How does a tick breathe when biting? - briefly
Ticks obtain oxygen through spiracles that remain open while they are attached to a host, allowing continuous gas exchange. Some species also supplement respiration by diffusion across the cuticle.
How does a tick breathe when biting? - in detail
Ticks respire through a tracheal network that terminates in external openings called spiracles. The spiracles are situated on the dorsal surface of the idiosoma, far from the mouthparts that penetrate the host’s skin. During attachment the openings remain exposed to ambient air, allowing continuous diffusion of oxygen into the tracheae and removal of carbon dioxide.
Oxygen enters the tracheae by passive diffusion driven by the concentration gradient between the external atmosphere and the internal hemolymph. The tracheal tubes branch extensively, delivering air directly to tissues without the need for a circulatory transport system. Carbon dioxide follows the reverse gradient, exiting the body through the same spiracular openings.
While the tick engorges with blood, the volume of the abdomen expands, but the dorsal cuticle stays rigid enough to keep the spiracles functional. Some ixodid species can partially close their spiracles to limit desiccation; in such cases cutaneous diffusion across the thin cuticle supplements tracheal respiration. The respiratory rate remains low because the arthropod’s metabolic demand is modest compared with vertebrate blood feeders.
Key points of the respiratory mechanism during feeding:
- Spiracles located dorsally stay open to atmospheric oxygen.
- Tracheal system supplies tissues directly, bypassing the circulatory system.
- Gas exchange relies on diffusion gradients; no active ventilation occurs.
- Partial spiracle closure may occur to reduce water loss, with cutaneous diffusion providing supplemental oxygen.
The combination of an external air source, a highly branched tracheal network, and diffusion‑driven gas exchange enables the tick to maintain respiration throughout prolonged blood meals.