Herbivore behavior in the anecic earthworm species Lumbricus terrestris L.?

Abstract

Earthworms dominate invertebrate biomass in many non-acidic terrestrial ecosystems and represent key detritivores. Anecic earthworms live in the soil but primarily feed on soil surface litter. Recent studies indicate that predation of seeds and seedlings may also contribute to earthworm nutrition. However, the biological significance of this behavior is unknown. Here, we present to our knowledge the first photographic and video evidence that the anecic earthworm species Lumbricus terrestris L. attacks living plants and damages leaves still attached to plants. This behavior could be observed repeatedly and in different locations, indicating that it may be a common process. Though based on uncontrolled observations and in situations of low litter availability, this herbivore behavior suggests that the role of earthworms within ecosystems should not be restricted to litter burial and decomposition, but should include aboveground herbivory. Our observations do not allow us to determine with certainty if the earthworms directly fed on fresh plant material or – more likely – transported it to its permanent burrows to facilitate microbial decay. We propose that this behavior and its implications for the composition and functioning of plant communities merits further scientific attention. For instance, given the detrimental effects of some common molluscicides on earthworm performance, assumed mollusk effects on plant growth and seedling survival reported in previous studies could be – at least in part – due to the action of anecic earthworms. Future studies should investigate the biological significance and the context-dependency of this behavior.