Scanning electron micrograph of the epidermal surface of the Pacific coho salmon. Ridge-like folds of the plasmalemma, called microplicae, display a labyrinth pattern across the surface, and a circumferential ridge at the borders of the polygonal-shaped cells. Image from Hawkes (1974) Cell Tissue Research, 149:147-158, reprinted with permission as Figure 42 from Chapter 2 (Specializations of the Free Surface) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.