A Structural and Systematic Study of the Sphaeropleaceae (Chlorophyceae) With Special Reference to Sphaeroplea
Buchheim, Mark Alan
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https://hdl.handle.net/2142/71289
Description
Title
A Structural and Systematic Study of the Sphaeropleaceae (Chlorophyceae) With Special Reference to Sphaeroplea
Author(s)
Buchheim, Mark Alan
Issue Date
1988
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Botany
Abstract
Structural and biochemical investigations of the Sphaeropleaceae were undertaken to address systematic and phylogenetic questions regarding this small, but distinctive group of green algae. Taxonomic descriptions of two new Sphaeroplea species, S. fragilis and S. robusta, are presented in which new, light microscopic characters for the Sphaeropleaceae are introduced. Ultrastructural studies of mitosis in antheridia of S. robusta revealed the production of (1) a centric, closed spindle with polar fenestrae, (2) indistinct kinetochores, and (3) perinuclear endoplasmic reticulum. These mitotic features ally Sphaeroplea with most chlorococcalean algae. Mitosis in antheridia of S. robusta is further characterized by the production of an extra-nuclear band of microtubules. This band appears to represent the precursor of a multistranded flagellar root that may function in facilitating centriolar movement. Ultrastructural studies of male gametes in Sphaeroplea show that most species possess a modification of the distal fiber termed an apical cone. In contrast, the distal fiber in male gametes of the sister genus Atractomorpha is unmodified. This distinction probably represents a fundamental difference between the two genera. Male gametes of S. fragilis are similar to Atractomorpha in that they also possess an unmodified distal fiber. All sphaeropleacean male gametes that have been studied possess directly opposed basal bodies and a "sphaeropleacean" stellate structure. The presence of these two features in motile cells of some chlorococcalean algae represents further evidence of a close phylogenetic relationship between these chlorococcalean algae and the Sphaeropleaceae. Results from cladistic analyses of morphological and electrophoretic data place S. fragilis at the base of the Sphaeroplea clade in both analyses. These data support the distinctiveness of S. fragilis among members of the genus Sphaeroplea. Results from cladistic analyses of electrophoretic data differed from the morphological analysis in that S. soleirolii va. crassisepta is allied with Atractomorpha in the former. These results suggest that S. soleirolii var. crassisepta has undergone extensive genetic divergence from the other members of the genus Sphaeroplea.
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