Fig. 8

Transmission electron microscopy images of P. californica juveniles 25 to 35 min after completion of inversion. Heavy metal-stained sections of fixed P. californica juveniles 25 to 35 min after completion of inversion (still inside the mother spheroid). a-e Transverse sections. a Juvenile alga 25 to 30 min after completion of inversion; CBs are located at the basal ends of the cells; the cells are separated from each other by electron dense ECM material; the ECM zones boundary zone (BZ), cellular zones 2 and 3 [85, 86] are labeled. b Magnified image of the framed area in (a); CBs are located at the basal ends of the cells. c Magnified image of the framed area in (a); transverse section of CBs. d Juvenile alga 30 to 35 min after completion of inversion; center of the image: transversally sectioned basal cell ends showing numerous CBs; image periphery: longitudinally sectioned cells; the ECM zones boundary zone (BZ), cellular zones 2 and 3 (CZ2 and CZ3) are labeled. E Magnified image of the framed area in (d) showing CBs. Yellow arrowheads: CBs; magenta arrowheads: flagella; black arrows: electron dense ECM; N: nucleus. Scale bars: (a, d) 5 μm; (b, c, e) 2 μm