[Zbrafish] help with parasite infecting embryos

David G. White via zbrafish%40net.bio.net (by dgw5079 from u.washington.edu)
Thu Jul 31 17:47:33 EST 2008

The little filaments are most likely fungal hyphae, saprolegnia etc and would come more problematic with a broken UV. One method of treating the embryos would be using methylene blue, which can be found at any pet store. Add enough to your egg medium until it turns blue. There is a few draw backs to methylene blue. It will kill bacterial beds so do not want to use it on any kind of water recirculating nursery with a biofilter. Also it can stain cells blue. The fungal spores will exist in your fish system water even with a fully-functioning UV.

If you use spawning cages you can try setting up your fish later in the day, so that you reduce the amount of fecal matter deposited in the cages with the eggs. We collect the eggs promptly in the morning. Pour the eggs through a 200 um screen and rinse them with fresh egg water in to a petri dish. Under the scope remove all debris and any infertile eggs. Good eggs should be perfectly round with a dark round yolk. If your not certain if the egg is good or not I would remove it because a few bad eggs can spoil the whole lot. The next day look over the eggs again, and clean if necessary. We do not use methylene blue.

You also might want to increase maintenance on your UV, replacing the bulb and cleaning the quartz sleeve or perhaps up-sizing it.

Good luck

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, 31 Jul 2008, lampe1 wrote:

> Hello!
> In our zebrafish facility, we frequently have embryos infected with
> some sort of parasite. It looks like little filaments of cotton which
> surround the embryo. When this happens, the embryos usually die within
> 24-72 hours. Usually bleaching (according to ZFIN protocol--0.1mL 5%
> sodium hypochlorite in 170mL system water, bleach 5 min, system water
> 5 min, bleach 5 min, rinse 2+ times in system water) and replacing the
> water stops this and saves the embryos.
> Recently, this parasite has been worse (likely due to our UV
> sterilizer being broken for ~1 week). One person in the lab bleached
> the embryos and rinsed them several times and yet they still all died
> and were infected with this parasite.
> Does anyone have any idea what this parasite may be? I am having
> trouble since I have no idea what kind of organism it even is. Does
> anyone have any ideas for other ways to bleach/otherwise save embryos?
> I appreciate any help!
> Thanks,
> Rebecca Lampe
> Fish Care Technician
> UMBC Department of Biology
> lampe1 from umbc.edu
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