Schematic depiction of gamete development in female X. laevis. Immature oocytes, ranging from the youngest (stage I) to the most developed (stage VI), are located within the ovaries. These oocytes can be surgically removed from the abdomen of the frog (shown in ventral view at top left) and are commonly used by electrophysiologists. Upon hormonal induction, stage VI oocytes mature into fertilization-competent eggs, which are laid by the frog (shown in dorsal view at top right). Oocytes and eggs differ with respect to membrane-localized proteins as well as the structure of the cytoskeleton.