Oogenesis in Centropages typicus (Copepoda, Calanoida)

We carried out a complete study of oogenesis in Centropages typicus using structural, ultrastructural and cytochemical data. The usual stages of oogenesis, i.e. germinative phase, premeiosis, primary and secondary vitellogenesis, were found. The latter two stages were the most typical. Primary vitellogenesis consisted of endogenous yolk accumulations; these substances, probably of lipoprotein or lipoglycoprotein nature, were produced at the granular endoplasmic reticulum level and then stocked in the reticulum cavities. During secondary vitellogenesis, endogenous yolk production continued, but we mainly observed the development of exogenous yolk accumulation (lipid droplets and protein globules) in the ooplasm. These accumulations resulted from the fusion of very numerous pinocytotic vesicles arising from the oolemma and containing substances probably brought to the oocytes by the hemolymph. The effect of various proteases on the vitellus globules caused a more or less marked digestion of their contents, tending to prove their protein nature. The end of vitellogenesis was marked by the appearance of vacuolar formations with dense lamellae which could correspond to cortical granules.