An Electron Microscope Study of Cortical Structures of Opalina Obtrigonoidea

Abstract

The pellicular framework of Opalina obtrigonoidea consists of numerous longitudinal ribs parallel to the kineties. These ribs lie erect on the cell surface, and each is composed of striated longitudinal fibers. A membrane covers the ribs and the ectoplasm between them. Flagella, of conventional structure, emerge from the ectoplasm between the ribs. The two central fibers of each flagellum end at the cell surface; the nine peripheral fibers continue for about 400 mµ into the cell to form an open tubular kinetosome. From the anterolateral curvature of each kinetosome arise two rows of fibrils, each fibril oriented perpendicular to the cell surface and about 150 A in diameter. The two rows converge anteriorly and probably meet the next adjacent kinetosome. Minute granules or tubules, arranged in oblique rows and at least sometimes accompanied by very fine fibers, lie at the surface of the ectoplasm but show no detectable connection with the kinetosomes. The whole flagellar apparatus of Opalina thus bears a general resemblance to the infraciliature of some holotrich ciliates, but the degree of evolutionary relationship between them remains uncertain.

Structure and Function in Cilia and Flagella

“…These seem to be morphogenetic mistakes of limited functional significance and occurrence, akin to similar phenomena at grosser anatomical levels (SATIR 1962b). Incomplete rings where one or more filaments are missing are also found (AFZELIUS 1963, PITELKA 1962. Incomplete rings where one or more filaments are missing are also found (AFZELIUS 1963, PITELKA 1962.…”

“…1,2, or more extra filaments are occasionally present among many cilia of normal pattern (AFZELIUS 1963, SATIR 1962b. The deletions may occur naturally or they can be induced (PITELKA 1962). The deletions may occur naturally or they can be induced (PITELKA 1962).…”

Fine Structure and Morphogenesis in Protozoa

“…Comparable subpellicular fibres have been described in P e r a m a (Roth, I959), Cryptobia (Pyne, 1959), Opalina (Pitelka 1956;Noirot-Timothte, 1958), Paramecium (Schneider, 1959;Roth, 19583) and Euplotes (Roth, 1957, 19583); their connexions with basal bodies have been noted earlier.…”

“…In these structures, however, in contrast to typical kinetodesmata, several fibrils arise from each basal body, and they are joined to a rectangular structure at its base, rather than to the cylinder of outer fibres (Noirot-TimothCe, 1958 a; see also Noirot-Timothie, (1958 b) for a more detailed account of the basal bodies of these organisms). Kinetodesma-like fibres also occur in Opalina (Pitelka, 1956;Noirot-Timothie,…”

“…It has long been known from light-microscopy that the surface of many protozoa is not smooth in contour; the electron microscope has revealed that foldings and invaginations, regular or irregular, are more widespread than previously supposed. Among many examples may be noted the longitudinal grooves in the surfaces of Opalina (Pitelka, 1956;Noirot-Timothie, 1958 c) and Trichonympha (Pitelka & Schooley, i958; Gibbons & Grimstone, 1960), or the smaller, more numerous, extremely regular ridges on the surface of some gregarines (Kummel, 1958;Beams et al 1959a; Thtodoridks, 1959; see also Lacy & Miles, 1959). The electron microscope also reveals that the surface of Amoeba bears convolutions and projections smaller than those visible in the light microscope (Schneider & Wolfarth-Bottermann, 1959; Wohlfarth-Bottermann, 1960).…”