Characteristic | V. carteri | V. globator |
---|---|---|
Type of inversion | A | B |
Duration of inversion | Approximately 50 min | |
Sequence of processes | The phialopore opens; the anterior hemisphere inverts; the posterior hemisphere contracts; the posterior hemisphere inverts; | The posterior hemisphere contracts; the posterior hemisphere inverts; the phialopore opens; the anterior hemisphere inverts; the phialopore closes |
Site of the initiation of inversion | Point-shaped initiation site at the anterior pole of the spheroid [22] | Ring-shaped initiation site at the equator of the spheroid |
Direction of cell shape changes | From the anterior pole to the posterior pole [22] | Initially, from the equator to the posterior pole; then, from the equator to the anterior pole |
Diameter of embryo | Immediately before inversion: approximately 65 μm [22] immediately after inversion: approximately 60 μm [22] | Immediately before inversion: approximately 80 μm Immediately after inversion: approximately 60 μm |
Relative size (volume) of the cells of the embryo during inversion | Reproductive cells are roughly 100 to 200 times larger than somatic cells [22] | Reproductive cells are roughly one to five times larger than somatic cells |
Cell shape immediately before inversion | All cells are teardrop shaped | |
Cell shape in bend region during inversion | Flask-shaped cells | Paddle-shaped cells (wedge shaped at the chloroplast ends) |
Cell shape of cells that have passed the bend region | Pencil-shaped cells (the column shape does not appear until inversion is completed) | |
Order of cell shape changes | All cells undergo the same consecutive cell shape changes: spindle → flask → column [20, 22, 24] | Posterior and anterior hemispheres invert with different cell shapes changes; cells in the posterior hemisphere: teardrop → spindle → paddle (except for the cells close to the posterior pole) → pencil → column; cells in the anterior hemisphere: teardrop → disc → pencil → column |
Shape of nuclei throughout inversion | Minor changes [20] | Major changes |
Cytoplasmic bridges | Between cells of the embryo and between embryonic and parent cells | |
Phialopore | Swastika-shaped opening; four lips of the cell monolayer curl outward and backward [20, 22] | Circular opening; while the opening widens, the cells and cytoplasmic bridges around the phialopore become passively stretched |
Denting | Before and after inversion | |
Flagella | Only flagellar stubs approximately 2 μm in length that do not grow during inversion; flagella grow asymmetrically after inversion [76] | Flagella grow symmetrically throughout inversion |