Is your dog looking a little too sexy? Is the cat's meow a bit too seductive? Chemicals in the water are causing inter-species mating...at least among fish.
Hormone-mimicking chemicals released into rivers have been found to impact the mating choices of fish, a new study has revealed. The controversial chemical BPA, which emits oestrogen-like properties, was found to alter an individual's appearance and behavior, leading to inter-species breeding. The study, published in Evolutionary Applications, reveals the threat to biodiversity when the boundaries between species are blurred.
The research, led by Dr Jessica Ward from the University of Minnesota, focused on the impact of Bisphenol A (BPA) on Blacktail Shiner (Cyprinella venusta) and Red Shiner (Cyprinella lutrensis) fish which are found in rivers across the United States. BPA is an organic compound used in the manufacture of polycarbonate and other plastics. It is currently banned from baby bottles and childrens' cups in 11 U.S. states.
Red Shiner
Credit: Wikipedia
"Chemicals from household products and pharmaceuticals frequently end up in rivers and BPA is known to be present in aquatic ecosystems across the United States," said Ward. "Until now studies have primarily focused on the impact to individual fish, but our study demonstrates the impact of BPA on a population level."
The team collected individuals of both species from two streams in the state of Georgia. The species were kept separated for 14 days in tanks, some of which contained BPA. On the 15th day behavioral trials were undertaken as individuals from different tanks were introduced to each other.
The scientists monitored any physiological or signalling differences the individuals displayed, such as colour, as well as any behavioral differences during courtship, such as mate choice.
BPA disrupts an individual's endocrine system, which controls the release of hormones. This impacts behavior and appearance, which in turn can lead an individual to mistake a newly introduced species as a potential mate.
This process poses long-term ecological consequences, especially in areas threatened by the introduction of invasive species. BPA and other hormone-mimicking chemicals can escalate the loss of native biodiversity by breaking down species barriers and promoting the invader.
"Our research shows how the presence of these manmade chemicals leads to a greater likelihood of hybridization between species," concluded Ward. "This can have severe ecological and evolutionary consequences, including the potential for the decline of our native species."
Bisphenol A (BPA) is an organic compound with the chemical formula (CH3)2C(C6H4OH)2. It is a colorless solid that is soluble in organic solvents, but poorly soluble in water. Having two phenol functional groups, it is used to make polycarbonate polymers and epoxy resins, along with other materials used to make plastics.
BPA is controversial because it exerts weak, but detectable, hormone-like properties, raising concerns about its presence in consumer products and foods contained in such products. Starting in 2008, several governments questioned its safety, prompting some retailers to withdraw polycarbonate products. A 2010 report from the United States Food and Drug Administration (FDA) raised further concerns regarding exposure to fetuses, infants, and young children. In September 2010, Canada became the first country to declare BPA a toxic substance. In the European Union and Canada, BPA use is banned in baby bottles.
Bisphenol A is a weak endocrine disruptor, which can mimic estrogen and may lead to negative health effects. Early developmental stages appear to be the period of greatest sensitivity to its effects, and some studies have linked prenatal exposure to later neurological difficulties. Regulatory bodies have determined safety levels for humans, but those safety levels are currently being questioned or are under review as a result of new scientific studies. A 2011 study that investigated the number of chemicals pregnant women are exposed to in the U.S. found BPA in 96% of women.
In 2009, The Endocrine Society released a statement citing the adverse effects of endocrine-disrupting chemicals, and the controversy surrounding BPA.
In 2011, the chief scientist of the United Kingdom's Food Standards Agency commented on a study on dietary exposure of adult humans to BPA performed by the EPA, saying, "This corroborates other independent studies and adds to the evidence that BPA is rapidly absorbed, detoxified, and eliminated from humans – therefore is not a health concern." In the study 20 subjects were tested for BPA every hour for twenty-four hours while consuming three meals consisting of canned food.
In 2012 a paper was written in response to this study, however, criticizing the study as lacking data and having flawed assumptions.
Overall, empirical evidence supporting the negative health effects of BPA varies significantly across studies. Opinions vary greatly about the health effects of BPA. Some studies conclude that BPA poses no health risks while others state that BPA causes a number of adverse health effects. In general, the European’s Scientific Committee on Food, the EUs European Chemicals Bureau, the European Food Safety Authority, and the US Food and Drug Administration have concluded that current levels of BPA present no risk to the general population. However, experts in the field of endocrine disruptors have stated that the entire population may suffer adverse health effects from current BPA levels.]Experts advise readers of scientific studies to consider who conducted the study, what their affiliations are, and what the purpose of the study was.
"Chemicals from household products and pharmaceuticals frequently end up in rivers and BPA is known to be present in aquatic ecosystems across the United States," said Ward. "Until now studies have primarily focused on the impact to individual fish, but our study demonstrates the impact of BPA on a population level."
The team collected individuals of both species from two streams in the state of Georgia. The species were kept separated for 14 days in tanks, some of which contained BPA. On the 15th day behavioral trials were undertaken as individuals from different tanks were introduced to each other.
The scientists monitored any physiological or signalling differences the individuals displayed, such as colour, as well as any behavioral differences during courtship, such as mate choice.
BPA disrupts an individual's endocrine system, which controls the release of hormones. This impacts behavior and appearance, which in turn can lead an individual to mistake a newly introduced species as a potential mate.
This process poses long-term ecological consequences, especially in areas threatened by the introduction of invasive species. BPA and other hormone-mimicking chemicals can escalate the loss of native biodiversity by breaking down species barriers and promoting the invader.
"Our research shows how the presence of these manmade chemicals leads to a greater likelihood of hybridization between species," concluded Ward. "This can have severe ecological and evolutionary consequences, including the potential for the decline of our native species."
BPA is controversial because it exerts weak, but detectable, hormone-like properties, raising concerns about its presence in consumer products and foods contained in such products. Starting in 2008, several governments questioned its safety, prompting some retailers to withdraw polycarbonate products. A 2010 report from the United States Food and Drug Administration (FDA) raised further concerns regarding exposure to fetuses, infants, and young children. In September 2010, Canada became the first country to declare BPA a toxic substance. In the European Union and Canada, BPA use is banned in baby bottles.
Bisphenol A is a weak endocrine disruptor, which can mimic estrogen and may lead to negative health effects. Early developmental stages appear to be the period of greatest sensitivity to its effects, and some studies have linked prenatal exposure to later neurological difficulties. Regulatory bodies have determined safety levels for humans, but those safety levels are currently being questioned or are under review as a result of new scientific studies. A 2011 study that investigated the number of chemicals pregnant women are exposed to in the U.S. found BPA in 96% of women.
In 2009, The Endocrine Society released a statement citing the adverse effects of endocrine-disrupting chemicals, and the controversy surrounding BPA.
In 2011, the chief scientist of the United Kingdom's Food Standards Agency commented on a study on dietary exposure of adult humans to BPA performed by the EPA, saying, "This corroborates other independent studies and adds to the evidence that BPA is rapidly absorbed, detoxified, and eliminated from humans – therefore is not a health concern." In the study 20 subjects were tested for BPA every hour for twenty-four hours while consuming three meals consisting of canned food.
In 2012 a paper was written in response to this study, however, criticizing the study as lacking data and having flawed assumptions.
Overall, empirical evidence supporting the negative health effects of BPA varies significantly across studies. Opinions vary greatly about the health effects of BPA. Some studies conclude that BPA poses no health risks while others state that BPA causes a number of adverse health effects. In general, the European’s Scientific Committee on Food, the EUs European Chemicals Bureau, the European Food Safety Authority, and the US Food and Drug Administration have concluded that current levels of BPA present no risk to the general population. However, experts in the field of endocrine disruptors have stated that the entire population may suffer adverse health effects from current BPA levels.]Experts advise readers of scientific studies to consider who conducted the study, what their affiliations are, and what the purpose of the study was.
Contacts and sources:
Ben Norman
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