, Volume 250, Issue 1, pp 261–272 | Cite as

Ultrastructural analysis of flagellar development in plurilocular sporangia of Ectocarpus siliculosus (Phaeophyceae)

  • Gang Fu
  • Chikako Nagasato
  • Toshiaki Ito
  • Dieter G. Müller
  • Taizo MotomuraEmail author
Original Article


Flagellar development in the plurilocular zoidangia of sporophytes of the brown alga Ectocarpus siliculosus was analyzed in detail using transmission electron microscopy and electron tomography. A series of cell divisions in the plurilocular zoidangia produced the spore-mother cells. In these cells, the centrioles differentiated into flagellar basal bodies with basal plates at their distal ends and attached to the plasma membrane. The plasma membrane formed a depression (flagellar pocket) into where the flagella elongated and in which variously sized vesicles and cytoplasmic fragments accumulated. The anterior and posterior flagella started elongating simultaneously, and the vesicles and cytoplasmic fragments in the flagellar pocket fused to the flagellar membranes. The two flagella (anterior and posterior) could be clearly distinguished from each other at the initial stage of their development by differences in length, diameter and the appendage flagellar rootlets. Flagella continued to elongate in the flagellar pocket and maintained their mutually parallel arrangement as the flagellar pocket gradually changed position. In mature zoids, the basal part of the posterior flagellum (paraflagellar body) characteristically became swollen and faced the eyespot region. Electron dense materials accumulated between the axoneme and the flagellar membrane, and crystallized materials could also be observed in the swollen region. Before liberation of the zoospores from the plurilocular zoidangia, mastigoneme attachment was restricted to the distal region of the anterior flagellum. Structures just below the flagellar membrane that connected to the mastigonemes were clearly visible by electron tomography.


Brown algae Ectocarpus Flagellar differentiation Transmission electron microscopy Electron tomography 



Transmission electron microscope


Electron tomography




Electron-dense materials


Crystallized materials


Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

709_2012_405_Fig10_ESM.jpg (40 kb)
Supplementary Fig. 1

a, b Vesicles in the flagellar lumen (arrows). Arrowheads indicate the flagellar membrane (JPEG 39 kb)

709_2012_405_MOESM1_ESM.tif (1.4 mb)
High resolution (TIFF 1441 kb)
Video 1

Paraflagellar body of the posterior flagellum. The video is composed of 60 adjacent slices (each 1.2-nm thickness) from a dual-axis tomogram corresponding to a paraflagellar body. Regular arrangement of crystalized materials can be detected. Scale bars = 50 nm. (MP4 220 kb)


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Gang Fu
    • 1
    • 2
  • Chikako Nagasato
    • 2
  • Toshiaki Ito
    • 3
  • Dieter G. Müller
    • 4
  • Taizo Motomura
    • 2
    Email author
  1. 1.Graduate School of Environmental ScienceHokkaido UniversitySapporoJapan
  2. 2.Muroran Marine Station, Field Science Center for Northern BiosphereHokkaido UniversityMuroranJapan
  3. 3.Electron Microscope Laboratory, Research Faculty of AgricultureHokkaido UniversitySapporoJapan
  4. 4.Fachbereich BiologieUniversität KonstanzKonstanzGermany

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