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

142
(b)
The exposure experiment:
Out of 15 D. antarctica samples (each cut in half), 13
released aftel.' being emergent for 1 hour, and 13 released Hhen kept
permanently submerged.
The two smnples which did not release ih
either treatment .. ,ere the same.
Samples temporarily exposed to 0ir,
exuded ova while they were drying, and these accumulated as stuall
mounds around the ostioles. Once the samples were ~ersed in
water these small mounds dispersed. In both treatments, the ova
formed a "print" of the conceptacle pattern on the glass slides
immediately beneath the lamina samples.
This experiment was not repeated for D. wiZlana which rarely~
if ever, becomes slightly dried in the field_
In winter, lamina.
samples of this species released ova irrespective of whether they
were in air or \'1a ter.
(c)
The agitation experiment~
Gamete release was only detected in the field when conditions
were exceptionally calm.
It was virt,ually impossible to check for
the release of gametes when the sea was rough.
Sections through
laminae had shown that paraphyses protrude slightly through the
ostioles, and it seemed possible tiiat these might g in s~~e way,
prevent a heavy release of gametes when the sea was very rough.
It therefore seemed pertinent to de termine whether lamina samples would
release in artificially created rough conditions (see Chapter 2) 0
For some reason, the D. antarctica samples used in this
experiment were slow to release under either rough or calm conditions.
The experiment had to be run for nearly ten hours before there was
any sign of a heavy release. D. willana samples on the other hand
released heavily within 2~ hours. Results are tab.t'.at..ed below.,
Table 6.5
Results of the agitation experiment"
D. ANTARCTICA
Jar and sample numbers
Conditions 1 2 3 4 5 6 7 8 9 10 11 12
Calm @ ® @ 0 6l /ill €I () i:9
Rough 0 0 (fl 0 Q @ ~ 0 0
Calm (satura ted) ,~. @ ® 0 ~ ® ~ ~ ~
D. WILLANA 1 2 3 4 5 6 7 8 9 10 11 12
Calm Ii
•
Rough 13! ~
Calm (saturated)
-k"", super satu:r.ated seawater i aerat.ed for 24 hours
O=' no relea,se; ~ very light release; @:=: heavy release