Axons of olfactory receptor cells of transsexually grafted antennae inducedevelopment of sexually dimorphic glomeruli in Manduca sexta

The influence of olfactory receptor cell (ORC) axons from transsexually gra fted antennae on the development of glomeruli in the antennal lobes (ALs), the primary olfactory centers,was studied in the moth Manduca sexta. Normal ly during metamorphic adult development, the pheromone-specific macroglomer ular complex (MGC) forms only in the ALs of males, whereas two lateral fema le-specific glomeruli (LFGs) develop exclusively in females. A female AL in nervated by ORC axons from a grafted male antenna developed an MGC with thr ee glomeruli, like the MGC of a normal male AL. Conversely, a male AL inner vated by ORC axons from a grafted female antenna lacked the MGC but exhibit ed LFGs. ORC axons from grafted male antenna terminated in the MGC-specific target area, even in cases when the antennal nerve (AN) entered the AL via an abnormal route. Within ectopic neuromas formed by ANs that had become m isrouted and failed to enter the brain, male-specific axons were not organi zed and formed terminal branches in many areas. The results suggest the pre sence of guidance cues within the AL for male-specific ORC axons, Depending on the sex of the antennal innervation, glial borders formed in a pattern characteristic of the MGC or LFGs, The sex specific number of projection ne urons (PNs) in the medial group of AL neurons remained unaffected by the an tennal graft, but significant changes occurred in the organization of PN ar borizations, In gynandromorphic females, LFG-specific PNs extended processe s into the induced MGC, whereas in gynandromorphic males, PNs became restri cted to the LFGs, The results indicate that male- and female-specific ORC a xons play important roles in determining the position, anatomical features, and innervation of sexually dimorphic glomeruli, (C) 1999 John Wiley & Son s, Inc.