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

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It is possibl~
that this distal branching is an. adaptation 'co
strong impact and drag forces along the top of the kelp zone. On
sloping shores such as at Tautuku, the upper fringe of the DurvilZaea
bel t bears the full brunt of the impact and. drag forces of er'tch
receding vJave I
and in many places plants at 'chis level have to
contend \'Iith torrents which pour down the slope when lllaves crest over
the back of the shore plat.forms.
plants lower down are in deeper
water, and are afforded some protection by the wide expanse of D,
wiZ lana.
On exposed places around the Chatham Islands, D. antapatiaa
plants along the uppe:r fringe of the kelp band exhibit an unusual
l(torphological featUre.
Their stipes axe capable of producing la_taral
processes in a manner superficially resembling D. wilZana stipes
(Fig. S.llc-f). These appear first as small rna late\processes
(up to 5 rom diameter), the tissue of which is continuous with
the cortex.
They grow to form narrow, honeycombed, whip-like
thongs up to 1.5 m long
which are covered with conceptacles. 1~ese
thongs are C£ten concentrated along one side of the stipe, in which
case, the stipe is usually bent.
Those closest to the base grow
the fastest.
Specimens with this feature are usually battered. In most
cO.ses (see the specimens illustrated) the lamina is greatly' tattered.
or missing.
Presu:mably the development of thongs is a regenerative
response to excessive loss of lamina tissue, in the particula.rly
severe conditions along the upper fringe of the kelp band.
The
feature was not found lower do\~
the shore, and appears to be
confined to Chatham Islands populations.
D. antarctioa stipes at the bottom of the D. antarctica belt
are significantly longer and more slender than stipes of plants at
higher levels on the shore ('fable 5. 3a) .
Presllunably a long
stipe confers same advantage to plants growing at the bottom of
the intertidal.
When the tide recedes, fronds are left draped one
on top of the other dO\m the shore. so that plants at the bottom
have to contend with a thick and often tangled mass of laminae.
A long stipe effectively prevents the broadest p~rt
of these lowest
plants being covered,
Plants at the bottom of the intertidal most
also compete against D. wiZlana plants for light.
Since the stipes
of this species c01IDl1only exceed 1 In, and have inumerable lateral
is probably an advantage for D. antarctica
specimens nearby 0