PUESCHEL, CURT1* and SUSSE WEGEBERG2. 1Department of Biological Sciences, State University of New York at Binghamton, Binghamton, New York 13902, USA; 2Marine Biological Laboratory, Strandpromenaden 5, 3000 Helsingor, Denmark. - Calcification and decalcification during epithallial cell turnover in coralline red algae.
Epithallial cells of the coralline red algae are characterized by
unusual structural specializations, which include deep invaginations
of the distal cell surface, and by unique development, which
culminates in senescence, shedding, and replacement of the cells.
Electron microscopic study of epithallial cell differentiation in
morphologically and taxonomically disparate species suggests that the
unusual features of epithallial cell structure and development stem
from the fact that these dynamics occur within a calcified matrix.
Distal wall ingrowths begin to form on the initial cells, cells whose
cleavage eventually gives rise distally to new epithallial cells.
After the distal wall ingrowths form, the overlying crosswall becomes
rich in organic material. For this organic wall material to be
deposited into the existing crosswall, the wall must first be
decalcified; therefore, the presence of abundant organic material in
the crosswall provides a marker of localized decalcification. We
propose that the location and time of origin of distal wall ingrowths
indicate a connection between the ingrowths and two coordinated
processes: localized secretion of wall material, and decalcification
of the overlying cell wall in preparation for the movement of the
young epithallial cell into a new location relative to the surrounding
calcified matrix. The large plasmalemmal surface area associated with
the distal wall ingrowths allows for a greater abundance of
membrane-associated components, such as proton pumps, that could drive
localized cell wall decalcification.
Key words: calcification, Corallinales, epithallial cells, red algae