Ultrastructure et mise en place des organelles buccaux au cours de la régénération orale chez Stentor coeruleus (Cilié Hétérotriche)

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Abstract
Differentiation of oral organelles during oral regeneration has been studied by electron microscopy. During a first phase, intense kinetosomal proliferation takes place resulting in an unorganized field where kinetosomes are precociously associated in pairs, one kinetosome in each pair being equipped with postciliary derivatives and the other with one transverse derivative. Observation of the next steps shows (a) that the different pairs have no particular orientation within the field and (b) that the differentiation of the adoral and then the paroral ciliatures may be interpreted as a progressive organization of these pairs. To the left, the pairs assemble at different levels along parallel lines; adoral membranelles must thus be considered as transverse sequences of kinetosomal pairs. To the right, the different pairs assemble along longitudinal lines, their positioning being progressive and leading to the formation of the "stychodyad" type at the level of the frontal field and of the "inverted pairs" type at the level of the cytopharynx. The ultrastructure of the paroral complex in Stentor is thus composite. The results demonstrate the possibility of formation of a "stychodyad" type paroral complex in a Polyhymenophora and illustrate that the coupling of kinetosomes as pairs or as dyads is directly dependent on the cell territory.[Journal translation]