Alterations in the Gill Filaments and Secondary Lamellae of Cirrhinus mrigala Exposed to “Nuvan,” an Organophosphorus Insecticide

Figure 1

Scanning electron micrograph of the gill filament and secondary lamellae of C. mrigala under control conditions (a) and exposed to 15 mg/L of “Nuvan” (f, h). Photomicrographs of cross-sections of gills of C. mrigala under control conditions (H/E) (b) and exposed to 15 mg/L of “Nuvan” (c, d, e, and g). (a) A part of the gill filament (arrows) showing arrangement of the secondary lamellae (barred arrows). Note the boundary of the adjacent epithelial cells is demarcated by microridges (arrow heads). Scale bar = 10 μm. (b) In gill filament epithelium, superficial layer epithelial cells are wedge shaped in gill filament epithelium (arrow), flattened in secondary lamellae epithelium (barred arrows), and the cores of secondary lamellae consist of pillar cells (winged arrows) in between blood spaces (arrow heads) having blood cells. Scale bar = 10 μm. (c) Epithelial cell membranes at free surfaces appear eroded (arrows). Note enlarged blood spaces (arrow heads) between pillar cells (winged arrows) (4 h). Scale bar = 20 μm. (d) Epithelium of gill filament is merged with epithelium of secondary lamellae (asterisks). Epithelium shows oedema and appears detached from the underlying cores of blood spaces and pillar cell (arrows). Sheets of epithelial cells exfoliated at the surface are discernible (arrow heads) (12 h). Scale bar = 20 μm. (e) Epithelium of gill filament merges with epithelium of several secondary lamellae forming an islet of interlamellar cell mass (asterisk). Note at intervals blood spaces between pillar cells appear disrupted and are located with difficulty (arrows) (1 d). Scale bar = 20 μm. (f) Adjacent secondary lamellae appear fused due to the formation of interlamellar cell mass (asterisk) (1 d). Scale bar = 10 μm. (g) An islet of interlamellar cell mass (barred arrow). Blood spaces between pillar cells in the core of the secondary lamellae appear disrupted resulting in aneurysm (asterisk). Note oedema and detachment of epithelium of secondary lamellae (arrows) and exfoliated cells at the surface (arrow heads) (2 d). Scale bar = 20 μm. (h) Uplifting and detachment of the epithelium of secondary lamellae (arrows) (2 d). Scale bar = 10 μm.

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