THE UNIQUE GONIMOBLAST PROPAGULES OF BATRACHOSPERMUM-BREUTELII (BATRACHOSPERMALES, RHODOPHYTA)

Batrachospermum breutelii Rabenhorst produces gonimoblast propagules w hich are zonately septated into 4-6 unequally sized, uninucleate chamb ers. The propagule initials are single-celled, invariably associated w ith the fertilized carpogonium and borne on one-celled gonimoblast fil aments. They are divided by simultaneous infurrowing. Mature propagule s are thick-walled; each chamber contains numerous chloroplasts, mitoc hondria, lipid globules, starch granules and small vacuoles. The chlor oplasts are typical of many Rhodophyta, having single thylakoids with a peripheral encircling thylakoid. Septations between chambers have pi t plugs with two cap layers, the outer of which is domed and unevenly stained. The propagules are released in their entirety and one or more chambers germinate into one or two unbranched Chantransiaphase filame nts. However, the cell contents are not entirely emptied into the germ inating filament, as seen in typical carpospore germination of other s pecies of Batrachospermum. These filaments may wrap around the parent gametophyte or attach to it by a pad of cuboidal cells. Like other mem bers of the Batrachospermales the Chantransia-phase filaments also app ear to act as a basal stage of the gametophyte. Chantransia-phase cell s have an ultrastructure similar to the propagule chambers. The chromo some number is n=c. 5 for spermantangial initials and 2n=c. 10 for Cha ntransia-phase filaments. Relative DAPI fluorescence values and hence DNA levels for fascicle and axial cells of the gametophyte, spermatang ia and carpogonia are approximately half those of the gonimoblast, pro pagule chambers and Chantransia-phase germling and basal filaments. Ba sed on these unique propagules, a new section of Batrachospermum is cr eated, Gonimopropagulum.