[Image source: Wired Science]
Here is one more of the nature’s fascinating acts of precision … the lifecycle of the cicada! The periodical cicada is one of the world’s longest-living insects, but nobody knows why it times its death with bizarre precision: It either lives for 13 years or 17 years, on the dot.
Now, as Wired Science reports, Japanese researchers have developed a model that may explain the animals’ mysteriously accurate biological clocks. Cicadas spend 99% of their lives underground, as juveniles. Once every 13 or 17 years, they emerge from the ground en-mass, feed on tree leaves, mate and leave behind the eggs that later fertilise and the parent cicadas die. However, this unique synchronisation of thousands of cicadas over long, prime number of years must have some strong reason behind it. A leading theory is that long, prime-numbered life cycles minimize the likelihood that the 13-year broods and 17-year broods will ever mate. Though this theory is mathematically sound, no one could say why the animals would need to minimize hybridization.
Jin Yoshimura at Shizuoka University has developed a mathematical model to explore the rationale. If 13-year and 17-year broods interbred, they might produce offspring with intermediate lifecycles. This could result in their emergence few years before or after the vast majority of their fellow cicadas. This is a problem because periodical cicadas find strength in numbers. They’re easy to catch and don’t bite or sting, so they easily become snacks for hungry predators. But by buzzing around with hundreds of thousands of other cicadas, the probability of any one being eaten is close to zero.
To read more about this exciting new theory that increases the awe about nature’s precision design, click on the link above in the post.
Citation: “Allee effect in the selection for prime-numbered cycles in periodical cicadas” by Yumi Tanaka, Jin Yoshimura, Chris Simon, John R. Cooley, and Kei-ichi Tainaka. PNAS, May 18 2009.