INTERNATIONAL INSTITUTE
OF BIOPHYSICS
Conference
on Biophotons 1999
Abstracts of the Conference Reports in
alphabetic Order
THE REALIZATION OF THE "DYNAMICALLY PREFORMED MORPH" PRINCIPLE
IN MORPHOGENESIS OF A MARINE HYDROID POLYP.
Yu.A. Kraus, V.G. Cherdantsev
Evolution Theory Department, Biological faculty of Lomonosov Moscow
State University, 119899, Moscow, Russia
According A.G. Gurvitsch the reason for changes in shape and axis orientation
of embryonic cells is that "the configuration of embryonic anlages is dynamically
preformed". This means that changes in the cell shape and cell axes orientation
has a feedback to the anlage configuration. The embryonic spatial structure
at any developmental stage defines not only the initial conditions but
also the directions of its own transformation. Up to this date this approach
to the analysis of a morphogenetic dynamics has been applied to the epithelial
cell sheets (ESS) which cells do not change their neighbors. Our study
of the early morphogenesis of a White Sea hydroid Dynamena pumila L. has
shown that the Gurwitsch principle of the "dynamically preformed morph"
(DPM) fits in well to the cases of morphogenesis based on an active coherent
cell movements, the cells changing their neighbors under the general constancy
of their shape except the change in the shape of their outer surfaces.
The early stages of Dynamenamorphogenesis consist in a formation of
a primary ESS from initially non-epithelial cells.The origination of a
local order of ESS cells in ESS fragments and the epithelization of a "distant
order" leading to a formation of the closed ESS fragments present two stages
of this process. The active movements of embryonic cells connected with
a differentiation of their leading and trailing edges, just like in singly
moving cells, were monitored by using the SEM microscopy from the beginning
of cleavage. These movements remain non-coherent up the completion of the
"distant order epithelization". The DPM on a local scale (on a scale of
ESS fragments) is close to the hemisphere. It is realized on the basis
of a strong feedback between the shape of cells, the orientation of their
axes and the ESS shape. The completion of epithelization is connected with
the origination of a new scale of cell interaction based on (+) and (-)
feedbacks between the active translocation of cells with the change in
their neighboring, the change in the ESS shape and the anisotropy of tensile
fields. In this case DPM defines not the directional change of the cell
shape, but a direction of a coherent cell movements. The cells form flows
which orientation corresponds to the future long axis of the embryo. DPM
at this stage corresponds to the ellipsoid of revolution. The morphogenesis
of the anterior and posterior ends of a planula is also connected with
a differential activity of cells in the "head" and "trunk" regions. It
is just a moment of generating the planula shape which is dynamically preformed
by the course of morphogenesis at earlier developmental stages.
© International
Institute of Biophysics 2001 E-mail: iib@lifescientists.de
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