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BSTRACT [ABSTRACT FROM AUTHOR]

A species complex in Spirogyra consists of the series of filament morphotoypes of various ploidal levels arising from an original morphotype within a clonal culture or in nature. A clonal culture of filaments identified as Spirogyra maxima (Hasall) Kützing produced several morphotypes, i.e. filament types of distinctly different widths and ploidal level. Banding patterns and satellites were visible on chromosomes stained at mitotic prophase and metaphase. The original culture of S. maxima contained filaments averaging 127 μm wide. Vegetative cells of the original culture contained six large chromosomes (>4 μm long), identifiable as three distinct pairs based on banding patterns and presence of satellites: (1) one pair of short chromosomes (ca. 5.0 μm); (2) one pair of long chromosomes (ca. 8.0 μm); and (3) a second pair of long chromosomes (ca. 9.0 μm) including a nucleolar organizing region and satellite. A larger morphotype averaging 175 μm in width contained 12 chromsomes, with two pairs of short chromosomes and four pairs of long chromosomes (satellites were usually indistinct). Aneuploid chromosome numbers ranging from 5 to 13 were observed in a few cells. Binucleate and trinucleate cells were also observed. A two-banded chromosome fragment was observed in a few cells with 6 chromosomes and a few cells with 12 chromosomes. The variety of morphotypes derived in this study could be identified as four different species of Spirogyra by conventional taxonomic criteria. The banding patterns and satellites on chromosomes suggest that three pairs of homologous chromosomes are present in filaments of the original clonal culture and that these filaments are themselves autopolyploid (diploid) descendants of an ancestral form with a base chromosome number of x = 3. [ABSTRACT FROM AUTHOR]

The nuclear cytology of 9 strains of Sirogonium is described. The interphase nucleus contains 1-3 nucleoli, a nucleolar-organizing track, and many (>100) chromocenters. During the division cycle the nucleoli are transformed into a nucleolar substance which becomes associated with the chromosome and is transported through mitosis on the chromosomes. All strains possess minute dot chromosomes varying in length at metaphase from 0.5 to 1.5 μ; satellite chromosomes are 2.5-3.5 μ long. The number of chromosomes varies from 48 ± 2 to 100 ± 2. No evidence of centromeric activity was observed. [ABSTRACT FROM AUTHOR]