Foamlike disorder in the developing Drosophila embryo

Convergent extension is the cell-rearrangement process by which a developing embryo elongates to establish the body axis. In Drosophila (fruitfly), this occurs within a one-cell-thick epithelial layer. Confocal microscopy was used to image the two-dimensional cell pattern at various stages in the process [1]. Increasing foamlike disorder was observed and analyzed via p(n), the frequency of occurrence of n-sided cells [2], and related statistical measures such as the Shannon entropy. During convergent extension in Drosophila, the peak at p(6) drops from 0.65 to 0.38 and the second moment of p(n) triples to 1.1. An initial degree of hexatic interface-orientation order disappears during the process. [1] J.A. Zallen and E. Wieschaus, Dev. Cell 6, 343 (2004); [2] J.A. Zallen and R. Zallen, J. Phys.: Condensed Matter 16, S5073 (2004).