A new study led by researcher Jessica Ward suggests that certain hormone-mimicking chemicals can cause interspecies reproduction, according to a University of Minnesota news release.
The chemical, called Bisphenol A (BPA), is used in the production of some synthetic materials such as polycarbonate. According to the National Institute of Environmental Health Sciences, BPA is found in a number of materials including food and drink packaging (water and infant bottles), compact discs, impact-resistant safety equipment, and medical devices. BPA can also be found in metal products such as food cans, bottle tops, and water supply pipes. The NIEHS says that some dental sealants and composites may also contribute to BPA exposure.
BPA, currently banned from use in baby bottles and children’s cups in 11 states, sometimes ends up in rivers and can adversely affect populations of fish. Ms. Ward’s study examined the impact of BPA on fish populations in rivers with BPA. For humans, the NIEHS says that the primary source of BPA exposure is through what one eats. However, air, dust and water are also possible sources of exposure.
BPA has significant estrogen-like properties. Estrogen is a major female sex hormone in a number of species, including humans. BPA’s functional resemblance to estrogen can alter the appearance and mating behavior of fish. In particular, the study focused on the Blacktail Shiner and the Red Shiner, two fish species present in a number of rivers throughout the United States.
“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. Until now studies have primarily focused on the impact to individual fish, but our study demonstrates the impact of BPA on a population level,” Ms. Ward says.
The chemical acts quickly. Ms. Ward’s project involved isolating individuals of the two species and keeping the different species in separate tanks for 14 days. Some of the tanks contained BPA while others did not. After 14 days, Dr. Ward and her team examined the fish for physiological changes and introduced individuals of different species to each other. These experiments demonstrated that fish exposed to BPA sometimes mistake members of different species as potential viable mates.
This case of species misidentification occurs because BPA can disrupt a fish’s endocrine system. The endocrine system controls the release and management of signaling molecules or hormones that can affect an animal’s behavior and appearance.
The study, published in Evolutionary Applications, also reports on possible ecological implications for this kind of cross-species confusion. It could, for instance, damage biodiversity by breaking down species barriers. This could be a particularly significant problem when invasive species are involved. If native species start to mate with invasive species, they may grant the invasive species a foothold in a new habitat. This can prevent a major risk to other species living in that habitat, especially if the invader relies on similar sources of food.
Ms. Ward warns that this kind of interspecies interaction has “the potential for the decline of our native species.”