(A) An ovary before (left) and 90 minutes after (right) light stimulation. Before light stimulation the ovary contains resting oocytes (as indicated by the presence of a large oocyte nucleus; arrow), which need to transform into mature eggs for fertilization. Light triggers the breakdown of the nuclear envelope and later the release of mature eggs from the ovary. (B) This image of the outer layer of an ovary has a lace-like appearance due to staining of the cell contours in white, with large round oocytes visible behind in grey. In this layer are scattered star-shaped cells that contain both the opsin light receptors and the peptides (labeled in green) that are released from these cells to stimulate the oocytes. In the close-up image on the right, the star-shaped cells are highlighted by staining their characteristic cytoskeleton in pink; the nuclei of the surrounding cells are visible in blue. The left image is about 760 microns across; the right image is about 100 microns across.
IMAGE CREDIT: Evelyn Houliston