Electron Microscopy of the Volvocaceae and Astrephomenaceae

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 192.122.237.41 on Sun, A B S T R A C T LANG, NORMA J. (U. Texas, Austin.) Electron microscopy of the Volvocaceae and Astrephomenaceae. Amer. Jour. Bot. 50(3): 280-300. Illus. 1963.-Clonal cultures of Gonium sociale, G. pectorale, Pandorina morum, Eudorina elegans, Eudorina sp., Volvulina steinii, V. pringsheimii, Platydorina caudata, Pleodorina illinoisensis, P. californica, Volvox aureus, V. tertius, V. globator, V.barberi, and Astrephomene gubernaculifera representing the Volvocaceae and Astrephomenaceae in the Volvocales were examined with the electron microscope and their ultrastructure compared. The ultrastructure of the various organelles is basically similar in the species studied and no increase in cellular complexity is found to accompany the evolutionary trends evidenced in the Volvocaceae. The ultrastructure of a colonial cell is basically that of Chlamydomonas. A cytoplasmic membrane having a unit membrane structure encompasses a cell and is continuous with the double-membraned flagellar sheaths. The flagella contain the typical 9 + 2 fibril arrangement with the 2 axial fibrils terminating in a cylinder at the flagellar base and the 9 peripheral pairs continuing into the cytoplasm as a basal body. The organelles comprising the cytoplasm are: mitochondria with plate-like cristae; dictyosomes composed of stacks of agranular cisternae; small, rough or smooth-surfaced vesicles; an endoplasmic reticulum of granule-bearing and agranular tubules, lamellae and broad cisternae; vacuoles which are either contractile, contain fine granular and fibrillar material, or have dense contents probably representing polyphosphate; lipid bodies; and dense granules 100-150 A which have been called ribosomes. The finely granular nucleoplasm is surrounded by a porous, double-membraned nuclear envelope and contains a centric nucleolus composed of dense, spherical granules. The outer membrane of the nuclear envelope bears granules and may have granular extensions into the perinuclear cytoplasm. Each extension appears to encompass one or several dictyosomes and has been termed an "amplexus." The amplexi are agranular on the surface contiguous to a dictyosome. A double-membraned chloroplast envelope is continuous around the single, cup-shaped chloroplast. The basic chloroplast units are discs closed at each end, occurring in stacks of varying number parallel to the envelope. The presumed proteinaceous matrix of the basal pyrenoid is penetrated by elongated, tubular elements which connect with the lamellar discs. Multiple rows of granules, associated with individual discs, form the anterior stigma within the chloroplast envelope. The colonial matrix is not a structurel...

Fine Structure of the Pseudocilia of Tetraspora

“…The ultrastructure of the basal region of the pseudocilium is similar in many respects to the flagellar basal body of other algal species as described by Lang (1963) and &Ianton (1964). Extending from each pseudocilial basal region into the peripheral cytoplasm is a root composed of several minute 'This investigation was supported in part b y National Science Foundation Grant GB3447 to the Marine Botany Course, illarine Bioloaica!…”

Evolution of Complexity in the Volvocine Algae: Transitions in Individuality Through Darwin's Eye

“…In reconstructing the history of these 12 steps, Kirk (2005) used the “volvocine lineage hypothesis” as a first‐order approximation of volvocine phylogeny (see, for example, his figure 6). The evolution of volvocine algae has often been viewed in the framework of this hypothesis, which holds that the members of this group represent a progressive increase in size and complexity from unicellular Chlamydomonas to Volvox and that the phylogeny of the group reflects this progression (Lang 1963; Van de Berg and Starr 1971; Pickett‐Heaps 1975). Although it was not a part of the original formulation, this hypothesis is often interpreted as implying that ancestral species in the lineage leading to V. carteri were morphologically and developmentally similar to extant volvocines of intermediate size and complexity (e.g., Nozaki and Itoh 1994, Nozaki et al 1999, 2000; Kirk 2005).…”

Ultrastructure of the extracellular matrix and taxonomy of Eudorina, Pleodorina and Yamagishiella gen. nov. (Volvocaceae, Chlorophyta)

“…8). Although Lang (1963) and Hobbs (1971, 1972 observed vegetative ultrastructure in E. illinoisensis, such endosymbionts were not described. Although Lang (1963) and Hobbs (1971, 1972 observed vegetative ultrastructure in E. illinoisensis, such endosymbionts were not described.…”