Through a Looking Glass: Lumbriculus worms in capillary tubes

Within 24 h, Lumbriculus worms will crawl into water-filled capillary tubes after tubes and worms are placed in a petri dish of water.  Such orientation behavior is referred to as thigmotaxis.  During thigmotaxic orientation, worms seek out cramped microhabitats that tend to maximize contact of the worm's body with substrate. In nature, suitably cramped microhabitats may include tight spaces between submerged, decaying leaves or crevices in submerged, decaying wood. These preferred habitats offer protection from predators as well as access to food. The capillary tubes in the photos have the following dimensions: OUTSIDE diameter = 1.0 mm, INSIDE diameter = 0.7 mm, LENGTH = 75 mm.  Detailed internal and external anatomy of worms may be seen under a dissecting microscope.  For viewing, worms can remain in the dish or tubes may be removed and viewed.  It is important to avoid: (1) injury to worms due to excess heating under microscopic illumination, and (2) injury to humans due to breakage and impalement by capillary tubes. Here are typical views of Lumbriculus worms in capillary tubes: