[Zbrafish] Embryo parisites, coleps, "twirlies"

christian lawrence via zbrafish%40net.bio.net (by clawrence from rics.bwh.harvard.edu)
Mon Feb 4 12:34:17 EST 2008


Gabe -- 

April's advice is very sound, as well as tried and true, so it should
certainly help you solve your problems and earn her the position as your
personal hero.

I would like to add also a bit on egg quality.  To put it simply, egg
quality is directly correlated with the condition of the mother, and to a
somewhat lesser extent, the father.    Many, many factors contribute to
this, but certainly diet and genetics are two of them.  Bad diet = bad eggs.
Bad genetics = bad eggs.  Bad eggs have, among things, smaller and less
complete yolks, and importantly with respect to the myriad opportunistic
animals that lurk in your water, lower quality chorions.  These differences
are often not apparent to the naked eye, and when things are good (i.e. if
you nuke everything else around them with bleach, methylene blue, etc.) they
are not (at least obviously) manifested. The thing is that chorions with
such low integrity are much less able to resist attacks by fungi, ciliates,
bacteria, etc. and render the animal inside much more vulnerable than they
would be if the chorion was of higher quality.  So the readout of this would
be that your eggs get "junky" if you don't do anything or only act minimally
to clean them.

The relationship between parental condition and egg quality, at least in
some respects, is a simple one that matters.  Honestly, you shouldn't have
to jump through hoops to keep your embryos/larvae from being trashed by
animals such as Coleps.  We do very little for our embryos aside from a
brief cleaning on day 1.  In most cases, no egg water, no E3, no bleaching.
But we have very little mortality to speak of early on, although our water
is full of ciliates, including I'm sure, Coleps, although we've never
confirmed their presence/absence.  In many instances, we can simply collect
the eggs on day 0, rinse them in fish water (from an off system source),
stick them in an incubator, and on day 6 they are ready to put on the
system, normally with little attrition.  There is some variation from time
to time, depending on background (the bad genetics reference, above), and
maybe age and clutch size, but in general nothing fancy is necessary to keep
the ciliates et al. at bay.  

What we do spend a ton of time, however, on ensuring that our diet is
selected, administered, and handled/stored properly.  We also work very hard
on ensuring, to the extent that we can, that our stocks are as genetically
diverse, and turned over as frequently (retire them before 15 months) as
possible.  So most of our fish are of relatively decent genetic stock, in
the prime of their reproductive lives, and are, for lack of a better way for
me to put it, "well-fed" with nutritionally complete (as close as we can
get) diets.   I believe that this has a lot to do with the fact that they
produce eggs that are generally much more resistant to the organisms that
are present in all of our systems.

Good luck, 

Chris


Christian Lawrence
Brigham and Women's Hospital
Karp Family Research Laboratories 06-004B
One Blackfan Circle
Boston, Massachusetts 02115
Tel: 617.355.9041
Fax: 617.355.9064

-----Original Message-----
From: zbrafish-bounces from oat.bio.indiana.edu
[mailto:zbrafish-bounces from oat.bio.indiana.edu] On Behalf Of finchg from ohsu.edu
Sent: Thursday, January 31, 2008 8:47 PM
To: bionet-organisms-zebrafish from moderators.isc.org
Subject: [Zbrafish] Embryo parisites, coleps, "twirlies"

____________________________________________________________________________
____

I am looking for more information about coleps.  These are a small protazoa
which parasatize larval zebrafish.  Under a dissecting scope they look like
little transparent hyperactive beans, less than one hundredth the size of a
zebrafish egg, comparable to a zfish blood cell in size.  I am only able to
see them at >5X mag.

-Here's a little mention in an old Zebrafish Science Monitor:
http://zfin.org/zf_info/monitor/vol5.1/vol5.1.html#Coleps,%20Scourge%20of%20
the%20Baby%20Zebrafish

Three seperate zebrafish labs at which I have worked have had minor problems
with these little guys (Perhaps I am the vector, dunno).
-Does anyone know more about these things than what is stated in the article
linked above?  E.g. Life cycle, response to dessication, drugs with which to
kill them?
-Anyone had problems with them that they have overcome?  What strategies
worked?  So far the only good strategy I know of is vigilant dish cleaning.
-We have lately been having problems in dishes which we have bleached, which
is perplexing.  Do other people see them surviving bleaching?
Killed by bleaching?  (We follow the Volhard protocol) -Some folks have
suggested raising water conductivity in our system.
Anyone agree?
-Also, does anyone know if UV can kill these or specifically what levels?

-Anyone offering up advice or results regarding these pesky things will be
my personal hero.

Thanks, Gabe

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