American Alligators: New Study Reveals Mechanisms Behind Sex Determination

The gender of American alligator hatchings is largely determined by temperature during incubation. While 33 degrees Celsius seemingly produces males, incubation at 30 degrees Celsius produces mostly females. This phenomenon -- also known as temperature-dependent sex determination (TSD) -- is ultimately controlled by a protein known as TRPV4 that is sensitive to temperature, researchers reveal in a new study.

TSD is common among many egg-laying reptiles, including many species of turtle. In American alligators, the key protein TRPV4 is present within the developing gonad inside the egg. Warm temperatures near mid-30s essentially activate cell-signaling, by inducing something called calcium ion influx. This then regulates gene transcription and produces either a male or female, according to a news release. 

"Reptiles can be difficult to study at times, but we were delighted to obtain such an interesting result and elucidate part of the alligator TSD mechanism. We still have much to research, but we are interested in how our results relate with other TSD species diversity and evolution," Ryohei Yatsu, one of the study researchers and Ph.D. student from the Graduate University for Advanced Studies (Japan), said in the release. (Scroll to read more...)

American alligators are something of an animal success story, having been brought back from near extinction. Now the large aquatic predators are thriving in many freshwater rivers, lakes, swamps, and marshes of the southeastern U.S. While a hatchling many only measure six to eight inches, these reptiles can grow to be upwards of 15 feet long. 

For their study, an international team of researchers from Japan and the U.S. examined the molecular mechanisms of the temperature-dependent sex determination by manipulating the key protein's function in eggs. Interestingly, researchers found the inhibition of TPRV4 greatly influences genes responsible for male development and feminization was observed at some male-producing temperatures.

"Organisms that have adopted TSD systems may be more susceptible to the risks of environmental change, such as global warming. In future, we would like to know how an unstable environmental factor such as incubation temperature was able to establish itself as a sex determination factor," Professor Taisen Iguchi of the Okazaki Institute for Integrative Bioscience added. 

Their study was recently published in the journal Scientific Reports. 

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