The Buccal Organelles in Paramecium aurelia During Fission and Conjugation, with Special Reference to the Kinetosomes

Abstract

SYNOPSIS. Stomatogenesis in Paramecium aurelia is shown to involve the lower kineties of the right vestibular wall, the endoral membrane and perhaps the quadrulus. The anarchic field for the new buccal organelles is formed by granules produced from somatic kinetosomes of the right vestibular wall. The endoral membrane becomes incorporated into the buccal anlage and probably regulates orientation and development of the new organelles. A production of heretofore unobserved buccal kinetosomes from the quadrulus is described and it is suggested that these may form the new endoral membrane for the proter. During conjugation the infraciliature dedifferentiates in the area of fusion between the conjugants. The buccal organelles dedifferentiate at the time of pronucleus formation and transfer. It is suggested that dedifferentiation of structures in the fusion area is caused by a partial solation of the cortex in this area. The dedifferentiation of the buccal organelles results from the solation of the cytoplasm and the cortex of the paroral cone during pronucleus migration. The redifferentiation of the buccal organelles and somatic kinetosomes is suggested to be a recrystallization or gelation of the cortex with the structures re‐forming in their normal positions and not from an anarchic field as at fission.

Oral morphogenesis during asexual reproduction in Paramecium tetraurelia

“…Despite numerous studies investigating stomatogenesis in diverse species of Paramecium (von Gelei, 1934;Roque, 1956aRoque, , b, 1961Yusa, 1957;Ehret & Powers, 1959;Porter, 1960;Ehret & de Haller, 1963;Gillies & Hanson, 1968;Ehret & McArdle, 1974;Kaneda & Hanson, 1974), at least two aspects of this process remain unclear. The first of these is the origin of the kinetosomes composing the aforementioned vestibular kinetosomal field.…”

“…Roque (1956aRoque ( , b, 1961 states that they arise by division of the kinetosomes composing the endoral kinety (EK), an additional oral structure, whose structure and disposition will be discussed later. Porter (1960) has postulated, alternatively, that the kinetosomes of the anlage field derive from the right vestibular kineties, i.e. rows of kinetosomes located within the vestibulum, with the EK acting as an organizer of stomatogenesis.…”

“…Secondly, despite the presumed cardinal importance of the endoral kinety as either a 'stomatogenic' kinety (Roque, 1956a(Roque, , b, 1961 or an 'organizer' of the kinetosomal field (Porter, 1960), the origin of this structure in the developing oral anlage has not yet been elucidated. Also unresolved is the question of the continuity of the endoral kinety in the original oral apparatus from one generation to the next.…”

Osmium tetroxide vapor fixation of dividing and regenerating Blepharisma

“…Such criteria may be misleading, since there is evidence that a visible color-change is not a conclusive method of judging osmium tetroxide reactions (Porter andKallman, 1953 andWolman, 1957); reactions between osmium tetroxide and the chemical components of the cell will also depend on the constituents of the vehicle (buffer, neutral salts) and on the physical-chemical state of the reaction sites during fixation (Afzelius, 1962). It is therefore somewhat dangerous to extrapolate in vitro evidence to varied conditions or to iji situ reactions and mechanics of fixation.…”

“…Porter (1960), Grimstone (1961), and Ehret and DeHaller (1963) all express reasons for the doubtful validity of this concept. Mazia (1961) summarizes the currently held objections to kinetosomal replication by division when he suggests that the division of the kinetosome is as difficult to envision as the formation of a bacteriophage by direct division.…”