Buzz
Among the already strange world of snails that hunt with venomous, harpoon-like teeth, the geography cone snail (Conus geographus) stands out as an extreme example.
Cone snails are a diverse group of vibrant sea creatures found mainly in the tropical Indian Ocean. They break two common misconceptions about snails: 1) they're not docile, and 2) they're not slow. These carnivorous snails are expert hunters of fish, worms, and mollusks. While they tend to move slowly, their strikes are quick as lightning. After silently closing in on their target, the snail ejects a venomous, barbed tooth from a long, tube-like structure called a proboscis, which encircles its mouth. This venom paralyzes, and sometimes kills, the prey, and once it's immobilized, the snail retracts the tooth and pulls the prey into its mouth. The entire process takes mere seconds.
The geography cone snail, the most venomous in the group and responsible for several human fatalities, has a unique hunting method. Unlike its relatives that stab their prey before drawing it in, the geography cone snail traps its victim first in a net-like structure that leads to its actual mouth, and only then injects venom. Essentially, it grabs before it stabs, rather than stabbing before it grabs.
To catch a fish, the geography cone snail uses its false mouth, but the process can be tricky. To make this easier, the snail releases a mix of toxins called the 'nirvana cabal' into the surrounding water, sedating and disorienting the fish before it captures them. Even more surprising is that researchers have found this chemical blend includes a special form of insulin that affects the prey's metabolism, alongside the usual neurotoxins that attack the nervous system.
Biologist Helena Safavi-Hemami from the University of Utah and her team made an intriguing discovery while studying the genes in the snail's venom gland. They identified a compound resembling insulin, a hormone vital for regulating blood sugar in animals. However, instead of being the type found in the snails' own bodies, Safavi-Hemami realized it resembled the insulin found in fish.
The researchers hypothesized that this fish-like insulin, named Con-Ins G1, was part of the snail’s 'nirvana cabal.' By altering insulin’s normal function and incorporating it into their venomous attack, they believed the snail could lower a fish’s blood sugar, causing it to become sluggish and easier to capture. To test this, they exposed fish to Con-Ins G1 in the water, and the fish became weak and sluggish, absorbing the insulin through their gills. When the researchers injected the insulin directly, the fish’s blood sugar levels dropped dangerously low.
After discovering the fish-like insulin in the geography cone snail, the researchers turned their attention to other cone snails that use a similar netting technique to capture mollusks and worms. They found that these snails produce insulin corresponding to the insulin of their preferred prey. In each case, the weaponized insulin was smaller than the natural version found in the victims, likely streamlined to act faster and bypass any defense mechanisms against an overdose.
To the researchers' knowledge, insulin has not been found in the venom of any other animals, but that doesn’t imply snails are the only ones using insulin as a weapon or targeting the metabolism of their prey. In 1982, Claus von Bülow was accused of attempting to murder his wife with an insulin overdose, resulting in two high-profile trials. The gila monster, a lizard native to the American Southwest, also exploits its prey’s hormones with a venomous protein that stimulates the secretion of insulin in its victim’s body.
