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Short Video: Volvox Flagella

by Pearson
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The first part of this video focuses through an individual Volvox, a multicellular green alga. Volvox has two types of differentiated cells, and so it is considered multicellular rather than colonial. A Volvox individual resembles a hollow ball whose outside wall is composed of one of its two types of differentiated cells: hundreds of biflagellated cells embedded in a gelatinous extracellular matrix. If isolated, these cells cannot reproduce. The alga also contains a second type of differentiated cells, those specialized for sexual or asexual reproduction. The large alga shown here initially contains six smaller daughter algae. In the video, you can see the release of one of the daughter algae from its parent. When the parent was in its juvenile stage, it contained 16 large, asexual reproductive cells called gonidia. As the parent Volvox grew, each of the gonidia underwent 11 to 12 rapid divisions to form a new set of 16 juvenile daughters within the parent. In the juvenile daughter that is being released, 16 gonidia are already present, having formed during the previous rapid divisions. The last segment of the video clip focuses through a Volvox individual at 600 times magnification. At first, the focus is on the outer wall closest to the viewer, then it moves through a daughter alga inside to the back side of the parent. Finally, the focus comes back up, ending midway through the daughter, with the flagella of the wall cells in the daughter clearly visible. You can see the structure of each cell and the cytoplasmic connections between them. Credit: Michael Clayton, University of Wisconsin, Madison.
The first part of this video focuses through an individual Volvox, a multicellular green alga. Volvox has two types of differentiated cells, and so it is considered multicellular rather than colonial. A Volvox individual resembles a hollow ball whose outside wall is composed of one of its two types of differentiated cells: hundreds of biflagellated cells embedded in a gelatinous extracellular matrix. If isolated, these cells cannot reproduce. The alga also contains a second type of differentiated cells, those specialized for sexual or asexual reproduction. The large alga shown here initially contains six smaller daughter algae. In the video, you can see the release of one of the daughter algae from its parent. When the parent was in its juvenile stage, it contained 16 large, asexual reproductive cells called gonidia. As the parent Volvox grew, each of the gonidia underwent 11 to 12 rapid divisions to form a new set of 16 juvenile daughters within the parent. In the juvenile daughter that is being released, 16 gonidia are already present, having formed during the previous rapid divisions. The last segment of the video clip focuses through a Volvox individual at 600 times magnification. At first, the focus is on the outer wall closest to the viewer, then it moves through a daughter alga inside to the back side of the parent. Finally, the focus comes back up, ending midway through the daughter, with the flagella of the wall cells in the daughter clearly visible. You can see the structure of each cell and the cytoplasmic connections between them. Credit: Michael Clayton, University of Wisconsin, Madison.