Oogenesis and formation of cortical rods in the black tiger shrimp, Penaeus monodon

This study aimed to investigate morphological changes of developing oocytes during oogenesis in the black tiger shrimp Penaeus monodon as well as elucidate the cellular pathway for the formation of cortical rods, the egg jelly precursor. The differentiating female germ cells in the mature ovary were divided into four stages (Oc1–4) based on the changes in ultrastructural characteristics. The prominent features in the developing oocytes (Oc1 Oc2 Oc3) were the abundance of ribosomes and dilated rough endoplasmic reticulum (RER) in Oc1 and Oc2 and the presence of yolk granules and lipid droplets in Oc3 all indicating active synthesis of protein and lipid components. The main characteristic of the mature oocyte (Oc4) was the presence of cortical rods (CRs) which were composed of the tightly packed structural units each resembling a bottle-brush. Immunostaining of cortical rod proteins which were part of the structural units indicated that they were first synthesized in the RER–Golgi complex of Oc2 and transported into the extracellular crypts of the mature oocyte (Oc4) where they were assembled into CRs.