Dear Deeplings: I thought I was a plant, but now I think I’m a killer!

Algae swam a worm larva

AHHHH! Why are we eating this baby worm? Slurrrrp. Slurrrrp. Mmm...worm juice... (Photo: Terje Berge/International Society for Microbial Ecology Journal)

Dear Deeplings,

I am a dinoflagellate – a single-celled microscopic plankton of the fine lineage Karlodinium armiger. I’m a pretty peaceful dude-lady – I just chillax on the ocean’s surface, spinning my flagella and soaking up the sun. The only thing I thought I had to worry about was getting eaten by one of those nasty copepods.

But now I’m afraid there might be something wrong with me. We were having a bloom event like we dinoflagellates do – sometimes you just gotta get your freak on, you know? All of a sudden I started to feel…hungry, which was strange because the sun was out. I blacked out and when I came to, my feeding tube was stuck in a giant dead worm larvae, and I was slurping up its innards! There were zooplankton bodies strewn everywhere, with my  K. armiger peeps were crawling all over their silent corpses! I mean, I know zooplankton are our ancient enemies, but this seems extreme. Now I’m afraid that I’m a psycho killer. Help!

Karlodinium armiger the 21,783,912th

Dear Karlo,

I know it must be alarming to go from a peaceful plant-plankton to voracious hell-beast, but apparently that is how K. armiger do it when you are having a bloom. While many dinoflagellates sup upon the occasional fellow single celled organism (this is called “mixotrophy“), you guys are the only ones who really go for balls-to-the-wall carnivory. Congratulations!

And you are indeed pretty scary. Using a potent neurotoxin, you can paralyze an adult copepod thousands of times bigger than yourselves in less than 15 minutes. Once your prey is helpless, you wriggle your feeding tube between its carapace segments and SLURRRP. In the lab, you and your buddies ate an entire copepod in less than two days. That is some serious hunger, my friend.

But eventually your bloom must end. Once most of you have died off, you’ll return to photosynthesizing and getting eaten by zooplankton. Once more you will be a fine upstanding member of the plankton community…at least until the next bloom….

I guess that wasn’t too comforting. Sorry, Karlo. You probably just should embrace your dark side.


Berge, T., L. K. Poulsen, M. Moldrup, N. Daugbjerg, and P. J. Hansen. 2012. Marine microalgae attack and feed on metazoans. The ISME Journal. doi: 10.1038/ismej.2012.29.

Thanks to K.H. for the original heads-up!

Miriam Goldstein (230 Posts)

5 Replies to “Dear Deeplings: I thought I was a plant, but now I think I’m a killer!”

  1. Thank you for that! Learn something new and amazing everyday. A funny read with just the right amount of dark side thrown in. I’m wondering what triggers the behavior? I mean, even with a bloom going on, it’s not as if the sun isn’t still providing all the energy needs of the individual. OTOH, those building blocks have got to come from somewhere, eh? It does strike me though, as a bloom of windsurfers disabling and then scavenging the Titanic.

    1. The authors of the paper think that this behavior is triggered by high densities of K. armiger – the dinoflagellates only eat animals when there’s more than 3500 dinoflagellates per milliliter. That’s a serious plankton bloom! The authors suggest that this behavior may make the bloom last longer by 1) removing their predators (eating the copepods before they eat them…ewwwwww) and 2) by increasing their growth rate. Eating other animals makes the dinoflagellate population grow 85% faster than they do when just photosynthesizing – so much for vegetarianism!

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