This is the holy grail of the science of reproductive biology * unlike mammals, in some animals and in fish there are other factors that affect the species besides heredity
Zoologists know that in many reptiles the mating of the offspring that hatch from the eggs is determined by the temperature, since the eggs are incubated without the intervention of the parents, the mating is determined by the ambient temperature. It is generally known that when the temperature is higher, most of the offspring will be male,
In the Australian Jacky dragon species (amphibolurus muricatus) when the temperature is between 23 and 26 degrees, or between 30 and 33 degrees, females will hatch, that is, when the temperature is between 26 and 30 degrees, males will hatch.
The phenomenon was known and researchers tried to understand its causes.
About thirty years ago, two researchers suggested that: "The fact that different pairs hatch at different temperatures has an evolutionary advantage." Prof. Rick Chernov and Prof. Jim Ball, who were then young biologists, offered their assumption without the possibility of proof.
Since then, the search for an explanation for the phenomenon has been the "holy grail" of many biologists. At least that's according to an Australian research team, under the guidance of Professor Rick Shine and with the participation of Dr. Daniel Warner from the University of Sydney (Australia) and the University of Iowa (USA).
According to their research: "The temperature at which reptile eggs are incubated determines not only their sex, but also allows the best chances for many offspring in future generations." The finding published in Nature presents for the first time the fact that "incubation temperature affects the success of reproduction in males and females that hatched from the eggs"!
According to Shane "with several species of reptiles - at certain incubation temperatures only males will hatch, and at other temperatures only females will hatch".
The problem of proving Chernov and Ball's theory was the fact that many reptiles reach sexual maturity relatively late and live a long time (about 60 years), so it is difficult to measure the number of offspring after more than one generation. To solve the problem, the Australian hornbill was studied - Z K. Jack reaches sexual maturity a year after hatching and lives for about four years. Another problem in the study was to cause the "wrong" mating to hatch, that is, to cause males to hatch at an incubation temperature that under natural conditions would cause females to hatch. To overcome this problem, the researchers "treated" the eggs with hormones, according to the researchers, the hormonal "treatment" did not harm the health of the offspring.
It turned out that males hatched under natural conditions were 7 times more active (sexually) and more fertile, "natural" females were 5 times more fertile. That is: the success of the species and its fertility depends on the incubation temperature in nature, where the greatest success comes from the offspring being more fertile. And so he brings more offspring because of adaptation to environmental conditions. A finding that corresponds exactly to Ball and Chernov's prediction from thirty years ago, or as the researchers say, "We have reached the Holy Grail"
Dr. Assaf Rosenthal, ecologist,
Tour guide/leader in Africa and South America.
For details: Tel. 0505640309 / 077-6172298,
Email: assaf@eilatcity.co.il
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A strange experiment.
I would do another, simpler experiment, hatching the eggs in an incubator under temperature conditions that are different from the ambient conditions. As soon as they hatched I would release them into the free air.
What about hormonal intervention?
It is still not clear to me what exactly it will be possible to conclude from the experiment regarding natural selection and the reason for the phenomenon.
Even for me, this "discovery" leaves a sense of nothing, what's more, we are supposed to trust the researchers' statement that the hormonal manipulations did not harm the fetuses.
How do they know that? Only from wishful thinking considerations.
The subject itself is interesting and the fact that with our brother Jacques it is not exactly the high temperatures but a temperature range in the middle that is particularly interesting.
The proposal for an additional explanation seems original and very interesting to me, but I have difficulty accepting it because of the combination of the following facts:
1. The species is determined by the temperature during the "incubation". The dragon is supposed to live until the age of 40, when in the first year - the one in which its species is determined - it does not breed at all. To what extent is the temperature range in which he was born a measure of the features of his life environment in his 39 years of fertility? This is a long period in which there are many changes.
2. If we try to claim that there is nevertheless a multi-year correlation (which is more appropriate if it is a population that does not migrate from place to place) then this creates another problem because it can cause the complete extinction of one of the species and consequently the extinction of the entire species. In fact, it is almost required that in order for both species to remain, this species will be characterized by migration between different climate zones and this can even be interpreted as adaptation to migration, but I remind you that in this subsection we are discussing a situation where there is no migration.
Arie is right, there is nothing new except the fertility, and this can be explained (perhaps in my opinion) by the range of temperatures comfortable for the development of male and female genitals in these varieties.
And even in humans the eggs are outside because of temperature. 🙂
Not a secret and not decipherable. The fact that the species is determined by the temperature was known a long time ago - as is also written at the beginning of the article. So now they found out that those born with temperature pairings are more fertile. (I would say it might be obvious because this mechanism is supposed to give an evolutionary advantage) OK, but what is the mechanism why males and females are more fertile because they were born that way according to the temperature?
1. What affects more the number of offspring, the number of males in the parents' generation or the number of females in the parents' generation? Since each male can fertilize many females, but each female can give birth to (or lay or spawn) only a limited number of offspring, increasing the proportion of females in the population will increase the number of offspring, while increasing the number of males will not necessarily result in more offspring. It can be assumed that even the decrease in the number of males will not necessarily result in a decrease in the number of offspring, the males that will be left will be able to fill the gap.
2. When it is hot (or in other places cold) there is more chance of more food. In conditions of abundance, there is an advantage to having more males in the population, because more individuals can be allowed to excel and compete for the favors of the females. The abundance will be enough for all females as well as males. When, due to the temperature, the likelihood of abundant conditions decreases, there is an advantage to having more females in the population, because it is desirable that fewer individuals compete for the same resources, but it is also desirable to maintain the number of females.