03373nas a2200277 4500008004100000022001400041245016600055210006900221260001600290300001000306490000700316520239000323653003902713653001502752653001202767653002002779653001402799653003002813653003302843653001102876100003602887700003502923700003002958700002102988856008603009 2021 eng d a1756-330500aPediculus humanus capitis: a study of the male genitalia using a combined stereoscopic, confocal laser scanning, and scanning electron microscopy approach0 aiPediculus humanus capitisi a study of the male genitalia using  cNov-17-2021 a10 pp0 v143 a

Background The male genital structures of arthropods are key features in the taxonomic and phylogenetic study of these organisms. The male genitalia of the head louse Pediculus humanus capitis are complex organs which are partly composed of structures that dynamically extrude during copulation.

Methods Here, we describe the morphology of the genitalia of P. humanus capitis at the copulation stage, and at rest, by using stereoscopic microscopy, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM).

Results CLSM and SEM images revealed that the vesica is composed of two distinct anatomical parts, the proximal lobe and the distal lobe. Both lobes have short and narrow spines, as well as long and wide scales with either sharp or rounded tips. The rounded scales vary in size and have a wavy base and rounded tips, and thus resemble a tongue in appearance. We identified a gland-like area on the penis with 11 shallow circular depressions, and a flat area with 14–16 exit orifices. The apical end of the penis has a foliaceous trifurcation and serves to expel the contents of the ejaculatory duct. These characteristics were recorded for all the specimens analyzed, indicating that these structures are highly conserved; to our knowledge, they have not been previously reported for any suborder of lice.

Conclusions To the best of our knowledge, our results reveal for the first time the morphological details, and complexity, of the male genitalia of the head louse P. humanus capitis at different stages of copulation. The new approach described here provided information that should be taken into consideration in future research on the genitalia of lice. Application of this approach will also impact the taxonomic and phylogenetic study of other insect taxa. Graphical Abstract

10aConfocal laser scanning microscopy10acopulation10aDilator10aGenital chamber10agenitalia10aPediculus humanus capitis10ascanning electron microscopy10aVesica1 aÁlvarez-Fernández, Blanca, E.1 aMorales-Suárez-Varela, María1 aNogueda-Torres, Benjamín1 aValero, Maria, A uhttps://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-021-05082-w