An insightful look at the sensory physiology of Pediculus humanus capitis (Human Lice)

GONZALEZ AUDINO, P; ORTEGA INSAURRALDE, I; BARROZO, RB; TOLOZA, A; PICOLLO, MI; MINOLI, S

Congreso; VI International Conference on Phthiraptera; 2018

Head louse (Pediculus humanus capitis) is a cosmopolitan hematophagous insectthat parasites humans. The high dependence on its host affects its behavior andphysiology during food and refuge assessment. Our goal was to study whether head licerely on chemical and physical information while they evaluate a potential host.First, we explored the morphology of the antennae of lice in order to describethe diversity of sensory structures. We identified 3 types of chemoreceptors: 2olfactory sensilla and 1 contact chemoreceptor (3rd flagellomere). In addition,we identified 2 tuft organs (2nd and 3rd flagellomere) and 1 pore organ (3rdflagellomere). Second, we analyzed the behavioral response of lice to chemical(human scalp), hygric (humid substrate) and thermal (heated substrate) stimuliin two-choice assays. We found that insects preferred the human scalp zoneinstead of the control zone. Similarly, when both zones of the arena weresettled at different temperatures, lice preferred resting at 32 °C instead of22°C. Finally, when humid versus dry substrates were offered, insects exhibitedaversion for the wet substrate. Under the ablation of the antennal segments, wefound that the detection of chemical, thermal and hygric stimuli wasconcentrated in the 3rd flagellomere. Third, in order to describe the centralstructures involved in peripheral processing, we traced the antennal neurons tothe brain. We found antennal projections arborising in a neuropil, that weidentified as the antennal lobe. This study integrates morphological andbehavioural aspects of the sensory machinery of head lice involved in hostperception.