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

ORTEGA INSAURRALDE, I; MINOLI, S; TOLOZA, A; PICOLLO, MARÍA INÉS; BARROZO, ROMINA B

Valparaiso

Congreso; V Congress Latino American Society of Chemical Ecology; 2018

Head louse (Pediculus humanus capitis) is acosmopolitan hematophagous insect thatparasites humans. The high dependence on its hostaffects its behavior and physiologyduring food and refuge assessment. Our goal was tostudy whether head lice rely onchemical and physical information while they evaluatea potential host. First, we exploredthe morphology of the main sensory organs of lice inorder to describe the diversity ofsensory structures. We identified 3 types ofchemoreceptors: 2 olfactory sensilla and 1contact chemoreceptor located at 3rd flagellomere. Inaddition, we identified 2 tuft organs(2nd and 3rd flagellomere) and 1 pore organ (3rdflagellomere), similar to thosedescribed in body lice. Second, we analyzed thebehavioral response of lice to hostassociated stimuli: chemical (human scalp), thermal(heated substrate) and hygric (humidsubstrate) stimuli in two choice assays. We found thathuman scalp stimuli were highlyattractive for head lice, being insects arrestedaround the stimulus. Similarly, when bothzones of the arena were settled at differenttemperatures, lice preferred resting at 32 °Cinstead of 22°C. Finally, when humid versus drysubstrates were offered, insectsexhibited aversion for the wet substrate. Under theablation of the antennal segments, wefound that the detection of chemical, thermal andhygric stimuli was concentrated in the3rd flagellomere. Third, in order to describe thecentral structures involved in peripheralprocessing, we traced the antennal neurons of the headlouse to the brain. By means ofanterograde backfills, we found antennal projectionsarborising in a neuropil, that weidentified as the antennal lobe.This study integrates morphological and behavioralaspects of the sensory machinery ofheadlice involved in host perception.