- Scientists have developed and validated a DNA test kit to help detect the critically endangered Yangtze softshell turtle, a species on the very cusp of extinction.
- The environmental DNA, or eDNA, kit was designed specifically for the species with the hope of finding any unknown individuals in the lakes of Vietnam, in order to eventually establish a captive-breeding program.
- The new method doesn’t require samples to be exported to laboratories abroad; it also allows researchers to obtain results quickly.
- Only two or three individuals of the Yangtze softshell turtle are known to exist; the last known female died in 2023, rendering the species functionally extinct.
It might sound hyperbolic to say that finding even one female turtle can revive an entire species.
However, nothing could be truer for the critically endangered Yangtze softshell turtle, a species for which no known female individuals are left on the planet. With the species functionally extinct, scientists and conservationists have ramped up efforts in recent years to find any unknown individuals that could help rewrite the fate of the turtle.
Now, a method specifically developed for this purpose might provide a faint glimmer of hope for the world’s largest freshwater turtle.
Scientists have developed and tested a portable environmental DNA kit to help detect the presence of the Yangtze softshell turtle (Rafetus swinhoei) in large bodies of water. With the help of this tool, they hope to find any as-yet-unknown turtles that might be swimming around undetected in the lakes of Vietnam.
“Their future existence really hinges on finding additional animals that may still exist in unexplored lakes, both in terms of protecting the animals and securing a captive breeding population,” Tracie Seimon, director of the molecular laboratory at the Wildlife Conservation Society, who was involved in the work, told Mongabay in a video interview.
A study published in the journal Environmental DNA describes how the kit was developed and validated. According to the study, the kit “bypasses the need to export samples to laboratories” and “allows researchers to obtain results within hours.” The kit uses quantitative polymerase chain reaction technology, or qPCR, which is often used for the detection of the DNA of targeted species. During one sampling campaign, the team yielded a positive result for a turtle that was already known to exist in Vietnam, serving as a validation for the method. The team has now put the kit into the hands of conservationists on the ground who are collecting samples from lakes across Vietnam to detect any unknown individuals.
The Yangtze softshell turtle is native to China and Vietnam, where it symbolizes longevity and resilience, respectively. The turtle also plays a significant role in Vietnam’s folklore. Legend has it that a magical sword given to the king by a turtle guard helped defeat Chinese forces. So ubiquitous was the turtle in historical times that children were asked to tread with caution while swimming, lest they be pulled down by the giant creature.
Despite its significance, wildlife trade and loss of habitat linked to the construction of dams have led to a precipitous decline in the species’ population. In April 2023, the last known female turtle was found dead in Lake Dong Mo in northern Vietnam, effectively rendering the species functionally extinct. As of now, only two or three individuals are known to exist: a male at Suzhou Zoo in China; another individual, sex unknown, in Lake Xuan Khanh in Vietnam; and one believed to live in Dong Mo. Since the turtles are highly elusive and spend much of their time submerged in the water, traditional tracking methods have proved challenging.
Sampling and analysis of environmental DNA, or eDNA, have long been used to detect animals living across larger landscapes. Scientists collect soil or water samples that likely contain genetic material shed by animals through their feces, skin and hair. They extract the DNA from these environmental samples and check it against established reference libraries to detect the presence of animals in any given region.
This technique, scientists hope, will help reveal any undiscovered female turtles that can potentially be used to revive the species’ population. The portable eDNA kit for the Yangtze softshell turtle was developed as a collaboration between WCS’s Zoological Health Program at Bronx Zoo, WCS Vietnam, the Asian Turtle Program, and Vietnam’s Central Institute for Natural Resources and Environmental Studies. The kit can be used and tested even by those not trained in molecular biology, enabling the team to deploy it more widely.
“It was a pie-in-the-sky idea,” Seimon said.
It took years to develop a mechanism that would work specifically for these turtles. The teams started working together in 2016 when they first collected samples from softshell turtle exhibits at Bronx Zoo. Once they were able to use those samples to successfully detect turtles, the team started working with samples collected from bigger lakes in New Jersey and Florida. “All of this was to really build up and optimize our protocols so that we could develop the rapid test,” Seimon said.
In 2018, the teams took the kit to Vietnam to train local conservationists on how to deploy and use it. During the pilot attempt, the team learned that the test was sensitive to inhibitors in water, which could interfere with the extraction and analysis process and lead to false results. They then worked to redesign the kit to address this concern.
Since then, local teams have used the kit to collect 500 samples from seven lakes in Vietnam. They’ve also been taking the time to communicate with local communities to get any additional information that might be crucial to spotting the turtles. “We interview local people about the last time they saw something big floating in the lake,” Hoang Bich Thuy, director of WCS Vietnam, told Mongabay in a video interview. “This helps us get evidence, but also persuades and convinces people as to why we need to work rapidly on this.”
If and when they eventually get a positive test result, Hoang said, the teams there would work to prioritize the monitoring and potential capture of the animal after a confirmed sex determination. This will be done to develop a breeding program that will potentially help the species return from the precipice of extinction.
“There’s not a lot of time,” she said. “We are in a hurry.”
Abhishyant Kidangoor is a staff writer at Mongabay. Find him on 𝕏 @AbhishyantPK.
Citation:
Seimon, T. A., Long, N. V., Le, M., McCormack, T. E. M., Nguyen, T. T., Ngo, H., … Calle, P. P. (2024). Development and application of a portable environmental DNA test for the detection of Rafetus swinhoei in Viet Nam. Environmental DNA, 6(5). https://doi.org/10.1002/edn3.70011
Scientists find unexpected biodiversity in an African river, thanks to eDNA
