Decalcification during epithallial cell turnover in Jania adhaerens (Corallinales, Rhodophyta)

Abstract

C.M. Pueschel, B.L. Judson and S. Wegeberg. 2005. Decalcification during epithallial cell turnover in Jania adhaerens (Corallinales, Rhodophyta). Phycologia 44: 156–162.Epithallial cells of the coralline red algae are characterized by structural specializations that include deep invaginations of the distal cell surface, and by a unique developmental pattern that culminates in senescence, shedding and replacement of the cells. Combined scanning and transmission electron microscopic study of epithallial cell differentiation in the geniculate coralline alga Jania adhaerens suggests that some of the unusual features of epithallial cell structure may be related to the need for localized wall decalcification as part of epithallial cell replacement. Distal wall ingrowths begin to form on the 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. The location and time of origin of distal wall ingrowths suggest a connection between the ingrowths and the coordinated processes of localized secretion of organic 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.