Creating value
2013
nofima.no
24
Senior Scientist Aleksei Krasnov uses this microarray scanner to measure the expression of thousands of genes at the same time.
photo: Jon-Are Berg-Jacobsen © nofima
“The methods are based on microarrays that enable us
to study expression of thousands of genes at the same
time,” says Senior Scientist Aleksei Krasnov. “The aim
of this research is to find what the genes can tell us
about fish health and to identify differences in the gene
expression of healthy versus sick fish.”
Have mapped genetic resistance to salmon lice:
Salmon lice is currently dealt with largely by treating fish
with medications. However, there is a strong desire to
use biological methods (e.g. wrasse) or breeding of fish
with increased resistance to lice.
“We didn’t know why some fish were more or less
resistant to lice before we performed the analyses of the
gene impressions,” says Krasnov.
He now has a better understanding of why some
salmon are more easily infected by lice than others. The
scientists conducted challenge experiments to iden-
tify the genes that control resistance to salmon lice.
Nofima has established a lice infection model at Tromsø
Aquaculture Research Station, which was used in the
experiment. The fish were divided into three groups.
One group received feed containing the sex hormone
testosterone, the second received estrogen and the third
was a control group. When the feeding ended, the fish
were pooled and infected.
“It was proven that salmon fed estrogen were far
more resistant to lice, and analyses of the gene expres-
sions showed specifically which genes were important
to increase this resistance,” says Krasnov.
However, there are many reasons, both ethical and
commercial, why giving fish estrogen to increase resist-
ance will never be an option, including the fact that
estrogen leads to earlier onset of sexual maturation.
Sex hormones were used only as a tool to identify the
genes that changed expression, and the changes in gene
expression indicated which genes contribute to increas-
ing resistance to salmon lice.
Scientists at Nofima are using a recently developed genomic tool to
identify why some salmon are more resistant to lice than others.
Studying fish health via genes
