ref to your Ulva gamete/spore release problem I have possibly have
some advice, however no literature cites, since this is all
personally carried on knowledge.
All in all Dame Ulva is a someqwhat tricky lady to deal with as far
as stimulating her is concerned. Gamete and spore release is
obviously connected to lunar periodicity and/or high and low tide
You might try the following:
WHen you culture Ulva, give her an artificial short night, i.e. in
the middle of the night, using a time switch connected to a simple
low watts light bulb, have that bulb switched on for 15 minutes. Make
sure, if necessary to light-seperate Ulva from other algae cultures
not to disturb those in her nightly calm. This night break for Ulva
should have the same effect as full moon (shining in its natural
habitat). Full moon = spring high/low tides = spore/gamete release.
However I must admit this system not always works that easy. Youmight
have to take Ulva into culture, keep it for a few weeks to adapt to
lab conditions and get into the artificial light/dark day/night
cycle. Yet occasionally, when you think everything works,
you will find Ulva having released its gametes/spores overnight, when
you enter the lab in the morning. Ulva tends to break out of
artificial cylces oppressed on it and seems to go bach to natural
cycles. However, once you have Ulva growing under your regime,
you might be independent from natures cycle.
Another way might be to force Ulva to release by changing her water
from nutrient rich culture medium to fresh water and vice versa. I
guess this only works when the thalli are already fertile but the
gametes or spores do not want to become free.
Both methods may work but you have to be patient.
When I was working
with Ulva and needed zoospores I found it much easier to wait for
full or new moon and around this day (1-2 days before until 1-3 days
after), go out into the field, if this is possible for you, and pick
up fertile thalli, where the rims have changes in colour already
(light/bright green). Carry them back in seawater, in the lab rinse
them quickly with filtered seawater to wash off adhering spores or
gametes (you never know who is fertilizing who) and dry the thalli
softly between paper towels. Place them on perspex/plastic/glass
plates and let them dry at room temperature unitl they start to
shrinkle and feel a little dry and hard. Then place the individual
thalli in seperate beakers filled with filtered seawater and place a
spot light on the beakers from one side. When they relesae spores and
gametes, you will easily see the spores being attracted to the light,
i.e. swimming to the surface near the light, while the gametes rather
stay away from the light and swim down to the bottom of the beaker.
Suck the little fellows out, check them out under the microscope (who
is who, i.e. 2 or 4 flagella) and use them.
Hope it all works.
Dipl.-Biol. Thomas Leya
Institut fuer Allgemeine Botanik
und Botanischer Garten
e-mail: [log in to unmask]