An endocrine disruptor is a term given to chemicals that, when absorbed into the body, either mimic or block hormones. Some chemicals that are released into the environment can have this harmful effect, particularly on the sexual development of humans and other wildlife.
A test that studies changes in the sexual development of fish is currently used to indicate whether a chemical has the potential to cause harm. International guidelines state that typically 800 fish should use per chemical when using zebrafish, the Japanese medaka and the three-spined stickleback.
I believed that this number could be reduced by 25% in any of these fish, which eventually led to a change in the guideline. But by using the stickleback exclusively for this test, our research showed the number could be reduced by 50%, to just 400 fish per test chemical.
Sticklebacks are the best option for testing
The three-spined stickleback is a small teleost fish species. Habitats stretch from full marine to freshwater bodies across the whole of the Northern hemisphere. It is one of the few endemic and ubiquitous species in Europe that offers scope for environmental monitoring.
It has a number of advantages as a model species in ecotoxicology as sticklebacks are:
- small, easy to keep and can reproduce under laboratory conditions.
- sensitive to environmentally relevant levels of contamination.
- unique traits for the detection of endocrine-disrupting chemicals, such as a genetic sex marker and a xenoandrogen-specific endpoint (the kidney glue protein, spiggin).
- Has a fully sequenced genome and number of molecular resources exist, such as microsatellites and cDNA microarrays.
Over 6 years of tests using grant funding
We have been conducting research for a number of years using stickleback. It started in 2008, when I received a grant worth nearly £400,000 from the NC3Rs. They supported our research into endocrine-disrupting chemicals, which also focused on reducing the number of animals used in ecotoxicological testing.
Government plans to reduce using animals in testing
A delivery plan to support the Coalition’s commitment of “Working to reduce the use of animals in scientific research” was published last week. Cefas features prominently due to the leading work we have delivered in reducing the use of animals across all our testing. This includes toxin testing, new procedures to reduce numbers of fish in experiments, and our moving away from death as an end-point in experiments. It is excellent to see these plaudits for Cefas at a national level.
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