Fig. 4

In vivo light micrographs of P. californica juveniles after completion of inversion. a Juvenile alga one minute after completion of inversion rotates within its embryonic vesicle; it is the same organism as the one shown in Fig. 3; anterior view. All cells have an elongated teardrop shape. Due to the different angle to the viewer, the elongated teardrop-shape cells in the center show almost hexagonal contours. b Juvenile about 30 min after completion of inversion; posterior view; the phialopore is still visible; the cells feature trapezoid contours (pink dashed line). c Juvenile about 40 min after completion of inversion. The cells are rounded, the phialopore is closed and the juvenile alga has adopted a spherical shape. d Juvenile shortly after release from its mother spheroid. The spherical cells already produced a significant amount of transparent ECM. Scale bars: 20 μm