Figure 6
(A–C) FIB preparations and diagrammatic presentation of canal raphe bearing systems in diatoms. (A) simonsenioid canal raphe: a wild population frustule of Simonsenia aveniformis cut in FIB. Note the raphe tube elevated over the valve surface on braces. The left valve shows the opening of a portula (= alar canal, white arrow) connecting the valve with the raphe (white arrowhead) bearing tube. The right valve demonstrates the braces to be solid structures (black arrowhead) and also shows the fenestrae (black arrow 1) and the siliceous membranes sealing the raphe bearing tube in the last stage of the valve morphogenesis (black arrow 2). Black arrow 3 shows the hymenate areolae occlusion. (B,C) a surirelloid canal raphe in a wild population Surirella sp., cut through the fenestrae. (B) Raphe canal (arrow) elevated on braces (arrowhead) showing that raphe tube is incorporated into the whole valve system. (C) The raphe system cut to show the portulae (alar canals: arrows). The diagrammatic insert is modified from Ruck & Kociolek22. (D) nitzschioid canal in Nitzschia sp. from wild population. Note the marginal position of the raphe canal. The raphe canal is separated from the valve lumen by a simple fibula (arrow). The diagrammatic insert is modified from Ruck & Kociolek22.
