Are they the loneliest animals?, The animal mentioned in "Dream of the Red Chamber" and "Journey to the West" has only two male zebra turtles left | Source | Dream of the Red Chamber

Author: Yue Ranran, journalist from Xinhua Daily Telegraph

There are only two confirmed turtles left on Earth, both of which are still male.

In 2012, when the last Pingta Island tortoise on Earth, Lonely George, passed away, the title of "Lonely Animal" fell on the head of the zebrafish.

The spotted turtle is a slightly unfamiliar name. It is the largest extant turtle in the world, a first-class protected animal in China, and a critically endangered species by the World Conservation Union. It has appeared multiple times in "Dream of the Red Chamber" and "Journey to the West": Jia Baoyu and Lin Daiyu swore to say "the toad turtle", the old turtle that once carried Tang Monk and his disciples across the Tongtian River, and the real reference is the spotted turtle.

Although the number of zebra turtles is measured in units, humans have not given up on rescuing them.

The male zebrafish still living in Suzhou Zoo. Photo by Lv Shunqing

The last known female zebrafish has left

In April this year, Vietnamese authorities confirmed the death of a female zebra turtle in Lake Tongmo.

This zebrafish is 1.56 meters long and weighs 93 kilograms, and the cause of death is not yet clear. It was released to Tongmo Lake after being sampled and marked in 2020, and is currently the only confirmed female zebrafish in the world.

This news surprised Rao Dingqi, an amphibian and reptile expert at the Kunming Institute of Zoology, Chinese Academy of Sciences. Since its identity was confirmed in 2002, the zebrafish has been following and researching this species.

"The death of this female zebra turtle has reduced the known number of zebra turtles on Earth from three to two. Unfortunately, the remaining two are male, one living in Suzhou Zoo in China and the other in Xuanhan Lake in Vietnam."

For a long time in the past, the spotted turtle was known as the "scabbard turtle" and was considered a species of turtle by the academic community. But upon careful comparison, there is a significant difference between the spotted turtle and the turtle——

Turtles are difficult to weigh over 100 kilograms, but zebrafish can weigh over 100 kilograms; The turtle has a circular body shape, while the spotted turtle has an elliptical body shape. In addition, the whole body of the zebrafish is scattered with fine yellow stripes, and the head pattern is bright... Even if the difference is obvious, people in the past mistakenly confused the two.

Until 1873, a British scholar realized that the "scabbard turtle" might be a new species and named it the "Si's turtle", but it did not receive much attention for more than 100 years thereafter. Until 1993, Chinese biologist Zhao Kentang, after extensive research, confirmed that the "scabbard turtle" was an independent species and named it "spotted turtle" in Chinese. Since then, this species that has lived on Earth for hundreds of millions of years and once lived next to dinosaurs has finally been identified.

The zebra turtle is the largest freshwater turtle in the world. It used to live widely in China's Yellow River, Yangtze River, the Taihu Lake Lake, Qiantang River, Red River, and the Majiang River basin in Vietnam. However, because it has been considered as other species, it has not attracted enough attention from human beings. As soon as its identity was determined, it began to be in danger. In 2005, the zebra turtle in Beijing Zoo died, just one year before people identified it as a zebra turtle. In 2006, a zebra turtle died at the Shanghai Zoo, less than three months after it was confirmed to be in its true body.

What factors are causing the endangerment of zebrafish turtles? Lv Shunqing, professor of the School of Life and Environmental Sciences of Mount Huangshan University, analyzed the reasons.

Lv Shunqing and Gerald are conducting field research. Respondents provide pictures

Firstly, this is related to the survival habits of the zebrafish. The zebrafish is a solitary animal with strong territorial behavior. Domain behavior is beneficial for animal feeding, reproduction, and nurturing of offspring. "Simply put, one zebra turtle has to occupy a large area. Once other zebra turtles invade, there will be a population struggle."

Secondly, due to the need to maintain its huge size, the spotted turtle is either eating or searching for food. Therefore, it needs such huge freshwater bodies as the Taihu Lake Lake and the Red River as its habitat.

With frequent human activities, the wild survival situation of zebrafish is getting worse and worse. Due to being cold-blooded animals, they are particularly sensitive to changes in their surrounding environment. "Since 1972, no zebra turtles have been found in the Taihu Lake Lake. According to the survival needs of zebra turtles, the only possible wild zebra turtles in China is Honghe."

Finally, the idea that eating turtles can lead to longevity has led to a decrease in the number of turtles. As early as the pre Qin period, Chinese soft shelled turtles were used as dishes for drinking. According to existing data, there were still dozens of spotted turtles in China in the 1950s. But under the concept that eating turtles can provide nutrition, prevent and treat diseases, people in the past excessively preyed on wild turtles.

"Even if turtles can live for hundreds of years, they can't withstand being eaten," said Lv Shunqing. From a physical perspective, the juvenile spotted turtle looks very similar to Chinese turtles, Shanrui turtles, and other turtles. In addition, it has been mistaken for its identity for a long time and cannot be protected. So, newly born small spotted turtles may be eaten as Chinese soft shelled turtles.

Scientists have worked hard to "renew the fragrance" for the zebrafish

Lv Shunqing's right thumb left a scar forever, which was his first and possibly his last time being bitten by a spotted turtle. Shortly after biting Lv Shunqing, this spotted turtle called "Xiangxiang" died.

This was the only female zebrafish in China at that time with a confirmed gender. In 2019, it died without warning during artificial insemination.

Speaking of the story with this female spotted turtle, Lv Shunqing had a tight throat and hair. "That starts with identifying it in 2007."

In January 2007, Lv Shunqing held a meeting in Suzhou and saw several photos of large turtles that needed to be identified at Changsha Zoo. He and Australian expert Gerard Kuklin keenly discovered that these could be zebra turtles. The two of them hurriedly flew to Changsha, and it was confirmed on site that this is a female turtles around 90 years old who can still lay eggs.

At that time, there were only a few zebra turtles in the world. The discovery in Changsha was very surprising, which meant that zebra turtles could reproduce naturally.

At that time, there was a male spotted turtle at Suzhou Zoo, and both families were reluctant to transport their babies to each other's gardens. In order to allow them to mate naturally, after a lot of work, Changsha Zoo finally agreed to "marry a daughter". In May 2008, this female spotted turtle, known as "Xiangxiang", arrived in Suzhou.

In 2009, the female spotted turtle "Xiangxiang" sunbathed its back at Suzhou Zoo. Photo by Lv Shunqing

Due to the fact that the two turtles had not seen each other for a long time, in order to prevent mutual harm, the staff used fences to block them. On the first day, the two turtles could only stare at each other. The next day, the fence was opened and the male turtle approached actively, while the Xiang Xiang hid in the water without appearing. On the third and the fourth day days, Xiangxiang basked his back on the bank, and male turtles swam around it. On the fifth day, the two of them became round houses.

Everything went smoothly. Xiangxiang quickly laid dozens of eggs, but disappointment came quickly, and not a single egg was successfully fertilized. Everyone began to analyze the reason, which is that the two turtles got along too short and did not mate successfully? Or is the food too single? Or is it a water quality issue? Some people also believe that they have successfully mated, but have not yet formed a fertilized egg. Due to the fact that male sperm from turtles can survive for months or even years in the female body, Xiangxiang may one day produce fertilized eggs and hatch babies.

Given the lack of experience in breeding zebrafish, scientists dare not act recklessly and can only wait.

After another 6 years, it still remains the same. They mate every year and Xiangxiang lays eggs, but they don't have a single fertilized egg. Scientists have begun to doubt the quality of sperm in male turtles, as they are already over 100 years old.

Scientists examine the eggs of zebrafish turtles. Photo by Lv Shunqing

In the following years, artificial insemination was unsuccessful. As the two spotted turtles grew older, the team planned to do it again in 2019, but no one expected that the relatively healthy and young Xiang Xiang would die.

On April 12, 2019, a team of Chinese and foreign experts conducted sperm collection and artificial insemination on couples of turtles. Before the surgery, the physical and chemical indicators and ultrasound health examination of the two turtles showed that they were in good health condition.

Similar to previous artificial insemination experiments, the process progressed smoothly without any complex situations. The only incident was that while preparing to administer anesthesia to Xiangxiang, Lv Shunqing was responsible for controlling Xiangxiang's left forelimb, but he was bitten by Xiangxiang, who was blindfolded.

After the surgery, everyone waited for Xiangxiang to wake up, but after two hours, it still hadn't woken up. The team became nervous, and the veterinarian followed the standard procedure for rescue. It wasn't until noon the next day that Xiangxiang occasionally woke up, but after a few moves, he didn't move anymore. On the afternoon of April 13th, Xiangxiang died, and all the ladies present shed tears.

Lv Shunqing's hand still felt a faint pain, but he felt even more heartbroken.

Chinese scientists have successfully deciphered the genome of zebrafish

After a brief period of decline, the expert group quickly threw themselves into the next work. The team collected ovarian tissue from Xiangxiang and stored it in liquid nitrogen for future use; The zoo quickly formed a third-party autopsy team composed of domestic and foreign experts.

Rao Dingqi also participated in it. In order to avoid the permanent loss of genetic information in the genome of female zebrafish and to continue the investigation and protection work of zebrafish, he collected tissue samples during the pathological anatomical examination of Xiangxiang.

More than a year later, the research results of Rao Dingqi's team were published. Through gene sequencing technology, they successfully assembled a high-quality reference genome sequence at the chromosome level of Xiangxiang. Subsequently, the team adopted strategies such as de novo prediction, homologous alignment, and transcript assisted annotation to successfully decode 26646 high-quality protein coding genes in Xiangxiang. Through chromosome analysis, the sex determination system of the zebrafish was clarified.

Based on genetic datasets and phylogenetic tree construction algorithms, the academic community has gained a better understanding of zebrafish——

The genome size of female turtles is approximately 2.24 billion bases; The relationship between zebrafish and Chinese soft shelled turtles is relatively close, and they parted ways 54.4 million years ago; The population of zebrafish has shown a continuous downward trend in history, which is related to its low genetic heterozygosity and genetic diversity.

Comparative genomic analysis also indicates that the longevity and large size of the zebrafish are mainly related to the rapid evolution of core genes related to growth, such as cell autophagy and DNA damage response. In addition, the genome of zebrafish lacks genes related to tooth formation, which can also explain why zebrafish, including species of turtles, do not have teeth

Rao Dingqi stated that the reason for retaining some of the tissues of Xiangxiang is mainly to determine the DNA sequence of the zebrafish, draw the genome map of this species, and decipher its genetic code. This will have significant implications for future field investigations, search, and protection of zebrafish. "For example, scientists can design more sensitive, specific, and effective genetic molecular probes, which can help us more effectively use environmental DNA methods to detect, search, discover, and identify more potential wild turtles in field investigations."

Turtle eggs. Photo by Lv Shunqing

Mammals can all be cloned, why can't turtles?

Zheng Ping, a researcher at the Kunming Institute of Zoology of the Chinese Academy of Sciences, explained: "Cloning technology is not as simple as people think. At present, cloning technology is relatively mature in mammals, while zebra turtles are reptiles and reproduce by laying eggs. Scientists have not yet explored their cloning technology."

Zheng Ping stated that when the population of a species falls below the lower limit, its gene pool is already incomplete and cannot be repaired. Even if cloning "resurrects", it only resurrects an individual, not this species.

In fact, the population of wild turtles and turtles in China has been declining. Although turtles are one of the most resilient and long-lived animals among existing species, the reality is that the overall wild turtles in China are becoming endangered. Currently, in the wild, Yunnan closed shell turtles, golden headed closed shell turtles, and black necked turtles are almost extinct; Turtles, four clawed land turtles, Pan's closed shell turtles, Baise closed shell turtles, Shanrui turtles, and concave armored land turtles are all in endangered or extremely endangered status.

A corner of Madushan Reservoir. Photo by Lv Shunqing

The last hope may lie in the Madushan Reservoir

Turtles have been dubbed "zombie species" by zoologists because they only have one or a few long-lived individuals left and cannot produce offspring.

But perhaps there is still a glimmer of hope.

Just a month after the death of the Vietnamese female turtles, Rao Dingqi hurriedly arrived at the Madushan Reservoir in Yunnan, which is believed to be a place where wild turtles may still exist in China.

There is evidence to trace the location of the Madushan Reservoir, which is connected to the Red River in Vietnam's Tongmo Lake. The Madushan Reservoir is located in Honghe Prefecture, Yunnan Province. In 2007, it was filled with water and submerged a 50 kilometer long riverbank. This section of the river may be an important habitat for zebrafish in the wild in China. Not long after the completion of the reservoir, local fishermen still saw giant turtles sunbathing their backs on sunny days.

Rao Dingqi and Lv Shunqing also heard some news. According to local fishermen, there may be one or even more zebra turtles living in the Madushan Reservoir. Many years ago, someone illegally caught fish, and fishermen once saw giant turtles floating on the water surface due to electric shocks. People who see giant turtles describe them as ancient and huge bodied turtles.

Rao Dingqi and Gerald visited villagers in the Red River Basin. Photo by Lv Shunqing

Two scientists have always believed that there may still be wild individuals or even populations of zebrafish in the Red River Basin. But the two are also concerned that if it is a solitary zebra turtle, it will have no practical significance for population reproduction. If it is paired, it would be even better.

Finding the trace of a zebrafish in a 50 kilometer long water body is indeed quite challenging. The two of them can't remember exactly how many times they went there. Due to the fact that turtles spend most of their time underwater, the likelihood of seeing them is very low, and they rarely come ashore to sun their backs, let alone lay eggs.

The environment in the Red River Basin, where zebrafish once lived. Photo by Rao Dingqi

During this survey, Rao Dingqi and his team went for more than 10 days. As long as he walked by the reservoir, he would stare at the water surface for fear of missing any sudden abnormal situations.

The team's method of finding zebrafish is very direct - walking along the coast, setting up observation points and installing cameras in the most likely exposed areas of the zebrafish, and using telescopes to survey the water surface or areas where it may be sunburned; The team also sampled water bodies and used environmental DNA methods to detect the presence of excrement, shed skin, and other debris containing DNA information from zebrafish turtles. Everyone believes that if one is lucky enough, they can take pictures and videos of the zebrafish and leave evidence behind.

In May 2023, members of Rao Dingqi's team searched for spotted turtles in the Red River Basin. Photo by Rao Dingqi

"Although it is impossible to cover the entire reservoir, we consulted with fishermen and compiled several sightings, focusing our main energy on these most promising areas." Rao Dingqi was not worried about the hungry turtles in the water. "There are still fishermen fishing in the Red River Basin, and if there are still turtles, they will not lack food.".

Rao Dingqi showed a video to the reporter. In a wide river bend, there was a faint gray figure that rose and fell against the surface of the river, but it never surfaced, so it was impossible to distinguish whether it was a spotted turtle. "It may also be other large turtles, such as turtles, Asian turtles, etc."

Sometimes Lv Shunqing would also make plans to go out into the wild with Rao Dingqi. They likened this work to "searching for the Loch Ness monster," which is said to be an ancient marine reptile that lived in a deep lake in Scotland, but has not been confirmed to this day.

"What we do is similar to finding the Loch Ness Monster, so we all refer to finding the zebrafish as' finding the Madu Mountain Monster '." Lv Shunqing said that the most urgent thing now is to find evidence of the survival of the zebrafish.

Scientists have even made plans for "once the spotted turtle is found" - once discovered, it must be protected and monitored on-site first, and then further searched for other companions. If they are of different genders, one can be caught, fitted with a locator, and placed in the water where the other is located to try natural mating and reproduction. If only females are found, cooperation can also be discussed with the Vietnamese side.

But the cost is destined to be high: there is little hope for the natural reproduction of male turtles in Suzhou, and they can only rely on artificial insemination; The current health status of male turtles in Vietnam is unknown. The future of zebra turtles is still shrouded in mist, especially in the absence of female turtles at present.

Even though the zebrafish is sliding towards the abyss of extinction, scientists have not given up hope——

"Never think of making amends when you lose, but put in more effort to prevent extinction," Rao Dingqi said.

"The meaning of extinction is never to be revived. It sounds sad, but thinking about it makes people sober up," said Lv Shunqing.