Biodiversity

Cone snails use the illusion of sex to catch their next meal

Paper: Torres, J. P., Lin, Z., Watkins, M., Salcedo, P. F., Baskin, R. P., Elhabian, S., … & Schmidt, E. W. (2021). Small-molecule mimicry hunting strategy in the imperial cone snail, Conus imperialis. Science Advances, 7(11), eabf2704.

Even some of the most gruesome animals take advantage of romantic moonlit evenings. Enticed by pheromones and the full moon, bristle worms come out of their burrows on the ocean floor to find a mate. Females lay their eggs and males fertilized them with sperm. But a new study published in the journal Science Advances points to a dark twist to this otherwise romantic tale. In some cases, the trail of pheromones lures bristle worms into a trap created by one of the deadliest predators of all – cone snails.

Deadly Hunters

Underneath that beautiful shell hides a lethal weapon – a harpoon-like that tooth pierces their prey’s tissues and injects venom. Credit: Wikimedia Commons

Cone snails are remarkable hunters. Inside the cone snail’s proboscis is a harpoon-like tooth that strikes at bullet speed – up to 400,000m/s2. This harpoon not only pierces their prey’s tissues, it injects venom. After several strikes, cone snails immobilize their prey and reel them back to their mouth where they swallow the animal whole.

Venom glands inside cone snails produce a wide range of chemical compounds. In fact, scientists have found that cone snail venom varies from species to species, and even from one shot to the next. Some compounds paralyze their prey, while others slow down their prey’s metabolism. With roughly 1,000 known cone snail species, the venom recipe book of cone snails seems endless. And scientists are just starting to figure out how these compounds work.

Compounds of Deceit

Platynereis dumerilii, the species of annelid worm preyed by cone snails in this study. Credit: Wikimedia Commons

In a recent study, scientists found two compounds created by Conus imperialis, a species of cone snail commonly known as the imperial cone, that have a special power; instead of paralyzing their prey, these compounds activate their prey’s sexual instincts. In a laboratory setting, scientists exposed Platynereis dumerilii, a species of bristle worm commonly known as fireworms, to conazolium A and genuanine. These two compounds have a similar structure to the pheromones released by fire worms during mating. Females exposed to conazolium A showed mating behavior. They swam in tight tail-chasing circles before releasing their eggs. Males exposed to genuanine released their sperm.

How these compounds work in the wild is still a mystery, but scientists believe that the hunting strategy of imperial cones may consist of a two-step process. First, the imperial cone lures its prey out of hiding with its mimic pheromones. Then it strikes its prey with venomous compounds. However, many questions still remain. This deceptive love potion only works during certain full moon nights when sexually mature fireworms are ready to mate. The role of mimic pheromones during non-mating times is unknown. And whether these mimic pheromones work on other bristle worms species also remains a mystery. Further research is needed.

Human Benefits

What lures and kills brittle worms, not only benefits cone snails, it might also benefit humans. In the last decades, scientists have found compounds produced by cone snails that relieve pain in the human body. These non-opioid pain compounds have led to one FDA-approved drug and many more drugs that are in clinical trials. 

The compounds found in this study, however, are different. Previous drugs inspired by cone snails venoms are made out of peptides – long chains of amino acids. These drugs are delivered to the body via an injection. The compounds in this study are much smaller. Due to their size, scientists believe that future drugs inspired by these newly found compounds could be delivered to the body via a pill instead of an injection. 

Mimicry is at the center of cone snail evolution and human survival. Over the course of millions of years, cone snails have adapted their venom cocktails to match the sex pheromones of their prey. Similarly, we humans have copied cone snail venoms to treat human illnesses. Besides mimicking these animals’ venoms, it is also important to mimic good conservation practices. Protecting these habitats will guarantee a sustainable future where scientists can continue to explore and learn from the vast library of venoms that cone snails produce. 

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