BPA is an endocrine disrupting chemical that is used in a wide range of everyday items, including plastic water bottles, food cans and till slips. It is a harmful contaminant that has been associated with many health issues in both humans and wildlife that are exposed to it. BPA makes its way into the environment, and tends to accumulate in aquatic systems where it can negatively impact aquatic wildlife that live there.
An earlier study conducted by scientists from the University of Missouri-Columbia on painted turtles revealed that BPA disrupts reproductive functioning and can feminize male turtles, causing them to develop female sex organs. In a more recent study, the researchers show how BPA not only physically feminizes male turtles, but it also reprograms the brain, making them exhibit behavioral patterns usually associated with female turtles. The scientists are concerned about the impact this could have on the population status of painted turtles, which could decline as a result.
According to Cheryl Rosenfeld, an associate professor of biomedical sciences in the MU College of Veterinary Medicine and co-author of this study, the initial study showed that BPA and ethinyl estradiol (EE2), a hormone used in oral contraceptives, could reverse the sex of male turtles, changing them into females.
"Painted turtles and other reptiles lack sex chromosomes," she explains. "The gender of painted turtles and other reptiles is determined by the incubation temperature of the egg during development. Studies have shown that exposure to endocrine-disrupting chemicals (EDCs), such as BPA, can override incubation temperature and switch the sex of males to females. In our latest study, we found that BPA also affects how the male brain is 'wired,' potentially inducing males to show female type behavioral patterns."
For their study, the scientists exposed painted turtle eggs to BPA and ethinyl estradiol (EE2) in liquid form, then placed the eggs in an incubator set at a temperature that would typically result in male hatchlings. When the hatchlings were 5 months old the researchers tested their spacial navigation skills to ascertain whether exposure to these chemicals would have any impact on the navigational ability — more specifically, to determine whether their navigational skills would be in line with that expected of females who are better navigators than their male counterparts. The results of the navigational test showed male turtles that were exposed to these hormone disrupting chemicals while still in the egg exhibited better spatial navigational learning and memory skills than male turtles incubated under the same environmental conditions, but which did not get exposed to BPA and EE2 whilst developing in the egg.
"While improved spatial navigation might be considered a good thing, it also may suggest that when they reach adulthood male turtles will not exhibit courtship behaviors needed to attract a mate and reproduce, which could result in dramatic population declines," explains Rosenfeld.
According to Professor Rosenfeld, this study is the first to show how these harmful environmental contaminants not only change the physical sexual characteristics of turtles, but affects brain functioning as well. Turtles are considered an 'indicator species' as they can be used to determine the environmental health of the broader aquatic ecosystem. Gaining a clearer understanding of how these endocrine disrupting compounds affect the sexual behavior and orientation of turtles, may enable scientists to better understand the potential impacts of these chemicals on other animal species, including humans.
The Berkey water filter, equipped with the black berkey filters, will filter out any BPA that may be in the water.
Lindsey K. Manshack, Caroline M. Conard, Sarah A. Johnson, Jorden M. Alex, Sara J. Bryan, Sharon L. Deem, Dawn K. Holliday, Mark R. Ellersieck, Cheryl S. Rosenfeld. Effects of developmental exposure to bisphenol A and ethinyl estradiol on spatial navigational learning and memory in painted turtles (Chrysemys picta). Hormones and Behavior, 2016; 85: 48 DOI: 10.1016/j.yhbeh.2016.07.009