die off of zebrafish babies
kacergis at box-k.nih.gov
Wed Sep 27 15:11:45 EST 2000
Here is the mystery:
We have been experiencing a random die-off of juvenile zebrafish
that began back on August 31. These fish have a wide range of
backgrounds, from wild types to carriers of severe mutations. The
majority of tanks die overnight but some died within three hours.
Occasionally, one or two survivors have been found and placed into
a fresh tank, but these typically died within a few hours.
The fish system:
MBI zebrafish system with 2500+ 2-liter tanks. System has been
operational for over three years. The water source comes from city
water run through an RO filter. If it were a system problem, one
would expect to see the die-off throughout the entire system.
The majority of mortalities were confined to the right half of one Z-
mod used to raise baby zebrafish. The entire baby section consists
of two adjacent Z-mods. A Z-mod consists of a six-shelf rack that
houses 14, 2-liter fish tanks per rack. Babies consist of fish aged 5-
40 days post fertilization. The majority of the deaths occurred in
tanks housing 30-day-old fish. Water exchange to these tanks was
done twice daily for 15 minutes prior to feeding with AZ 100 and
"baby brine". Tanks are siphoned 3 times per week.
All old feed has been replaced by new stock.
Just recently, die-off has been seen in the adjacent Z-mod.Thinking
that there was a correlation to location, we moved babies to
another location in the facility. Despite the move, five more tanks of
fish died in the new location.
Under the dissection scope, we saw protozoa in tremendous
numbers inside the zebrafish carcasses. These protozoa were
identified as Tetrahymena. We are not sure if these protozoa are
responsible deaths or just opportunistic feeders.
Has anyone experienced a similar sudden die-off of fish within the
30-day-old range? Could Tetrahymena lethally effect babies without
Could the problem be bacterial? What are normal quantitative levels
for bacteria in fish systems? We have no base line data to make a
Kacergis at nih.gov
Laboratory of Molecular Genetics
NICHD, Building 6B, Room 315
National Institutes of Health
Bethesda, MD 20892
E-mail kacergis at box-k.nih.gov
More information about the Zbrafish