Editor’s note: This story was originally published in April 2022.
A toxic, predatory invasive worm capable of unlimited self-cloning has arrived in Maine.
The first sightings were reported in fall 2021 from southern and central parts of Maine of the hammerhead worm, a flatworm that can range from 8- to 15-inches long and is distinguished by the unique hammer or shovel-shaped head.
“We have a couple of reports of them already,” said Gary Fish, state horticulturist with the Maine Department of Agriculture, Conservation and Forestry. “I don’t think anyone in Maine is up to speed on them.”
The discovery is bad news for Maine’s gardeners since hammerheads prey on earthworms, which contribute to the health of Maine soil by turning organic materials into useful compost. Earthworm activity also helps aerate the soil, which increases soil nutrients and moisture intake. The hammerhead worm has no known predators.
The hammerhead worm is native to Asia and has been reported as far south as Florida, as far west as California and now as far north as Maine, according to the University of Florida.
The biology of the hammerhead reads like a horror movie. It does not have respiratory or circulatory systems or a skeleton, and it may or may not have eyes. What it does have is a single opening on its head that serves as both its mouth and its anus.
Liz Baker spotted one slithering up her foundation in Lewiston wall last fall.
“I was fascinated,” said Baker, who took a video of the creature. “Totally creepy and strange but I love learning about different species [and] I had never seen anything like it.”
The truly amazing trait of hammerhead worms is that they are basically immortal. Like other flatworms, they reproduce asexually by what is known as “fragmentation.” For example, they leave the tip of their tail stuck to something, and it will develop on its own into a new worm.
That also means if you cut a hammerhead into pieces, in 10 days or so you are going to have multiple new hammerheads — all capable of fragmentation.
They are also the first land invertebrates found to produce the same toxin that is found in pufferfish. In the fish, the toxin is lethal to humans with one pufferfish containing enough to kill 30 adult humans. Little is known about the hammerhead toxin’s effects on humans, but it is believed a person would have to eat a large quantity of them to be lethal. However, it is a good idea to wash your hands after handling hammerhead worms.
After researching the worm, Baker said she is glad she did not touch it.
“I haven’t seen any other since, which is good,” she said. “I’m mystified where it could have come from.”
There is a bit of good news: It is believed hammerhead worms prey on invasive Alabama jumping worms, according to Fish. Not only do those worms pop up out of the ground like snakes, they destroy any nutrient value of soil.
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