Morphology of the Cortical Reaction in the Eggs Ofpenaeus Aztecus

The morphology of large cortical specializations (rods) located in the peripheral ooplasm is described in oocytes of the shrimp Penaeus aztecus and confirmed with P. setiferus. The rods, which are perpendicular to the oolemma, are "club"-shaped and approximately 39.9 µm long, with an apical diameter of 9.3 µm and a basal diameter of 4.6 µm. They are composed of numerous, tightly packed, fibrillar structures. Each cortical rod lies within a partially membrane-bound crypt and is separated from the external media by a thin investment coat. The investment coat lies directly adjacent to the oolemma and completely surrounds the egg. Upon exposure to sea water, the cortical rods begin to emerge from the crypts and appear to lift the investment coat off the egg surface. A corona is formed around the oocyte as the rods are expelled, but quickly dissipates. Extensive membrane vesiculation associated with cortical rod crypts is apparent at this time.