Are Hammerhead Worms Really Dangerous?

These large, land-dwelling flatworms are invasive and toxic -- but they're not dangerous (unless you eat a lot of them, or happen to be an earthworm). Learn more in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/animal-facts/hammerhead-worms.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff, Lauren
Vogelbaum here. Every now and again, Americans get word that
a new killer creature is invading our country. Killer bees,
murder hornets, fire ants, and on and on. It keeps
the news. Spicy hammerhead flat worms commonly called hammerhead worms,

(00:26):
occasionally make their way into the rotation because they're not
native to many places in the world, and they're toxic
and aggressive predators, and they're slimy and leech like with
anvil shaped heads. But unlike many other terrestrial worms, they
can grow to around eighteen inches or forty five centimeters long.
People sometimes mistake them for snakes, but hammerhead worms aren't

(00:50):
anything to get too fussed about. They're not a new
thing in the US nor in most other places in
the world. They've been common residents of American gardens the
early nineteen hundreds. These predatory planarians are native to tropical
and subtropical regions of the globe. Over the course of
the past couple hundred years, a global commerce has helped

(01:11):
the hammerhead worm wriggle its way into most suitable habitats
in the world, and there are a lot of suitably warm,
wet habitats out there, though you're unlikely to find them
in a desert or at the top of a mountain.
For the article, this episode is based on how Stuff Works.
Spoke with Matt Bertone, an entomologist at NC State University.

(01:33):
He said, as some have been here for over a
hundred years, so they're well established. They easily hide among
objects and in soil where there's moisture, so moving any
type of container or plants around the world has allowed
them to colonize new areas. Thus, they are highly invasive
and frequently show up in new regions. Hammerhead worms are

(01:55):
carnivorous and often cannibalistic. They're sensitive to light and our
active mostly at night, feeding on a variety of small,
soft bodied animals snails, slugs, and earthworms mostly, though they
occasionally feed on other small invertebrates like insects. Bertone explained
they wrap around their prey with sticky mucus and use

(02:16):
a mouth located on their belly in the middle of
the body to consume prey. They use special enzymes to
digest the prey outside of their body after the digestive
juices have done their business effectively turning prey into a
puddle of goo. The hammerhead worm sucks its victim in
with the help of a bunch of tiny hair like
structures on its underside, called cilia. The cilia also helped

(02:40):
the worms in locomotion, acting like hundreds of microscopic legs
to pull them along on a thin film of slime
that the worms excrete. The life cycles of flatworms are
complex and differ from species to species. Hammerhead worms are hermaphroditic.
They have both male and female productive organs, and can

(03:01):
reproduce either sexually or asexually, though asexual reproduction is more common.
For instance, a species native to Southeast Asia but common
worldwide typically reproduce by fission, especially when they're outside their
native range. In this process, a small portion of the
body near the tail pinches off and becomes a new worm,

(03:22):
a clone of its parent. Another species, Eggs are produced
when they mate with other worms, self fertilize or clone themselves.
But why are they considered so hazardous? Bertone explained. Species
of hammerhead flatworms are the only known terrestrial invertebrates that
produce to trototoxin, the poison that makes pufferfish deadly. However,

(03:45):
they do so only in small amounts and are not
dangerous to humans in less eaten in large numbers. Thus
their danger is often overexaggerated. Hammerhead worms do pose a
real threat to earthwork populations, however. For instance, researchers are
concerned about the populations in France, where the presence of

(04:06):
hammerhead worms had somehow gone undetected by scientists and gardeners
alike for more than twenty years. The concern is that
hammerhead worms, which don't aerrate and fertilize the soil the
way that earthworms do, have been eating earthworms and other
helpful soil fauna in scarcity. Today's episode is based on

(04:29):
the article hammerhead worms are toxic and invasive, But are
they dangerous? On holstaffworks dot com written by Jesslyin Shields.
Brainstuff is production of by Heart Radio in partnership withhustaffworks
dot com, and it is produced by Tyler Klang. Four
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