Abnormal sex-specific serotonin expression in the abdominal ganglia of fru mutant males. These images are whole (A, B, D,F) or partial (C,E, G) projections of stacked images through a given ganglion, viewed in the confocal microscope from the ventral side. A, B, Abdominal ganglia of 4- to 7-d-old wild-type adult male and female, respectively; in the latter (representative of five female VNCs processed), there were no anti-5-HT-mediated signals like those observed in this region of the male CNS, whose cluster of s-Abg cells (compare Fig. 6) are designated by an asterisk in A (representative of 12 male VNCs observed); the arrow in Apoints to axonal projections from male s-Abg neurons.C–G, Serotonergic neurons in the abdominal ganglia offru mutants. C, Infru¹ (n = 5), s-Abg cell bodies (asterisk) and processes (arrow) were weakly stained (uniformly among the specimens, in contrast to fru⁴ ) (see below). D, In fru² (n = 8), the s-Abg neuronal cluster (asterisk) and projections from such cells (arrow) were normal or nearly so (in terms of numbers of cell bodies and staining intensities) among the several specimens. The image shown depicts strong signals, although in this one there were weak signals in a serotonergic neuropil that usually gives strong staining (E, G, black arrowheads) in abdominal ganglia of all frugenotypes (including fru² ).E, In fru³ (n = 6), no 5-HT immunostaining in s-Abg cells or neurites was observed; the white arrowhead points to where the cell bodies should be. F, Infru⁴ (n = 5), two specimens showed no 5-HT immunoreactivity in s-Abg neurons, whereas three gave weak staining in one to three s-Abg cell bodies and their processes (as exemplified in the case shown and itsasterisk for cell bodies and black arrowfor processes). G, Infru^sat (n = 5), relatively few s-Abg neurons were stained by anti-5-HT (although more than in fru⁴ ), and the cell bodies and processes in which signals were elicited (asterisk, arrow) gave weak signals (uniformly among the specimens). Scale bars: A, B, 50 μm;C–G, 100 μm.