An insightful look at the sensory physiology of Pediculus humanus capitis

ORTEGA INSAURRALDE, ISABEL; MINOLI, SEBASTIÁN; TOLOZA, ARIEL CEFERINO; GONZALEZ AUDINO, PAOLA; PICOLLO, MARÍA INÉS; BARROZO, ROMINA

Congreso; 6th International Conference on Phthiraptera; 2018

Head louse (Pediculus humanus capitis) is a cosmopolitan hematophagous insect that parasites humans. The high dependence on its host affects its behavior and physiology during food and refuge assessment. Our goal was to study whether head lice rely on chemical and physical information while they evaluate a potential host. First, we explored the morphology of the antennae of lice in order to describe the diversity of sensory structures. We identified 3 types of chemoreceptors: 2 olfactory sensilla and 1 contact chemoreceptor (3rd flagellomere). In addition, we identified 2 tuft organs (2nd and 3rd flagellomere) and 1 pore organ (3rd flagellomere). Second, we analyzed the behavioral response of lice to chemical (human scalp), hygric (humid substrate) and thermal (heated substrate) stimuli in two-choice assays. We found that insects preferred the human scalp zone instead of the control zone. Similarly, when both zones of the arena were settled at different temperatures, lice preferred resting at 32 °C instead of 22°C. Finally, when humid versus dry substrates were offered, insects exhibited aversion for the wet substrate. Under the ablation of the antennal segments, we found that the detection of chemical, thermal and hygric stimuli was concentrated in the 3rd flagellomere. Third, in order to describe the central structures involved in peripheral processing, we traced the antennal neurons to the brain. We found antennal projections arborising in a neuropil, that we identified as the antennal lobe. This study integrates morphological and behavioural aspects of the sensory machinery of head lice involved in host perception.