Road salt can change sex ratios in frog populations

Common road salts used to melt ice on pavements have natural chemicals which were found to have affects sex ratio in nearby frog populations. This could lead to a reduction in the size of the population and its viability. A study done by researchers at Yale School of Forestry & Environmental Studies showed that in a tadpole population exposed to the road salt which contains sodium chloride, the proportion of females were reduced by 10 percent. The data lead the team to suggest that the salt has a "masculinizing" effect. More than 22 million metric tons of road salt is applied to roads in the United States each year.

"Many scientists have studied similar effects from exposure to pharmaceuticals and pesticides, but now we're seeing it from chemicals found in common road salt and leaf litter," said Max Lambert, a doctoral student at the university and lead author of the paper.

In the experiment, the team created water tanks containing various levels of salt and maple and oak leaves. The leaves were used to mimic a natural forest environment. The researchers took the data collected from different tanks and compared them. They found that in populations surrounded by leaves and no salt, there was a females-biased ratio of 63 percent. In the salt exposed population, the ratio was reduced by 10 percent. This discovery can cause concern for the frogs because the health and abundance of females are crucial to success. They also examined the tadpole sizes in various tanks. The results showed that the developing females were consistently larger than the males in the leaf litter environment; however, when exposed to salts, the females decreased in size. A smaller female may not be able to produce as much eggs as a normally larger female. The eggs produce might also be lower in quality.

So the researchers were seeing not only fewer females but less successfully reproductive ones too. They hypothesized that it is a phenomenon caused by a mechanism known as sex reversal during development. The salts used every winter do not stay on the roads. It turns into run-off which ends up in ponds and comes in contact with the frogs in the habitat. The sodium in the salts used bind to the receptors in the cells which mimics the action of testosterone.

This gives us glimpse of anthropogenic impacts on aquatic ecosystems occurring constantly. This article also touches upon ecology and environmental suitability which are both important to understand especially now, considering the current state of our planet.

New Reasons why Crocs are a Better Birth Control

The Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin has noticed a peculiar trend. Male amphibians are being exposed to an extreme amount of synthetic hormones, skewing the ratio of males and females, and causing a decrease in population.

It turns out that the main ingredient of the pill is 17a-Ethinylestradiol (EE2), an aestrogenic endocrine disrupting chemicals (EEDCs). It is completely man made and because of such, waste plants cant completely remove the hormone from urine. Thus it returns back to natural water supplies. ln the three species accounted for in this study, sex reversal occurred in 15 to 100 percent in the males.
Also another study in small mouth bass, 85% displayed the synthetic hormone inducing "inter-sex" as cause for decreasing population. Ecologists are starting to become anti-pill for such reasons. It has been around for decades, yet presently"..more than 100 million women use the pill." With that huge magnitude it is understandable how water is being affected, and how ecological damage is surmounting.

This led me to wonder what they effects are for humans, since this synthetic hormone may also remain in our water. Even if it is in small amounts, could this be a reason that youth appear to be going through puberty earlier?

If I put a real picture of me the point would be proven more, but I didn't want to do that to you guys.
It would be interesting to have data regarding the presence of EEDC's in water sources, as well as what level promotes a reaction, and if synthetic hormones incite maturation. I believe more research should be invested into to ensuring better ingredients, to allow women to still have control over their bodies yet in a more sustainable, natural way.

Deletion of One Gene Causes Sex Reversal

Researchers from the Institute of Molecular Biology (IMB) in Mainz have discovered a gene that initiates the development of male sex organs. The researchers' finding uncovers a signaling device, which acts early in development to determine the gonads in males. This discovery sheds light on the genetic network that controls how embryos develop as males or females.

 

When testing on mice the researhers found that the deletion of one gene, Gadd45g, made the male's external genitalia match that of females. Then when they looked at the internal reproductive organs the male's also looked identical to the females. So the deletion of this one gene, Gadd45g, caused a complete sex reversal in the male mice. Christof Niehrs, Director Professor at IMB, said, "when breeding Gadd45g mutant mice we were puzzled why we got only females, until we discovered that some of these females actually carry a Y-chromosome." The scientist furthered showed that the Gadd45g gene controls the Sry gene by signaling it to work or not. The Sry gene is the know master regualtor of male sex expression. They think the Gadd45g gene regulates Sry by binding to p38, a key signaling protien, and activating the transcription factor Gata4. Once active, this factor binds to the Sry gene and ultimately turns it on. "This study both identifies a new role for Gadd45g and suggests a novel signaling pathway that could have important implications for research into disorders of sexual development."-Medical News Today.

I think this article is interesting because it shows how perfect DNA copying has to be, becuase the deletion of just one gene could have a huge effect. It makes me wonder if the scientist's discovery could be applied to human sex determination though. I do think it's cool that their discovery also shows how narrow the timeframe is in an embryo for sex organs to develop correctly.