(Warm reminder: This article involves some of the actual pictures of African large snails, in fact, it is just a snail with a large head, and readers who are really afraid of it are cautious Oh ~)
In recent years, residents in many parts of southern China often see huge snails flocking to the roadside after the summer rains, "running amok" on the side of the road, and at the same time, many people have noticed that the small snails that can be seen everywhere in childhood seem to be gone? In fact, this is due to an invasive creature that many people may have heard of - the African snail.
As a large snail that is now more common in southern China and can grow up to 20 centimeters in size, the African snail will appear in various news or hot searches in a very frightening way from time to time, like -
The image comes from the Internet
Sometimes it can be transformed into a terrible killer full of germs, as if people will get sick or even die when they touch it; sometimes it is said to like cannibalism, leaving no piece of armor everywhere it goes, even cement can eat; and sometimes it becomes a table delicacy as a white jade snail, or a popular novelty pet in the pet market.
So, are these claims about the African giant snail true or false?
Adult palm-sized African snail (Credit: © R. Zimmerman, USDA-APHIS)
The African giant snail that climbed into China
The standard Chinese name of the African giant snail on the mainland is the brown cloud agate snail, and the "African giant snail" is a name from Taiwan Province. It belongs to the mollusk phylum, really has the lung class Eupulmonata, agate snail family Achatinidae, it once belonged to the agate snail genus Achatina, but recent morphological and molecular biological studies confirm that the African large snail and the agate snail genus are more distantly related, should be classified in the slippery agate snail genus Lisachatina, so the scientific name is now Lisachatina fulica.
On the left is an individual with a shell of nearly 20 centimeters, and on the right is an African snail of an ordinary individual (Image: wikipedia)
The world's largest snail, is the African giant snail in West Africa relative of the true agate snail Achatina achatina, currently has not invaded the country, the shell length can be nearly 30 cm, the soft body up to 40 cm, weighs 900 grams (Image source: pinterest)
As its name suggests, the African Giant Snail comes from as far east as Africa as well as Madagascar. In fact, the African giant snail is one of the most notorious invasive species and can now be found in almost all tropical and subtropical regions of the world. However, the reason why snails without wings and cannot swim can invade everywhere in this way is inseparable from the help of humans, intentionally or unintentionally.
The first case of African large snails in China was recorded in Xiamen in 1931, and according to research, it is likely that the tropical plants brought from Singapore by returned overseas Chinese at that time were mixed with snail larvae or eggs. After that, this kind of foreign snail spread all the way to Fujian, Liangguang, and Hainan with the trend of burning the plains, and in addition, this snail also sneaked into Taiwan and Yunnan provinces from other paths, and gradually flooded in some places. In addition to accidental introductions, breeding escape and rewilding is also a major reason for the repeated invasion of African large snails throughout the south.
Legends about terrorist killers
As a tropical snail, the African giant snail cannot survive winters with average temperatures below 5 degrees, so its invasion within the country is currently limited to the south. However, due to its extremely wide range of feeding habits and superior reproductive ability, there are almost no native snails that can be its competitors in the areas where it can survive.
Speaking of this, I have to mention a common saying, saying that African snails can eat anything, and even cannibalize, even eat cement, is it really so terrible?
In fact, the African giant snail is basically vegetarian, but compared to many other snails, its teeth appetite is super good, from all kinds of fruits and vegetables to ornamental plants, and even to the leaves of rubber trees, pepper vines, tea leaves, banyan trees and other street trees... This snail can eat more than one-tenth of its body weight every day, and its huge amount of food has led to a serious reduction in the yield of cash crops grown outdoors in many areas and even no harvest. Therefore, to some extent, the African giant snail can indeed be said to be a terrorist killer of plants, and its strong competitiveness has also made many native snail species gradually disappear.
African giant snail nibbling on a hard green papaya (Image: wikipedia)
On the other hand, African giant snails also have super hunger tolerance, according to research, African large snails can shrink in the shell and completely eat or drink for up to 8 months. Its extensive plant-based diet and super endurance make it difficult to encounter situations where it is necessary to eat the same kind of corpse or other meat, of course, it is not excluded that some people have indeed observed the behavior of eating the same kind of corpse, but in fact this is very rare.
As for the so-called "eating cement" phenomenon, it is likely that it is due to the fact that it has been observed to eat the surface of the wall. In fact, this is found in many other snails, because all shelled snails need to ingest calcium to construct their own shells, in the wild, calcium carbonate limestone is the most common source of minerals, and in the city, the various unpainted, bare facades are a common choice for snails, including local snails.
Other claims claim that the African giant snail is the creature with the most teeth, with 25,000 teeth! But this statement is not entirely accurate.
The snail's teeth used to grind food is a special structure called a tooth tongue, which is generally rather than calcium, similar to a tongue covered with dense rows of teeth, and the snail can use this tongue to scrape the surface of food. However, each row of teeth and tongues on the "tongue" can indeed be removed individually like teeth, and its form and number are also an important basis for the classification of various mollusks.
The tooth tongue wears and grows continuously throughout the snail's lifetime, so the number is always changing, and common snails may range from a few thousand to 20,000. In addition, the African large snail is far from the mollusk with the largest number of toothed tongues, according to research, the Chinese umbrella snail Umbraculum umbraculum can accumulate more than 750,000 such teeth and tongues in its lifetime.
Schematic diagram of the working of the snail tooth tongue. This image shows the snail's oral cross-section, the blue is the food, the dark red part is the muscles around the tooth tongue, and the reddish part is the so-called "tongue protrusion", which is covered with tiny pieces of toothed tongue, which scrapes the food by using muscles to control the "tongue protrusion" movement that covers the tooth tongue (Image source wikipedia)
So can you eat it?
For such a large meat thick African snail, many people inevitably have to ask: can you eat it? Is it tasty?
Many articles claim that this is absolutely not okay, and even a touch can be very dangerous, saying that it "carries a lot of bacteria and viral parasites, which can cause tuberculosis, meningitis and other diseases." So is this really the case?
In fact, like another famous invasive organism in China, the crayfish (Protocrayfish Crawfish), the African giant snail also has both wild and farmed situations, and the main purpose of breeding this snail is to eat.
Most of the farmed African large snails are artificially selected melanin-deficient breeds with snow-white flesh, so they are called "white jade snails". This white jade snail is sometimes even dyed and appears in the pet market. However, individuals who are dyed can die easily and are not recommended to buy as pets.
In fact, many restaurants in China use this white jade snail for roasting French large snails, rather than the loose large snail Cornu aspersum or the lidded large snail Helix pomatia commonly used in France. Generally speaking, as long as it is from a regulated farm and restaurant, it is very safe to eat this farmed white jade snail.
White jade snail (Image: wiki commons)
Stir-fried white jade snails in some restaurants (Image source: Internet)
Since this kind of African snail is so common in the southern wild, can you pick up some stir-fry and eat it yourself like a snail? The answer is definitely not recommended.
The African giant snail itself, like wild snails, will certainly carry some bacteria, but there is no conclusive evidence that it can spread bacterial diseases such as tuberculosis, but this does not mean that we can take it lightly. What really links the African giant snail to the terrible killer is the so-called "Guangzhou tube ringworm disease".
"Guangzhou tube strongyloidiasis" is a disease caused by the parasite Guangzhou strongyloides into the human brain, with eosinophilic meningoencephalitis as the main feature, symptoms such as headache, fever, neck stiffness, facial nerve paralysis, etc., severe cases can cause dementia, and even death.
The ultimate host of this parasite is mainly various rodents, mainly parasitizing the lungs of mice, but its larvae must be in the body of mollusks to develop successfully. In recent years, a large number of studies have found that the African giant snail is one of the most important intermediate hosts of this parasite, with infection rates ranging from 10% to 40%, compared with other snails and snails, the probability of infection with this parasite is very low, with only sporadic records.
Life history of The Guangzhou TubeWorm (Image source: Spratt, 2015)
Although this parasite is not tolerant to high temperatures, but because the African large snail is relatively large, it is difficult to fully fry in a short period of time, and the long time of frying will be like an eraser, which has higher requirements for cooking methods, so eating African snails caught in the wild is a very risky behavior.
In addition, if you do not wash your hands in time, there is a real risk of parasites, and eating lettuce contaminated with snails or freshwater shrimp, crabs and frogs may also become infected.
Therefore, friends living in the Guangzhou Tube Roundworm epidemic area (mainly Fujian, Liangguang, Hainan, Taiwan) must avoid eating any wild snails or wild freshwater shrimp and crab frogs, rather than worrying about whether they will be caught, it is better to buy white jade snails from regular farms and cook them thoroughly.
Is salt sprinkling useful?
As an invasive species that seriously endangers local vegetation crops and native snails in China, the African giant snail undoubtedly needs to be controlled and eliminated as much as possible, of which salt sprinkling is a more familiar method of elimination.
Snail skin itself is very weak moisturizing ability, will secrete a layer of mucus on the surface of the body for moisturizing and auxiliary crawling, once sprinkled with a large amount of salt, the mucus will become thick salt water, thus forming a high osmotic pressure environment around the snail's fragile skin, resulting in the snail's body water is pumped out in large quantities, and eventually dehydrated and dies. However, although salt sprinkling is indeed an effective way to control the number of snails, this method is more suitable for dealing with small snails, and it is undoubtedly necessary to completely kill large snails such as the African giant snail, which will have a negative impact on plant soil and other factors, and it is difficult to use it on a large scale.
In practice, we will use a variety of snail killer agents with higher environmental safety and better efficiency to poison African large snails, such as iron phosphate, aluminum sulfate, tetraacetaldehyde, etc., and generally will manually capture a large number of unified killing. Therefore, if we really want to effectively clean up the African snails in a region, we still need the relevant local departments to carry out professional, standardized and large-scale elimination. As ordinary people, let's forward and share this tweet to more people!
bibliography:
[1]https://en.wikipedia.org/wiki/Lissachatina_fulica
[2] Lv, S., Zhang, Y., Liu, H. X., Hu, L., Yang, K., Steinmann, P., ... & Zhou, X. N. (2009). Invasive snails and an emerging infectious disease: results from the first national survey on Angiostrongylus cantonensis in China. PLoS neglected tropical diseases, 3(2), e368.
Guo Jing, Zhang Jia'en, Wu Ruishan, Zhao Benliang, & Yang Huirong. (2015). Research status and prospect of African giant snail in China. Southern Journal of Agricultural Sciences, 46(4), 626-630.
Li Ping, & Li Yan. (2008). Research on the occurrence and control of African giant snails in Yunnan Province. Journal of Yunnan University: Natural Science Edition, (S1), 203-205.
[5]https://en.wikipedia.org/wiki/Radula
[6] Spratt, D. M. (2015). Species of Angiostrongylus (Nematoda: Metastrongyloidea) in wildlife: A review. International Journal for Parasitology: Parasites and Wildlife, 4(2), 178-189.
Source: Science Compound
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