Fig. 3. Longitudinal sections of ventral photophores from M. norvegica. 5-HT-IR fibres are found throughout the light organ (A; for example, at the arrows) following capillaries and ending at the lantern (C; for example, at the arrows). Staining is abundant at the junction (D, arrow) between C-cells (D, arrowhead) and capillaries where the capillaries open into the lantern. Controls without primary antibody do not show any non-specific binding of the secondary antibodies (B). La, lantern; Le, lens; R, reflector. Scale bars, 50 µm in A,B; 10 µm in C,D.