(A) Location of the distal medulla neuropil glia (dMnGl) among other glial cells that are marked by REPO-specific immunofluorescence in the optic lobes (frontal section). The nuclei of the dMnGl (arrowheads) reside at the border between the cortex (Mc) and the neuropil (Mn) of the medulla. R, retina; Lc, lamina cortex; Ln, lamina neuropil; EGl, epithelial glial cells. Scale bar: 20 μm. (B) Frontal section of Pdf0 optic lobe immunolabeled with anti-PER antibody. R, retina; Lc, lamina cortex; Ln, lamina neuropil; Mc, medulla cortex; Mn, medulla neuropil. The nuclei of the dMnGl (frame) reveal high level of PER-specific immunofluorescence in comparison with the nuclei of glia in Lc (arrowhead). Scale bar: 20 μm. (C,D) Small fragments of the Mc/Mn interface of Pdf0
(C) and CS (D) shown in higher magnification reveal the unexpected presence of the dMnGl displaying low level of fluorescence (P2). The P2 cells are well visible in Pdf0
(C). They are positioned next to cells of high fluorescence (P1) in almost alternating order. Such arrangement can be also observed, although less clearly, in CS (D). The images shown in (C,D) were collected at the same image acquisition parameters. Scale bar for (C,D): 10 μm. (E) The frontal surface of Pdf0 medulla. The fluorescence in P2 is comparable to the fluorescence in glial cells of the medulla cortex (arrowheads). Scale bar: 10 μm. (F) The average level of fluorescence (±SD) in P1 and P2 cells of Pdf0 (****p < 0.0001).