6,000 worms in one snail! What kind of snail can eat so much?

Audit expert: Li Weiyang

Well-known science writer

When summer comes, people can't help but think of those tempting delicacies in the night market: stir-fried snails, spicy crayfish, fried chicken, grilled skewers...especially snails. It is a wonderful thing to eat snails with friends and have a beer at a busy roadside stall at night.

Source: A shopping website

It has to be said that snails are a delicious food suitable for chatting and gathering. You can complete the whole process from picking up and sucking to eating the meat and throwing the shell with just one hand, and it does not affect the other hand to browse the phone or hold the cup at all - except for one thing: the small snail meat is too little. Although it tastes delicious, it always feels a little unsatisfying. Some friends think, wouldn’t it be wonderful if there was a kind of snail with big meat?

The good news is that large snails do exist, but the bad news is... they are not edible! This snail that made people feel disappointed is the famous golden apple snail (Pomacea canaliculata).

What is the golden apple snail? Why can't we eat it?

The golden apple snail belongs to the Ampullariidae family and is an omnivorous freshwater snail. Many species of this type of snail (as well as individuals with color variations) can be seen at the ornamental fish stalls in flower and bird markets. It is a very common ornamental snail. In addition, in some countries and regions, the golden apple snail is also used as an edible snail. For example, some foreign video bloggers often upload videos of cooking golden apple snails (however, some videos have serious health and safety risks, so everyone must not imitate them).

Screenshot of a video showing the eating of golden apple snails abroad

Source: Foreign video blogger hagna

In fact, the golden apple snail was originally introduced to various parts of the world for the purpose of being used as food and feed. However, as a food ingredient, golden apple snails have considerable risks: unlike the field snails we often eat, golden apple snails are highly infected with the Guangzhou roundworm. Some snails have up to 6,000 Guangzhou roundworm larvae in their bodies. In addition, they also carry many other types of parasites. If they are not cooked thoroughly, there is a risk of infection with parasitic diseases.

According to a survey report published in the Chinese Journal of Epidemiology in 2011, among the four common freshwater snails surveyed around Erhai Lake, the infection rate of Angiostrongylus cantonensis in the Golden Apple Snail was as high as 11.5%, much higher than the 3% of the second-ranked Erhai Lake Snail.

Angiostrongylus cantonensis

Source: Wiki

In addition, the golden apple snail has another characteristic, that is, when it is fully cooked, the snail meat will become dry and woody, and eating it is like chewing rubber, which means that after completely heating and cooking the golden apple snail, it avoids the risk of infection, but also avoids the favor of diners. In this way, it is not surprising why such a large freshwater snail rarely appears on the menu of regular restaurants.

In fact, in 2006, Beijing had an outbreak of Angiostrongylus cantonensis caused by golden apple snails. At that time, a restaurant used cheap golden apple snails to replace conch meat to make cold-mixed snail slices in order to save costs. When making it, the snail meat was only blanched in boiling water and served cold, resulting in the parasites in the snails being eaten by diners without being killed, which then evolved into a public health incident that infected more than 160 people.

News page about parasitic infections caused by golden apple snails in 2006

Source: News Photo

Since then, the golden apple snail has basically disappeared from the market and restaurant menus. Although golden apple snails can occasionally be seen for sale in vegetable markets in southern my country, they are generally not popular because of parasites and meat quality issues.

Golden Apple Snails in Southeast Asian Markets

Source: pixabay

How to distinguish between golden apple snails and field snails?

Some friends think that golden apple snails and field snails are both round freshwater snails and look very similar. So how do we distinguish between the field snails that are safe to eat and the dangerous golden apple snails?

The first and most intuitive point is that the snails we usually eat are mostly Chinese round field snails and Chinese round field snails, as well as the square stone field snails commonly used in snail noodles. These freshwater snails are usually not very large, about the size of the thumb or index finger knuckle; while the golden apple snail can grow quite large, with a shell height of up to 7 cm and a length of more than ten cm, which is equivalent to the size of a small apple or nectarine!

Comparison between Golden Apple Snail and two kinds of river snails

Source: Claude & Amandine EVA

If you don't look at the body shape, you can also use other methods to distinguish between field snails and golden apple snails: for example, the tail of the field snail is relatively pointed, while the tail of the golden apple snail is flat; the shell of the field snail is generally green, while the shell of the golden apple snail is yellowish brown; the egg mass of the field snail is small and transparent, and some field snails will produce young snails through oviposition, while the egg mass of the golden apple snail is obviously pink and is laid on the water surface; the snail mouth is relatively small and the mouth cover is relatively round, while the mouth of the golden apple snail is larger and the mouth cover is relatively flatter...

Comparison between golden apple snail and river snail

Source: Biological characteristics and prevention of golden apple snails

There is an easier way to distinguish between field snails and golden apple snails. Field snails grow slowly, so their shells are thicker and stronger, and cannot be easily broken by pinching. The shells of golden apple snails are relatively thin and brittle, and can be easily broken if you pinch them hard. If you find field snails and golden apple snails of similar size in the vegetable market, you can easily distinguish them by pinching their shells.

How destructive is the golden apple snail?

Apart from the parasites they carry, golden apple snails are also highly destructive invasive species and agricultural pests. The International Union for Conservation of Nature's Species Survival Commission has named golden apple snails as one of the world's top 100 invasive alien species. my country's State Environmental Protection Administration has also listed golden apple snails as one of the major dangerous agricultural invasive alien species.

In Southeast Asia and Hawaii, invasive golden apple snails have been eating large quantities of crops grown in water, such as rice, causing serious economic losses. In 1979, an overseas Chinese introduced golden apple snail eggs to Taiwan Province for breeding promotion. Subsequently, the golden apple snails that escaped and were abandoned by farmers ate large quantities of tender stems and seedlings of plants, causing losses of up to NT$5.1 billion.

Not only that, as a very successful invasive species, the golden apple snail will greatly squeeze the living space of native freshwater snails and even cause the extinction of native freshwater snails.

Apple snails in a pond in Xiamen Park

Source丨Author

As the temperature rises in summer, golden apple snails in many places begin to mate and lay eggs. If we see pink objects attached to stones or plants near the water, they are undoubtedly golden apple snail eggs.

To deal with the eggs of the golden apple snail, you can push them directly into the water. The eggs of the golden apple snail can only hatch near the water, and they will drown if they fall into the water. Alternatively, you can throw them into a dry area far away from the water to let them dry out, or simply crush the eggs directly.

Pomacea canaliculata eggs

Source: Baidu Encyclopedia

As for adult golden apple snails in the water, in addition to catching and crushing them, some parks and farmlands also kill them by spraying drugs. A more environmentally friendly approach also includes manually collecting golden apple snails to make animal feed. In recent years, golden apple snails have also been found in some park waters in Beijing. If we see these annoying guys when we go out for fun, we can also kill them.