|Étude sur les corallinacées 1. Caractères généraux de la cytologie = Study on the Corallinaceae. I. General cytological characters|
Cabioch, J. (1971). Étude sur les corallinacées 1. Caractères généraux de la cytologie = Study on the Corallinaceae. I. General cytological characters. Cah. Biol. Mar. 12(2): 121-186
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723, more
The present work is the first part of a study on the morphogenesis of the Corallinaceae and it deals with the cellular peculiarities proper to that family of Algae. The main cell-components are described in the first chapter of the paper. After a brief review of our knowledge on the cell-wall calcification phenomenon, the description of some structural transformations, related to the vegative stage of the alga, is given. Some features of the vacuolar system are described and also the synthesis of floridean starch, which seems to take place, in some cases, in a peculiar cytoplasmic amylogenetic area (Pseudolithophyllum expansum). The occurrence of 2 kinds of siderophilic inclusions is shown. In the 2nd chapter, some important cytological phenomena, from the point of view of systematics and phylogeny, are presented. Those are the formation of lateral connexions between neighbouring cells of adjacent filaments and the production, sometimes complicated, of trichocytes and megacells. A comparison is drawn with similar phenomena, observed in other Florideae. The lateral connexions seem to result from the senescence of the tissues; they arise, after dissolution of a cell-wall area, either as direct secondary pit connexions, without any nuclear correlated activity, or through a cell fusion, which involves the fusion of the cytoplasms and even sometimes of the nuclei. The question whether these phenomena are or not parasexual is discussed. As regards the haircells and trichocytes, a comparative example, chosen out of the Corallinaceae, is that of Dumontia incrassata: the formation of haircells is the result of a series of cell differentiations and differentiations. In the Corallinaceae, it is accompanied with cell-wall transformations. 2- or 3-celled trichocytes originate in perithallial initial cells and keep included in a single calcified cell wall. Their top cells take the form of celluloso-pectic hairs, without any cell division. A series of stages of increasing complexity is described. In the simplest cases (Fosliella), the trichocytes stay, without further modification, all the algal life long. In more complex cases (Jania, Metagoniolithon), they are ephemeral; after the top hair-cell has disappeared, the underlying cell begins to divide and these divisions restore the normal aspect of the tissues, whereas in the most complex cases (Neogoniolithon, Porolithon); it takes the form of a big cell, called megacell. The arrangement of those persistent megacells in the tissues is often characteristic.