The sensory physiology of host-associated stimuli evaluation in head lice

A. C. TOLOZA; MINOLI SEBASTIAN; ROMINA BARROSO; ISABEL ORTEGA INSAURRALDE; PICOLLO MI

Valparaiso

Congreso; 5th congress of the latin American association of chemical ecology (ALAEQ); 2018

Head louse (Pediculus humanus capitis) is a cosmopolitan hematophagous insect thatparasites humans. The high dependence on its host affects its behavior and physiologyduring food and refuge assessment. Our goal was to study whether head lice rely onchemical and physical information while they evaluate a potential host. First, we exploredthe morphology of the main sensory organs of lice in order to describe the diversity ofsensory structures. We identified 3 types of chemoreceptors: 2 olfactory sensilla and 1contact chemoreceptor located at 3rd flagellomere. In addition, we identified 2 tuft organs(2nd and 3rd flagellomere) and 1 pore organ (3rd flagellomere), similar to thosedescribed in body lice. Second, we analyzed the behavioral response of lice to hostassociated stimuli: chemical (human scalp), thermal (heated substrate) and hygric (humidsubstrate) stimuli in two choice assays. We found that human scalp stimuli were highlyattractive for head lice, being insects arrested around the stimulus. Similarly, when bothzones of the arena were settled at different temperatures, lice preferred resting at 32 °Cinstead of 22°C. Finally, when humid versus dry substrates were offered, insectsexhibited aversion for the wet substrate. Under the ablation of the antennal segments, wefound that the detection of chemical, thermal and hygric stimuli was concentrated in the3rd flagellomere. Third, in order to describe the central structures involved in peripheralprocessing, we traced the antennal neurons of the head louse to the brain. By means ofanterograde backfills, we found antennal projections arborising in a neuropil, that weidentified as the antennal lobe.This study integrates morphological and behavioral aspects of the sensory machinery ofhead lice involved in host perception.