A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

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the darker granula.r protoplasts of the outer cortical cells. In
young specimens, this early stage is usually found in cell layers
just beneath the meristoderm. In older specimens where there are
several dark bands of cells in the outer cortex (Fig S.2d), -the
small cavities appeared most frequently beneath the outermos dark
band. Occdsionally they were found at lower levels.
In D, antaratica these small cavities were detected almost as
soon as the previous season's conceptacles had stopped releasing gametes,
They were clearly visible in Kaikoura and Tautuku scl.:mples collected
in October, Their presence was not detected in D. wi Zlana until mid
s l1lJU1ler •
The rows of outer cortical cells bend to acoommodate the increase
in size of these cavities. Cells lining the lumen, and others
behind them, are compressed, and become more elongated than otiler
outer cortical cells. They ultimately form a conceptacle wall
comprised of several layers of hyphae-like cells which stain faintly
blue with toluidine blue. In D. willana the wall is usually smooth,
but in D. antarctica it forms several processes that prpject like
incomplete septa into the lumen.
The conceptacle ,,,all gives rise to masses of branched and unbranched
hairs, which may, in the -case of D. antarctica, completely
fill the lumen by mid summer. Gametangia develop on most of these
hairs, and are clearly visible in both species by late summer. At
the same time, the wall in the neck region of the conceptacle pushes
outwards, separating the rows of cortical cells to form an ostiole
in the autumn. Meanwhile, the conceptacle enlarges sufficiently for
the hairs to spread out in the lumen. By autumn, antherozoids are
clearly visible, and ova begin to form.
When most gametes are shed, the rows of outer cortical cells
bend inwards around the ostiole, A new layer of cells, up to 12
cells thick, forms on the surface and seals off the ostioles (Fig.
6.1c) .
cells.
This new layer is at first compo sed of very small pale
As previously described, they enlarge, the thickness of the
layer increases, and 'd1e protoplasts of the cells become
dark and granular. FOrllla tion of this layer is an annuo.l phenomenon.,
Marked specliuens that were three years old contained tllree dark
bands alternating \"ith wider; and relatively pale bands (Fig. S.2d).
In formalin preserved material ~1e protoplasts of the darker cells
are densc:!ly packed with golden brol/In organelles I wheYeas the pro-to--
of the cells in the more pale bands are less
and gl:.'eenish.