The New York Times has picked up a recent article in Physical Review Letters by Stephanie Höhn and colleagues (Höhn, S., Honerkamp-Smith, A.R., Haas, P. a., Trong, P.K. and Goldstein, R.E. 2015. Dynamics of a Volvox embryo turning itself inside out. Phys. Rev. Lett., 114: 1–5. doi 10.1103/PhysRevLett.114.178101).
Höhn and colleagues imaged Volvox globator during inversion using selective plane illumination microscopy and used the resulting measurements to fit a mathematical model of inversion. Inversion is crucial for all of the algae in the family Volvocaceae, since they find themselves in an awkward configuration at the end of cell division: with their flagella pointing inward. Having your flagella on the inside is obviously not much use for swimming. Through changes in cell shape and movements relative to the cytoplasmic bridges that connect cells, these algae turn themselves completely inside out, ending with the flagella on the surface where they can do some good.
Inversion in Volvox has often been compared to the process of gastrulation in animals, during which the blastula invaginates and forms the three germ layers: endoderm, mesoderm and ectoderm (for example, Leo Buss makes this comparison in his book The Evolution of Individuality). The simpler process that occurs in Volvox serves as a more tractable model system that can nevertheless add to our understanding of the physical processes involved in gastrulation.
Dr. Höhn is a postdoctoral researcher in Ray Goldstein’s lab at the University of Cambridge.
This is a comment concerning a comparison of Volvox inversion with gastrulation in multicellular animals.
Despite the fact that such great authorities as Buss and Keller wrote about this point, I perceive that the similarity of this two processes may be exaggerated. Perhaps later I shall write about that in more detail.
Hmmm. Sounds like a pretty kludgy design to me. Maybe God was hungover on the day he made Volvocaceae.