Irradiation of rainbow trout at early life stages results in legacy effects in adults

Abstract

Purpose: Communication of signals from irradiated to non-irradiated fish has been demonstrated by our group for adults. Major questions are however, whether the effects persist for significant lengths of time (meaning there are memories or legacies of the exposure) and whether they are induced in young animals or very early stages in the life cycle.

Methods: To address these questions we used a reporter cell clonogenic bioassay to detect the effects of radiation exposure and of ‘bystander’ signals, emitted from irradiated fish, on non-irradiated fish. The legacy of radiation exposure or receipt of bystander signals was investigated in rainbow trout irradiated as eggs at 48 h, eyed eggs at one month, yolk sac larvae (YSL) at two months and juveniles at three months after fertilisation. The irradiated and bystander fish together with shams and unhandled husbandry controls were grown on in a hatchery and examined as they reached each of the remaining life stages. They were also re-examined as one-year-olds with and without further irradiation and finally examined as sexually mature two-year-olds.

Results: The data indicate a clear legacy effect of irradiation at any early life stage in the adult fish.

Conclusion: The data suggest that bystander signals can be transmitted in vivo and once induced are persistent during the animals' lifespan.

Keywords:

• low radiation dose effects
• bystander effects
• adaptive response
• fish radiobiology
• life stage effects

Acknowledgements

We acknowledge funding from the Natural Sciences and Engineering research Council (NSERC) Industrial Chairs Programme, Canada Deuterium Uranium (CANDU) Owners Group, Bruce Power, The Canada Chairs Programme. We also acknowledge our participation as non-funded third country partners in the European Union's Non Targeted Effects integrated project (NOTE). Finally we would like to express our grateful thanks to Michael Burke, David Bevan, Michael Kirk and Neil MacBeth, Alma Aquaculture Research Station, University of Guelph, for the rearing and husbandry of all the fish used in this investigation.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.