Accessible Requires Authentication Published by De Gruyter May 14, 2021

New insights on Laminaria digitata ultrastructure through combined conventional chemical fixation and cryofixation

Christos Katsaros, Sophie Le Panse, Gillian Milne, Carl J. Carrano and Frithjof Christian Küpper
From the journal Botanica Marina


The objective of the present study is to examine the fine structure of vegetative cells of Laminaria digitata using both chemical fixation and cryofixation. Laminaria digitata was chosen due to its importance as a model organism in a wide range of biological studies, as a keystone species on rocky shores of the North Atlantic, its use of iodide as a unique inorganic antioxidant, and its significance as a raw material for the production of alginate. Details of the fine structural features of vegetative cells are described, with particular emphasis on the differences between the two methods used, i.e. conventional chemical fixation and freeze-fixation. The general structure of the cells was similar to that already described, with minor differences between the different cell types. An intense activity of the Golgi system was found associated with the thick external cell wall, with large dictyosomes from which numerous vesicles and cisternae are released. An interesting type of cisternae was found in the cryofixed material, which was not visible with the chemical fixation. These are elongated structures, in sections appearing tubule-like, close to the external cell wall or to young internal walls. An increased number of these structures was observed near the plasmodesmata of the pit fields. They are similar to the “flat cisternae” found associated with the forming cytokinetic diaphragm of brown algae. Their possible role is discussed. The new findings of this work underline the importance of such combined studies which reveal new data not known until now using the old conventional methods. The main conclusion of the present study is that cryofixation is the method of choice for studying Laminaria cytology by transmission electron microscopy.

Corresponding authors: Christos Katsaros, Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 157 84, Greece, E-mail: ; and Frithjof Christian Küpper, Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA, 92182-1030, USA; School of Biological Sciences, University of Aberdeen, Cruickshank Building, St Machar Drive, Aberdeen, AB24 3UU, SC, UK; and Department of Chemistry, Marine Biodiscovery Centre, University of Aberdeen, Aberdeen, AB24 3UE, SC, UK, E-mail:

Funding source: European Union’s Horizon 2020

Award Identifier / Grant number: 730984

Funding source: Natural Environment Research Council (NERC)

Award Identifier / Grant number: NE/D521522/1, NE/F012705/1

Funding source: National Science Foundation

Award Identifier / Grant number: CHE-1664657

Funding source: National Oceanic & Atmospheric Administration

Funding source: Scottish Funding Council

Award Identifier / Grant number: HR09011


We would like to acknowledge Susan Loiseaux-de Goër, Bernard Kloareg, Philippe Potin and Akira F. Peters for their hospitality and support to FCK and CK during their visit to Roscoff.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: The research leading to these results received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 730984, ASSEMBLE Plus project 370, supporting access of CK and FCK to the Station Biologique de Roscoff. This work was conducted in conjunction with the European Marine Biological Resource Centre (EMBRC-ERIC), EMBRC-France. French state funds are managed by the ANR within the Investments of the Future program under reference ANR-10-INSB-02. Also, funding from the UK Natural Environment Research Council (NERC) through grants NE/D521522/1, NE/F012705/1, and Oceans 2025 (WP4.5) programs to FCK; the National Science Foundation (CHE-1664657) and the National Oceanic & Atmospheric Administration to CJC and FCK; and the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council and contributing institutions; grant reference HR09011) is gratefully acknowledged.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


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Received: 2020-10-23
Accepted: 2021-04-08
Published Online: 2021-05-14
Published in Print: 2021-06-25

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