The ganoine membrane of the scales of Polypterus senegalus includes a labyrinth-like structure

The ganoine membrane is a basement membrane-like structure appearing between the maturation stage inner ganoine epithelium (IGE) and mineralized ganoine of polypterids and lepisosteids. In the present study, further ultrastructural investigation of the ganoine membrane of Polypterus senegalus was made and it was confirmed that it possessed a specialized labyrinth-like structure. The complete ganoine membrane was composed of six distinct zones: (1) a filamentous zone facing the distal plasmalemma of IGE, (2) lamella zone I, (3) vertical striation zone, (4) lamella zone II, (5) electron-dense zone, (6) electron-lucent zone directly facing the maturing ganoine surface. The ganoine membrane sometimes partially lacked some of these zones, but the electron-dense zone was usually present. Oblique or horizontal sections of the membrane showed that the vertical striation zone was made up of a typical labyrinth-like structure. Certain sulfated glycoconjugates were localized at the filamentous zone, especially adjacent to the lamella zone I and over the electron-dense zones.