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Perception of breath components by the tropical bont tick, <i>Amblyomma variegatum</i> Fabricius (Ixodidae): I. CO<sub>2</sub>-excited and CO<sub>2</sub>-inhibited receptors
Auteur(s)
Steullet, Pascal
Date de parution
1992
In
Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology, Springer, 1992/170/6/665-676
Résumé
Wall-pore olfactory sensilla located in the capsule of Haller's organ on the tarsus of <i>Amblyomma variegatum</i> ticks bear cells responding to vertebrate breath: one of these sensilla contains a CO<sub>2</sub>-excited receptor and a second sensillum has a CO<sub>2</sub>- inhibited receptor. Each of these antagonistic CO<sub>2</sub>-receptors, which display typical phasic-tonic responses, monitors a different CO<sub>2</sub>-concentration range. The CO<sub>2</sub>-inhibited receptor is very sensitive to small concentration changes between 0 and ca. 0.2%, but variations of 0.01% around ambient (ca. 0.04%) induce the strongest frequency modulation of this receptor. An increase of just 0.001–0.002% (10–20 ppm) above a zero CO<sub>2</sub>-level already inhibits this receptor. By contrast, the CO<sub>2</sub>-excited receptor is not so sensitive to small CO<sub>2</sub> shifts around ambient, but best monitors changes in CO<sub>2</sub> concentrations above 0.1%. This receptor is characterized by a steep dose-response curve and a fast inactivation even at high CO<sub>2</sub>-concentrations (>2%). In a wind-tunnel, <i>Amblyomma variegatum</i> is activated from the resting state and attracted by CO<sub>2</sub> concentrations of 0.04 to ca. 1%, which corresponds to the sensitivity range of its CO<sub>2</sub>-receptors. The task of perceiving the whole concentration range to which this tick is attracted would thus appear to be divided between two receptors, one sensitive to small changes around ambient and the other sensitive to the higher concentrations normally encountered when approaching a vertebrate host.
Identifiants
Type de publication
journal article
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