DECAPSULATION OF ARTEMIA CYSTS
Sent: October 18, 2000
From: <InABgCntry@aol.com>
To: <BRINE-L@LISTSERV.UGA.EDU>
QUESTION:
I have a small marine ornamental hatchery, and recently I have
noticed
that my brine shrimp eggs are taking over 15 hours to hatch. It
seems that the time to completely shed the egg shell is taking longer.
What is the preferred method to decapsulate eggs, and will this improve my
hatching time? For the record, the hatches are good in number, but
the actual time is longer.
Edward Ramirez
www.liquidlifeusa.com
***************
COMMENTS 1:
Check BrineShrimpDirect.com for some information, as I remember they had
a procedure for decapsulating eggs posted on their site somewhere. They
also sell decapsulated eggs. Somewhere I remember reading that this
process kills the shrimp though, so if speeding up hatch time is what you
want, decapsulation probably isn't the answer. Decapsulated, unhatched
eggs are supposed to be better for fish fry than newly hatched nauplii,
though it's probably more of a trick to get young fish fry to eat
something that doesn't move.
It's not uncommon for brine shrimp eggs to take 36 to 48 hours to
hatch. If you get some to hatch in 15 hours, that's pretty fast. You could
accelerate the hatch process if you raised the temperature of the water to
about 80°F (26.7°C), but you're also risking killing the
nauplii.
I have experimented with hatch water temperatures ranging from 70°F
to 80°F (21.1-26.7°C). At the lower range, the maximum hatch is
reached in about 2 days. Some hatch before that time, so you may want to
stop the aeration and remove the early hatchers (hatch water is terrible
stuff, full of bacteria, so you want to remove them soon after a bunch
have emerged - and rinse them well in tap water before doing anything else
with them). At the higher temperature range, the hatch percentage is lower
and it's very easy to wipe out an entire batch... but I've had them hatch
out in 24 hours. The optimal temperature is about 76F, most of them hatch
in a bit over a day (perhaps 30 hours at that temperature), and I'll
sacrifice losing a few to get them hatched that fast.
Robert Manning
RobertM782@aol.com
**************
COMMENTS 2:
It doesn't help very much, but decapsulation does not kill the eggs. They must be stored in concentrated brine until used. BS Direct decapsulates low-hatch-rate eggs, and then dehydrates them, which does kill them.
Most fish fry will eat decapsulated cysts if they have had a few days of the live nauplii to get used to taste and color.
Most reliable sources suggest temperatures in the range 25-30°C. If
too low, the hatch stretches out and the first hatched lose their
nutritional value when they molt. As you point out, multiple collection is
required.
Two big tricks for earlier hatch are reduced salinity and higher
temperature. Brighter light can also help. Much over 90F kills, and
bacteria may grow too fast over 86F (depending on how clean the eggs
are). Try a half-ounce of chlorine bleach per gallon of hatch water to
keep bacteria low. The bubbling drives off most before the eggs hatch, so
chlorine doesn't bother the nauplii.
Many folks underestimate the photosensitivity of the newly hydrated
eggs, and get a less-than-perfect hatch as a result. I keep a reflector
lamp near the hatchery jug and move it to to get the temp I want in the
low 80s. I may change from a compact fluorescent in summer to an
incandescent in winter to get the extra heat. Brilliant light --
approaching sunlight -- in the early stages is very important.
With GSL eggs, I get reliable 90%+ hatches in 24 hours. With SFB eggs
(priced out of my range, now) I get the same hatch in about 18 hours. Some
of the Asian eggs I have tried are worthless, because the hatch was so
slow and spread over about 2 days. I think (hope?) the producers are
finding better sources, now, than the ones I tried.
Wright Huntley
E-mail: huntley1@home.com
***************
COMMENTS 3:
The hatching time is normally a function of incubation temperature...ie,
the higher the temperature (up to 30°C or 86°F) the faster
the cysts will hatch. Fifteen hours is considered a FAST hatch.
Most people plan on 18-24 hour eclosion rates. If you have good
hatches and good separation I would not recommend going through the hassel
of decapsulation. If this process is not carried out precisely, you will
burn many cysts and reduce your hatch. In addition to the chemical
cost you have additional labor in the process. If the cyst source
has changed, for instance Great Salt Lake to Siberian cysts, this can
cause a difference in eclosion times.
Check with your cyst supplier to find if he/she has changed sources
of
Artemia cysts.
Howard W. Newman
Desert Lake Technologies, LLC
E-mail: BShrimp@aol.com
www.desertlake.com or www.rossha.com
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