Why does a tick react to valerian? - briefly
Ticks are drawn to valerian because it emits volatile compounds, notably actinidine, that resemble host scent cues and stimulate the tick’s sensory organs. These chemicals activate the Haller’s organ, causing the arachnid to move toward the source.
Why does a tick react to valerian? - in detail
Ticks locate hosts by detecting volatile chemicals emitted from potential blood‑meal sources. Valerian (Valeriana officinalis) releases several low‑molecular‑weight compounds, notably actinidine, valeric acid, and isovaleric acid. These substances bind to receptors in the Haller’s organ, the main olfactory structure on the tick’s forelegs. Electrophysiological recordings show strong neuronal firing when the organ is exposed to actinidine, indicating a direct sensory stimulus.
The attraction mechanism operates in three steps:
- Emission: Plant roots and aerial parts exude volatile organic compounds (VOCs) into the surrounding air.
- Detection: Tick sensilla capture the VOCs; receptor proteins tuned to amine and carboxylic acid groups generate action potentials.
- Behavioral response: Increased neuronal activity triggers questing behavior, causing the tick to ascend vegetation and move toward the source.
Research on Ixodes ricinus and Dermacentor variabilis demonstrates that actinidine elicits a dose‑dependent increase in questing frequency. Field traps baited with valerian extracts capture significantly more ticks than control traps, confirming the laboratory findings.
The ecological relevance stems from the fact that many mammals—particularly rodents and lagomorphs—frequently graze on or near valerian plants. By responding to the plant’s scent profile, ticks improve their chances of encountering a suitable host.
In summary, the tick’s reaction to valerian results from the presence of specific VOCs that activate olfactory receptors in the Haller’s organ, leading to heightened questing activity and increased host‑seeking efficiency.