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1 September 2006 Cleavage pattern of Volvox aureus (Volvocales)
E. Wujek Daniel, Timpano Peter, Rufus H. Thompson
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Historical and recent reports on Volvox aureus have not satisfactorily explained cellular differentiation and development in this organism. The diagrammatic illustrations in these reports fail to accurately depict the division pattern of the developing embryo. In reinterpreting Volvox embryogenesis, the dextral spiral adjustment which occurs between each cell division can be identified as an important factor in understanding the how and when reproductive and somatic tissues are segregated and positioned. As cleavage of the asexual gonidium commences, each division is preceded by a period of enlargement and adjustment which helps position the axis of cytokinesis and the alignment of the resulting cells. Previous reports do not fully appreciate the importance of these movements; therefore, their diagrams do not compensate for the cellular aligned, diagrams are not wholly valid. By correctly adjusting and aligning these embryonic cells, it is possible to recognize the third cleavage which results in an 8-cell individual as the division which delineates the animal from the vegetal pole. In all subsequent divisions, new cells are cut off toward the phialopore; therefore, cellular products from animal and vegetal regions do not mix. The integrity of these distinct regions is always maintained. By the 32-cell stage, the 16 pregonidial initials are formed. Future divisions on these 16 cells are unequal, ultimately resulting in 16 gonidia and their somatic derivatives. The final result, after inversion, is a clearly defined organism with reproductive potential located in the posterior of the individual.

E. Wujek Daniel, Timpano Peter, and Rufus H. Thompson "Cleavage pattern of Volvox aureus (Volvocales)," Transactions of the Kansas Academy of Science 109(3), 139-148, (1 September 2006).[139:CPOVAV]2.0.CO;2
Published: 1 September 2006

cell division
life cycle
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