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[Zbrafish] Fungi in Zebrafish embryo

David G. White dgw5079 at u.washington.edu
Thu May 4 13:05:59 EST 2006

The scope of your question is a bit ambiguous, but to add to what was already written, clean your petridishes or 
whatever container you use to collect embryos. You often see fungal hyphae arise from fecal matter and unfertilized 
eggs (unfertilized eggs are darker and often appear to have an erupting egg yolk) deposited along with the embryos. After 
you collect the embryos thoroughly clean them, transfer them to a new petridish and top it off with embryonic medium. 
Methylene blue works, but is not necessary, it can stain cells and can kill a fish systems biofilter, which could lead to a 
whole other set of problems.

I have not heard of "white mosquito larvae" many labs use paramecium or rotifers. Either way make sure your not 
overfeeding, and your culture is clean. Check to see if there is a lot of mosquito larvae still with the fish an hour  after 
feeding if so you might be overfeeding (or in the case of really young fish be sure that they can actually digest 
their food, too big etc).

Some fungi are common in adult housing systems, such as saproglegnia, but nursery containers need to be clean.

David G White
Research Coordinator
H225 Zebrafish Lab
University of Washington
Department of Biological Structure
HSB G514 Box 357420
1959 NE Pacific Street
Seattle, WA  98195-7420
Tel. 206-685-7512
FAX 206-543-1524

On Thu, 4 May 2006, christian lawrence wrote:

> By "fish embryo culture", what do you mean exactly?  Eggs and newly hatched
> larvae before they go on a system?  Your nursery?  Or your adult holding
> system?  In any event, fungal contamination usually arises as a result of an
> abundance (or overabundance of decaying organic matter.  Throw in warm
> temperatures, and you have a very fungi-favorable environment. Typically, if
> you reduce waste, you can go a long way to reduce fungal contaminations.
> Other issues play into it as well.  If the fungus is attacking embryos and
> larvae - or even adults, you should consider that fish of poorer quality,
> whether or not this comes about as a result of bad genetics, unfavorable
> environment, poor diet or a combination of those factors, are also less able
> to fight off infestations.
> Hence, the rampant use of methylene blue in many zebrafish culture
> facilities.   There is no need for such an additive if your fish are robust
> (and you are not deliberately manipulating them in some way that stresses
> them, in which case it may be necessary).  So yes, I am suggesting that
> either 1)conditions in many culture facilities that use m.b. are unfavorable
> or 2) people use it for no reason aside from the pretty color and feeling of
> security that it provides them.  But that is another issue for another
> discussion.
> Simple answer to complex question is if you reduce your waste input and
> ensure that your husbandry is scientifically sound, you should not have to
> worry much about fungus.
> 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 at oat.bio.indiana.edu
> [mailto:zbrafish-bounces at oat.bio.indiana.edu] On Behalf Of françois
> Sent: Thursday, May 04, 2006 5:13 AM
> To: bionet-organisms-zebrafish at moderators.isc.org
> Subject: [Zbrafish] Fungi in Zebrafish embryo
> Hello,
> I have a fungi contamination in my fish embryos culture. I was thinking that
> it might be related with the fish food. In our facilities, fishes are daily
> fed with " weiße Mückenlarve" which could be approximately translated as
> "white mosquito larvae".
> I don´t know if any of you worked with this and if it is really suited for
> mature zebrafish. I am open to any commentary!
> françois
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