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Abstract
Iida H., Nishii I. and Inouye I. 2011. Embryogenesis and cell positioning in Platydorina caudata (Volvocaceae, Chlorophyta). Phycologia 50: 530–540. DOI: 10.2216/10-80.1
The colony formation of Platydorina caudata (Volvocaceae, Chlorophyta) was studied in detail using time-lapse video and scanning and transmission electron microscopy. A unique feature of P. caudata, a horseshoe-shaped flattened colony comprising 16 cells arranged in a single twisted layer, is formed by ‘intercalation’, the rearrangement of embryo cells within the colony, which proceeds subsequent to the embryo inversion that brings flagellar ends of cells from the concave to the convex surface. Cell fate is precisely decided in colony formation, suggesting that intercalation is a precisely regulated process in which given cells are intercalated into particular parts of the colony. The presence of flask-shaped cells with an elongated stalk and cytoplasmic bridges during the inversion process strongly suggests that a similar mechanism known in Volvox is also involved in the colony formation of Platydorina.
ACKNOWLEDGEMENTS
We wish to thank Dr H. Yamagishi and Dr K. Ishida (University of Tsukuba) for useful suggestions. We also thank Dr S. Ota (University of Oslo) for assistance in our experiments.
Supplementary Data. DIC time-lapse video micrographs of inversion and intercalation of Platydorina embryos taken at focus intervals of 2 µm along the z-axis. (http://gallery.me.com/ichiron/100321; user: iida; password: pla11).
