The use of triploids in salmon farming has been debated for a while, as these fish – being sterile – pose less of threat to wild salmon populations should they escape. They have also, in some cases, been shown to grow more rapidly that diploids. However, the performance of triploids has been questioned, in particular when these fish are exposed to higher water temperatures.
As the scientists behind the new research explain, “marine organisms living at low temperatures tend to have larger genomes and larger cells which suggest that these traits can be beneficial in colder environments. In fish, triploidy (three complete sets of chromosomes) can be induced experimentally following fertilization, which provides a model system to investigate the hypothesis that larger cells and genomes offers a physiological advantage at low temperatures.”
The researchers tested this hypothesis by measuring metabolic rates and swimming performance of diploid and triploid Atlantic salmon (Salmo salar) post-smolts acclimated to 3 or 10.5 °C.
Their results showed that, at 10.5 °C, triploids had significantly lower maximum metabolic rates, which resulted in a lower aerobic scope compared to diploids. In addition, triploids initiated ram ventilation at lower swimming speeds, providing further evidence of a reduced capacity to meet oxygen demands during strenuous activity at 10.5 °C.
However, at 3 °C, metabolic rates and critical swimming speeds were similar between both ploidies, and – as expected – substantially lower than at 10.5 °C.
The researchers conclude that, as a result, “triploidy in colder environments did not provide any advantage over diploidy in terms of metabolic rate traits or swimming performance in Atlantic salmon”.
This leads them to speculate that “traits, other than aerobic scope and swimming performance, contribute to the trend for increased cell and genome size in marine ectotherms living in cold environments.”
Further information
The full article has been published in the Journal of Thermal Biology under the title, Is it advantageous for Atlantic salmon to be triploid at lower temperatures?
