The first studies in daily rhythms of fish microbiomes shows that disrupting their body clocks is bad for their health

New research involving several English universities reveals data of great importance for the aquaculture industry: the body clocks of rainbow trout shape daily rhythms of their immune system and the microorganisms that inhabit their skin.

Keeping fish under constant light – often used by fish farms to enhance growth or control reproduction – disrupts these daily rhythms and leads to increased susceptibility to parasites.

This work by researchers at Bangor, Cardiff and Aberystwyth Universities, recently published in the journal Microbiome, demonstrates how important understanding the “chronobiology” of animals is for maintaining their health.

Lead author Amy Ellison, a lecturer at Bangor University’s School of Natural Sciences explains: that “rainbow trout have daily or ‘circadian’ rhythms in their immune activity and these rhythms appear to shift the composition of the microbial communities which live on their skin over day-night cycles. These fish skin ‘microbiomes’ are a first line of defence against invading parasites and pathogens, so this could be very important for their health.”

“We found that raising fish under continuous light severely impacted the timings of their immune system and microbiomes. Worryingly, when infected with parasitic skin lice, fish under constant light were less able to rid themselves of infection,” Ellison assures.

Abundance of pathogenic bacteria

Skin lice are a widespread problem in aquaculture. This research also revealed lice infections significantly alter trout skin microbial communities, increasing the abundance of pathogenic bacteria.

In the other hand, the co-author, Jo Cable, from Cardiff University School of Biosciences commented that “this is the first study to look at the daily rhythms of fish microbiomes. There is increasing interest in the aquaculture industry to maintain ‘healthy’ microbiomes in farmed fish to improve their disease resistance. However, current farming practices could have unintended consequences for fish health.”

In his part, the other co-author of the study, David Wilcockson from Aberystwyth University Institute of Biological, Environmental and Rural Sciences added that “chronotherapies – the appropriate daily timing of vaccines and other treatments – is beginning to revolutionize human medicine. But this is yet to be applied to farmed animals. Our study raises the possibility similar approaches could be used to help maintain fish health and welfare on farms.”

This study is part of a BBSRC Discovery Fellowship funded project for Biotechnology and Biological Sciences Research Council to investigate the chronobiology of fish, their parasites and microbiomes.

BBSRC is part of UK Research and Innovation, a new body which works in partnership with universities, research organisations, businesses, charities, and government to create the best possible environment for research and innovation to flourish.

They aim to maximise the contribution of each of their component parts, working individually and collectively. “We work with our many partners to benefit everyone through knowledge, talent and ideas”, they say.

BBSRC invests in world-class bioscience research and training that is helping society to meet major challenges, including food security, green energy and healthier, longer lives, underpinning important UK economic sectors such as farming, food, industrial biotechnology and pharmaceuticals.

The BBSRC supports projects for researchers that have completed a successful PhD by 30 November 2021. “Your project’s full economic cost (100% fEC) can be up to £500,000. We will fund 80% of this (£400,000). Your host research organization must agree to fund the rest”, they explain.

The professionals applicant must show that have potential to become a future research leader; wish to conduct their own independent research within a host lab; and wish to gain leadership skills. “Also your project must be within the remit of BBSRC. We encourage projects that fit BBSRC’s strategic priorities.”

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