This Lizard Changes Sex Based On Temperatures, and Becomes Extra Fertile


Like most animals, bearded dragons have a genetic sex based on chromosomes. Rather than mammals' X and Y chromosomes, these reptiles have Z and W—a ZZ chromosome pairing normally makes a male, and ZW a female. However, in a 2007 lab study, scientists found that temperature-induced changes—a rare but recognized feature of some reptiles—could override a lizard's genetic sex. At an incubation temperature over 32 °C (90 °F), all the eggs hatched female, even those that had ZZ chromosomes. It was unclear if this just happened to be a fluke associated with the laboratory environment, or if the same conditions would affect sex out in the wild.

A team of Australian researchers led by Clare E. Holleley set out to investigate this phenomenon for a paper published recently in Nature. With very little fear of humans, the lizards were easy to scoop up and analyze, with scientists checking for demonstrable sex, as well as chromosomal composition.

Of the 131 lizards the team studied, lab tests showed that 11 females had no W chromosome, meaning they were originally males whose sex had changed in response to temperature pressures. Surprisingly, these ZZ females were not only fertile, they laid almost twice as many eggs as ZW mothers. Having mated with ZZ males these extra fecund ZZ females laid eggs that had only Z chromosomes.

"They've completely lost a whole chromosome in one generation," Holleley told New Scientist. The Z generation are technically all genetically male but their genetically male mothers seem to have passed on a propensity for sex change. Their "sons" switched sex at even slightly lower temperatures than they themselves had.

This discovery represents the first known time that two forms of sex determination have coexisted in the wild. This particular moment in bearded dragon evolution is notable because with climate change creating ever warmer weather, temperature determination could change more and more males into ZZ females, driving the species towards extinction.

Martin Wittfooth
The Cat Art Show Is Coming Back to Los Angeles in June
Martin Wittfooth
Martin Wittfooth

After dazzling cat and art lovers alike in 2014 and again in 2016, the Cat Art Show is ready to land in Los Angeles for a third time. The June exhibition, dubbed Cat Art Show 3: The Sequel Returns Again, will feature feline-centric works from such artists as Mark Ryden, Ellen von Unwerth, and Marion Peck.

Like past shows, this one will explore cats through a variety of themes and media. “The enigmatic feline has been a source of artistic inspiration for thousands of years,” the show's creator and curator Susan Michals said in a press release. “One moment they can be a best friend, the next, an antagonist. They are the perfect subject matter, and works of art, all by themselves.”

While some artists have chosen straightforward interpretations of the starring subject, others are using cats as a springboard into topics like gender, politics, and social media. The sculpture, paintings, and photographs on display will be available to purchase, with prices ranging from $300 to $150,000.

Over 9000 visitors are expected to stop into the Think Tank Gallery in Los Angeles during the show's run from June 14 to June 24. Tickets to the show normally cost $5, with a portion of the proceeds benefiting a cat charity, and admission will be free for everyone on Wednesday, June 20. Check out a few of the works below.

Man in Garfield mask holding cat.
Tiffany Sage

Painting of kitten.
Brandi Milne

Art work of cat in tree.
Kathy Taselitz

Painting of white cat.
Rose Freymuth-Frazier

A cat with no eyes.
Rich Hardcastle

Painting of a cat on a stool.
Vanessa Stockard

Sculpture of pink cat.
Scott Hove

Painting of cat.
Yael Hoenig
Tony Karumba, AFP/Getty Images
How a Pregnant Rhino Named Victoria Could Save an Entire Subspecies
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Tony Karumba, AFP/Getty Images

The last male northern white rhino died at a conservancy in Kenya earlier this year, prompting fears that the subspecies was finally done for after decades of heavy poaching. Scientists say there's still hope, though, and they're banking on a pregnant rhino named Victoria at the San Diego Zoo, according to the Associated Press.

Victoria is actually a southern white rhino, but the two subspecies are related. Only two northern white rhinos survive, but neither of the females in Kenya are able to reproduce. Victoria was successfully impregnated through artificial insemination, and if she successfully carries her calf to term in 16 to 18 months, scientists say she might be able to serve as a surrogate mother and propagate the northern white rhino species.

But how would that work if no male northern rhinos survive? As the AP explains, scientists are working to recreate northern white rhino embryos using genetic technology. The San Diego Zoo Institute for Conservation Research has the frozen cell lines of 12 different northern white rhinos, which can be transformed into stem cells—and ultimately, sperm and eggs. The sperm of the last northern white male rhino, Sudan, was also saved before he died.

Scientists have been monitoring six female southern white rhinos at the San Diego Zoo to see if any emerge as likely candidates for surrogacy. However, it's not easy to artificially inseminate a rhino, and there have been few successful births in the past. There's still a fighting chance, though, and scientists ultimately hope they'll be able to build up a herd of five to 15 northern white rhinos over the next few decades.

[h/t Time Magazine]


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