La Réorganisation Infraciliaire au Cours de la Conjugaison et l'Origine du Primordium Buccal dans le Genre Euplotes

Abstract

RESUME L'infraciliature ventrale est presque entièrement détruite lors de la conjugaison: la totalité des structures buccales, tous les cirres fronto‐ventraux et transversaux, certains cirres caudaux. Le retour à l'état végétatif s'effectue en 2 étapes. Première Etape.–Différenciation d'un nouvel ensemble de cirres, dépourvu du cirre 1/I (selon la nomenclature de Wallengren); néoformation, à partir d'une ébauche située sur le territoire présomptif du cirre manquant, d'une partie des structures buccales (la moitié antérieure de la frange adorale de membranelles). Deuxième Etape.–Remplacement de tous les cirres par un nouvel ensemble comportant le cirre 1/I; différenciation des structures buccales manquantes (moitié postérieure de la frange adorale, ciliature parorale) Les rapports morphogénétiques entre le cirre 1/I et la ciliature parorale suggèrent que le territoire de ce “cirre paroral” est homologue des territoires stomatogènes d'autres Hypotriches tels que Kahliella et Stylonychia. SYNOPSIS. During conjugation of Euplotes, the ventral ciliature, including the entire oral apparatus, all the fronto‐ventral and transverse cirri, and some of the caudal cirri, is nearly completely lost. As followed in silver‐stained preparations, the redifferentiation of the ciliature proceeds in 2 steps. The first step entails differentiation of a new complement of cirri, except for cirrus 1/I (according to the nomenclature of Wallengren), and neoformation of the anterior part of the adoral zone of membranelles (AZM) from a primordium located in an area that would be expected to give rise to the missing 1/I cirrus. The 2nd step involves replacement of all the cirri, including 1/I, and completion of the oral apparatus by redifferentiation of the posterior half of the AZM and of the paroral ciliature. The spatial morphogenetic relationships between cirrus 1/I and the paroral ciliature suggest that the area of this “paroral cirrus” is homologous with the stomatogenic areas of other Hypotrichida, such as Kahliella and Stylonychia.

Description of the Rare Marine Ciliate, Uronychia multicirrus Song, 1997 (Ciliophora; Euplotida) based on Morphology, Morphogenesis and SS rRNA Gene Sequence

“…This mode is also present in Euplotes and Diophrys (Hu 2008;Tuffrau, Tuffrau, and Genermont 1976), implying that it is a conservative feature having a long evolutionary history. In addition, another event needs to be clarified: the left-most frontal cirrus in both proter and opisthe is formed de novo rather than generated from the UM-anlage like that in most hypotrichs s. l. This situation is also present in at least two other morphologically rather specialized genera, Aspidisca (Song 2003) and Euplotes (Tuffrau et al 1976). Thus, it is considered to be a plesiomorphic character.…”

Mating by conjugation in two species of the genus Aspidisca (Ciliata, Hypotrichida): an electron microscopic study

“…The morphogenetic pattern during the mating reaction of species of the genus Aspidisca for many aspects can be referred to that described in Euplotes species (Diller 1966;Kloetzel 1975;Tuffrau et al 1976), although differences in the relative timing of events have been observed. The formation in exconjugants of a third cirral generation, for which Diller provided only some evidence, is here definitely demonstrated, as well as the formation of a new AZM at the locus of the old one.…”

“…Also, with reference to the BC [which corresponds to the 1/I cirrus according to Tuffrau's (1960) scheme for the numbering of the cirral field of a generalized representative of Aspidisca], similarities and differences between Aspidisca and Euplotes species have been found: in the species of both genera this cirrus arises only once from a field separated from other cirral structures. However, it is formed during the third generation morphogenetic event in Euplotes species (Diller 1966;Kloetzel 1975;Tuffrau 1976) while in Aspidisca species it arises in conjunction with the second generation event.…”

“…This fact, while definitely ruling out the idea of a homology of these two structures (Diller 1975), confirms that the ACO corresponds to the anterior part of the AZM of Euplotes species (Rosati et al 1987) which arises, during mating, in a similar position before the separation of the two partners. Then, after the separation, this portion of the AZM integrates with the successively formed posterior portion (Kloetzel 1975;Tuffrau et al 1976). Also, with reference to the BC [which corresponds to the 1/I cirrus according to Tuffrau's (1960) scheme for the numbering of the cirral field of a generalized representative of Aspidisca], similarities and differences between Aspidisca and Euplotes species have been found: in the species of both genera this cirrus arises only once from a field separated from other cirral structures.…”

Nuclear Roles in the Post‐Conjugant Development of the Ciliate Euplotes aediculatus. III. Roles of Old Macronuclear Fragments in Nuclear and Cortical Development1

“…complex series of events follows conjugation in ciliates, A involving both cortical and nuclear components. In Euplotes, a new oral apparatus and a complete cirral set are developed in clearly defined stages (8,(13)(14)(15)31) and these accompany the maturation of the new macronucleus (2, 8,14,25). The old macronucleus concomitantly breaks down, usually into four fragments, two quickly becoming pycnotic in the an-' Supported by a grant from the National Science Foundation (PCM 80-04057).…”