Abstract
We present in vivo observations of chicken embryo development which show that the early chicken embryo presents a principal structure made out of concentric rings and a secondary structure composed of radial sectors. During development, physical forces deform the main rings into axially directed, antero-posterior tubes, while the sectors roll up to form cylinders that are perpendicular to the antero-posterior axis. As a consequence, the basic structure of the chicken embryo is a series of encased antero-posterior tubes (gut, neural tube, body envelope, amnion, chorion) decorated with smaller orifices (ear duct, eye stalk, nasal duct, gills, mouth) forming at right angles to the main body axis. We argue that the second-order divisions reflect the early pattern of cell cleavage, and that the transformation of radial and orthoradial lines into a body with sensory organs is a generic biophysical mechanism more general than the chicken embryo.
Highlights
Pattern formation in biology has for long been a matter of debate
The progress in developmental biology and especially genetics, has demonstrated the causal character of genes in animal development [4, 5], there is a continued interest in the physical, biomechanical, aspects of animal development and evolution, since physical principles should underlie all developmental processes at some level
We demonstrate that buckling of the sectors drives the formation of secondary cylinders or tubes that will eventually become the sensory organs, and we give in the end a generic model of blastula deformation supporting a simple mechanistic picture of vertebrate morphogenesis
Summary
Pattern formation in biology has for long been a matter of debate. The view that physical processes play an important role in development has been put forward by classical embryologists such as His [6], and by such physical embryologists as Gordon [7] or Belousov [8], and others. It has been argued by Newman [9] that there exists fundamental physical kernels of development which are repeatedly used by nature to form animals. The interplay of physics and biology has started to be unravelled at a mocelular level, in the study of gastrulation [10] or of organogenesis [11], and there is a steady flow of work on mechanotransduction [12], durotaxis [13], tensegrity [14], etc
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