Running thousands of miles! How can this locust fly so fast?

Produced by: Science Popularization China

Author: Insect intern (Chinese Academy of Sciences)

Producer: China Science Expo

Many students may have fantasized about flying freely like birds. It is a wonderful evolution in nature that has given birds wings to fly. But you would never have thought that seemingly inconspicuous insects are actually the earliest flying animals in the world.

In 2020, the locust plague caused by desert locusts quietly crossed the Red Sea from East Africa, entered Europe and Asia, and reached our neighboring countries Pakistan and India.

The tiny locusts actually traveled thousands of miles, bringing great disasters to the countries along the way and seriously endangering human food security. Although the desert locusts living in the desert area cannot adapt to the environment of my country and have not caused any harm to us, this scene is still scary. Because the locust plague caused by the migratory locust, a close relative of the desert locust, has been a disaster in my country for thousands of years. It was not until the founding of New China that Chinese scientists finally eradicated the locust plague in China through multi-faceted governance.

Desert Locust

(Photo source: veer photo gallery)

Living in groups is a "marathon", while living apart is a "hundred-meter race"

Desert locusts, as the name implies, are locusts that live in the desert. The name "migratory locust" shows its strong flying ability, and its migration distance can reach thousands of kilometers. However, migratory locusts have two forms. One is the gregarious migratory locusts that live in groups. This marathon-like long-distance migration of swarms of migratory locusts is the main cause of locust plagues; the other is the solitary migratory locusts that prefer short-distance fast flights.

After reading this, are you wondering why the same kind of locust has two completely different flying strategies at different population densities?

Locusts in flight

(Photo source: China Science Daily)

Early studies believed that gregarious locusts are good at flying, while solitary locusts are not good at flying. However, the team of Kang Le, an academician of the Chinese Academy of Sciences, has revealed the truth about the two forms of locust flight, that is, the gregarious "marathon" and the solitary "100-meter race": the flying speed of gregarious locusts is not fast, and they fly continuously for a long time at a relatively low speed, just like "long-distance runners" in flight; while the solitary locusts have fast flying speeds and strong explosive power, but lack endurance, just like the cheetah, the "champion" of sprinting in the animal kingdom. It is really not simple for an insect that is only the size of a little finger.

The "marathon" flight characteristics of gregarious locusts are conducive to long-term and long-distance flight, which enables them to find sufficient food and suitable breeding grounds, while the "hundred-meter sprint" flight characteristics of solitary locusts are conducive to finding mates and quickly escaping from natural enemies. When the environment is not suitable for survival, the gathered locusts can change to a gregarious mode to achieve migration and find food and habitats.

Kang Le's team found that there was no obvious difference in the types of energy substances used by the two states of locusts, mainly lipids and sugars. Although the gregarious locusts stored more triglycerides, when there were differences in long-distance flight ability, there was no obvious consumption of triglycerides for energy storage during the flight. This changed the traditional view that "the difference in flying ability between the two types of locusts is caused by differences in energy storage."

They also found that the flight muscles of solitary locusts provide more energy for flight through high energy metabolism, but more reactive oxygen species are produced during flight, which can cause damage to the organism. In order to prevent the muscles from being damaged too much, solitary locusts cannot fly long distances. In contrast, the energy metabolism level of gregarious locusts is lower, which enables them to produce less reactive oxygen species during long-term flight, thus maintaining the balance of muscle cell life activities for a long time and supporting their long-distance flight.

Migratory locust

(Photo source: veer photo gallery)

“More haste makes waste” is perfectly illustrated by locusts. If they fly fast, they cannot fly far, and if they fly far, they cannot fly fast. The difference between the two flight characteristics is actually caused by the clustering and dispersion of locusts. Isn’t it amazing?

The story does not end here. If a "cheetah" runs a marathon, it may "die of exhaustion" because its body is overwhelmed. This is because long-term rapid consumption of oxygen will produce a large amount of heat and reactive oxygen, which will damage cells and even endanger life in severe cases. So why can gregarious locusts maintain long-distance flight? What keeps their body metabolism stable and does not cause damage due to long-term flight?

New discoveries, new insights

Here is a piece of knowledge. In 1991, people discovered a specific DNA-protein complex that changes with changes in oxygen concentration. This protein was named "hypoxia-inducible factor" (Hif). In 2019, the Nobel Prize in Physiology or Medicine was awarded to three scientists for their discovery of Hif and its function in regulating hypoxia adaptation. After that, it was generally believed that Hif would only be activated when there was low oxygen.

When studying the oxygen consumption of locusts during flight, researchers from Kang Le's team also studied the Hif protein. A puzzling situation arose: locusts have two Hif proteins, only one of which is activated when hypoxia occurs, and the other is activated when flying under normal oxygen. At this point, they proposed a creative conjecture: Could this protein be the reason why locusts maintain metabolic homeostasis during flight?

After a series of studies, they found that this newly discovered protein was "missing" a part compared to the previous Hif. Experiments have found that it is precisely because of the lack of this part that the new protein can maintain a high activity in a normal oxygen environment. They named this new protein Hif-1α2, and Hif-1α2 will directly activate the expression of the gene DJ-1. The protein encoded by DJ-1 is a key detoxification and antioxidant enzyme in animals, which can effectively remove reactive oxygen and other harmful metabolites accumulated in the muscles of locusts during flight, so that gregarious locusts can maintain long-term flight.

Hif-1α2 mechanism of action

(Image source: References)

This study also breaks the traditional concept that Hif only works in low-oxygen environments (such as in tumors), indicating that Hif also has important biological functions under normoxic conditions. This discovery will have a huge impact on the research of Hif.

I didn’t expect that behind a seemingly small problem, there is a very complex mechanism, and it has also promoted research in other fields! Isn’t this what scientific research is like? People continue to discover problems from every aspect of life, and on the road to solving these problems, our civilization has been moving forward.

Editor: Sun Chenyu

References:

Mingyu Shin, Jiwon Shim (2022) Alternative Splicing: A new role for Hif-1α eLife 11:e82028

https://doi.org/10.7554/eLife.82028