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Movement of the cirri during the creeping of Euplotes crassus (Ciliata, Hypotrichida)

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The beating cycle of several cirri (frontal cirri 1/0, 3/I, 3/II, 3/III; transverse cirri; one caudal cirrus) of the ciliate Euplotes crassus was studied and described thoroughly in specimens that were actually creeping along the substrate. The beating cycle of the frontal cirri was measured both spatially and temporally, and it was found that (i) the single beating cycle was formed by an active propulsion phase (about 70% of the single step), followed by a recovery phase that so far has never been described and is where the cirri are transferred forwards passively (about 30% of the step); (ii) whenever the euplotes stops, it assumes its "zero position," repositioning all of its frontal cirri to their respective "standard positions"; and (iii) at the beginning of a new creeping phase the frontal cirri were reactivated in a well-defined order. The transverse cirri were kept still during forward creeping, while their angular position was changed with respect to the substrate during the stops and backward movements of the ciliate. The first left caudal cirrus beats constantly and its operating cycle appeared to be independent of the creeping or immobile state of the organism. The findings are discussed from the functional point of view and in the context of available literature on the internal beating potentialities of the different cirri.

Le cycle des battements de plusieurs cirres (cirres frontaux 1/0, 3/I, 3/II et 3/III; cirres transverses; un cirre caudal) chez Euplotes crassus a été étudié et décrit en détail à l'examen d'individus en reptation sur le substrat. Les battements des cirres frontaux ont été mesurés des points de vue temporel et spatial et nous avons constaté que (i) le cycle complet comporte une phase de propulsion active (environ 70 % du cycle) suivie d'une phase de récupération encore jamais décrite au cours de laquelle les cirres sont poussés vers l'avant (environ 30 % du cycle); (ii) lorsque l'organisme s'arrête, il adopte la « position zéro », replaçant tous ses cirres frontaux à leurs positions de départ; et (iii) au début d'un nouvel épisode de reptation, les cirres frontaux sont réactivés selon un ordre bien défini. Les cirres transverses sont immobiles durant la reptation vers l'avant et ils modifient leur angle par rapport au substrat au cours des arrêts et des déplacements vers l'arrière. Le premier cirre caudal gauche bat constamment et son cycle des battements semble indépendant de l'état de reptation ou d'immobilité de l'organisme. Ces données sont examinées d'un point de vue fonctionnel et dans le contexte de la littérature existante sur les possibilités des battements internes des différents cirres.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: August 1, 2001

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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