Eur. Phys. J. B 27, 167-172 (2002)
https://doi.org/10.1140/epjb/e20020142

Hydrodynamics and cell motion during the rounding of two dimensional hydra cell aggregates

¹ Département de Physique des Matériaux, Université Claude Bernard – Lyon I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
² Tohoku Institute of Technology Yagiyama-Kasumi, Taihaku, 983, Sendai, Japan

Corresponding author: ^a rieu@dpm.univ-lyon1.fr

Received: 21 December 2001
Published online: 15 May 2002

Abstract

Using a two dimensional experimental geometry, we study hydrodynamics and cell motion during the rounding-up of three kinds of hydra aggregates (ectodermal, endodermal and mixed). The relaxation of initially elongated aggregates toward a circular shape is exponential and the relaxation time is proportional to the aggregate size as expected from hydrodynamics laws. As for viscous liquids, aggregate rounding is driven by tissue surface tensions σ and resisted by tissue viscosity η. The ratio is the same for the three kinds of aggregates. With a reasonable value  mN/m, we obtain an estimate larger than 10⁴ Pa s for the tissue viscosity. Cell motion during rounding is strongly cooperative and cell displacements exhibit some specific patterns in each aggregate. These results point out the role of adhesive bonds in the observed kinetics.