Egg development in the octopus Eledone cirrhosa

The development of egg/follieular cell complexes is described in maturing females of the octopus Eledone cirrhosa. Follicle cells proliferate to enclose the oocyte in a single epithelial layer which becomes deeply infolded. Active cell division of the follicle cells and recruitment of cells from an outer (thecal) layer generate this expansion of follicle cell epithelium. The onset of the main phase of vitellogenesis, secretion of protein yolk, occurs when eggs reach about 2 mm in length and is marked by the columnar appearance of the follicle cells and an increased number of larger and more complex nuclei. A significant proportion of the egg population fails to develop beyond 2–3 mm in length and these eggs subsequently degenerate.