Underground Miners Come Out to the Surface – Trails of Earthworms

Abstract

ABSTRACTSurface trails of earthworms exhibit a similar pattern and geometrical arrangement at three different localities in southern, western, and central Europe and, hence, document distinct behavioral modes of the producers. Straight to slightly winding trails (gutters bounded by levees) are a record of normal behavior moving to a new habitat. Earthworms tend to use, at least for some distance, trails of other earthworms. In order to explore a new habitat, earthworms make blind-ending probings at an acute to sharp angle to either side of their course. When deviating from the main direction at a sharp angle, a pseudospreiten is produced, while the posterior part of the body is obliquely dragged to produce a shortcut. When earthworms leave subsurface tunnels they occasionally produce stellate probing structures. If the substrate is very soft, earthworms may use the anterior or posterior body part as anchor by bending it away from the direction of movement; the body may also be twisted to form meanders. Circular overcrossing, looping trails record the death throes of earthworms and dead producers are often found at the end of these trails. If the substrate is muddy and soft, subtle details can be preserved such as imprints parapodia (setae) or body segmentation. The fossilization potential of earthworm trails is like that of rain-drop imprints. Their occurrence characterizes temporarily wet surfaces in continental environments where the substrate contains some organic matter.