Combining Three Microscopy Techniques to Analyze Morphology of the Ecdysial Pattern of Pediculus humanus capitis Exoskeletons

Development of insects relies on ecdysis, a process entailing periodic production of a new exoskeleton and detachment of the previous one. Combining light microscopy, confocal laser scanning microscopy, and scanning electron microscopy, we described the morphological details of naturally molted exoskeletons of the head louse, Pediculus humanus capitis De Geer. All exoskeletons had visible expansion and a consistent pattern of the ecdysial opening anterior on the dorsal medial line of exoskeletons ending at the vertex of the metathorax. Early genital differentiation was observed in nymph III even without a complete molt. The respiratory system composed of thoracic and abdominal spiracles, tracheae, tracheoles, and taenidia, adheres to the exoskeleton. The abdominal spiracles had a circular peritrema with concentric wavy shapes. Within the spiracular atrium were structures resembling valves that control entry of oxygen into the respiratory system. These were observed in all specimens, indicating the exoskeleton and respiratory system are completely replaced at each stage of metamorphosis. This is the first study of morphology of the P. h. capitis exoskeleton by combination of state-of-the-art microscopy techniques. The results serve as the basis for future research on physiological characterization and regulation of morphological development and ecdysis of head lice.