RE: [Killietalk] odd things in my spawning tank

["Richard Pierce" <Dr_Plankton at att_net>]

Hi Diane,

Your fast swimmers are copepods.  Copepods are a type of crustacean.  They
are propably the most abundant metazoan animal in the plankton of  the
marine environment, and are also often abundant in freshwater plankton,
although cladocera (Daphnia & their relatives) are also abundant in
freshwater environments.  Copepods are a very diverse group with thousands
of species.  In addition to planktonic species, there are benthic species
(even some adapted to living between grains of sand), and parasitic species.
They are important parasites of fish, but don't worry, yours are a
free-living species.

	Most freshwater free-living copepods belong a group called "Cyclopoids",
named after the genus Cyclops (because it appears that they have a single
eye in the center of their "forehead").  That is the red spot at the front
of your specimen.  They typically swim with a jerky, hopping motion.  Female
cyclopoids often carry 2 egg sacs behind them.  The eggs hatch into nauplii
which undergo several moults before turning into copepodites, and
eventually, after another half dozen moults, into adult copepods.  The
nauplii are very small, on the same size as larger protozoans, and are often
the first food for marine fish larvae.  Nauplii look like tiny swimming
ticks, but are totally harmless to your fish.  Copepods of all sizes are
good food for fish.  They can be cultured similar to daphnia.  Isolate a few
females carrying egg sacs and place them in a clean container.  Aeration
will help, but not too vigorous. Feed them green water.  By the way,
"copepod" literally translates into "oar-foot".  If you watch some swim
under the microscope you will understand why.  You can often see copepods in
ponds and container gardens in the summer along with Daphnia.

I agree that your slow swimmers are probably ostracods, also a type of
crustacean.  I don't think that they make as good a food for fish because of
their hard shell.  The "cilia" are actually the hairs on their legs which
stick out of a clam-shell like body to propell them and sweep food from the
water.  They are harmless to fish and are often found in the same waters as
copepods and cladocera.

Let me know if you have any more questions or unidentified critters.

Rich Pierce


-----Original Message-----
From: killietalk-bounces+dr_plankton=att_net at aka.org
[mailto:killietalk-bounces+dr_plankton=att_net at aka.org]On Behalf Of
Diane Brown
Sent: Sunday, February 29, 2004 6:09 PM
To: killietalk at aka_org
Subject: [Killietalk] odd things in my spawning tank


After removing some j floridae from my spawning tank, and taking the
java moss and putting it into another tank where any eggs could hatch
undisturbed, I wondered whether there might be any eggs in the deep
layer of mulm on the bottom of the tank--I was going to change all the
water but didn't want to throw out any eggs if there were a few in
there.  Using my 2X or so magnifying visor, I peered at detritus but
didn't see any eggs.  I didn't see any by eye, so took a sample to play
with under the microscope here at work, and I again found no killie
eggs, but there were some other interesting critters instead.

I put pics of two types on my AKA gallery site (album:  Diane's Live
Food Cultures, last three pics), in case some clever person on the list
can tell me what they are.  I am just curious--I presume they're part
of the normal fauna of the aquarium and aren't pathogenic.

One group were quick, darting little transparent critters that I didn't
see until I had them under the microscope. They look a little like a
flea but were clearly aquatic.  Some of them appeared to be trailing
(incubating?) eggs.  They ranged from about the same size as baby brine
nauplii to a quarter or less of their size (maybe tasty first bites for
fry?).  These I labelled the "fast swimmers".

Another group were ovoid, gray, swimming in little bursts, and when
viewed under transmitter light, quite transparent except for a few
bands of pigment oriented transversely.  They have what looks like a
"seam" down their longitudinal axis.  And they have lots and lots of
cilia.  Some were a little larger than a freshly hatched baby brine,
and some were quite a bit smaller.  These I labelled the "slow
swimmers", because although they swam quickly, they were easier to
catch than the "fast swimmers".

Anybody recognize these animalacules?

Diane Brown in St. Louis

P.S.  Now that my campus network is on good terms with aka.org, I also
put the pictures of my synthetic white worm cultures up, the ones I
posted about a few weeks ago that were getting fungus.



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