[Zbrafish] Chordal structure Malformation

françois via zbrafish%40net.bio.net (by busquet.francois At gmail.com)
Tue Nov 21 07:51:51 EST 2006

Dear all,
since one week, a third of my fish embryos incubated in fish medium at
26°C,  developed chordal structure malformation like a ,,zigzag"
after 24hpf. I didn't know from which aquarium it comes from because
I collected all the eggs from the boxes in one big petri dishe.
Therefore, I first checked in which aquarium this could come from. I
collected once again fish eggs depending on the aquarium origin and I
incubated the fish eggs in fish medium at 26°C.

Today, I figured out that more than 80% fish embryos displayed again
chordal structure malformation for every aquarium. Moreover, I changed
all the population for one aquarium last weekend and replaced by
younger ones (around 8 months) but in the same water. It didn't make
any differences, the chordal malformation was also for 80% of fish eggs
for this aquarium.

We use a static system where fish medium is totally replaced every 15
days. The fish medium is based on deionized water + CaCl2 + MgSO4
(with Ca:Mg ions is 4:1) + NaHCO3 + KCl (with Na:K ions is 10:1). I
heard that chordal structure malformations could be linked to heavy
metals presence or from some infectious diseases or even vitamin
Any comment are very welcome!
françois busquet
PhD student/ Ecotoxicological Institute/ Merck KgaA/ Germany.

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