TIL: The World's Longest Animal Is Over 50 Meters Long and It's A Worm!

If you hadn't read the title of the post and I asked you to guess what's the world's longest animal what would your answer be? Well, if you are like me you might have said blue whale or some kind of snake like anaconda. Blue whale is a good answer. After all, blue whales get to be almost 30 m long. As for anacondas, contrary to what the 1997 film would have you think, they are much, much smaller than that, with the biggest verified specimen being about 5.2 meters long.

So, you can imagine my suprise when I stumbled upon this press release today, mentioning that the world's longest animal is actually a worm and it gets to be a whooping 50 something meters long! The scientific name of the worm is  Lineus Longissimus and the press release is all about a new study on the species that found how it produces neurotoxins that can kill crabs and cockroaches. But more on the study later. Let's first get to know this worm a bit better. 

The species is commonly known as the bootlace worm and it belongs to the Nemertea phylum, a group of worms known as "ribbon worms" or "proboscis worms". The common name "proboscis worm" is due to an internal organ they have (called proboscis, duh!) that comes out of their mouth and helps them to eat and kill prey. Here's a video of another species, if you are curious how this proboscis thing looks in real life. Just jump to 00:55 for the good part! The content is a bit disturbing, you have been warned:

Although bootlace worms have the potential to grow extremely long, they have a width of only 5 to 10 mm. Their body is brown with lighter (longitudinal) stripes and like other ribbon worms they use their proboscis to immobilize prey. Most adults are 5-15 m long, with the record belonging to a specimen discovered back in 1864. That specimen was... 55 fucking meters long! 

Here's a photo to give you a better idea of how they look like:

Lineus longissimus, picture taken in Grevelingen near Scharendijke (the Netherlands)  (CC BY 3.0 ,credit)

And here's a really cool video, showing a Lineus longissimus specimen swallowing in hole a bunch of dead annelids:

Individuals are usually found at depths of 10m or deeper, on sandy and muddy shores and in tide pools. Their  distribution ranges from Iceland eastwards to the Atlantic, North Sea and Baltic Coasts of Europe and it is the most commonly recorded nemertean in Britain.

Like with most ribbon worms, there is really not much we know about these creatures and the published scientific literature is very limited. Now, let's see what the new study found out.

The New Study

As aforementioned, a new paper on these creatures came out a few days ago, appearing on the Scientific Reports journal. The name of the paper is "Peptide ion channel toxins from the bootlace worm, the longest animal on Earth." and no academic access is required to read it. The study was conducted by a research team from three Swedish universities and colleagues from Belgium and Australia, led by Ulf Göransson, Professor of Pharmacognosy, Department of Medicinal Chemistry in Uppsala University.

The too long didn't read version of the paper is that this is the first study to show that these worms produce, when threatened, a mucus containing a potent mix of neurotoxins. The researchers then isolated the most abundant toxin in the mixture and tried it on two model organisms, green crabs (Carcinus maenas) and Blaptica dubia cockroaches. In both cases, the toxin caused paralysis and death. 

Toxins often often work by affecting ion channels, which are pore-forming membrane proteins that allow ions to pass through the channel pore. In this case, the toxin messes with the sodium channels of crustaceans and insects. However, further testing showed that this reaction appears to be significantly less potent on mammals.

In their paper, the authors note that these findings are very encouraging and could be used to develop potent yet safe for humans insecticides:

Strong selectivity for insect over human sodium channels indicates that α-nemertides can be promising candidates for development of bioinsecticidal agents.

 These data are encouraging for the further exploration of α-1 as a bioinsecticide. [credit]

And that's pretty much the dumbed down version of the paper. It's a bit technical but if you have a  background in chemistry and/or life sciences you can check it out if you want to read all the technicalities.

Here's what  Prof. Göransson had to say about the study:

"This peptide toxin is the most poisonous substance to have been found in Sweden's animal kingdom and the fact that it may be possible to use it makes the discovery even more exciting. We already know that peptide toxins are found in, for example, cone shells that live in tropical waters. These ribbon worms live in colder waters, for example, the coastlines of Great Britain and Norway and the west coast of Sweden.

The peptide toxin has a very powerful effect on crustaceans and cockroaches, which is why it could serve as a very effective insecticide.  From a research point of view, it's exciting to have discovered a new toxin in our own fauna, in a group of animals that has basically never been explored. Moreover, the whole chain of research can be attributed to our team's effort, from discovering the substance in the bootlace worm to describing the structure of the toxin and studying its effect." [source] 

Reportedly, Prof. Göransson  even once tried to touch  a specimen bare-handed and didn’t feel much of anything. Still, he says he plans to use gloves routinely in future research. 

The End

So, today you learned that Lineus longissimus worms are the world's longest animals and they produce toxins that show very promising results for pesticide use in agriculture. Unfortunately, like with most "promising" research I doubt we will ever see any real life applications :)

Lately I am making a habit to close my posts with cool but totally unrelated animal videos and you seem to enjoy them, so here's another one, this time of a young mantis being preyed by a jumping spider.. Will it manage to escape? The ending might surprise you:

Oh yeah, here's another interesting fact I learned today. Apparently, a man in 2017 successfully received a penis transplantation after losing his own, 17 years prior to the surgery. There was a small problem though. He was black. And the donor was white! So, he had to receive medical skin darkening tattoos in order to correct the skin tone differences XD

Ok, I will stop now before getting more sidetracked!

See you tomorrow!

References & Further Reading

 - All references are provided in the form of clickable links in the main body of the post :)