Table 1 Comparison of inversion in V. globator and V. carteri.
| Characteristic | V. carteri | V. globator |
|---|---|---|
| Type of inversion | A | B |
| Duration of inversion | Approximately 45 min [20, 22] | Approximately 50 min |
| Sequence of processes |
The phialopore opens; the anterior hemisphere inverts; the posterior hemisphere contracts; the posterior hemisphere inverts; the phialopore closes [20, 22, 26] |
The posterior hemisphere contracts; the posterior hemisphere inverts; the phialopore opens; the anterior hemisphere inverts; the phialopore closes [25, 36, 37] |
| 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 spindle shaped [20, 22] | All cells are teardrop shaped |
| Cell shape in bend region during inversion |
Flask-shaped cells (radially symmetrical at the chloroplast ends) [20, 22, 24] | Paddle-shaped cells (wedge shaped at the chloroplast ends) |
| Cell shape of cells that have passed the bend region | Column-shaped cells [20, 22] | 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 | Only between cells of the embryo [20, 22, 24, 29] | 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 | Only before inversion [20, 26, 39] | 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 |