[Zbrafish] Unfertilized eggs

Heather S McAllister hmcallis at Princeton.EDU
Fri Aug 11 11:14:07 EST 2006

I took some of the suggestions I previously the, and it seems that our largest facility is back to normal.  The fish are laying great.  These are all our mutants.  However, the room where we keep our wildtypes as well as the larvae have stopped laying almost altogether.  For instance, last night I set up 24 tanks and 5 laid, which is well below what we have previously experienced.  Two of these clutches were unfertilized, and one consisted of 12 eggs, and the other two were unhealthy.  This problem seems to be repeated on a daily basis.  The fish I set up have previously laid great clutches, even up to about a month ago.  Most were about a year old, though some were younger.  I set up WIKs, TLs, Nacres, and ABs.  The WIKs I didn't expect to lay that well.  I also set up 28 tanks in our quarantine room, and two laid, unfertilized clutches.  Again, they are pairs that previously laid well.  I am unsure the age of most, but at least 3 pairs were less than a year old.  

All of our rooms are supplied with R.O. water from the same system.  We have an AHAB system, with 1L (between 1 and 4 fish), 2.75L (between 10 and 20 fish) and 9L (up to 50 fish), but the density of fish in the tanks are about the same in both rooms.  We monitor the water quality with a YSI system.  The pH is generally around 6.8 and the conductivity between 300 and 600.  The temperature in the main facility is about 28 degrees, while the wildtype room and the quarantine room are about 30 degrees (I know this is a high temp, but it has been consistently higher, so I am inclined to think that isn't the issue.)  I test the NH3, NO2 and NO3 once a week, and the nitrate is the only one that is ever elevated, and no more than 30 ppm.  As far as I know, the town hasn't changed the method of treating the water (but both rooms use the same water).  The light cycle has an alarm so that we will know if they are staying on all night (we previously had that problem), plus people are som
etimes down there when the lights go out, so I am confident that is not the problem.  The only other difference between the two rooms is the lighting.  The main facility has lower lighting than the wildtype room, mainly because there are more racks arranged differently.  We feed Zeigler food in the morning and brine shrimp in the afternoon, but I think the breeding has improved since we switched to the Zeigler's.

Another thing that is making this frustrating is that when wildtype males are taken from that WT room to be bred with a mutant female in the main room, the eggs are almost always fertilized.  When WT are incrossed, more often than not whatever clutches are laid are unfertilized.  They are set up about once a week.  We do a lot of injecting in our lab and this is really starting to impact the research.  Any suggestions would be greatly appreciated.  
I apologize for the length of this submission, but I hope that I have provided all the information one might need to know.  Thanks.

Heather McAllister 
Research Specialist 
Burdine Lab 
Molecular Biology 
Princeton University 
Washington Rd. 
Princeton, NJ 08544 

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