A new study, conducted in a lab by scientists from the U.S. Geological Survey, led by USGS genomics researcher Dr. Laura Robertson revealed that largemouth bass injected with estrogen produced lower levels of hepcidin, an iron-regulating hormone that may also act as an antimicrobial peptide in mammals, fish and frogs. These antimicrobial peptides are the first line of defense against many disease causing bacteria and some viruses and fungi in vertebrates.
For hundreds of years, humans have released countless numbers of synthetic compounds into the environment. Many pharmaceuticals, cleaning products, cancer treatments and pesticides are known endocrine disruptors and have disastrous effects on fish populations.
Endocrine disruptors that mimic estrogen hormones have a severe impact on fish fertility and reproduction. They can lead male fish to undergo feminization, a process where males turn into females. They experience a serious decrease in testosterone level and many male fish are found with immature female eggs in their testes. Exposure to estrogen does not stop with the intersex problem. It also reduces production of immune-related proteins in fish which makes them more susceptible to disease.
“Our research suggests that estrogen-mimicking compounds may make fish more susceptible to disease by blocking production of hepcidin and other immune-related proteins that help protect fish against disease-causing bacteria,” said Robertson.
USGS researchers Drs. Vicki Blazer and Luke Iwanowicz have documented intersex occurring in fish in the Potomac and Shenandoah rivers. It is likely that the fish lesions and fish kills found in the same area are not due to coincidence but, instead, due to the effect of endocrine disruptors on hepcidin.
Copyright © 2009 by Marine Science Today, a publication of OceanLines LLC