An insight on Pediculus humanus capitis behaviour and physiology on the evaluation of its host

MINOLI SEBASTIAN; ROMINA BARROSO; TOLOZA AC; ISABEL ORTEGA INSAURRALDE; PICOLLO MI

Conferencia; International Conference on Phthiraptera 6; 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 objective was to study whetherhead lice make host-evaluation decisions relying on  chemosensory and physical  information. First, we  explored the morphology of the antennae andmouthparts of lice searching for putative chemo-, thermo- and higroreceptorssensilla. We identified two types of olfactory sensilla and one potentialgustatory-type sensillium in the tip of the antenna and tuft and pore organssimilar to those described in body lice. We also analyzed the behavioral response oflice to chemical (human scalp), thermal and hygric stimuli using a software ofvideotracking. We found that scalp-rubbed papers induced head liceto decrease average locomotor activity and to remain arrested on the treatedpaper performing an specific behaviour presumably associated to the search forblood on the skin. Hygric stimuli caused aversive behavior and thermal stimuli,preference. Under ablation of antenna segments, the response to chemical,thermal and hygric stimuli was modified.Finally, we started to describe thelouse brain, and by means of antennal backfills we followed up the antennalprojections to the brain. Neurobiotin and rhodamine dextran anterograde stainingrevealed the antennal nerve innervating a neuropil in the deuterocerebrum thatwe identified as the antennal lobe. This is the first study on head louse that integrates physiological andbehavioral aspects related to the detection, evaluation and processing ofinformation from the host.