New research from the University of Exeter and King's College London has shown how a population of brown trout can survive in the contaminated waters of the River Hayle in Cornwall where metal concentrations are so high they would be lethal to fish from unpolluted sites. The team believe this is due to changes in the expression of their genes. The research was funded by NERC and the Salmon and Trout Association.
The researchers compared the trout living in the River Hayle with a population living in a relatively clean site in the River Teign. The results showed that the accumulation of metals in the kidney and liver where metals are stored and detoxified - were 19 and 34 times higher in the Hayle trout, respectively. In the gill, concentrations averaging 63 times higher were present in the Hayle fish, but there were no differences in metal content in the gut. This accumulation of metals in the Hayle fish highlights their extraordinary tolerance of the extreme metal concentrations in their environment.
In order to investigate how the Hayle brown trout are able to tolerate such high levels of metal exposure, and also look for potential signs of toxicity, advanced high throughput sequencing was conducted at the Exeter Sequencing Facility to sequence the genes and then measure changes in their expression between the two river sites. The gene encoding a protein, metallothionein, responsible for binding, storing and detoxifying a number of metals, was found to be highly expressed in the River Hayle trout, indicating its importance in their ability to tolerate metals in their environment. Evidence of the presence of other metal-binding and transporting proteins, particularly those responsible for handling iron, was also found.
Usually metals cause toxicity in fish by causing oxidative damage and disrupting the balance of ions in the body. The team found evidence that to counter this toxicity, Hayle fish showed changes in genes responsible
|Contact: Dr. Johanna Bowler|
University of Exeter