How do locusts swarm into disasters? Stinky!
Economic Daily·China Economic Net reporter Shen Hui
How terrible is it when the black locusts are overwhelming? According to the judgment of the United Nations Food and Agriculture Organization, a locust swarm of 1 square kilometer can eat 35,000 people's rations in one day. How did these locusts that "eat food without blinking" swarm into disasters? Let's listen to what the experts say.
Recently, a team of Kangle academicians from the Institute of Zoology, Chinese Academy of Sciences published research results in the top international journal Nature, revealing the mystery of migratory locusts "groups of evil": from migratory locusts scattered in twos and threes to thousands of large-scale gatherings of locusts The reason why migratory locusts who are accustomed to being alone give up "free life" is because of a specific volatilized smell from gregarious migratory locusts. This odor contains a low-release but very high biologically active compound called 4-vinylanisole (4VA, 4-vinylanisole), which can respond to changes in the population density of migratory locusts, and changes with the increase in population density. increase. The migratory locusts who were "bewitched" by them began to gather in groups, and eventually led to a devastating locust plague.
"These discoveries made us for the first time truly aware of the clustering pheromone of locusts. This can not only be applied to basic research, but also very promising for locust management in the wild." Bilhan, director of the Max Planck Institute of Chemical Ecology, Germany Sen said.
The locust plague that cannot be ignored
Although the little locusts are not good looking, if hundreds of millions of them gather together, the destructive power is disastrous. Locust plagues, droughts and floods are the three natural disasters in the history of our country. Historical records over the past 2000 years show that my country has experienced more than 800 large-scale locust plagues.
Unlike the migratory locusts that mainly attack our country, although desert locusts are only distributed in Africa, the Middle East, Southern Europe and South Asia, the records of their harm can be traced back to more than 5,000 years. From 2019 to June 2020, the desert locust outbreak spread from the Horn of Africa to more than 20 countries and regions. The Food and Agriculture Organization of the United Nations judged that the desert locust plague affected an area of more than 260,000 hectares, with a scale of once in 25 years, and the food supply of 11.9 million people along the way was directly threatened.
The locust plague has been accompanied by the history of human development for a long time. However, our scientific understanding of the cause of the locust plague is less than a century. Yuvalov, a famous international entomologist and the father of locust studies, discovered that the reason why the migratory locusts are plagued is because the locusts can transform from a low-density dispersal type to a high-density gregarious type. Because of his outstanding contributions to locust research, he He was awarded the title of knight by the British Royal Family. Before Yuvalov put forward the theory of locust type change, people once thought that the scattered and social locusts were two different species. Due to its low density, scattered locusts do not migrate and are generally considered harmless; once the gregarious locusts form, they will cause locust plagues.
However, how do locusts that like to live alone form locust swarms, and what is it that plays a key role? In the past 80 years, scientists have put forward many hypotheses about this, such as food, breeding grounds, sexual maturity, cluster pheromone, climate, etc. However, which factor plays the main role, and what is the mystery and mechanism? No one knows.
Towards the unknown. In the 1970s, scientists gradually realized that swarming pheromones may be the most critical factor in the gathering of locusts. Since then, after more than 50 years of continuous efforts by scientists, several compounds are considered to be the clustering pheromone of locusts, and they have been named locust alcohol and locust phenol. However, none of these compounds can meet all the criteria for clustering pheromones. For example, some are effective in the laboratory, but are not valid in the field population verification; some are effective against female locusts, but not against male locusts.
"A qualified cluster pheromone should have no gender preference, regardless of size or age." Kang Le emphasized.
Identification found the "culprit" of the locust plague
So, what is the truth about locusts gathering in disasters? In 2004, the Kangle team began to study the molecular mechanism of locust type mutation gene expression regulation and epigenetic regulation. Now, the research team has discovered a key chemical that lures destructive clusters of locusts.
By analyzing the body surface and fecal volatiles of gregarious migratory locusts and scattered migratory locusts, the research team identified a chemical pheromone-4-vinyl anisole among 35 compounds, and determined it through a series of behavioral experiments. No matter it is very attractive to gregarious or scattered migratory locusts, female migratory locusts, male migratory locusts, migratory locust larvae or adult migratory locusts, it has a strong attraction, and can respond to changes in the population density of locusts, increasing as the population density increases .
What's more interesting is that scientists also found that only 4 to 5 scattered locusts are needed to gather, and this group pheromone can be produced and released, which in turn promotes the formation of huge locust swarms.
On the basis of the above-mentioned research, the researchers found that 4VA specifically caused the cone-shaped sensory response in the four main sensor types on the antennae of migratory locusts. Among the hundreds of olfactory receptors in locusts, the olfactory receptor OR35 located in the cone-shaped sensilla is a specific 4VA receptor. When OR35 was knocked out using gene editing technology, the neuroelectrophysiological response of the antennae and sensilla cone of the migratory locust mutant was significantly reduced, and the mutant also lost its response behavior and attractiveness to 4VA.
So, can 4VA attract and gather locusts in the outdoor and natural environment? Researchers have proved through outdoor grass double selection and trapping experiments that 4VA is very attractive to laboratory populations outdoors. Furthermore, they conducted large-scale experiments in Beidagang, Tianjin, and once again proved that 4VA can not only attract wild populations, but also is not affected by the background density of locusts in the natural environment.
“This research is the first to conduct comprehensive and adequate identification and verification of the pheromone of migratory locust colonies from chemical analysis, behavior verification, neuroelectrophysiological recording, olfactory receptor identification, gene knockout, and field verification. It is the pheromone of migratory locust swarms." In Kangle's view, this research has brought chemical ecology research to a new stage and is an important breakthrough in entomological research.
Green and sustainable prevention and control become possible
For a long time, people's prevention and control of locust plagues mainly relied on the large-scale spraying of chemical pesticides, which would have a huge negative impact on food safety, ecosystems and human health. This latest research not only reveals the mystery of locust colonies, but more importantly, makes it possible to prevent and control locusts green and sustainable.
Kangle believes that this research will change people's concepts and methods for controlling locust plagues in many ways. For example, the use of synthetic pheromone can monitor the dynamics of locust populations in the field for a long time, and serve for forecasting and forecasting; the use of synthetic pheromones can design traps and traps. Collect locusts, and use chemical pesticides or biological agents to eliminate them in the trap zone, thereby greatly reducing the use of chemical pesticides; design antagonists according to the structure of 4VA to prevent locusts from gathering; the discovery of olfactory receptor OR35 is used for gene editing It is possible to establish 4VA response deletion mutants by technology. Once this mutant is released into the wild for a long time, it is possible to establish a population of locusts that cannot live in groups in the hardest-hit areas, which not only maintains a certain number of locusts, but also sustainably controls them, and organically combines environmental protection and pest control.
"Therefore, the discovery of 4VA and its receptors will greatly change the strategies and technologies for locust control," said Kangle.
"This work has made an exciting discovery. It has found a locust swarm pheromone molecule that people have been looking for for a long time. The article contains surprising multiple levels of research." Rockefeller University professor Leslie Voss Hall made it clear.
"This is a huge contribution made by Chinese scientists to international entomology and locust control. This is the first time that scientists have truly confirmed the clustering pheromone of migratory locusts after 50 years of exploration." FAO Plant Production and Protection Director Xia Jingyuan stated in the congratulatory letter, “The discovery of 4VA will greatly improve the prediction and control of locust plagues, and provide important clues for people to develop new locust plague control methods. At the same time, the research also provides important information for the research and control of desert locusts. reference."