Fig. 4. Sections of ventral photophores from the hatchetfish, Argyropelecus hemigymnus showing acetylated tubulin-like (A–C; AcT-LI IR, green fluorescence) and nitric oxide synthase-like immunoreactivity (D–H; NOS-LI IR, brownish precipitate). Blue fluorescence in A–C is autofluorescence from the photocytes. (A) AcT-LI IR nerve fibres in the filter area, and among the photocytes. (B) Nerve bundle (arrow) entering the photocyte chamber through the reflector. (C) Nerves branching among the photocytes from a common point (arrow) at the median narrowing of the photophore. (D) NOS-LI IR (nNOS sc1025) in the cytoplasm of the outer filter cells (arrows). (E) NOS-LI IR (nNOS sc1025) in nerve bundle (arrows) leading to photophore. (F,G) Varicose nerve fibres (arrows) among photocytes showing NOS-LI IR (F, nNOS sc1025; G, nNOS 31030). (H) Intra- or extra-cellular structures with NOS-LI IR (arrows; nNOS 31030) at the cell membrane of a photocyte. f, filter cell area; p, photocytes; r, reflector. Bars, 50 µm.