The tick Ixodes ricinus uses its mouthparts to penetrate the skin of its host
and to remain attached for about a week, during which time Lyme disease
spirochaetes may pass from the tick to the host. To understand how the
tick achieves both tasks, penetration and attachment, with the same set of
implements, we recorded the insertion events by cinematography, interpreted
the mouthparts’ function by scanning electron microscopy and identified their
points of articulation by confocal microscopy. Our structural dynamic observations suggest that the process of insertion and attachment occurs via a
ratchet-like mechanism with two distinct stages. Initially, the two telescoping
chelicerae pierce the skin and, by moving alternately, generate a toehold. Subsequently, a breaststroke-like motion, effected by simultaneous flexure and
retraction of both chelicerae, pulls in the barbed hypostome. This combination
of a flexible, dynamic mechanical ratchet and a static holdfast thus allows the
tick to solve the problem of how to penetrate skin and also remain stuck for
long periods of time.