Impact of circadian entrainment on immune function in Atlantic salmon (Salmo salar)
Purpose:
An endogenous biological oscillator, known as a circadian (24 h) rhythm, drives daily cycles of physiology, including the immune response. This biological rhythm needs to be synchronized with the daily environment, and for most organisms, the most important synchronizing factor is the daily light / dark cycle (Ref1). Disturbance of the daily light / dark cycle can disrupt the circadian rhythm and negatively affect the physiological outputs it controls (Ref2). In mammals, light driven disruption of the circadian clock by exposure to constant light negatively effects the immune response (Ref3). However despite the fact that constant light is used routinely in aquaculture, the relationship between light, circadian rhythms, and immune function is unexplored in salmonids.
To address this knowledge gap we here apply for an experiment to compare the immune responses of Atlantic salmon smolts produced using two comparative lighting environments. One group will be housed under typical constant light used in aquaculture smolt production. The second group will be kept under a simulated summer photoperiod of long days and short nights. Once smolt status is established we will challenge the immune responses of the groups using an intraperitoneal SAV3 treatment, and compare the impact of the treatment by longitudinal sampling of the two populations.
Distress:
The cohort of SAV3 treated fish will experience sub-lethal pathology associated with SAV3 infection.
Expected Benefit:
In Norway alone, over 50 million salmonids are lost in aquaculture production each year. Many of these fish due from disease. Improved understanding of how the aquaculture environment shapes the immune system in salmonids may drive significant improvements in the survival, health and wellbeing of farmed fish.
Number of Animals, what kind:
We will use 320 Atlantic salmon (Salmo salar).
How to adhere to the 3Rs:
Replacement -
There are no alternatives to the use of live animals as we must imitate what happens in Norwegian salmon farming.
Reduction -
We have performed a power analysis using data from previous experiments. This analysis gives us confidence that we use the minimum quantity of animals in our experiment to make confident assessments of immune status.
Refinement -
Anesthesia/analgesia: For viral / control challenge, fish will be anaesthetized during the procedure using benzocaine (60ppm) in tank water. Benzocaine is also a local anesthetic which will alleviate any immediate discomfort.
Endpoints: Fish will be monitored for evidence of difficult in swimming, buoyance or balance. Fish which do not reestablish equilibrium after challenge will be euthanized.
Sampling techniques: terminal blood sampling will be performed under anesthesia (benzocaine 60ppm) followed by immediate euthanasia by decapitation.
Ref1 Koronowski and Sassone-Corsi, “Communicating clocks shape circadian homeostasis” Science. doi: 10.1126/science.abd0951.
Ref2 Martino et al., “Circadian rhythm disorganization produces profound cardiovascular and renal disease in hamsters” Am. J. Physiol. Regul. Integr. Comp. Physiol. doi: 10.1152/ajpregu.00829.2007.
Ref3 Mizutani, Tamagawa-Mineoka, Minami, Yagita, and Katoh, “Constant light exposure impairs immune tolerance development in mice” J. Dermatol. Sci. doi: 10.1016/j.jdermsci.2016.12.016.
An endogenous biological oscillator, known as a circadian (24 h) rhythm, drives daily cycles of physiology, including the immune response. This biological rhythm needs to be synchronized with the daily environment, and for most organisms, the most important synchronizing factor is the daily light / dark cycle (Ref1). Disturbance of the daily light / dark cycle can disrupt the circadian rhythm and negatively affect the physiological outputs it controls (Ref2). In mammals, light driven disruption of the circadian clock by exposure to constant light negatively effects the immune response (Ref3). However despite the fact that constant light is used routinely in aquaculture, the relationship between light, circadian rhythms, and immune function is unexplored in salmonids.
To address this knowledge gap we here apply for an experiment to compare the immune responses of Atlantic salmon smolts produced using two comparative lighting environments. One group will be housed under typical constant light used in aquaculture smolt production. The second group will be kept under a simulated summer photoperiod of long days and short nights. Once smolt status is established we will challenge the immune responses of the groups using an intraperitoneal SAV3 treatment, and compare the impact of the treatment by longitudinal sampling of the two populations.
Distress:
The cohort of SAV3 treated fish will experience sub-lethal pathology associated with SAV3 infection.
Expected Benefit:
In Norway alone, over 50 million salmonids are lost in aquaculture production each year. Many of these fish due from disease. Improved understanding of how the aquaculture environment shapes the immune system in salmonids may drive significant improvements in the survival, health and wellbeing of farmed fish.
Number of Animals, what kind:
We will use 320 Atlantic salmon (Salmo salar).
How to adhere to the 3Rs:
Replacement -
There are no alternatives to the use of live animals as we must imitate what happens in Norwegian salmon farming.
Reduction -
We have performed a power analysis using data from previous experiments. This analysis gives us confidence that we use the minimum quantity of animals in our experiment to make confident assessments of immune status.
Refinement -
Anesthesia/analgesia: For viral / control challenge, fish will be anaesthetized during the procedure using benzocaine (60ppm) in tank water. Benzocaine is also a local anesthetic which will alleviate any immediate discomfort.
Endpoints: Fish will be monitored for evidence of difficult in swimming, buoyance or balance. Fish which do not reestablish equilibrium after challenge will be euthanized.
Sampling techniques: terminal blood sampling will be performed under anesthesia (benzocaine 60ppm) followed by immediate euthanasia by decapitation.
Ref1 Koronowski and Sassone-Corsi, “Communicating clocks shape circadian homeostasis” Science. doi: 10.1126/science.abd0951.
Ref2 Martino et al., “Circadian rhythm disorganization produces profound cardiovascular and renal disease in hamsters” Am. J. Physiol. Regul. Integr. Comp. Physiol. doi: 10.1152/ajpregu.00829.2007.
Ref3 Mizutani, Tamagawa-Mineoka, Minami, Yagita, and Katoh, “Constant light exposure impairs immune tolerance development in mice” J. Dermatol. Sci. doi: 10.1016/j.jdermsci.2016.12.016.