Figure 15

The eyestalk neuropils as shown in vibratome sections that were double labelled (E, F) for synapsin immunoreactivity (SYN; red) and RFamide-like immunoreactivity (RF; green), or triple labeling for these two substances plus the nuclear marker (NUC; A-E2); conventional fluorescence combined with the Apotome structured illumination technique for optical sectioning (A-E2) and confocal laser scan microscopy (E, F). A, B and D are rendered at the same scale to compare the size of a median hemi brain (A; see also Fig. 3D) with that of the eyestalk neuropils. The eyestalks contain the lateral protocerebrum which is composed of the medulla terminalis (MT) and the hemiellipsoid body (HE). Furthermore, the four optic neuropils lamina (La), medulla (Me), lobula (Lo) and lobula plate are enclosed in the eyestalks. The low power views presented in B-E2 show four different eyestalks to show the individual variation between specimens. The hemiellipsoid body (HE; encircled by a dotted line in B) is a large spherical neuropil that is associated with a compact, laterally situated cluster of densely packed neurons, the lateral protocerebral interneurons (LPI). With the synapsin label, several neuropil compartments are visible within the hemiellipsoid body, the peripheral cap neuropil (Cap) which is separated by the unlabelled intermediate layer 1 (IL 1) from the strongly synapsin immunoreactive core neuropil 1 (Co1). A second unlabeled intermediate layer (IL 2) separates core neuropil 1 from the more proximally located core neuropil 2 (Co2). Asterisks in B-E2 and F mark the point where the two intermediate layers meet. The boxed area in C1 is shown at a higher magnification in E. The demarcation between the medulla terminalis (MT) and the hemiellipsoid body is difficult to draw. The opposed arrows in B-E tentatively mark the border between these two structures. From the medulla terminalis, strongly labeled RFamide-like immunoreactive fibers invade the core neuropils 1 and 2 (Co1, Co2) of the hemielliposid body where they terminate in a circumscribed field with very fine varicosities (E, F). Intermediate layers IL1 and IL2 are unlabeled. The arrows in F identify patches of neuropil that seem to extend across the intermediate layer 1.