Fig. 6. Confocal microscope images of wet mounts of seawater-adapted killifish opercular epithelium. All are paraformaldehyde/glutaraldehyde-fixed, permeabilized and stained with Oregon Green phalloidin with or without Mitotracker Red pretreatment. (A) Fluorescence image of the opercular membrane at 1.5µm below the plane of the pavement cells. Note the actin rings (arrows) of apical crypts. Scale bar, 5.0µm. (B) The same frame as for A but 6.0µm deeper into the tissue. Arrows are in the same locations and indicate apical crypts over mitochondria-rich chloride cells stained with Mitotracker Red. The asterisk indicates an adjacent cell. (C) Compare this image of opercular membrane fixed in paraformaldehyde with 0.1% glutaraldehyde at the plane of the pavement cells with D, which shows the same frame but at a focal plane 2.0µm below the plane of the pavement cells. Scale bar, 5.0µm. Note the thick actin ring just below the opening of the apical crypt (arrow). (E) Opercular epithelium stained with Oregon Green phalloidin. The image was collected at the plane of the microridges of pavement cells. This tissue was pretreated with cytochalasin D and has typical angular gaps and holes between pavement cells (arrows), but the actin cords are for the most part intact. Scale bar, 5.0µm.