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Volvox Reproduction - Asexual

The Individual cells in a VolvoxVolvoxColonyCellFlagLab.jpg (73544 bytes) Colony resemble Chalmydomonas.

However, Volvox Colonies have two types of cells, Generative & Somatic.

Generative Cells subdivide by Mitosis to produce small Daughter Cells.

This process continues until a small bubble-shaped, invaginated Daughter Colony develops.

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The strips above illustrate the Inversion process as seen with an SEM (left) & Light Microscope (right).

These are formed inside-out so they must Invert prior to their release from the Parent Colony.

The Daughter Colonies are released upon the death of the Parent Colony.

The two Photographs on the right side of the Table above illustrate the Inversion process. Photos a-e were made with a Scanning Electron Microscope. Photos f-i were made with a light microscope

Volvox Reproduction-Sexual

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Volvox aureus

Sexual Reproduction is Oogamous. VolvoxSexReproDiag200.jpg (55885 bytes)

Some Generative Cells undergo repeated cell divisions to produce "Sperm Packets"

These swim away as a unit in search of Eggs.

Eggs develop from Generative Cells that have not undergone Mitosis.

Following Fertilization, the Zygote forms a thick Spiny Cell Wall that is frequently red. This functions as a "resting" stage.

Meiosis occurs inside the "resting" structure. Each Meiospore produces a new Colony.

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