Electron Microscopy of the Longitudinal Fibrillar Bundle and the Contractile Fibrillar System in Spirostomum ambiguum

Abstract

SYXOPSIS.A study of the 'longitudinal fibrillar bundle' (LFB) and the 'contractile fibrillar system' (CFS) of a large protozoan ciliate, Spirostomum ambiguunt, has been performed by means of an electron microscope. .4 system of sub-pellicutar fibrils has been newly found and its function is discussed. Each LFB runs parallel with a longitudinal row of ciliary bases. I t seems to be identical with the so-called kinetodesma. I t is composed of tubular fibrils arranged in layered sheets, each of which contains 13 to 3. 5 fibrils with the same diameter as the intra-ciliary fibrils and has a close connection to each EVERAL large ciliates that are capable of rapid S change of form in response to stimuli-Condylostoma, Stentor, Vorticella, Carchesium, Zoothamnium and others-have special cell organelles which are directly instrumental in their body contraction. The fibrous structures of these organelles have been studied since nearly a century ago, and since Lieberkuhn ( 3 ) found 'Muskelfasern' in the ectoplasm of Stentor, the corresponding structures have been recognized in several contractile ciliates and named mvoneme, myophane, neurophane, neuroid and the like. At present, the term myoneme seems to be generally and widely used for the structure considered as a contractile element, but it is still doubtful whether or not such fibrous structures actually contract. As far as we know, the so-called myoneme of Spirostomum

Osmium tetroxide vapor fixation of dividing and regenerating Blepharisma

“…The complex will be referred to as the sub-pellicular filament system. A similar organiza tion of filaments has been reported for Spirostomum (Yagiu and Shigenaka, 1963;Finley ^ al-j 1964).…”

“…A trabecular band of fibers similar in both morphology and location to that just described has been observed in Spirostomum (Yagiu and Shigenaka, 1963;Finley et ^., 1964).…”

“…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.…”

“…No connection is observed between the filaments nearest to the right side of the ectoplasmic ridge and the inner membrane of the pellicle complex as has been reported for Spirostomum (Yagiu and Shigenaka, 1963;Finley et al, 1964); there is, however, less space separating the sub-pellicular filaments in this region (Fig. 18).…”

“…A similar system is described for the flagellate Peranema (Roth, 1959) and for Spirostomum (Yagiu and Shigenaka, 1963;Finley, ^ al•, 1964) but has not been found in the heterotrichs Gondylostoma or Stentor. Roth identifies the complex as the "subpellicular filament system" and suggests that it may be involved in the slow, contractile movements of Peranema.…”