In May of this year, after 13 years underground, huge populations of cicadas will rise (and are already rising) to the surface in the southern US to breed.
Nature is steeped in clocks. The most commonly used clock is the length of day and night, that predictable 24-hour cycle that results from the rotation of the Earth on its axis. This cycle helps the different species determine their hours of activity, for example. In this cycle is combined an annual cycle of the duration of daylight hours based on the rotation of the earth around the sun - the days get longer and the nights get shorter for the hot season (summer) and vice versa, the days get shorter and the nights get longer for the cold season (winter). The shortening of the days helps, for example, migratory species to determine the time of their departure as well as the breeding time of species in a way that will allow the offspring to arrive in the season of abundance - spring. Other cycles are those of the tides, the lunar cycles, temperature cycles (usually combined with another cycle) and more.
There are also weirder cycles like the cycle of the cyclic cicada in the USA. In May of this year, after 13 years underground, huge populations of cicadas will rise (and are already rising) to the surface in the southern US to reproduce. Their mass courtship songs can reach up to 100 decibels (something like a busy main road) and make the lives of local residents particularly noisy. By July they will die and a new generation will begin its 13-year maturation process underground.
Most species of cicadas have an annual cycle, and these are the species that exist in Israel. But in the USA, along with the annual species, there are also several species that maintain cycles of 13 and 17 years. Since there are several species in different places in the USA that maintain such a cycle, every few years one of them comes to the surface, as is happening this year. One of the few places where two species of cicadas exist, one 13 years old and the other 17 years old also experiences years of union, but this rare event will not occur until 2219. (A site that tracks cicada cycles in the US).
The currently accepted explanation for this strange cycle is that of victory in the predator-prey arms race. When the cycle of a prey species is annual, the predator will adapt relatively easily and adopt a similar cycle. A species that adopts a biennial cycle forces the predator one of two options: switching to a biennial cycle or living in a situation of a year of abundance and a year of scarcity. Large prime numbers like 13 and 17 make it very difficult for a potential predator to adjust to the cycle of the prey. Any cycle except 13 and 17 will leave the predator without food for many years and lead to its extinction.
If so, only occasional predators remain that are an obstacle to the cicada that has been underground for 13 (or 17) years. The cicadas deal with this obstacle through their enormous numbers. The numbers are so large that the first settlers in these areas thought they were locusts. Since entire populations emerge from the ground at once, no predator, no matter how talented, will not be able to harm the stability of the population.
Today, a considerable number of genes affecting biological clocks are known, but the genetic factor in the cicadas has not yet been identified. 2009 study posited a mathematical model predicting such a genetic factor.
There are documented cases where the population clock went wrong and caused cicadas to rise earlier than expected, as happened in 2009 when a population rose four years earlier than expected. The researchers think that a warmer and drier winter than usual that year affected the cicadas.
31 תגובות
Nissim, thank you, this is an interesting explanation that I am hearing for the first time.
Uri Greenberg
There is another possible explanation for the 13 and 17 year cycle, not related to predators. There are 6 species of cicada, divided into 3 pairs. The difference between the two sexes in each couple is mainly the length of the cycle - 13 or 17 years.
The fact that both cycles are primary ensures that only rarely will the two species (in each pair) emerge together - every 221 years.
If there is a disadvantage in reproduction between two different species (in each pair) then it is possible to understand how two different primary cycles were created.
There is a similar situation with a finch bird (Gould's finch) in Australia. There are three very closely related species that can in principle interbreed, but there is a problem if both parents are not of the exact same species.
Note that you should always ask what is the process that led to a certain situation, and not what is the advantage in this situation. Think of the peacock's tail.
I didn't quite understand what advantage cycles 13 and 17 have in cicadas?
The claim is that a prime number of years gives them an advantage over predators, because if, for example, there was a species of cicadas that emerge from the ground once every 12 years (a non-prime number), then predators with a life cycle of 2, 3, 4 or 6 years would be able to adapt to this cycle and establish their diet on the cicadas.
But this argument never "made sense to me", because even if there is a predator with a life cycle of 4 years for example (in the example I gave earlier) then in any case it means that only one cycle of predators (one generation) will be able to enjoy the cicadas, and then there will be Two generations (two additional cycles) that will not be able to base their diet on the cicadas...
So what does it matter if the life cycle of the cicadas is 12, 13, 14 or 15 years? After all, in any case, even if it is an initial number of years or not - in each such cycle there will be only one generation of predators that can rely on the cicadas as food, while the next generations of predators will have to find other sources of food in any case and in any case.
If the predators are able to survive several generations even without cicadas, then why is there an evolutionary advantage to cicadas with a life cycle that is an initial number of years?
Hope the question is understood.
Done. Now the link is
https://www.hayadan.org.il/cicadacycle-190504
Abram:
In my opinion you hate religious people and the projection of religious people only to present them as complete fools.
I think you missed the point.
The Creator of the world, the Holy One, blessed be He, schedules these creations for us to show us His power and the strength of His hand.
There is nothing in nature other than Him and His creation, and the holy fact that these creatures return and emerge exactly every 13 years (about the number of Bar Mitzvah years) is absolute proof of the creation of the world by the Holy One, blessed be He, and not by evolution or any other nonsense.
The return of these human beings now should be a sign and a sign for all of us to strengthen ourselves and stick to the work of the Creator and prepare ourselves for His wonders.
I finally found an article of mine that explains the mechanism of a 13 or 17 year life cycle.
https://www.hayadan.org.il/%D7%9E%D7%AA%D7%A7%D7%A4%D7%AA-%D7%94%D7%A6%D7%99%D7%A7%D7%93%D7%95%D7%AA-%D7%A2%D7%9B%D7%A9%D7%99%D7%95-%D7%91%D7%90%D7%A8%D7%94%D7%91-%E2%80%93-%D7%9E%D7%93%D7%95%D7%A2-%D7%93%D7%95%D7%95%D7%A7/
Avi. Please link this to my article compilation.
R.H.:
In the correct part of your response this:
https://www.hayadan.org.il/once-in-13-years-0707113/#comment-301172
You're just repeating things I said.
Even in her response you responded, I was careful with the wording and wrote "meeting just like before" (since it was equally possible that they had not met before either).
In this response:
https://www.hayadan.org.il/once-in-13-years-0707113/#comment-300978
I specifically raised the possibility that they would not be encountered at all in the case that it is even more general.
The matter of the comparison between "members of the same species" and a predator is completely absurd because it is known that there is no genetic transfer of traits between the cicadas and their predators.
The last link convinced me that crazy bans caused the two sexes to appear separately.
Their model actually shows that any other development of numbers of years will leave too few individuals at an early stage (in the case of the model - 100), who will not be able to create new generations, and also demonstrated that if there is no lower quantitative limit (such as 100), the number of years does not matter.
They explain the lower limit by the breeding and mating habits of cicadas, which breed in swarms...
I also didn't follow how they ruled out 19 (they initially got 13, 17 and 19 as options.)
By the way, I inquired a little more, and it turns out that one of the enemies of the cicadas is the wasp.. I understand the cicadas.
One cent?
For those who are interested, a mathematical model for creating the life cycle of the cicadas:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2690011/?tool=pubmed
God,
First of all, who said that the three cicada species are in the same cycle? It is possible that everyone starts counting 13 or 17 in a different year and thus never meet. It's worth checking out.
Secondly, all the considerations you raised are also valid for a predator. Replace the words "sons of the same sex" in your message with "predator" and it is equally true.
R.H.:
And another thing I forgot to mention is that in order to "escape" from your own kind you don't have to switch to a different prime number.
If the cycle of members of your own sex is primary (and escaping from members of your own sex obviously does not explain this) - all you need to do to escape from members of your own sex is to add a year to the cycle (or subtract a year) and the frequency of meetings will be in a ratio of one to the size of the original cycle.
That is why the "escape" from your own kind cannot explain two primes (and of course it is not good to explain even one prime)
R.H.:
You are a first-time author even though you say completely different things.
H Rishon says that for some reason it is not good for two species of cicadas to meet.
This is a strange claim in light of the fact that the three (not two) species of cicadas meet exactly as before.
Your argument doesn't really add up either.
After all, if the problem was competition between members of the same species of cicadas, then after separating into two subspecies with a different cycle - each can continue to reproduce as before and very quickly they will return to the same population sizes and the same competition within the new subspecies, so why does the process not continue?
By changing the cycle time you can escape from a madman but you can't escape like that from your own kind!
H. the first one,
I agree with you. I also thought that the reason for these different cycles probably lies in some kind of competition between the two types of cicadas. Perhaps because of their vast numbers they compete for the same foods and there is an advantage in that they appear together on the rare occasion of once in 221 years. This hypothesis is strengthened by the quote from Dawkins that appears above, which states that each cicada species has 17 subspecies and 13 subspecies, meaning that the selection happened within the species between individuals competing for exactly the same food.
The predator's reasoning is not so convincing. It is true that a predator whose sole diet is cicadas will not be able to survive in this way, but for predators that exist all the time such as birds, other insects, amphibians and bats that eat cicadas as an appetizer, it does not matter when they appear. All in all, the year of the appearance of the cicada will be recorded in their calendar as a year of satiety, but nothing will stand or fall on it.
First H:
The price is exorbitant
I know a little about prime numbers.. I am a neighbor of a prime number.
In my opinion, the reason for 13 and 17 consists of:
1. Why prime numbers?
There is an evolutionary flaw (that I don't understand) in the meeting between the two species of cicadas.
In order for them to meet as few times as possible, prime numbers are needed.
If the numbers were 12 and 16 for example, then every 48 years (3 or 4 cycles) they would meet.
Thus they meet in every exact multiple of the numbers, in this case 13 and 17: every 221 years.
2. Why not more low or high numbers?
I'm not convinced by the predators' argument so much, because cicadas come in huge masses..
In my opinion, there is a balance created in evolution:
The cicadas are probably not able to wait over 20 years for another cycle, whether for food reasons or for other reasons. This is an upper limit to the numbers.
Why no less? Let's consider the possible prime numbers.. 11 and 13 are the next pair.
If so, the two species of cicadas would meet every 143 years. A very significant difference from 221 years, and that may be the reason.
Just my 2 cents.
In my opinion, what is at play here is the combination of starvation and flooding and the cycle of a high prime number.
This is also the logic behind Dawkins' words.
There is a difference between a multi-cycle famine that ends with only a few and a low-cycle famine that ends with more.
For each non-prime number, there are possible cycles of the predator's life that will allow the predator to experience a small number of starved cycles until the next flood and thus arrive at the flood with more individuals.
If the cycle is 13 or 17, however, then there is no way to experience less than 13 or 17 (respectively) starvation cycles until the next flood.
It doesn't seem logical to me that these are constraints imposed by the mechanism from which the biological clock is built.
On the contrary – since most creatures share similar biological clock mechanisms – the same constraints would have also affected the potential predator's clock and the cicada would have gone extinct.
for a cat and a cat,
Starvation and flooding alternately, to me also sounds like a mechanism with logic behind it.
What is strange of course is the particular cycles of the outbreak, the matter of 'matching the life cycle of predators and parasites' still sounds like a shot in the dark.
I get the impression that predators are opportunists, in the year of the outbreak everyone suddenly eats cicadas (especially fat bats bend the tree branches and even the squirrels crack cicadas instead of nuts :-)).
In terms of parasites, what about parasites whose life cycle is only a few weeks?
These will not miss the cicadas even if the outbreak happens every 4, 7, 22 or 13 years and in these cases there is no
Relevance to a cycle with an initial number of years.
And again I repeat hunger and flooding alternately, there is a mechanism with logic behind it.
What's more, the initial cycles are approximations, deviations of a few years more or less have also been observed.
It is interesting whether the mechanism that causes the cicadas to erupt is related to an internal clock or whether an 'external signal' causes the outbreak.
To Moshe - it doesn't matter that much to a predator, but it matters a lot to cicadas. A predator who is ready and willing to take advantage of the opportunity will hurt cicadas much more than a predator who actually "despaired" of encountering cicadas.
And after all this, I think there is room for another hypothesis that better explains the strange skips. The assumption (hidden or overt) of the hypotheses so far was as if the 13 or 17 developed gradually from below and were therefore preferred in the test of the surviving result over 3, 5, 8 and 11, for example. But if the genetic mechanism that activates the delayed life cycle is activated in a way that jumps to large prime numbers for completely different reasons that need to be looked for in genetic clocks, then 13 and 17 are precisely the smaller numbers that survived, since the larger jumps were no longer able to meet to reproduce...
A quote from the book "The Blind Watchmaker" by Richard Dawkins:
And you have a really wonderful fact. It turns out that there is simply not one species of 13-year cicadas and one species of 17-year cicadas. Instead there are three species, and each of them has a strain (or race) of 13 years and 17 years.
This division into varieties of 13 and 17 years happened separately, no less than three times.
It turns out that the intermediate periods of 14, 15 and 16 years were bypassed in convergent evolution, no less than three different times. Why? We have no idea. The only idea that anyone managed to come up with is that there is something special about the numbers 13 and 17, compared to 14, 15 and 16, and they are prime numbers. A prime number is a number that is not divisible without a remainder by any other number (except itself and 1).
The idea is that a species of animal that sometimes erupts as an "epidemic" gains an advantage when it overwhelms its enemies - predators or parasites - and alternately starves them. And if these epidemics are carefully timed to occur at intervals of years represented by a prime number, it is much more difficult for enemies to adjust their life cycle to this rhythm. If the epidemics broke out once every 14 years, for example, even parasite species with a seven-year life cycle could take advantage of them.
My clarification:
Dawkins adds here the idea of alternating starvation and flooding.
This has the following logic.
During the long periods of starvation, the number of individuals in the predator species adjusts itself to the reduced amount of food (if too many predators are born - some die of starvation).
The predator reaches the flooding period with thinned ranks and then the number of its individuals is not large enough to cause significant damage to the prey population.
Moshe:
I was talking about preference and not absolute dependence.
You can also read the chapter on the Life cycle here:
http://en.wikipedia.org/wiki/Cicadidae
I read your answer, but what to do I did not understand it.
I will try to formulate my question again in a clearer way that might clarify my intention. With the same potential predator, in any case, there are generations that do not meet the cicadas at all, it seems that the same predator can do well even without this part of the menu and still manage to survive, so what does it matter to him if he meets the cicadas regularly every 4 generations, or once he meets The same in generation 5 and then in generation 4 and then again in generation 5?
After all, it doesn't matter when the cicadas came out of the ground, the descendants of that predator can always take advantage of the momentary opportunity and eat them regardless of what happened in previous generations.
Moshe:
As I told you - there is a big difference between 4 and 17 or 13
My father, it seems to me that your comment was directed at me, in any case, on the face of it, it seems that there really is something to do with prime numbers (as long as the time measurement was really done accurately and no one "rounded" or rounded the results to give the impression that it is related to prime numbers) I'm just trying to understand the logic of things .
As I said, if the cicadas were to come out every 12 years, and a creature that might prey on them has a life cycle of 3 years, that means that 3 generations of the same creature would not see cicadas, and only the fourth generation would see and be able to prey on them, and again 3 generations would not see cicadas, And only the fourth generation will see them.
So it's hard for me to understand how such a predator can even schedule something related to cicadas, if for 12 years he managed to survive without cicadas, that means he doesn't need them to survive, and if he does include them in the menu, then what does it even matter to him when they come out? Any generation of the same creature that is available at that moment will in any case be able to devour them and diversify its menu.
In short, the mechanism that causes this is not really understandable to me in terms of logic.
(The truth is that you could perhaps create a computer simulation of a similar situation and see if it really converges to prime numbers, it could be an interesting experiment)
Some cicadas have a cycle of 13 years and some have 17. Doesn't that seem strange to you?
"There are documented cases where the population's clock went wrong and caused the cicadas to rise earlier than expected, as happened in 2009 when the population rose four years earlier than expected." Did this happen to cicadas 17 years that came up after 13 years? If so, this could be a clue to trace the genetic coding for this phenomenon.
In an article I wrote on this topic years ago here in Science, there was a detailed explanation of why prime numbers are large, including in the comments.
Moshe:
An animal whose life cycle is 3 years will encounter a cicada with a cycle of 12 years, once every 4 life cycles (or will not encounter it at all).
4, as we know, is significantly smaller than 13.
man:
It is clear that cicadas have many predators, but these are not predators that have developed a preference for cicadas over other species and this fact protects the cicadas.
There are many predators of cicadas, the menu of these also has other dishes.
Perhaps the cycle is actually related to the cicadas' recovery time for food, if they eat leaves of a certain type
of trees, these trees need time to leave the market.
When they die, the cicadas help fertilize the soil.
Maybe…
The story with the initial numbers sounds a bit strange to me too, let's say the cicadas would come to the surface once every 12 years, and there is a carnivorous animal whose life cycle is 3 years, what exactly will that help it? What will he eat for 12 years until the cicadas arrive? And if he managed 12 years without them (4 life cycles) why would he develop a special tendency to devour them?
The reason is simple.
A prime number has no divisors, so for an animal to encounter it frequently enough to develop a tendency to devour it, its life cycle must be a multiple of that prime number.
If the prime number is 13 then any animal whose life cycle is not a multiple of 13 will encounter the potential prey only once every 13 cycles.
Primes? It's hard for me to find a connection to prime numbers in predator-prey relationships. 13 could easily have been 12 or 14 and it wouldn't have changed anything. It seems to me... I would love to hear reasons regarding the importance of prime numbers in the life cycle of animals.
Best regards,
Ami Bachar