The 1-mm-long transparent worm Caenorhabditis elegans lives in damp, temperate soil. Most of the time, it reproduces when one of its sexes, the hermaphrodite, fertilizes itself. The cell division that ensues is remarkably robust. All adult worms end up with the same number of cells, which have undergone the same migration and differentiation pathways. How does C. elegans achieve that consistency? In 2016 Matthias Weiss of the University of Bayreuth and his collaborators proposed an answer. After having monitored embryonic cells using light-sheet fluorescence microscopy, they discovered that a cell’s lifetime before division is inversely proportional to cell volume during the early stage of embryogenesis, when the cells form a single-layered raft of fixed total volume and, perforce, shrinking cell size. The anticorrelation could be explained if the total number of copies of a rate-controlling chemical component remains constant—and hence becomes limiting—as cells proliferate. Because it doesn’t need cell-to-cell coordination, the geometrically preordained process is inherently robust. Now Weiss and his team have extended their investigation to stages of embryogenesis when the larval worm takes shape. Their extended model accounts for rate-controlling components whose total number increases during later stages of embryogenesis when cells’ protein factories become more productive. Although the model needs tuning for the four main cell lines in C. elegans, it remains free of the complicated cell-to-cell coordination that higher animals rely on during their embryogenesis. Observations confirmed the model’s general validity and a specific prediction: The log of the duration of mitosis depends inversely on ambient temperature. (R. Fickentscher, S. W. Krauss, M. Weiss, New J. Phys. 20, 113001, 2018.)
