Lazarus Rising: The Attempted Resurrection of the Gastric Brooding Frog
By Sonia Choy 蔡蒨珩
The arrival of Dolly, the first cloned mammal in 1996, marked an important page in human history. It was the first time humans were able to create a mammal in a laboratory. Pictures of Dolly made headlines across the world. But did you know that scientists also tried to use the same technology to bring extinct frogs back to life?
The southern and northern gastric brooding frogs (Rheobatrachus silus and Rheobatrachus vitellinus) were discovered in 1972 and 1984 in Queensland, Australia respectively. Both being very small (about 30–54 mm for the southern and 55–80 mm for the northern species) and living in a limited rainforest area (less than 1000 km2), they lived in streams of the Queensland mountain ranges [1, 2]. Like many native Australian species, the frogs were unique to the land down under, and possessed extremely unique characteristics.
One such thing that caught headlines at that time was how they reproduce [3]. The mother swallows a number of eggs and stops producing acid in its stomach to allow the eggs to hatch into tadpoles, and later into frogs. It was suggested that a substance called prostaglandin E2 secreted by the tadpoles can inhibit the acid secretion of the mother [4]. Then the mother does not eat for six weeks and stops breathing through the lungs but the skin, as its bloated stomach has squeezed the lungs to collapse. Eventually, the mother gives birth to fully formed baby frogs via “propulsive vomiting”, much like a Russian doll. This dramatic method caught the attention of many, including zoologists who couldn’t believe this was true…until they saw it for themselves. Sadly, these frogs did not live very long, and by 1981, the southern breed had gone extinct in the wild; the northern breed was also extinct in 1985, within a year after its discovery.
Mike Archer, a researcher from the University of New South Wales, had read about the frog and decided to do something no one had seriously attempted before – to bring it back to life [3]. His plan was to use somatic cell nuclear transfer (SCNT) to transfer a somatic cell nucleus obtained from the frozen frog sample to a fresh egg of a reasonably close but existing relative, the barred frog (Mixophyes fasciolatus). With a full set of the southern gastric brooding frog’s DNA as the blueprint of life, they hoped the cell can divide and develop into a full-fledged individual.
SCNT is divided into a few main steps. The first step was to use ultraviolet radiation to destroy the nuclear DNA of a donor egg [5]. Into this “empty” egg, scientists inserted a nucleus collected from the long frozen gastric brooding frog’s tissue sample. For the cell to divide and grow into an embryo, an electrical or chemical stimulation is usually given to activate the manipulated oocyte [6]. After many cell divisions, the embryo then underwent the crucial step of development, known as gastrulation, when cells in its exterior migrate internally – and there it stopped [3]. In the best-case scenario, the cell division and differentiation would continue further, to the point that we have a fully formed tadpole of the southern gastric brooding frog.
Current technology is very far from even creating a southern gastric brooding frog tadpole, but Mike Archer’s great dream is to bring the frog back to life. This is partially for the potential medical benefits it may bring. As mentioned earlier in the article, female frogs temporarily stop the production of gastric acid after they swallow the egg and let it hatch. However, the species was extinct before scientists could further study them [7, 8]. If the cloning process is successful, this would lead to a better understanding of the southern gastric brooding frogs, and potentially help human patients suffering from too much or unwanted gastric acid. From acid reflux to ulcers and even more serious diseases, this could be a potential, permanent cure.
But Archer’s goal seemed simpler. Quote, “If we were responsible for the extinction of the species, deliberately or inadvertently, we have a moral responsibility or imperative to undo that if we can [3].” Over the last century, many species have gone extinct from human activities. Widespread deforestation and global warming have destroyed the habitats of many species, especially very rare ones that are endemic to Australia. Some, including Archer, believe that our responsibility is to restore these endangered species to their natural habitats, and undo the damage we have caused in the past.
However, there are ethical issues surrounding this. First of all, extinction is part of nature’s cycle; species regularly fall on and off the earth all the time. By cloning the southern gastric brooding frog and bringing it back to life, we are upsetting Mother Nature. By Archer’s logic, if species died out by human behavior, then we should help restore those species back to the wild. The problem is that species go extinct due to a myriad of reasons; the Australian government, for example, lists the pathogenic fungus Batrachochytrium dendrobatidis as a possible extinction reason of the gastric brooding frogs [1, 2]. This is not to underplay the role of humans in destroying nature over the past century, but what is to say that the species definitely died only by human influence? In this case, why shouldn’t we just let nature take its course?
Also, the world has changed since the southern gastric brooding frog went extinct. The current Queensland mountains are no doubt different from the ranges where the frog last thrived over 50 years ago. By sending them back into the wild after hatching in the laboratory, we may be sending them to a second death, as it is very likely that they will not survive for an extended period of time. In this case, what is the point of doing this? More fundamentally, which species should be brought back from extinction? Should humans be playing God? At least, most countries across the world agree that cloning should not be done in humans, making generating alternative organs from individuals currently impossible.
Cloning technologies no doubt leave us with many unanswered questions. It is a tool that can be used, and misused; the very thin line between the two will continue to be discussed for some time.
References
[1] Department of Climate Change, Energy, the Environment and Water, Australia Government. (2023). Rheobatrachus silus — Southern Gastric-brooding Frog. Species Profile and Threats Database. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1909
[2] Department of Climate Change, Energy, the Environment and Water, Australia Government. (2023). Rheobatrachus vitellinus — Northern Gastric-brooding Frog, Eungella Gastric-brooding Frog. Species Profile and Threats Database Profile. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1910
[3] Yong, E. (2013, March 15). Resurrecting the Extinct Frog With a Stomach for a Womb. National Geographic. https://www.nationalgeographic.com/science/article/resurrecting-the-extinct-frog-with-a-stomach-for-a-womb
[4] Tyler, M. J., Shearman, D. J. C., Franco, R., O'Brien, P., Seamark, R. F., & Kelly, R. (1983). Inhibition of Gastric Acid Secretion in the Gastric Brooding Frog, Rheobatrachus silus. Science, 220(4597), 609–610. https://doi.org/10.1126/science.6573024
[5] TED. (2013, June 27). Michael Archer: How we'll resurrect the gastric brooding frog, the Tasmanian tiger [Video]. YouTube. https://youtu.be/ErexJkoDhGI
[6] Gouveia, C., Huyser, C., Egli, D., & Pepper, M. S. (2020). Lessons Learned from Somatic Cell Nuclear Transfer. International Journal of Molecular Sciences, 21(7), 2314. https://doi.org/10.3390/ijms21072314
[7] UNSW. (2015, July 6). Back from the dead: Catastrophic Science [Video]. YouTube. https://youtu.be/dirLxqvXQG0
[8] Wondracz, A. (2019, April 2). Mysterious frog that reproduces by regurgitating its young could hold the key to treating stomach ulcers...but it hasn't been seen in almost 40 years. Daily Mail. https://www.dailymail.co.uk/news/article-6875381/Gastric-brooding-frog-help-treat-stomach-ulcers.html