Triploid Atlantic salmon, temperature, early development, and the potential for epigenetic programming

Abstract

Triploidy is the only technique approved for inducing sterility in fish intended for human consumption. To increase the environmental sustainability and public perception of the aquaculture industry, scientific understanding of triploids must increase, assumptions must be challenged, and the additional costs linked with triploid production must be reduced. The gap between triploids and diploids in terms of performance is shrinking, but temperature tolerance remains a significant hurdle. In this thesis we aimed to tackle some of these issues. A suite of microsatellites was developed to verify triploidy, a protocol was established for extracting usable DNA (Deoxyribonucleic acid) from embryos between 26-78 degree days. In combination, these tools can reduce the cost and resources related with triploidy validation. The held assumption that triploids develop at the same rate as diploids during embryogenesis was validated; although differences in the timing of hatch were observed, with triploids hatching earlier. Optimal cleaning solution was determined, providing a useful tool for further studies. Triploidy was shown to have no significant negative impact on health or performance after thermal shocks at around 360 degree days, providing more support for the acceptance of triploids. Triploids performed well incubated at 4°C till eyeing and 6°C until hatch, with only a slight differential in radiological vertebral abnormalities found and no ploidy difference in mortalities or other malformations. Transcriptomic analysis after embryonic thermal shock and during thermal challenge later in life improved scientific understanding of triploids, revealing slight the differences between ploidy. Epigenetic analysis revealed triploids increased variability in the case of DNA methylation patterns. The potential of thermal programming to improve temperature tolerance was first demonstrated in a fish species, with shocked triploids experiencing increased growth under thermal stress. Raising the exciting prospect of not only removing a major barrier in triploid acceptance, but also providing a vital tool as the aquaculture industry faces rising temperatures worldwide.