How ticks get under your skin - Insertion mechanics
of the feeding apparatus of Ixodes ricinus ticks
The tick Ixodes ricinus uses its mouthparts to penetrate the skin of its host and remain attached for about a week. With cinematography, scanning-electron and confocal microscopy, we recorded and interpreted the insertion events of the tick's mouthparts. Initially, the paired 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. Analgesic substances in the pharmacological cocktail of the saliva permit the tick to do so without the host's notice. The ratchet-like motility of their flexible chelicerae allows Ixodes ticks to dynamically penetrate the soft substrate of the host's skin and use their rigid hypostome for robust static attachment.
Publication: Richter D, Matuschka F-R, Spielman A, Mahadevan L. How ticks get under your skin - Insertion mechanics of the feeding apparatus of Ixodes ricinus ticks. Proc Roy Soc B, 2013, doi: 10.1098/rspb.2013.1758
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© Dania Richter
Look into a tick's mouth.
Apical view onto the feeding apparatus of a female Ixodes ricinus tick. The dorsal surface of the hypostome resembles a shallow basin (100µm across) and is fringed by rows of prominent, recurved denticles. The ventral surfaces of the paired cheliceral shafts roof the hypostome dorsally such that a "tube" is formed, channeling the flow of food into the oral opening of the tick and, vice versa, of tick saliva into the skin of the host. The cheliceral digits are splayed to the sides.
Cinematographic representation of the process of attachment of a nymphal Ixodes ricinus tick to host skin.
© Dania Richter
Animated graphics "Surface coursing".
Each of the paired cheliceral bundles, extending beyond the tip of the hypostome, alternately flexes toward the centerline and then forcefully sweeps to the side.
© Dania Richter
Animated graphics "Cheliceral insertion".
Each of the cheliceral bundles alternately extends to engage in the matrix of the skin and subsequently flexes at its hinge to bury into the skin.
© Dania Richter
Animated graphics "Hypostomal envelopment".
Simultaneous retraction of the flexed cheliceral bundles via a breaststroke-like movement that causes both cheliceral shafts and their hinges to flex into a V-like form. This ratchet-like action causes the ventrally barbed hypostome to enter the skin of the host.
© Dania Richter
Confocal microscopic rendering of the hypostome, chelicerae and palps of a nymphal Ixodes ricinus tick.
© Dania Richter
Opaque and transparent confocal microscopic rendering demonstrating the positions of the paired chelicerae of a nymphal Ixodes ricinus tick relative to the surface of a host and the articulation of the cheliceral digits within the chelicera.
© Dania Richter
Opaque and transparent confocal microscopic rendering of the partially flexed cheliceral digits of a nymphal Ixodes ricinus tick demonstrating the curvature of the digital hooks and the opposing arcs of movement of the cheliceral bundles. The ball joint as well as the lateral and medial tendons are discernible in the transparent rendering.
How ticks get under your skin - Insertion mechanics of the feeding apparatus of Ixodes ricinus ticks