FORMATION OF THE MULTIPLE-LAYERED FERTILIZATION ENVELOPE IN THE EMBRYO OF CALANUS-SINICUS BRODSKY (COPEPODA, CALANOIDA)

In Calanus sinicus, a multiple-layered fertilization envelope is formed from materials sequentially released from the embryo after spawning and fertilization. The mature oocyte in the ovary does not have any envelopes, and contains spherical granules and yolk bodies in the cytoplasm. Just after spawning, a thin dense layer (L1) separates from the cell membrane of the fertilized egg. Then dense materials are released into the perivitelline space and form a flocculent matrix (L2). Before the first cleavage, spherical granules begin to be released, and form a dense layer (L3) and a thick striated layer (L4). Furthermore, an embryonic envelope (L5) appears during early cleavage stages. The layer 5 is composed of electron-dense and pale layers arranged alternately. Eventually, the fully developed envelope complex is made up of 5 layers. These 5 layers are in contact with each other. The cell surface of the embryo is extremely electron dense. Layers 1 and 2 together form foldlike processes (blisters) on the surface of the envelope.