Locomotion
When at rest, A. triangulatus rolls itself up and can appear like a very tiny Swiss roll. When it starts to move, it uncurls, at the same time as the circular muscles beneath the epidermal cells at the anterior end contract. The paler head-end extends forward, becoming as thin as the lead in a pencil. During movement it is repeatedly raised a couple of millimetres from the substratum before being lowered again. As movement continues, circular, diagonal and longitudinal muscles in the rest of the body contract. Friction between the ventral surface and the substratum is reduced by mucus produced by the ciliated epidermal cells. A. triangulatus can achieve speeds of up to 17m per hour.
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