Meet the Hammerhead Slug, The World's Largest Terrestrial Flatworm

I am sure you have heard about hammerhead sharks, but have you heard about hammerhead slugs? Yep, that's a real thing, just watch this video:

What you just saw is an individual of the Bipalium kewense species, or a hammerhead slug as it is commonly known. Now, I don't think I need to explain why they are called this way. However, to be a bit more precise, all the species in the Bipalium genus are called this way, thanks to their distinctive crescent-like head. Two other common names they come by are "hammerhead worms" and "broadhead planarians". Here's a photo of  another species, Bipalium strubelli:

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With over 60 recognized Bipalium species, I would need a lifetime to talk about them all, so in this post I will restrict myself to Bipalium kewense, the largest and probably best known Bipalium species.

Is It An  Earthworm or Something?

No! They might look somewhat similar but they are not closely related AT ALL! The only relationship they have is that they both belong to the animalia kingdom, but other than that, their first common ancestor is far, far, far, far, far, far, far away in the evolutionary tree!

Bipalium species are actually planarians, a type of flatworm of the Turbellaria class. Most planarians live in aquatic enviroments (both salt and fresh) but some of them like Bipalium are terrestrial. Here's a link to wikipedia if you want to learn more about planarians, they are really interesting, I promise!

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Where Can I Find One?

EVERYWHERE!  The species is believed to originate from Southeast Asia but thanks to human activity (trading) it has now become a cosmopolitan species. The best place to look for one are greenhouses, hence their other common moniker, "greenhouse planarian".

 They tend to burrow themselves in moist soil so be ready to do some digging if you really want to see one.

The species was first discovered in 1878 in the area of the Kew Park in the London Borough of Richmond upon Thames, United Kingdom, hence the specific epithet "kewense".

How Big Do They Get?  

To my knowledge, B. kewense is the world's largest terrestrial planarian with fully matured adults reaching an astonishing length of up to 30 cm! After doing some research I also believe it's the longest planarian in general, but I may be wrong. Feel free to correct me in the comments down below.

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What Do They Eat?

They are predatory animals, mainly feeding on earthworms. Do you know I really like earthworms? Why did it have to be earthworms?  :(

Other than that, they might occasionally eat each other if there is a lack of prey.

Here's a heart-braking video showing one of those fuckers eating a poor earthworm: 

What About Sex?

This is a hermaphroditic species but it doesn't seem to enjoy sex much since sexual reproduction appears to be the exception. Instead, the preferred method of reproduction appears to be asexual fragmentation which is exactly what it sounds to be. TL;DR: These critters don't party much.

Can I Eat One?

Yeah, but dunno if it's a good idea. First, they probably taste like shit with dirt. And secondly, they are known to produce tetrodotoxin, a potent neurotoxin that causes paralysis. They probably use it to paralyze their prey and/or to defend themselves against predators. I doubt the dosage is enough to do any real harm to humans but still, better eat something else.

Fun Fact: Their mouth has a double role. It's also their ass. Yep, what goes in, comes out from the same hole :D

The End

And that's pretty much all you need to know about these disgusting little critters. Feel free to click the various links in the article if you want to learn more.

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