Sammendrag
Atlantic cod is one of the most economically important marine finfish species to be farmed in
Europe and widely consumed in Italy. Precocious sexual maturation has a negative impact on
somatic growth. Indeed, under normal breeding conditions, after precocious maturing and
spawning, the fish need an additional 3 or 4 months to reach a harvestable size. This
significant increase in production time results in major economic losses for the cod farming
industry. It is now well known that continuous light treatment can be used to delay sexual
maturation.
In spite of the wide use of this technique in aquaculture, to date there are no reported studies
on the health of fish exposed to these unnatural light conditions . It is therefore intuitive to
ask if these rearing conditions have some negative effect on the health status and quality of
the fish.
In this study we investigated how continuous light affects cod health by using a set of stress
biomarkers on two groups of juvenile Atlantic cod reared under different photoperiod
conditions. One group was kept under continuous illumination, whereas the other was reared
under a light regime that corresponded to natural photoperiod conditions in Bodø (Norway, 6
7°N) from January to July 2010.
Immunohistochemistry and gene expression quantification by real-time PCR revealed that
expression levels of enzymes that detoxify free radicals are higher in fish reared under
continuous illumination. Apoptotic activity was more pronounced in these fish and efficiency
of the immune system seems compromised, probably by low levels of melatonin due to the
absence of darkness. Neurotransmission also seems altered in juveniles exposed to
continuous light compared to natural light conditions. These data have been integrated with
miRNA profiles between the two different light conditions.
Vis fullstendig beskrivelse