FIGURE 7

Subdomain organization of habenulae in the European eel. (A–M) transverse sections of habenulae in A. anguilla (silver specimens) following ISH with probes for Aakctd12b (A–D), Aakiss1 (E–H) and Aasox1 (I–M). The orientation of section planes is shown in a schematic lateral view of A. anguilla brain and section levels along the antero-posterior axis are shown as red dotted lines on a front view of habenulae schematized in the top right corner. (B1,F1,J1,D1,M1) are higher magnification views of the areas boxed in (B,F,J,D,M). Black arrowheads point towards the left dorsal nucleus positive for pax6, and negative for PCNA and Aakctd12b. The thin arrow in (M,M1) points towards Aasox1 positive neural progenitors. The dotted line in (F1) and adjacent sections (B1) and (J1) delimits the Aakiss1 positive territory, which is adjacent to, but largely excludes Aasox1 expression at anterior-most levels of the habenulae. At this level, Aakiss1 expands dorsally but it is restricted to the organ ventral parts at medial to posterior levels. Scale bars = 200 μm.