Range: Asia and Madagascar; Introduced to the Americas and Europe Habitat: Soil, under logs, and under rocks Size: Up to 10 inches (25.4cm) long Diet: Earthworms, slugs, snails, and more Threats: Unknown Life span: Unknown

Transcript:

Today on Animal Fact Files we’re discussing hammerhead flatworms. You can hammer that sub button for more episodes! Thank you to Patricia Russell for today’s request. We’ve talked about flatworms in general in the past, but today we’re going to look at some that look like a cross between a shark and a worm. Interestingly, hammerhead flatworms have not only a shark-like appearance but also a shark-like strategy for eating. Hammerhead flatworms are carnivorous predators and their favorite meals are earthworms! There are currently around 160 described species of hammerhead flatworms, though it should be noted that more research could reveal previously unknown species, so, as per usual, take that statistic with a grain of salt.

Natively, hammerhead flatworms are thought to come from South and East Asia as well as Madagascar, though many species have invasively made their all around the world including American and European tropics and subtropics. It’s thought hammerhead flatworms were brought to these areas of the world through trade of potted plant species, and now they’ve made a name for themselves as a menace.

Hammerhead flatworms aren’t necessarily dangerous to humans, but they almost exclusively eat earthworms. Earthworms, as we discussed in our episode describing them, while also invasive to some areas themselves, are considered beneficial to soil health in many habitats, so some people worry about the impact hammerhead flatworms may have on earthworm populations. Of course, earthworms can negatively impact some habitats, so it really just depends on the perspective!

A hammerhead flatworm eats through a mouth that’s located on its underside towards the middle of its body. The hammerhead flatworm will release digestive enzymes and suck up its liquified prey. It’s also been observed that hammerhead flatworms are able to release a toxin that paralyses their prey. It’s the same toxin found in the blue ring octopuses we’ve talked about in a previous episode! This toxin doubles as a defense mechanism as animals eating hammerhead flatworms have been observed responding negatively to their touch. Apparently that doesn’t stop them from eating each other, though.

When pickings are scarce, hammerhead flatworms are able to consume parts of their own bodies. Yeah, these guys aren’t only cannibalistic, they’re autocannibalistic. It kind of makes sense, though, because they’re able to regenerate the pieces they eat. See, hammerhead flatworms are able to reproduce by producing eggs fertilized by the sperm of another hammerhead flatworm, but generally speaking these guys reproduce by dropping the end section of their body and leaving it behind to grow into another new hammerhead flatworm. Pfft. Who needs to worry about impressing others when you can just chop yourself up and make copies?

Most of their activity happens at night, but during the day they lazy about in soil under rotting logs, under rocks, and just about anywhere that’s moist and away from the sun. They love hot, humid environments like greenhouses. Some hammerhead flatworms can be nearly a foot long, though others are much smaller. Like snails and slugs, they leave behind slime trails which they use to move around. Some hammerhead flatworms have even be seen hanging from strings of slime to reach the ground after climbing trees!

For more facts on hammerhead flatworms, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!