Written by Shen Mengxi
Humans have always hated mosquitoes. People who grew up in the countryside may have a deep understanding of this: the buzzing sound of blood-sucking mosquitoes in the summer is always disturbing, and it is common to find it difficult to sleep in the middle of the night; after being bitten by mosquitoes, redness and itching will make us irritable. Since the development of modern medicine, human disgust with mosquitoes has risen to the extreme - in 1881, cuban epidemiologist Carlos Juan Finlay began to recognize that mosquitoes can transmit yellow fever; around 1900, doctors in India and Italy began to find that mosquitoes can also transmit malaria; and then more and more studies proved that mosquitoes can also transmit dengue fever, Japanese meningitis and other diseases. Because of this, mosquito control is becoming an increasingly important task.
Mosquitoes are probably our most hated creatures of the summer, not one of them in The Picture/Wikipedia
In order to kill mosquitoes, people in the early 20th century came up with many methods, but most of them had a very important negative impact on the environment. At that time, people found that mosquitoes breed in large areas of wetlands, and their life cycle has four stages: eggs, larvae, pupae, and adult insects. Mosquitoes will lay eggs on the surface of the water, and after the eggs hatch, they will become larvae, which is familiar with the widow (jiejue), which hangs upside down on the surface of the water and breathes with the tail end, while the organic matter in the water by mouth filter grows into a pupa, and the pupa matures into a nasty adult worm - mosquito.
The widow below the water/wikipedia
Therefore, if you consider the problem from the perspective of the growth cycle of mosquitoes, the first method that is thought of is to drain the water of the entire wetland, but this is not only labor-intensive, but also unrealistic - some areas of wetland area are so large that it is impossible to drain the water in it; the second method is to fill the wetland with oil - as we all know, oil is lighter than water, and when the water surface is covered with a layer of oil, the oil layer will isolate the air, so that the widows in the water will suffocate and die. New York City had widely used oil to kill mosquitoes in 1901, and achieved very good results, but this also led to a large number of deaths of livestock and fish, so it was quickly abandoned.
It was william seal, a former employee of the U.S. Fish and Fisheries Commission, and Dr. W. Vecchio, a family doctor in New Orleans. H. Veazie) has noticed a "top- and" small fish, no more than 5 centimeters long, very adaptable, and very fast-breeding, so that it is extremely widely distributed in the southeastern Part of the United States, even the shallowest and dirtiest beaches, and the best thing is that they feed on the larvae of widows and freshly feathered mosquitoes, and each small fish can average hundreds of babies per day, and there is a place where it lives "cannot find any kind of widows." The fish was subsequently known as mosquitofish for its mosquito-eating properties, and soon after it began to be consciously released as a biological weapon into mosquito-infested water bodies.
Female mosquito-eating fish Photo/wikipedia
Mosquito-eating fish in predators Photo/Youtube
Because mosquito-eating fish are really effective in controlling the number of mosquitoes, by around 1920, many places in North America even had professional mosquito-eating fish farms, which would give away mosquito-eating fish for free. At the same time, their daimyo also began to attract other mosquito-stricken regions of the world, so they were introduced to Hawaii in 1905, to the island of Taiwan in 1911, to the Philippines in 1913, to Japan in 1919, to Europe in 1921, to Chinese mainland in 1927... Although it cannot be proved that mosquito-eating fish can be effective in controlling mosquitoes everywhere, there are very few examples of excellent mosquito control effects that are enough to advertise it. For example, the former Soviet Union's Sochi was built on a swampy land, so the mosquito infestation was serious, resulting in a high malaria prevalence, after the introduction of mosquito-eating fish in 1925, the mosquito population declined significantly, and after 1950, there were almost no more people suffering from malaria in the local area, so the locals also erected a monument to this small fish. These advertisements made mosquito-eating fish very popular all over the world, and once made it the most beautiful boy in the mosquito industry that year.
Monument to mosquito-eating fish in Sochi Photo/wikipedia
However, after the mid-to-late 20th century, scientists began to question the mosquito control effect of mosquito-eating fish, and gradually found that in 4 of the 20 countries that intended to introduce mosquito-eating fish, only 4 achieved mosquito control effect, and the effect in other places was better than nothing. In a study of mosquito-eating fish in some of these areas, it was found that although mosquito-eating fish feed on mosquito larvae, mosquito larvae make up only a very small part of the intestinal contents of mosquito-eating fish, and the rest are mainly zooplankton, other fish and amphibian eggs. As a result, the introduction of mosquito-eating fish has instead suffered from the poison of mosquito-eating fish – in California, the indigenous salamanders in the rivers that introduced mosquito-eating fish have almost disappeared, and the population of red-legged frogs has decreased significantly; in Australia, mosquito-eating fish have hunted the tadpole of an endangered frog, the green golden-bellied frog; in Spain, it has posed a major threat to two species of toothed carp in the Iberian Peninsula; and in Yunnan, China, it has led to the shrinking of the range of medaka, such as in a fish pond in Jinghong, where the medaka was everywhere in 1973. But more than a decade later, in 1986, it was all occupied by mosquito-eating fish.
Mosquito-eating fish not only pose a threat to local indigenous organisms, but also lead to a rapid decline in the quality of local water bodies. Mosquito-eating fish like to eat zooplankton, and zooplankton feed on phytoplankton, after losing the control of zooplankton, the local water body in the phytoplankton will increase in large quantities, resulting in a decline in water oxygen content, green water, transparency, water quality and other phenomena. Because of the devastation caused by mosquito-eating fish to the local ecology and the widespread invasion of mosquito-eating fish, the IUCN has included it in the list of 100 most threatening invasive alien species in the world.
Mosquito-eating fish swimming in shallow water, which cause algae growth and water quality declines Figure/Flickr-schizoform
And our current ability to control these invasive species is still extremely limited, can use nothing more than physical, chemical and biological three methods, of which physical methods are artificial fishing, chemical methods are simply understood to be poisoning, biological methods are the introduction of natural enemies - these three methods are undoubtedly costly, and the consequences are uncontrollable, such as chemical methods can remove mosquito-eating fish, but it is likely to cause more serious consequences to the ecosystem, biological methods are not good to bring new invasive species. Moreover, because many parts of the world are still introducing mosquito-eating fish on a large scale in order to fight malaria, the invasion of this organism may be intensified in the future.
Recently, however, scientists have invented a "boat new" method that can curb the expansion of mosquito-eating fish - using robotic fish! This is actually a relatively new biological control program, and scientists believe that the reason why mosquito-eating fish cause great ecological damage is not simply because they appear in indigenous water bodies, but also because they lack predator pressure, which leads to their wanton behavior. Even if it only brings them fear of predators, it can affect their behavior, which can greatly hinder their expansion. Based on this line of thinking, the scientists made a robotic fish bass based on the image of one of the natural enemies of mosquito-eating fish, the largemouth bass, and put it together with the mosquito-eating fish.
The largemouth bass is a ferocious carnivorous fish that, along with the mosquito-eating fish, is on the list of the world's top 100 invasive species figure/Flickr-NOAA
The results were so encouraging that after a few weeks, mosquito-eating fish under the threat of robotic fish changed their habits and began to tend to live together, losing the desire to explore the outside world; at the same time, perhaps due to the constant fear, their body size became smaller, and their sperm count began to decrease (because of fear, the body was hollowed out?). ）。
Robotic Fish and Mosquito-Eating Fish in experiments Screenshot of the Sciencenews webpage
The biggest result of this experiment is, of course, not just to tell us that robot fish can deal with mosquito-eating fish (after all, they are the same hundred invasive species, they are also very likely to be able to touch in the wild, not worse than these robot fish), but also tell us that just making these invasive species feel fear can control their expansion, after all, they are just ordinary creatures, not invincible aliens.
So, if we think differently, such as using the smells and sounds of predators, can we also control them? These methods are more targeted and do little harm to the environment. If the pattern is enlarged a little more, will it be possible to use this set for all invasive animals? We can wait and see.
Resources:
https://docs.qq.com/doc/DSUJ5bVZTWXhjR0dQ
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Original title: The former anti-mosquito hero, now the world's top 100 invasive species, forced scientists to use robotic fish to scare it
Source: Bring science home
EDIT: just_iu