Journal article
A radio-labelled study of earthworm behaviour in artificial soil cores in term of ecological types
A new apparatus developed by Capowiez et al. (Eur J Soil Sci 52:365–375, 2001), called “gamma column”, enables the continuous movements of radio-labelled earthworms to be tracked in artificial soil cores (3D space). Each individual was radio-labelled by injecting a small source of 60Co (13 μCi) into its coelomic cavity, then individuals were released into artificial soil cores for 12 to 23 days.
An analysis of tracks divided the continuous movements of earthworms into three kinds of movements (“burrowing”, “displacement”, and “inactivity”). Trajectories of several earthworm species presumed to be anecic, such as Nicodrilus giardi (NG), Lumbricus terrestris (LT) and Nicodrilus nocturnus (NN), or presumed to be endogeic, such as Aporrectodea icterica (AI) and Octalasium lacteum (OL), were studied.
Analysis of these trajectories revealed ecological differences between species, in particular in terms of morphologies of the burrow systems (burrows created by LT were the simplest and those by NG and NN more complex), the ratio between the time spent to burrow and the time spent to reuse, called time allocation (TA) ratio (LTTA<1; NNTA=NGTA=1; OLTA=4; AITA=6), and the time spent in inactivity (LT>NN=NG=OL>AI).
For L. terrestris and A. icterica the match between the observed characteristics of behaviour and their theoretical characteristics based on usual ecological types was demonstrated. These species could be considered as archetypes of anecic and endogeic ecological types, respectively. By contrast, the behaviour of N. giardi and N. nocturnus was unexpected, particularly regarding their anecic description, because not only did they reuse existing burrows intensively but they also created numerous and long burrows.
The reuse of burrows was also strongly heterogeneous for these two species, with a partition of the burrow system in permanent and temporary burrows. Similarly, O. lacteum could not be considered as a purely endogeic species since it reused its burrows. Assessment of the ecological types of earthworm species will be improved by analysing earthworm behaviour using this tracking method.
This will lead to better prediction of the effects of the various behaviours on burrow structures and their contribution to soil functioning.
Language: | English |
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Publisher: | Springer-Verlag |
Year: | 2005 |
Pages: | 320-327 |
Journal subtitle: | Cooperating Journal of International Society of Soil Science |
ISSN: | 14320789 and 01782762 |
Types: | Journal article |
DOI: | 10.1007/s00374-005-0847-6 |