Fine Structure and Function in Stentor polymorphus

Abstract

ABSTltACTThe fine structure of the ciliate Steutor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor.Descriptions have been given of the structure of the macronncleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 # and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system. Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, NI bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations.

Intramitochondrial Fibers With Dna Characteristics

“…[Although the typical fibers have not as yet been demonstrated in kinetosomes (centrioles and basal bodies), there is abundant evidence that these structures also fit the above generalization (56,65, cf. also references 40 and 45).…”

Osmium tetroxide vapor fixation of dividing and regenerating Blepharisma

“…These projections are usually between 0.3 and 0.6 p in length and have a diameter near 16 m|i except at the bulbous end which is about 50 m|a in diameter. Similar structures are reported for the membranellar cilia of Stentor (Randall and Jackson, 1958) and Nyctotherus (King et al, 1961) and for the cirri of Euplotes (Roth, 1956). …”

“…In Stentor polymorphus, Randall and Jackson (1958) Yagiu and Shigenaka (1963) and Finley, Brown, and Daniel (1964) have reported almost parallel observations on the ectoplasm of Spirostomum The observations of Roth (1957), Shigenaka (1964), Beams andAnderson (1961), and Pitelka (1961), dealing with protozoan fibrillar systems are also of value in interpreting the present work. Reviews by Fawcett (1961), Sleigh (1962), Pitelka (1963), andGrimstone (1961) provide excellent sources for comparison of ciliate fibrillar systems and have been used extensively.…”

“…There are, however, some observa tions indicating that kinetosomes arise de novo from sub-organellar-level pools (Ehret and Powers, 1959). In this regard, the presence of nucleic acids in kinetosomes has been tested in a variety of ways; biochemical isolation (Seaman, 1960 andHoffman, 1964); cytochemically (Randall and Jackson, 1958); electron microscopic techniques (Rampton, 1963;Swift, Adams, and Larsen, 1964). The general conclusion is that RNA is probably present while DNA is either absent or present in insignificant amounts.…”

Is it possible to consider «kinetomics» and «argyromics» as novel trends of functional morphology and systems biology of parasitic and nonparasitic protozoa? a brief analytical review

“…According to the first electron microscopic observations of those structures (Metz, 1953;Sedar, 1955), the bundle fibrillar structure morphostructurally corresponds to the neuronemes or kinetodesmes, but there was no synapse-like connection observed between them in the pioneer works, while the other workers (Randall, 1958;Ehret, 1959;Yagiu, 1959) argued that many fibrils from several neighbouring kinetosomes can be connected to the kinetodesmic fibril. Coordinated motor activity of the cilia (Párducz, 1954) with the high level of reactivity to the electrostatic and electrodynamic sources and monovalent cations until the reverse movement of the cilia, provided by the fibrillar ectoplasmic structures with the system acetylcholine + cholinesterase localized within the ROI (Seaman, 1951;Seaman, 1951a;Seaman,1952), indicates the presence of a kind of similarity between some network structures in Protozoa and their neurophysiological / electrophysiological homologs and "hierarchical prototypes" of the high level connectome self-assembly in Metazoa.…”