Fig. 4

Scanning electron micrographs showing the olfactory lamellar surface of Micropterus salmoides. a the olfactory rosette of young fish under 15 cm (SL); b the olfactory rosette of adult fish over 35 cm (SL); c the surface area divided into two regions, sensory and non-sensory epitheliums; d the sensory epithelium with numerous cilia; e the non-sensory epithelium with mucous openings and motile cilia; f the non-sensory epithelium consisting of two regions, with and without cilia; g the non-sensory epithelium with spiral patterns of microridges; h the sensory epithelia among the non-sensory epithelium. Arrow, cilia; arrowhead, mucous opening; circle, non-sensory area without cilia; ellipse, non-sensory area with cilia; L, lamellae; R, medium raphe; SE, sensory epithelium; NSE, non-sensory epithelium. The bars indicate 200 μm in A, 500 μm in B, 20 μm in C, D, E, F, 5 μm in G and H, respectively