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

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An important feature concerning these data, NaS that the sample
of D. willana from Tautuku was collected in the upper fringe of the
D. wi Llana be 1 t. 'l'hus unl ike the sample from Par i ti tahi. where t.he
D, wiltana band was t~aversed, the Tautuku sample contained no very
large subtidal specimens" If these had been included, then the
differences beb'leen the mean measurements in Table 505 \'llDuld have
been much greater.
5.6 CHAPTER SUMMARY
Germling development and subsequent developmental stages of
both Durvillaea species are described. These deve stages
account for some of the morphological variation seen in samples.
Morphology of plants is to a large extent determined by ,.,.ave action.
OVerall plant size, the degree of division of laminae, size and
shape of holdfasts and honeycombing are all influenced by wave force.
Three forms are commonly found, although intergradations occur:
A high impact form in areas where the impact force of waves is
exceptionally strong, a more widely occurring thonged form on steep
shores where wave action is strong, and a cape form on very gently
sloping shores or in the semishelter"of harbours.
Stipe size, and in the case of D. antarctica, honeycombing,
increases down shore. The morphology of D. anta~ctica plants forming
the upper fringe of the kelp band differs appreciably from that of
plants growing at lower levels.
Grazing by fish and other animals, and the effect of Herpodiscus
also influence the morphology of DurviZlaea fronds, mainly by
increasing the division of the lamina.
There is some evidence of latitudinal variati'>n in the morphology
of both species, although results clearly show that Wave action
('.n:erts a much greater influence than latitude. The morphological
differences between D, antaJ"ctica plants growing on diffe:cent fa,ces
of a cliff far exceeds any morphological differences between samples
from Auckland ahd Otago. When looking for latitudinal variation it
is therefore important to compare samples from 1:he same wave exposure.
In general, D. cmtaratica in the southern half of the .south Island
and stewart Island are larger, and have larger stipes than plants in
north Auckland or on the north Westland coast. 'l'here is
proportionate:ly greater developmen't. of stipe (relative to la.l'I1ina)