour. In this review we highlight that within anecic earthworms, Lumbricus anecic species (here after “LAS”) mainly consume fresh plant-derived materials on the soil surface modifying the quantity and spatial organisation of said materials. In contrast, Aporrectodea anecic species (here after “AAS”) consume mainly aged plant-derived materials already incorporated into the soil and only a small proportion of surface-available plant-derived materials. Furthermore, the AAS have a denser and more complex burrow network than LAS. This suggests that AAS burrow into the soil to search for soil organic matter incorporated in the soil whereas the LAS essentially focus on burying the surface litter into their burrow. Consequently, LAS seem to benefit from easily assimilated substrates, grow faster and reach maturity in a shorter time span than AAS species. This distinction between anecic Lumbricus and Aporrectodea earthworms is expected to have different consequences for soil trophic network and soil functioning such as carbon and nutrient cyclings, water regulation and soil structure maintenance.