Category Archives: North Carolina

Cicadas, or how I Am Such A Scientist, or a demonstration of good editing

Charles Q. Choi runs a bi-weekly series on the Guest Blog over at Scienctific American – Too Hard for Science? In these posts, he asks scientists about experiments that cannot be or should not be done, for a variety of reasons, though it would be fun and informative it such experiments could get done.

For one of his posts, he interviewed me. What I came up with, inspired by the emergence of periodic cicadas in my neighborhood, was a traditional circadian experiment applied to a much longer cycle of 13 or 17 years.

Fortunetaly for me, Charles is a good editor. He took my long rant and turned it into a really nice blog post. Read his elegant version here – Too Hard for Science? Bora Zivkovic–Centuries to Solve the Secrets of Cicadas.

Now compare that to the original text I sent him, posted right here:

The scientist: Bora Zivkovic, Blog Editor at Scientific American and a chronobiologist.

The idea: Everything in living organisms cycles. Some processes repeat in miliseconds, others in seconds, minutes or hours, yet others in days, months or years. Biological cycles that are most studied and best understood by science are those that repeat approximately once a day – circadian rhythms.

One of the reasons why daily rhythms are best understood is that pioneers of the field came up with a metaphor of the ‘biological clock‘ which, in turn, prompted them to adapt oscillator theory (the stuff you learned in school about the pendulum) from physics to biology.

And while the clock metaphor sometimes breaks down, it has been a surprisingly useful and powerful idea in this line of research. Circadian researchers came up with all sorts of experimental protocols to study how daily rhythms get entrained (synchronized) to the environmental cycles (usually light-dark cycles of day and night), and how organisms use their internal clocks to measure other relevant environmental parameters, especially the changes in daylength (photoperiod) – information they use to precisely measure the time of year and thus migrate, molt or mate during an appropriate season.

These kinds of experiments – for example building Phase-Response Curves to a variety of environmental cues, or a variety of tests for photoperiodism (night-break protocol, skeleton photoperiods, resonance cycles, T-cycles, Nanda-Hamner protocol etc.) – take a long time to perform.

Each data point requires several weeks: measuring period and phase of the oscillation before and after the pulse (or a series of pulses) of an environmental cue in order to see how application of that cue at a particular phase of the cycle affects the biological rhythm (or the outcome of measuring daylength, e.g., reproductive response). It requires many data points, gathered from many individual organisms.

And all along the organisms need to be kept in constant conditions: not even the slightest fluctuations in light (usually constant darkness), temperature, air pressure, etc. are allowed.

It is not surprising that these kinds of experiments, though sometimes applied to shorter cycles (e.g., miliseconds-long brain cycles), are rarely applied to biological rhythms that are longer than a day, e.g., rhythms that evolved as adaptations to tidal, lunar and annual environmental cycles. It would take longer to do than a usual, five-year period of a grant, and some experiments may last an entire researcher’s career. Which is one of the reasons we know so little about these biological rhythms.

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Living out in the country, in the South, just outside Chapel Hill, NC, every day I open the door I hear the deafening and ominous-sounding noise (often described as “horror movie soundtrack) coming from the woods surrounding the neighborhood. The cicadas have emerged! The 13-year periodic cicadas, that is. Brood XIX.

I was not paying attention ahead of time, so I did not know they were slated to appear this year in my neck of the woods. One morning last week, I saw a cicada on the back porch and noticed red eyes! A rule of thumb that is easy to remember: green eyes = annual cicadas, red eyes = periodic cicadas. I got excited! I was waiting for this all my life!

Fortunately, once they emerge, cicadas are out for a few weeks, so my busy travel schedule did not prevent me from going to find them (just follow the sound) to take a few pictures and short videos.

There are three species of periodic cicadas that emerge every 17 years – Magicicada septendecim, Magicicada cassini and Magicicada septendecula. Each of these species has a ‘sister species’ that emerges every 13 years: M.tredecim, M. tredecassini and M.tredecula. A newer species split produced another 13-year species: Magicicada neotredecim. The species differ in morphology and color, while the 13 and 17-year pairs of sister species are essentially indistinguishable from each other. M.tredecim and M.neotredecim, since they appear at the same time and place, differ in the pitch of their songs: M.neotredecim sings a higher tone.

So, how do they count to 13 or 17?

While under ground, they undergo metamorphosis four times and thus go through five larval instars. The 13 and 17-year cicadas only differ in the duration of the fifth instar. They emerge simultaneously, live as adults for a few weeks, climb up the trees, sing, mate, lay eggs and die.

When the eggs hatch, the newly emerged larvae fall from the trees to the ground, dig themselves deeper down, latch onto the tree roots to feed on the sap, and wait another 13 or 17 years to emerge again.

There are a number of hypotheses (and speculations) why periodic cicadas emerge every 13 or 17 years, including some that home in on the fact that these two numbers are prime numbers (pdf).

Perhaps that is a way to fool predators which cannot evolve the same periodicity (but predators are there anyway, and will gladly gorge on these defenseless insects when they appear, whenever that is, even though it may not be so good for them). Perhaps this is a speciation mechanism, lowering the risk of hybridization between recently split sister species?

Or perhaps that is all just crude adaptationist thinking and the strangeness of the prime-number cycles is in the eye of the beholder – the humans! After all, if an insect shows up every year, it is not very exciting. Numerous species of annual cicadas do that every year and it seems to be a perfectly adaptive strategy for them. But if an insect, especially one that is so large, noisy and numerous, shows up very rarely, this is an event that will get your attention.

Perhaps our fascination with them is due to their geographic distribution. Annual cicadas may also have very long developmental times, but all of their broods are in one place, thus the insects show up every year. In periodic cicadas, different broods appear in different parts of the country, which makes their appearance rare and unusual in each geographic spot.

In any case, I am more interested in the precision of their timing than in potential adaptive explanations for it. How do they get to be so exact? Is this just a by-product of their developmental biology? Is 13 or 17 years just a simple addition of the duration of five larval stages?

Or should we consider this cycle to be an output of a “clock” (or “calendar”) of sorts? Or perhaps a result of interactions between two or more biological timepieces, similarly to photoperiodism? In which case, we should use the experimental protocols from circadian research and apply them to cicada cycles.

Finally, it is possible that a ling developmental cycle is driven by one timing mechanism, but the synchronization of emergence in the last year is driven by another, perhaps some kind of clock that may be sensitive to sound made by other insects of the same species as they start digging their way up to the surface.
The problem: In order to apply the standard experiments (like construction of a Phase-Response Curve, or T-cycles), we need to bring the cicadas into the lab. And that is really difficult to do. Husbandry has been a big problem for research on these insect, which is why almost all of it was done out in the field.

When kept in the lab, the only way to feed them is to provide them with the trees so they can drink the sap from the roots. This makes it impossible to keep them in constant conditions – trees require light and will have their own rhythms that the cicadas can potentially pick up, as timing cues, from the sap. So, the first thing we need to do is figure out a way to feed them artificially, without reliance on living trees for food.

Also, we do not know which environmental cues are relevant. Is it light cycle? Photoperiod? Or something cycling in the tree-sap? Or temperature cycles? What are the roles of developmental hormones like Juvenile Hormone or Ecdysone? We would have to test all of them simultaneously, hoping that at least one of them turns out to be the correct one.

Second, more obvious problem, is time. These experiments would last hundreds of years, perhaps thousands! Some experiments rely on outcomes of previous experiments for the proper design. Who would do them? What funding agency would finance them? Why would anyone start such experiments while knowing full well that the results would not be known within one’s lifetime? Isn’t this too tantalizing for a scientist’s curiosity?

The solution? One obvious solution is to figure out ways to get to the same answers in shorter time-frames. Perhaps by sequencing the genome and figuring out what each gene does (perhaps by looking at equivalents in other species, like fruitflies, or inserting them into Drosophila and observing their effects), hoping to find out the way timing is regulated. This will probably not answer all our questions, but may be good enough.

Another way is to set aside space and funding for such experiments and place them into an unusual administrative framework – a longitudinal study guided by an organization, not a single researcher getting a grant to do this in his or her lab. This way the work will probably get done, and the papers will get published somewhere around 2835 A.D.

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See? How long and complex my text is? Now go back to the post by Charles to see again how nicely he edited the story.

Cicadas, Brood XIX, northern Chatham Co, NC [Videos]



American Scientist’s Pizza Lunch – NC FIRST Robotics competition

At American Scientist‘s next Pizza Lunch, it’s time to turn our attention from accomplished scientists to budding scientists. At noon, Tuesday, March 29 come hear Marie E. Hopper, regional director of NC FIRST Robotics, talk about a different kind of science lesson. FIRST Robotics stages competitions among high school students. Kids who sign up design and build remotely operated robots that can succeed in specially designed “games”. Each year, the rules of the games change. Students don’t see the rules until six weeks before the starting buzzer.

Thanks to a grant from the N.C. Biotechnology Center, American Scientist Pizza Lunch is free and open to science journalists and science communicators of all stripes. Feel free to forward this message to anyone who might want to attend. RSVPs are required (for the slice count) to cclabby@amsci.org

Directions to Sigma Xi, the Scientific Research Society in RTP, are here: http://www.sigmaxi.org/about/center/directions.shtml

Sigma Xi Pizza Lunch – ‘ Friends or Foes: Social Relationships Among Female Chimpanzees’ with Anne Pusey

To keep keeping you on your toes, we’ll host Pizza Lunch on a Wednesday again this month, rather than on a Tuesday. And it promises to be another good one.

Come hear Anne Pusey, chair of evolutionary anthropology and a James B. Duke professor at Duke, speak at noon Wed., Feb 23 at Sigma Xi. Her talk: Friends or Foes: Social Relationships Among Female Chimpanzees. Pusey has studied competition, cooperation and social bonds in multiple species. Most of her work focuses on our close evolutionary cousins, the chimpanzees. Early in her career, Pusey observed juvenile and adolescent development under the direction of Jane Goodall at Tanzania’s Gombe Stream Reserve. She still has ties. Her research team maintains and digitizes data collected at Gombe, where Goodall started observing chimpanzees more than 50 years ago.

Thanks to a grant from the N.C. Biotechnology Center, American Scientist Pizza Lunch is free and open to science journalists and science communicators of all stripes. Feel free to forward this message to anyone who might want to attend. RSVPs are required (for the slice count) to cclabby@amsci.org

Directions to Sigma Xi, the Scientific Research Society in RTP, are here: http://www.sigmaxi.org/about/center/directions.shtml

Sigma Xi Pizza Lunch (if you have stomach to eat at the time): Everything you wanted to know about Bedbugs but were too afraid to ask

You’ve heard the media buzz about bed bugs. But what of the science? Join us at noon, Jan. 25 here at Sigma Xi to hear N.C. State University entomologist Coby Schal offer the facts. He’ll discuss the basic biology of the insects and some of the new research strategies aimed at finding ways to better control them.

Thanks to a grant from the N.C. Biotechnology Center, American Scientist Pizza Lunch is free and open to science journalists and science communicators of all stripes. Feel free to forward this message to anyone who might want to attend. RSVPs are required (for the slice count) to cclabby@amsci.org

Directions to Sigma Xi, the Scientific Research Society in RTP, are here.

Science Cafe Raleigh: Rain Forests – Going, Going, Gone?

Happy New Year! We are excited to be starting a new year of science cafes. Our January Science Café (description below) will be held on Tuesday 1/18 at Tir Na Nog on South Blount Street. Our speaker for the evening will be Dr. Meg Lowman, Director of the Nature Research Center (a new wing of the Museum of Natural Sciences currently under construction). Dr. Lowman is a world famous canopy researcher. To learn more about her and her work please see the information listed below (be sure to look at her website). We will have a fun and informative discussion about the amazing (and sometimes strange) diversity of life that can be found in the earth’s rainforests as well as how researchers have figured out ways to study sometimes elusive plants and animals. We will talk about the importance of what is being discovered in the rainforests and how these discoveries can affect our way of life. I hope that many of you can come.

Tuesday, January 18, 2011

6:30-8:30 p.m. with discussion beginning at 7:00 followed by Q&A
Tir Na Nog, 218 South Blount Street, Raleigh, 833-7795

Every child grows up with a sense of awe about tropical forests — extraordinary creatures including poison dart frogs, sloths, orchids and jaguars representing a veritable treasure-trove of biodiversity. But scientists estimate that more than half of Africa’s rain forests are gone, with at least 40 percent losses in Asia and Latin America and 95 percent in Madagascar. Even with new technologies, measuring tropical deforestation is not easy, and illegal logging is epidemic in many parts of the world. What is the prognosis for the future of tropical rain forests? And how will human beings fare if these vital ecosystems disappear? What essential services do tropical forests provide for the planet, and how can we conserve them for our children?

About our speaker:

Dr. Meg Lowman (www.canopymeg.com) is Director of the Nature Research Center, North Carolina Museum of Natural Sciences and a research professor at NC State University. Over the past three decades, “Canopy Meg” has earned an international reputation as a pioneer in forest canopy ecology, tropical rain forest conservation, and for designing canopy access tools including ropes, hot-air balloons, walkways and construction cranes. Equipped with degrees in biology, ecology and botany, Lowman developed her childhood interest of building tree forts into mapping canopy biodiversity worldwide and spearheading the construction of canopy walkways in tropical forests for conservation. She uses science education to influence government policy and encourage environmental stewardship. Her book, “Life in the Treetops,” earned a cover review in the New York Times Sunday Book Review.

Sigma Xi pizza lunch lecture – Science in the current media environment

Next Tuesday at Sigma Xi:

Hi all. Normally we aim to hold pizza lunch on the 3rd Tuesday of each month. In November, that date conflicts with the ship date of the January-February 2011 issue of American Scientist. So we’ll convene a week later. Still, I think you’ll find the session—something different this time—worth the wait.

Join us on Tuesday, Nov. 23 to hear one of our own, veteran science blogger Bora Zivkovic, talk about the shifting ecosystems within his craft. Zivkovic has had a front seat to much of that change, as author of the influential A Blog Around The Clock, as co-founder (with Anton Zuiker) of the international conference ScienceOnline in RTP, as the former online community manager at Public Library of Science and, now, as the new blog and community editor for Scientific American magazine. For a long time, people spoke of the day when print and online media would converge. In a growing share of the publishing world, that convergence has occurred. And Bora, when it comes to science journalism, has been a catalyst in that change.

Thanks to a grant from the N.C. Biotechnology Center, American Scientist Pizza Lunch is free and open to science journalists and science communicators of all stripes. Feel free to forward this message to anyone who might want to attend. RSVPs are required (for the slice count) to cclabby@amsci.org

Directions to Sigma Xi, the Scientific Research Society in RTP, are here: http://www.sigmaxi.org/about/center/directions.shtml