Environmental contaminants, climate change, and amphibian development and plasticity.

 

Recently, we have been discussing vertebrate sex determination and the diverse mechanisms that have evolved to control and regulate these important developmental decisions. Traditionally, many vertebrate species have been governed by genetic sex determination (GSD) or environmental sex determination (ESD). However, several studies have found that in many species both GSD and ESD mechanisms operate simultaneously in response to a broad range of heritable and environmental factors. This is thought to be the case for many amphibian species. One aspect of this that I find particularly interesting is the role of environmental contaminations and how they may modify the traditional amphibian sex ratios and the mechanisms of sex determination.  

 

A paper published in 2016 by Max Lambert and colleagues entitled “Interactive effects of road salt and leaf litter on wood frog sex ratios and sexual size dimorphism” had me thinking about the role of not only organic but also inorganic chemical contaminants on vertebrate development. Additionally, a recent paper published in 2021 by Sagan Leggett and colleagues entitled “The Combined Effects of Road Salt and Biotic Stressors on Amphibian Sex Ratios” had me thinking about these questions once again. (Overall, the content of these papers are relevant to the topics we have discussed in class and if you are interested in reading them I have provided the citations at the end.) Furthermore, I have recently been thinking about the broader impacts of climate change and the widespread use of road deicing salts.

 

I grew up in the Midwest where the use of road deicing salts is very common. However, in Georgia (and throughout the south) winter conditions are typically milder and road salts are not commonly used every year. However, as I write this post, a majority of the United States has been recently impacted by an extreme widespread winter storm. North Texas, for example, experienced the coldest day in 72 years, with the Dallas-Fort Worth area reaching a record low temperature of -2 degrees Fahrenheit this week (Irfan). Due to this winter storm, Texas has been documented using road deicing salts throughout the state this year. This had me thinking a lot recently about these past studies done by Lambert et al. in 2016 and Leggett et al. in 2021. Both of these studies were conducted on frog populations in upstate New York, where the use of road salts is common practice. Thus, it is safe to assume that these frog populations have continually been exposed to some concentration of road salt contamination since around the time it was first introduced in the United States in 1938. Therefore, these populations have had the time to be able to adapt and respond in one form or another to road salt contamination. However, the amphibian populations in Texas have not had this same exposure to road salts in the past and therefore, there is the potential for these populations to have a very different response to road salt contaminations. I wonder if these studies (Lambert et al. 2016, Leggett et al. 2021) were repeated with frog populations found in Texas would they find similar results? Is there some sort of exposure threshold required in order for amphibians to have (or evolve) a plastic response? As climate change and unpredictable extreme weather events continues to be a prominent issue in the future, I wonder more broadly how aquatic systems across the country will be increasingly impacted and threatened by novel anthropogenic use of synthetic chemicals and contaminants.

 

Sources:

 

News Article- Texas:

Irfan, Umair. “Scientists are divided over whether climate change is fueling extreme cold events” Vox News, 18 February 2021, https://www.vox.com/22287295/texas-uri-climate-change-cold-polar-vortex-arctic

 

Scientific Papers:

 

Lambert, M. R., Stoler, A. B., Smylie, M. S., Relyea, R. A., & Skelly, D. K. (2017). Interactive effects of road salt and leaf litter on wood frog sex ratios and sexual size dimorphism. Canadian Journal of Fisheries and Aquatic Sciences. Journal Canadien Des Sciences Halieutiques et Aquatiques, 74(2), 141–146.

Leggett, S., Borrelli, J., Jones, D. K., & Relyea, R. (2021). The Combined Effects of Road Salt and Biotic Stressors on Amphibian Sex Ratios. Environmental Toxicology and Chemistry / SETAC, 40(1), 231–235.