Now bring me a T. rex tapeworm!

cordyceps440I had planned to spend today NOT writing about parasites, but this morning I’ve already gotten comments and tweets informing me about a very cool new paper that was published today, documenting parasitized zombies 48 million years ago.

All right, then. The parasite overlords cannot be ignored.

The parasite in question is the fiendishly awesome Cordyceps, a fungus that forces its insect hosts to climb up high on plants, clamp down, and hold fast. The fungus then sprouts out of the ant’s body, showering down spores on hapless insects below. I wrote about Cordyceps in my book Parasite Rex, and followed up last year with a blog post on some great work by David Hughes of the University of Exeter and Harvard. Hughes and his colleagues wondered if the fungus was controlling its host in a fine-tuned adaptation, or if the ants were becoming zombies because they were just sick. After all, if your body was shot through with fungus threads, you’d probably feel lousy as well. But Hughes made a strong case that Cordyceps really is in charge, because it so consistently sends its hosts to the same kind of place in the canopy, finding a location that benefits the parasite. The parasitized insects even bite down on the same place on a leaf.

Out of this research, Hughes got a brilliant yet very simple idea. If Cordyceps causes its hosts to behave in such a fixed way, maybe that behavior has been preserved in the fossil record. Hughes and his colleagues went through a big collection of 48-million-year-old fossil leaves in Germany and discovered a leaf with distinctive snips that closely match those made today by Cordyceps-infected ants.

There’s precious little evidence of parasitism in the fossil record. It’s not surprising when you consider the delicate, squishy nature of most parasites. Most of the evidence scientists have found is indirect. The bacteria Mycobacteria tuberculosis, for example, leaves scars on the bones of some of its victims, including–possibly–a 500,000-year-old hominid with TB.  Hughes’s new paper is important because it points not just to a particular parasite 48 million years ago, but a particular form of parasite manipulation. Ancient fungi appear to have evolved all the sophisticated biochemistry they needed to control an animal a very long time ago, and they’ve been using it to manipulate insect hosts ever since.

This new research is just a tiny glimpse into what is, I’m sure, a vast world of paleoparasitology. Parasitism is the most successful way of life today, and there’s no reason to think that wasn’t true 100 million years ago. Where there are hosts, there are parasites, and lots of them. Let’s see if scientists can continue to think up new ways to open up that world and document the parasitic history of life on Earth. Whether they’ll discover dinosaur tapeworms, I don’t know. But I can hope.

(You can read more about Cordyceps from Ed Yong and Nature)

[Image: David Hughes]

10 thoughts on “Now bring me a T. rex tapeworm!

  1. Amazing stuff, but the nicks in the leaves is still indirect evidence, right?, like the TB scars on bone. Fossil parasites themselves are incredibly rare. At a parasitology conference in the Czech Republic in 1999 I saw a scientist from Latvia give a talk about some Devonian fish fossils that were so immaculately preserved that you could see fragments of parasitic worms (mostly hard parts like attachment hooks and so on) preserved on the gills. As far as I know its still the only study that provides direct fossil evidence of parasitic flatworms. Its not a T. rex tapeworm exactly (in fact, the fish were tiny), but it gives a glimmer that maybe one day we could find one. How cool would that be?

    [CZ: Yes, the Cordyceps evidence is also indirect. I hadn’t heard about the fish fossils. Was that ever published?]

  2. Yes, Upeniece I. (2001) Mitt. Mus. Nat. Kd. Berlin 4:101-119.

    Its cited and reviewed in the much more accessible:
    Poinar G. (2003) A Rhabdocoel Turbellarian (Platyhelminthes, Typhloplanoida) in Baltic Amber with a Review of Fossil and Subfossil Platyhelminths. Invertebrate Biology 122(4) 308-312

    I found this latter reference while looking for the former. It looks like there have been some other reports since the one I mentioned. *cool*

  3. “Whether they’ll discover dinosaur tapeworms, I don’t know. But I can hope.”

    Well Carl, I’m sure you’ll be interested in this:

    Poinar Jr., G. and Boucot, A.J. (2006) “Evidence of intestinal parasites of dinosaurs” Parasitology 133:2:245-249

    Abstract:
    “Protozoan cysts and helminth eggs preserved in a coprolite from the Early Cretaceous Bernissart Iguanodon shaft in Belgium demonstrate that representatives of 3 phyla parasitized dinosaurs by that period. These fossil parasite stages are described and their possible effect on dinosaurs discussed. These findings represent the earliest fossil records of protozoan and helminth parasites of terrestrial vertebrates.”

    Not quite your Tyrannosaurus rex tapeworm, but the closest we have at the moment.

    Incidentally these discoveries an unlikely marriage between two of my favourite, yet incompatible, fields of biology – parasitology (which looks at tiny and often squishy things) and palaeontology (tiny and squishy things don’t fossilize well). I’ve only managed to make a career in the former but I’ve always wondered what if I am able to combine them…

  4. Speaking of ‘fossilised’ parasites & T rex, I am reminded of a paper from last year, where Ewan Wolff & colleagues re-interpreted well-known lesions on a significant proportion of Tyrranosaurid jawbones. Usually, these holes have been interpreted as partially healed bite-wounds, but they look uncannily like these created in avian jawbones by a modern-day parasitic infection, Trichomonosis.
    Check it out, it’s open access:
    http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007288

  5. I wonder what would be the consequences if Cordyceps moved on to infest more advanced life forms, such as humans.

    Might we have an explanation at to all those zombie plagues of recent Hollywood movies and TV shows like the Walking Dead?

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