This ‘Immortal’ Toxic Worm Multiplies When You Cut It in Half

It sounds like something straight out of a mythological tale. A creature that, when struck down and cut in two, doesn’t die. Instead, each piece regenerates, creating two new beings where there was only one. It’s the stuff of legends, reminiscent of the Lernaean Hydra that battled Heracles. But this creature isn’t a myth. It’s real, it’s toxic, and it might just be in your back garden.

Meet the hammerhead worm, a bizarre invasive pest that has wildlife officials issuing warnings across the United States. With its distinctive spade-shaped head, this creature is an unsettling sight, but its appearance is the least strange thing about it.

The Unkillable Worm

The hammerhead worm (Bipalium kewense) is a type of terrestrial flatworm originally from Southeast Asia. It’s believed to have hitched a ride to North America in the soil of horticultural plants as far back as the late 1800s. For decades, it has been quietly establishing itself, particularly in warmer, humid areas, but is now being spotted further north in places like Maine.

What makes this worm so extraordinary is its method of survival. If you find one and your first instinct is to chop it with a spade, you’ve just made the problem worse. Much worse.

As the Maine Department of Inland Fisheries and Wildlife warns, “Don’t squish or cut them. That’s how they multiply!”

Hammerhead worms reproduce asexually through fragmentation. If you cut one, each segment can regenerate into a whole new worm within a couple of weeks. It’s a superpower that has allowed this invasive species to spread so successfully, turning one problem into many with a single slice. It’s a trait that puts them in the same strange biological club as other seemingly immortal creatures, like the fascinating immortal jellyfish.

A Toxic Threat in the Soil

Beyond its frankly incredible regenerative abilities, the hammerhead worm poses a serious ecological threat. Its primary food source is the humble earthworm. Earthworms are the unsung heroes of our ecosystems, aerating the soil, improving drainage, and breaking down organic matter. Hammerhead worms are voracious predators, and with few natural enemies in their new environment, they can completely wipe out local earthworm populations.

This can have a devastating knock-on effect, impacting soil health and the growth of native plants. But the danger isn’t just for the soil.

According to research mentioned by the Star-Telegram, these worms produce a potent neurotoxin called tetrodotoxin in their mucus. Theresa Dellinger, an entomologist at Virginia Tech, explains that the worm uses this toxin to subdue its prey. While they can’t bite or inject it, handling them without gloves can cause skin irritation. The real risk is to curious pets who might try to eat one, which can lead to nausea and vomiting.

How to Deal with a Real-Life Hydra

So, if you can’t cut them or crush them, what are you supposed to do when you find one of these strange invaders? Experts have a clear, if slightly unusual, set of instructions.

• Don’t touch it with your bare hands. Wear gloves to protect yourself from the toxic mucus. You can find plenty of sturdy gardening gloves on Amazon.
• Capture it. Coax the worm into a sealable bag or container it can’t escape from.
• Dissolve or freeze it. The most effective methods are to either sprinkle the worm with salt or citrus oil, or drown it in soapy water or vinegar. Alternatively, you can seal it in a container and freeze it for at least 48 hours.
• Report it. Officials encourage people to report sightings on citizen science apps like iNaturalist. This helps scientists track their spread and better understand the scale of the invasion.

These worms are a stark reminder that the world is full of weird and wonderful creatures that blur the line between science and folklore. They are a biological oddity, a creeping monster from a myth, and an ecological problem all rolled into one slithering, regenerating package.

In Pure Spirit

The hammerhead worm is a perfect example of how nature can be far stranger than any fiction we could invent. It’s a creature that defies our basic understanding of life and death, a real-world monster that regenerates right in our own gardens. What do you think? Have you ever encountered one of these bizarre worms? Let us know in the comments below.

Bipalium kewense. Photo by Pierre Gros / Source: Wikimedia Commons.