Laboratoire Matière et Systèmes Complexes

Gastrovascular morphogenesis of the jellyfish Aurelia aurita

Condorcet building, Amphithéâtre Pierre-Gilles de Gennes

Thursday, June 28 2012 14h30

Camille Gambini’s PhD work was directed by Annemiek Cornelissen.

Morphogenesis of living systems is controlled by a complex of processes in which also physics plays an essential role. In this PhD thesis, we have investigated mechanical self-organized processes involved in gastrovascular morphogenesis of the jellyfish Aurelia aurita. The gastrovascular system of this jellyfish is a branched network of canals, which role is to distribute nutrients and oxygen in its umbrella. The organization of this network is relatively simple. We have observed the growth of this canal network and studied the structure and mechanical properties of the surrounding tissues. Canals grow in a flat and thin cellular sheet, the endoderm, and are surrounded by the extracellular matrix. These different tissues are periodically compressed by muscular contractions. Macro- and microrheology experiments have shown that the extracellular matrix behaves as a soft viscoelastic gel, which structure and mechanical properties evolve during jellyfish development. These changes can be put in connection with physical constraints exerted in the extracellular matrix by muscular contractions. Besides, we have shown by optic and electronic microscopy that canals grow locally by accumulation, stacking and differentiation of endodermal cells into canal cells. Numerical simulations and experimental results suggest that this process is induced by compressive constraints, which are locally enhanced in the endoderm, at the tip of a growing canal, during each muscular contraction of the jellyfish.

Keywords: jellyfish, morphogenesis, mechanics, growth, viscoelasticity, differentiation