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Biol Fertil Soils (2009) 45:789797 DOI 10.1007/s00374-009-0393-8
ORIGINAL PAPER
Earthworm burrowing behaviour in 2D terraria with single- and multi-species assemblages
Daniel Felten & Christoph Emmerling
Received: 3 April 2009 /Revised: 17 June 2009 /Accepted: 24 June 2009 /Published online: 16 July 2009 # Springer-Verlag 2009
Abstract Experiments were performed in 2D terraria to investigate the burrowing behaviour of different earthworm species from various ecological categories in single- and multi-species assemblages. The burrowing behaviour was quantified using image analysis software during a 2-week period. Terraria were found to reveal realistic impressions of the burrowing behaviour of various species according to the ecological classification of Bouch into epigeic, endogeic and anecic species. Results of the study also permit the recommending of classifying various earthworms as intermediate species, e.g. Aporrectodea longa as endo-anecic and Lumbricus rubellus as epi-endogeic. Burrowing activity of endogeic species was significantly reduced in multi-species compositions compared to single-species treatments. Moreover, burrowing activity of Octolasion tyrtaeum was significantly reduced in the presence of Lumbricus terrestris compared to the specific single treatment. This endogeic species profited from the burrowing behaviour, e.g. bioturbation, of L. terrestris, and as such this is circumstantial evidence for commensalism (species interaction, in which one partner benefits while the other is unaffected) between anecic and endogeic earthworm species. Simultaneous burrowing activity of a combined assemblage of both endogeic species, Aporrectodea caliginosa and O. tyrtaeum, was also significantly reduced compared with the particular single treatments. Thus, this seems likely to be a response of interspecific competition and trophic niche separation between endogeic species.
Keywords Earthworms . Ecological categories . Burrowing behaviour . 2D terraria . Interspecific competition . Commensalism
Introduction
Bouchs (1977) classification of earthworms into the functional categories of epigeic, endogeic and anecic species is now generally accepted. This classification mainly considers the preferred living habitat within the soil matrix and the burrowing behaviour of the different species of earthworms.
Generally, burrowing behaviour can be regarded as a function of diet (Lavelle and Spain 2001). Accordingly, anecic species excavate sub-vertical (Kretzschmar 1978, 1982), permanent burrows down to a depth of a few metres. They feed at the surface by collecting litter. Because their burrows mainly function as a refuge, burrowing activity is low as long as an adequate food source is available...