Figure 5

External morphologies and cortical structures of glabrous-type thalli of Galaxaura pacifica Tanaka. (A-B, D-G) Female gametophyte from Small Port. (C, H-N) Male gametophyte from Small Port. (A) Voucher specimen of female glabrous-type thallus for DNA analysis. Arrows indicate the basal villous branches in the lower portion of thallus; (B) Magnification of the villous basal portion (arrows); (C) Specimen of male glabrous-type thallus showing small villous basal portion (arrows); (D) Tip of the branch of the glabrous-type thallus showing annulations that are caused by the alternation of the calcified cortical regions and less calcified cortical regions (arrowheads). Reproductive structures are located throughout the glabrous branches (arrows); (E) Longitudinal section of the tip of the glabrous branch showing the sunken growing point with a cluster of slender cortical filaments (cf). Subsequently, these cortical filaments develop outward to form a layer of 3-celled cortex (co). The medullary filaments (mf) remain undifferentiated; (F) Cross section of the upper branch of female glabrous branch showing cellular cortex (co) and medullary filament (mf); (G) Surface view of cortical cells showing a stellate chromatophore with a pyrenoid (py); (H) Magnification of the villous basal portion (arrows); (I) Cross sections showing the comparison between lower part of the villous branch and the upper part of the villous branch. The upper part of the villous branch comprises of longer assimilatory filaments (af) whereas the lower part of the villous branch comprises of few assimilatory filaments (af); (J) Cross section of the villous basal portion showing that numerous assimilatory filaments (af) arise from a mass of medullary filaments (mf); (K) Assimilatory filaments (af) issued from undifferentiated and non-tumid basal cell (bc). (L) The glabrous branch (arrows) issued from the villous branch that comprises of numerous assimilatory filaments (af); (M) Longitudinal section of the transition zone between the glabrous branch and the villous branch showing that cortical structure transforms from assimilatory filaments (af) to cellular cortex (co). Medullary filaments (mf) are denser in the villous branch than that in the glabrous branch; (N) The magnification of the transition between the glabrous branch and the villous branch showing assimilatory filaments (af) from the villous branch and cellular cortex (co) from the glabrous branch. Noted that medullary filaments (mf) are very dense in the villous branch.