Biological extinction is something we don't like. When we see some species extinct or on the verge of extinction in news reports, we always feel sad. But do you know that in the past 50 years, a group of creatures have experienced a tragedy of near complete extinction, but they are not well known? Next, let's understand the whole story of this tragedy and how the remaining creatures escaped extinction.

The diversity of snails in the Pacific islands ranks first in the world. The general public may not be interested in snails, but on many islands in the Pacific Ocean (from French Bolivia to Hawaii), local aborigines are very interested in snails. This is because many native snails on these islands have bright shells. Aborigines like Tahiti and Hawaii will collect and process these beautiful snail shells as jewelry and decorations to show status symbols.

According to research, the diversity of snails in the Pacific Islands is the highest in the world, so these snails not only attract indigenous people, but also attract many experts who study biodiversity to make a pilgrimage.

The arrival of a war has not only disrupted the lives of the island residents, but also brought unexpected bloodshed to these snails who live smoothly on the island.

Hawaiian snail shells sold as decorations. Wikipedia's alien species were in chaos, and the native species of snails suffered from fish in the pond. During World War II, the African snail (Lissachatina fulica) was introduced to these Pacific islands in large quantities as a war preparation food. After the war, these African snails soon became a hidden danger to the local islands.

African giant snails are exotic species that are seriously harmful to agriculture. They eat a lot and eat a variety of foods, from crops, flowers to trees, and their breeding speed is extremely fast, which makes African giant snails spread all over the island soon. Although African giant snails did not threaten the survival of native snails, the large number of African giant snails with huge food intake soon threatened the crop production on the island. In order to fight against African snails, human beings decided to get rid of them by biological control. And this decision has awakened the death knell of the extinction of native snails on the island.

African snail. Simply speaking, Wikipedia's biological control method is to use the balance of natural creatures, that is, to use various natural enemies such as predatory insects and insecticidal microorganisms to eliminate alien species. In order to fight against the African giant snail, the biological control method used by human beings is to introduce another exotic species-Euglandina rosea.

Rose snail is a medium-sized snail native to forests in southern North America. Unlike ordinary snails, rose snails are carnivorous snails that eat other snails! So people want to eat up the African snails on the island by rose snails. 1955, the United States * * * began to introduce rose snails into the Hawaiian islands, and other Pacific islands began to follow this practice in succession in1958.2. But after the introduction of the rose snail, people soon found that things were big.

Rose snail. Wikipedia: First of all, the number of African giant snails has not decreased, and they are still destroying crops wantonly. Then, the number of native snails on the island became less and less. Later, it was found that rose snails prefer native snails to African snails. However, the native snail has no resistance to the fierce foreign killer, the rose snail, and can only wait to be slaughtered.

When people finally realized the seriousness of the problem and prepared to intervene, it was too late. According to research, there were 8 1 species of native snails in Hawaii. However, ten years after the introduction of the rose snail, 90% of the native snails on the island were slaughtered by the rose snail, and Hawaii and the scientific community were unable to stop this horrible massacre. Finally, they had to move the remaining native snails to zoos or protected areas for protection. In 20 19, the last golden-topped Hawaiian tree snail (Achatinella apex fulva) died, which marked the extinction of another native Hawaiian snail. The situation of other Pacific islands is not much better. Take Tahiti as an example, there were 6/kloc-0 species of native snails on the island. In the ten years since the introduction of the rose snail, 56 species of native snails have been wiped out.

This decision to introduce the rose snail can be described as a major "failure" case in biological control law, which not only failed to eradicate the African snail, but also dealt a devastating blow to the native snail. This case also warns people that they must think carefully when they want to use biological control law again in the future.

However, in this desperate situation, there are still a few native snails who are strong enough to survive in the wild. This has aroused the curiosity of many scientists, who want to know how these native snails escaped the poisonous hands of rose snails. Biologists and engineers from the University of Michigan, on the other hand, formed a cross-disciplinary research team to work together to find out the possible reasons.

How do snails escape from the deadly killer, by reflecting light? Partula hyaline (P. hyalina) is one of the few native snails still living in Tahiti forest. They have white shells and most of them live on the edge of the forest. And these two clues made Dr Cindy Bick, two scientists in the Department of Ecology of the University of Michigan who specialize in the extinction of snails in the Pacific Islands, and Diarmaid, his advisor? Dr. Foighil, there is a hypothesis that P. hyalina escaped the rose snail.

Sleeping P. hyaline (left) and M3 microcomputer (right). Snails in news.umich.edu generally live in damp places, which are out of direct sunlight, because snails need to maintain mucus on their skin. If it is too hot, it will make its skin lose mucus, which is fatal to snails. P. hyalina lives on the edge of the forest, which means that the environment she lives in will receive more sunshine and higher temperature than the rose snail living in the forest. And such an environment will make the rose snail lose its mucus because of overheating, so that the rose snail does not want to get close.

But isn't this environment too hot for P. hyalina? Because the shell of P. hyalina is white, it can reflect more sunlight, which can reduce the influence of sunlight on it. Therefore, Bick and Foighil believe that P. hyalina can live in high sunshine areas because of her white shell, so as to avoid the pursuit of rose snails.

To verify this idea, we only need to install a light sensor on the snail, and measure and compare the light values of the living environment of P. hyalina and rose snail. Well, it's easy to say, but not easy to do.

Because the existing light sensors must be equipped with button-type batteries, the size of the sensor (12*5*4 mm) will seriously affect the snail's action. If it will affect the snail's action, it will be difficult to restore their real life pattern, so the obtained light value will not be accurate.

Just as Bick and Foighil were worried about not having a good light sensor, Bick got a message: The University of Michigan has developed the smallest microcomputer-Michigan Micromote (M3) 6, which is only 2*5*2 mm in size, and this size is very suitable for snails. So she immediately contacted M3' s R&D team, hoping that they could provide assistance. M3' s R&D team decided to form a joint research team with Bick and Foighil after deeply understanding the needs of Bick and Foighil. They modified the program of M3 and transformed it into a miniature light sensor that can generate electricity by solar energy.

The research team first tested the installation of M3 on the rose snail in the field of Michigan, which will not affect the action of the rose snail, and M3 can also detect the light value for a long time. After confirming that everything was in order, they went to Tahiti for an experiment.

The research team successfully tested the installation of M3 on the rose snail in the field. Source: Reference 5