THE TUFT ORGANS OF THE HUMAN-BODY LOUSE, PEDICULUS-HUMANUS-CORPORIS -CRYOFIXATION STUDY OF A THERMO-HYGROSENSITIVE SENSILLUM

The tuft organs of the human body louse, Pediculus humanus corporis, d isplay a complex cuticular apparatus without wall pores, consisting of the cuticular cone. cuticular pocket, and the sensillar peg with 5-6 tuft processes. The cuticular wall of the sensillar peg exhibits sever al layers of differing electron density tightly surrounding the dendri tes. The sensillar peg is innervated by the unbranched dendrites of tw o receptor cells which do not reach into the tuft processes. A third r eceptor cell forms a lamellar outer dendritic segment which wraps arou nd the two other dendrites and terminates before reaching the base of the sensory peg. This type of receptor cell is named stratoterminal wh ile for those which end within the cuticular apparatus the term conote rminal is proposed. Five auxiliary cells are associated with each tuft organ. The pore organs display a porous cuticular plate innervated by the branching dendrites of four receptor cells. A fifth receptor cell terminates more proximal and resembles the stratoterminal cell of the tuft organ. From the fine structure it is evident that the tuft organ s represent thermo-/hygrosensitive sensilla whereas the pore organs ma y have an olfactory function.