The Drosophila antenna: ultrastructural and physiological studies in wild-type and lozenge mutants

The physiology and ultrastructure of the antenna in Drosophila melanogaster have been examined in wild-type and lozenge mutants. Scanning electron microscopy (SEM) of sensilla on the antennal surface has revealed that in the wild-type the basiconic sensilla contain linear arrays of pores connected by longitudinal furrows and transected by shorter furrows. Sensilla trichodea also are shown to have pores, as revealed by examining transverse sections by transmission electron microscopy (TEM); these data directly address a longstanding controversy. Coeloconic sensilla, previously described as "pit sensilla" and as "grooved" sensilla, are shown to rise directly from the antennal surface, as opposed to lying below the antennal surface in pits; the previously observed grooves correspond to the junctions between bundled, finger-like projections. This description of coeloconic sensilla is supported by analysis of lz mutants, in which the projections of coeloconic sensilla splay apart. Coeloconic sensilla are also shown to undergo duplication on the lz3 antenna. Physiological recordings from the antenna show that responses to all odorants tested are severely decreased in lz mutants. Measurements made from different parts of the antenna show similar defects. Evidence is provided that both the physiological and ultrastructural defects map to the lz locus.