Olfactory-mediated repellency is obsevred in Blattella germanica exposed to pyrethroids

BONÉ EMILIANO ; PAOLA GONZALEZ-AUDINO; SFARA VALERIA

Congreso; 1st Joint Meeting ISCE/ALAEQ; 2016

Pyrethroids are synthetic insecticides used worldwide. Although their insecticidal effect, it has been reported that pyrethroids are also repellents. This repellency is associated to an increase in the locomotor activity of insects caused by the interaction of the pyrethroid with central nervous system target. As a consequence of the increase in locomotion insects avoid the source of the pyrethroid, with a kinetic response. This phenomenon is called excito-repellency. On the other hand, an insect repellent is defined as a chemical compound that produces oriented movements of the insect against the source of the repellent. In this case, the repellent interacts with olfactory receptors. In this work we studied whether d-allethrin elicits an oriented repellency response mediated by olfaction in Blattella germanica. Behavioral experiments were conducted in a circular arena with one half of its floor treated with d-allethrin. Three experimental series were performed: insects exposed to a film of d-allethrin; insects exposed only to d-allethrin vapors at room temperature; insects exposed to d-allethrin vapors at 40 C. One male of B. germanica was placed in the center of the arena and its spatial distribution was determined. Additionally, the electrical activity of the cockroaches? antennae was recorded using electroantennography, to ensure that the insecticide was detected by olfactory receptors.In the behavioral experiments repellency was observed in a dose-dependent manner. When insects were exposed only to d-allethrin vapors, repellency was not observed, except when the volatility of the insecticide was increased by heating. In the electroantenographic assays a significant electrical response was recorded when the antennae were exposed to a concentration of d-allethrin that produced repellency in the behavioral bioassays. This indicates that the insecticide is detected by olfactory sensilla, and repellency is the behavioral associated response to that stimulus. We conclude that d-allethrin produces olfactory-dependent repellency in B. germanica.