The residue of design


As a scientist, you know you’ve made it when Boing Boing covers your stuff. I recently collaborated with a team of scientists (Steve Yanoviak, Robert Dudley, and George Poinar) on a manuscript coming out in The American Naturalist. It’s about a nematode whose life cycle has it spending time in the guts of birds and ants, and that has a pretty unique way of doing it. Here’s the, um, straight poop.

Worker ants of the species Cephalotes atratus, like many ants of the treetops, have a hankering for bird poop (lots of nitrogen and salts in a piece of bird poop). Some bird poop, however, is infected with the eggs of our nematode parasite. Now most adult worker ants can’t take solid food; they feed it, instead to their brood back in the nest. However, when infected poop is fed to the brood of Cephalotes atratus ants by their older sisters, the nematodes cause the brood to grow up with bright red (dare we say, berry-like?) gasters. In the paper we build a plausible hypothesis that birds mistake the red gasters (now full of nematode eggs) for fruit, harvest them, pass them as feces, the feces are harvested by Cephalotes workers who bring them back to the nest, and the cycle continues (one key bit of evidence–it’s easy to pluck off an infected gaster and much, much harder to remove the gaster of a healthy ant).

There is no evidence this is a voluntary arrangement–we see no advantage to the ants of harboring these nematodes. Rather, this seems to be another case of a parasite, once inside its host and with its hands on the wiring and machinery, tweaking the host to do its bidding (my endocrinologically inclined pal points out that the nematodes and ants share a host of neurochemicals, so replace “hands” above with “hormones”). The nematodes even make infected ants raise their gasters vertically, making the egg-filled butt-berries infinitely pluckable.

Long before there were neurobiologists, apparently, there were parasites paving the way.

Below the fold, the real story of how this sordid story of manipulation came about.

Robert, Steve, and I have been friends and collaborators for years (a previous story, on how Cephalotes ants glide, also made it to Boing Boing). We have gotten into the habit of getting together on Barro Colorado Island in Panama for a couple of weeks every summer to work on projects, and, critically, drink beer at the end of the tropical day, which, being near the equator, is conveniently scheduled at 6:00, right before dinner. These conversations which tend to range far and wide, often settle on strange things we have encountered in our walks through the forest.

Steve Yanoviak, Mike Kaspari, Robert Dudley on Barro Colorado Island, photo by Deborah Kaspari

Steve Yanoviak, your’s truly, and Robert Dudley. Photo by Deborah Kaspari.

One day two years ago we had been doing follow-up work on the aerodynamics of Cephalotes, and thus needed sizeable quantities to drop from said balcony (to film their trajectories). As Cephalotes lives in the treetops, getting lots of these ants is no mean task. Luckily, Robert and Debby , my wife, knew of a low-hanging nest in a forest gap. As they were collecting they noticed that some of the ants had red butts (or gasters).

So fast forward to the balcony. Robert, beer in hand, was waxing eloquent about these red-butted forms of Cephalotes atratus. I was, as the balcony’s designated myrmecologist-of-the-day, skeptical, and suggested they were probably a different species. Robert, (whom I might note here is a lepidopterist by training, and thus had only recently learned that ants come in more forms than “black and red, painful and inconsequential”) remained unconvinced. We bet a beer on it, which, on the balcony of BCI, is akin to wagering a glass of water.

Then Steve wanders onto the scene, bottle in hand, and comments that these red-butted Cephalotes had a peculiar feature–the butts tended to fall off if the poor ants were around carried too long. The sight of little red gasters rolling in a tupperware bowl amidst black gasters firmly affixed to their owners pretty much sealed the deal. I had lost the bet, and sadly walked to the cooler to retrieve three more beers. Suddenly, the conversation got interesting. Over the next 24 hours, Steve, Robert, and I fleshed out the working hypothesis. Over the next two years, with Steve’s gift for experiment (and, later, George Poinar’s key knowledge of nematode parasites), the “berry ant” story turned into the paper that has caught some folk’s imagination (with the help of the massive publicity machine that is the University of California Berkeley, where Robert teaches).

In summary, here are some keys to a happy scientific life: a balcony, beer, curiosity, a bit of competitiveness, a tropical forest, and good friends who are also crackerjack scientists.

Tropical forest scene by Deborah Kaspari

Tropical forest scene by Deborah Kaspari


3 Responses to The residue of design

  1. bginvest says:

    Lol, I never thought science can have such a funny and crazy side.

    Greetings fom Bulgaria,


  2. […] all about how to thrive as a young scientist. Some of his more serious advice seems to involve beer consumption, so take it with a grain of […]

  3. […] The nematodes travel to the ant’s abdomen, and as they mature, cause the abdomen to grow round and bright red! The ants will hold their abdomens, or gasters, high as if to draw attention -which they do. The red […]

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