Source: Xinmin Evening News 2022-09-04 22:02 published in Shanghai
A small fry at the beginning
turned into a "water bully" after being released
In the past few days
The emergence of crocodile gar
has turned several lakes in my country upside down
At the end of August this year, a crocodile gar was discovered in a park in Hunan Province Source/Eastern IC
The frequent appearance of "strange fish in the lake" has accelerated the investigation of biological invasion situations in various places, and the public's attention to biological invasion has also greatly increased. At present, we can only passively defend against exotic species like the alligator gar, and even capture them at the cost of draining the water body. So is there a way to sound the alarm in advance? With questions, the reporter walked into the recently established Environmental DNA Technology and Aquatic Ecological Health Assessment Engineering Center of Shanghai Ocean University.
Shanghai Ocean University Environmental DNA Technology and Aquatic Ecological Health Assessment Engineering Center was recently established Photo courtesy of interviewee
A "bully" with good attack and defense capabilities
Professor Li Chenhong, director of the Engineering Center, introduced that the alligator gar is also called the big gar, and it belongs to the order Gar, family Gar, and genus Bone Gar. . This ferocious fish has been swimming in the rivers of its "home" North America for tens of millions of years. It is the largest of the seven existing species of gar.
The alligator gar is the largest of the seven existing species of gar. Source/Oriental IC
Anyone with the word "crocodile" in their name is not a good person. The most striking feature of the alligator gar is naturally its protruding snout like a crocodile, and its upper and lower jaws are densely covered with two rows of small but sharp teeth. "When hunting, the crocodile gar will bite the prey firmly with its upper and lower jaws, slowly adjust it, and swallow it whole from the beginning, instead of tearing the prey into pieces before eating." Li Chenhong introduced.
In addition to having good attack power, Alligator Gar's defense power is also amazing. When you buy live fish to take home, you must first scrape the scales. These scales are round scales or comb scales. The alligator gar is covered with a layer of diamond-shaped blue-grey hard scales. This armor-like scale is difficult to penetrate in nature. In North America, except for a few crocodiles that pose a threat to the alligator gar, it has few enemies in rivers.
In North America, a few alligators may be the only natural enemies of the alligator gar. Source/Oriental IC
"Of course, the origin of the crocodile gar has formed an ecosystem, and other fish will eat the eggs of the crocodile gar, and its reproduction is subject to checks and balances." Li Chenhong told reporters that although the crocodile gar is a freshwater fish species, but they are actually not picky about salinity. They can be seen from freshwater lakes to salty swamps, from the upper reaches of rivers to the estuaries of the sea.
In addition, crocodile gars also have a special skill: their swim bladders not only provide buoyancy, but also assist in breathing air like lungs! This means that the alligator gar can not only adapt to water bodies that other fish find difficult to survive, but can even survive outside the water for a period of time. As a carnivorous fish, the alligator gar is not "picky" and will eat almost all living creatures in the water, including various fish, crustaceans, amphibians, reptiles and birds that fly near the water. .
has amazing attack power, explosive defense power, and super adaptability. dominated it in its hometown. When it comes to the new environment, it can only be described in four words: does whatever it wants. "It can hardly be contained by biological control of ."
Raise awareness of preventing alien species
Why did the North American aborigines cross the ocean and come to China to cause chaos? The reason is likely to be random release.
The currently verifiable information generally agrees that the time when several species of gar entered China should be in the 1990s At that time, it was introduced as an ornamental fish because of its unique appearance and ferocious habits, and then gradually became a frequent visitor to the domestic ornamental fish market. However, as its size grew, its appetite also became astonishing, and many fish consumed it. If the friend's home cannot afford to raise him, he will quietly "release" him to the Nearby rivers or lakes - the family is relaxed, but the ecosystem of the "release site" suffers!
Previously, gar were introduced to domestic culture as ornamental fish! Source/Oriental IC
"The apple snail that everyone has heard of is also an invasive alien species. "Li Chenhong said that when they first came to China, apple snails could only settle in southern water bodies, but after gradually adapting, changes have taken place. The emergence of apple snails has been reported in Shanghai and Beijing - this reminds biological researchers that is very important to foreign species. Research on the habits and adaptability of invasive species in their origin and invasion areas requires Develop in time.
"The same goes for the alligator gar. In North America, the temperature where it lives is still very high; it may not survive the winter in northern my country, but once the population reproduces and its adaptability continues to increase, no one will be able to survive in the future. It's hard to say for sure. " Li Chenhong explained.
The reporter learned that since 2003, our country has released 4 batches of "China's Invasive Alien Species List", which include apple snails, bullfrogs, Procambarus clarkii, and This summer, a large number of pink snails appeared in a lotus pond in a park in Yunnan. of eggs Source/Oriental IC
Starting from April 2021, the "Biosafety Law of the People's Republic of China" will come into effect, which stipulates that anyone who introduces alien species without approval will be fined 50,000 yuan in addition to confiscating the introduced alien species. A fine of more than 250,000 yuan is imposed without authorization. Those who release or discard alien species shall be ordered to capture and recover them within a time limit and be fined. If the circumstances are serious, the " Criminal Law " also stipulates a prison sentence of not more than 3 years or criminal detention. In addition, the " Invasive Alien Species Management Measures ". 》, also since August 1 this year It is understood that my country is promoting the management and restoration of invasive alien species. For ordinary citizens, it is necessary to increase their awareness of preventing biological invasions and do not blindly release or arbitrarily release species that they are not sure whether they are alien species. Disposal.
changes from "passive defense" to "active monitoring"
A few days ago, the Environmental DNA Technology and Aquatic Ecological Health Assessment Engineering Center of Shanghai Ocean University was established. "Take aquatic organisms as an example. The DNA they release into the environment includes mucus, shed scales, excrement, and reproduction. DNA, etc. all belong to environmental DNA. " Li Chenhong explains.
Li Chenhong (right) leads students to collect environmental DNA samples Photo provided by the interviewee
Environmental DNA sampling is convenient and does not require classification expertise. At the same time, the amount of data obtained is large and diverse. In the context of the Yangtze River Protection, it is not subject to the restriction of fishing ban "Even if there is only one in a water body. Two foreign organisms can be identified using existing technology even when the environmental DNA concentration is very low. " Li Chenhong said that "can even identify the size of DNA fragments to determine whether environmental DNA comes from living organisms or tissues discharged by human waste. "
Li Chenhong introduced that environmental DNA has broad application prospects. In addition to monitoring invasive species, it can also be used to protect endangered species.Previously, Li Chenhong's team developed a kit for real-time monitoring of salamander . The water body was sampled and filtered and dropped on the reagent card. The appearance of "two bars" proves the presence of salamander, while "one bar" indicates that it does not. In addition, Li Chenhong's team is also trying to use environmental DNA technology to conduct field surveys of Yangtze River shad - although shad has not been discovered for a long time.
The engineering center team conducts environmental DNA experiments on campus
In recent years, aquatic organism invasion incidents have occurred frequently. In addition to the alligator gar, starfish, white mud ants, apple snails, etc. have all become "killers" of the local ecosystem. "We hope to establish an environmental DNA database, improve the monitoring mechanism, and turn the 'alarm' of aquatic alien organisms into an 'early warning'." Li Chenhong told reporters.
At the same time, the Engineering Center will also cooperate with other research institutions to conduct research on the molecular mechanisms of alien species in order to inhibit the survival of alien organisms by releasing chemical substances or interfering molecules.
Original article by Xinmin Evening News
Reporter: Gaoyang
Editor: Shi Yu
