Will you die if you are "licked" by the tongue of a conch? The past and present of the mysterious "killer" cone snail

The man in front of me slowly stopped moving, as if he was about to fall asleep. In a little while, his breathing would fail and his heart would slowly stop. Before that, he still had time to roll himself a cigarette. He might not know it yet, but I knew that he would not live long. After all, no one could cure my poison. If no one could continue to give him CPR after he fell into a coma, praying for a miracle to keep him alive until the poison dissipated, he would definitely die.

However, I don't sympathize with him at all. I will never show mercy to anyone who dares to covet my beautiful appearance and scratch me with a knife. He thought he wouldn't get hurt by wearing gloves, which was really naive. Not to mention gloves, even a diving suit can't stop my fangs. However, I'd better leave before someone comes around.

If I don't work on protecting myself, I'll soon end up like this | Amada44 / Wikimedia Commons

Guess who I am

Soon, other people on the beach would discover that someone had been poisoned to death, and the person who did it was me - Conus geographus, also known as the killer cone snail.

Cone snails have existed on Earth for 55 million years. During this long period of time, many original species have disappeared, and many new species have emerged. However, cone snails have not only survived but also developed successfully due to their strong survival and adaptability. The cone snail family is now widely distributed in warm seas around the world, with a large number of branches and species. At present, more than 800 species have been discovered.

Scientific illustration of cone snail | Biodiversity Heritage Library / Flickr

These different types of cone snails all come from the same ancestor that ate insects. Although some cone snails now eat fish, some eat insects, and some eat snails, we still have some common characteristics. According to biological classification, cone snails belong to the phylum Mollusca, class Gastropoda, family Conidae. Cones are big at one end and small at the other, and look a bit like taro, so they are called cone snails; some people think they look like chicken hearts, so they are called cone snails; English speakers think we look like cones, so we are called cone snails.

These are all about the shape of the shell. The shell of cone snails is exquisite and beautiful, with various patterns on it, and has a high appreciation and collection value. In this vase-like delicate shell, we hide our body that is softer than flowers. In this soft body, there is a huge killing intention brewing. This is another common feature of our cone snails - toxins.

Various cone snails | Wikimedia Commons

All cone snails are poisonous. The venom is a very special hunting tool evolved by cone snails. In the stomach of cone snails, there is a venom gland, which secretes venom that flows through the venom tube and enters the hollow radula in the mouth. Cone snails use their poisonous radula to hunt. However, cone snails with different feeding habits have different toxicity. The most toxic of them is the cone snail that eats fish.

Deadly killer

There are roughly three ways cone snails use poison to catch fish. The most common method is to use the radula as a harpoon, just like the thin-line cone snail. These cone snails usually hide in the sand, and when the chemical receptors on their bodies sense prey passing by, they extend their long radula (sometimes this radula is several times longer than the shell) to approach the prey, waiting for an opportunity to insert the poisonous radula into the prey's body, inject venom, and then drag the prey, which is paralyzed by the poison, into their open mouths. A less common method is tracking. After this type of cone snail shoots the radula into the prey's body, the prey will not be poisoned immediately, and the cone snail will not drag it back, but will follow the prey until the prey is poisoned, and then swallow it into its mouth.

You may not believe how fast a cone snail carrying a large shell can go. Can it catch up with fish? You are right. We cone snails do not walk fast, but our radula is very fast. At the fastest speed, the radula can be launched at a speed of more than 25 meters per second. It only takes 100 microseconds to shoot the radula into the body of the prey.

The purple cone snail Conus purpurascens preys on fish by extending its radula to stab them like a harpoon | Baldomero Olivera et al. / Journal of Comparative Physiology A (2017)

Although fast, these fishing methods can only catch one fish at a time. If you want to catch many fish at once, you have to use the "casting net method" like our cone snails. After seeing the school of fish, the cone snail will spray venom at the school of fish. The venom contains a special insulin. This insulin is useless to the cone snail itself, but it is useful to fish. It can quickly lower the blood sugar of fish and put the fish into hypoglycemic shock. Soon, a large number of fish will lose their ability to move due to poisoning, and can only wait for the cone snail to swallow them into its mouth. Next, the cone snail stings them with its poisonous radula, completely paralyzing them. After an hour or two of eating, these cone snails will spit out the bones of the prey together with the used radula, and the other soft parts will be eaten into the stomach.

The cone snail opens its mouth wide to release toxins and then swallows the fish | Baldomero Olivera et al. / Journal of Comparative Physiology A (2017)

The amount of venom in the tongue of cone snails is not large, but the toxicity is very strong. This venom is a cocktail of various toxins, which is called conotoxin. Although the venom of cone snails is called conotoxin, in fact, no two conotoxins are the same. Each cone snail contains as many as 100-300 toxins with different sequence structures. Therefore, there are many types of cone snails, and the toxins they contain are also many different.

There are two main ways that cone snail toxins act on prey. One is commonly used by cone snails that project radulas, which use toxins to inhibit the sodium and potassium channels in the prey's body, blocking its nerve conduction, causing shock and paralysis of the prey; the other is commonly used by cone snails that "cast nets to catch fish", which uses tranquilizer toxins to calm the prey, and then uses paralytic toxins to paralyze the prey to achieve the purpose of predation.

Conus bandanus uses hydraulic power to eject its radula | Deep Look / youtube

Léon

A wide variety of conotoxins have unique biological activities and are a valuable natural drug library. Different toxins have precise selection capabilities for various ion channels in the body, making conotoxins an important research tool in neuroscience, used to study different ion channels or different conduction functions of neurons.

At present, some studies have found that the ω cone snail toxin used by our cone snails when casting nets to catch fish can close the N-type voltage-dependent calcium ion channel. Closing this channel is equivalent to closing the nerve pain sensation, so this toxin can paralyze the nerves and play an analgesic and calming role. The drug with sedative and analgesic function developed based on this toxin is much more effective than morphine, and it is not addictive or dependent.

Various cone snail shells | Pet / Wikimedia Commons

The components of cone snail toxins all have such precise attack target properties, so they can help the research of many human diseases. Currently, there are related drugs under development for anti-epilepsy, Alzheimer's disease, depression and cardiovascular system diseases. So, you don't have to shudder at the sight of cone snails.

Alas, as a Breaking Bad star, I am so lonely that I accidentally told you so much. Now that you know so many of my secrets, you won't expose me, right? Well, I guess you don't like to fall into hypoglycemic shock, although this method of murder is not uncommon in human history. Let me show you my little fangs, cute, right?

Comparison of the radulas of various cone snails | Sébastien Dutertre et al. / Marine and Freshwater Toxins (2016)

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