Generally speaking, spawning organisms include reptiles, birds, most fish and insects in the ocean. Except fish, most of their fertilized eggs have hard shells, so they can adapt to the dry environment on land.
Viviparous animals generally refer to mammals, such as dolphins, whales, seals and walruses in the ocean. There are more mammals on land, including us.
This reproductive mode in which the fetus matures in the mother can adapt to a more complex environment. Although the breeding cycle is longer, it can ensure a species to develop in a more complicated direction and avoid the risk of fertilized eggs from the outside world during the breeding period.
But we have never heard that some existing species can spawn and viviparous, which are obviously two different ways of reproduction and should not exist in the same species. But nature always surprises us.
There is a creature on the earth called Saifuping. The population of this creature has two ways of reproduction: oviparous and viviparous.
Although their reproductive methods are different, they can mate with each other to breed offspring without reproductive isolation, indicating that they are still the same species.
Just living in different areas and facing different environmental pressures, Saiphos equalis, who lives in Sydney, Australia, uses ovoid eggs.
Their eggshells are very thin, and their embryos are almost fully developed after laying eggs, which means that their eggs can hatch in a short time, only five days.
Saiphos equalis, who lives in northern Australia, adopts viviparous method to give birth to cubs directly, saving the five-day incubation period.
A species has two different reproductive strategies. This shows the magic of environmental selection on biological evolution. Scientists think this creature is a miracle of evolution, but the surprise doesn't stop there.
When studying this creature, biologists found that one of them, Saiphos equalis, gave birth to three eggs and a living cub in the same pregnancy.
This indicates that there are two different reproductive strategies for the same organism. Scientists believe that this three-toed skink (Saiphos equalis) is in a transitional stage between a rare oviparous organism and a viviparous organism.
The study was published in Molecular Ecology.
One of the main authors of this paper, Camilla, an evolutionary biologist at the University of Sydney? Whittington said: this discovery is of great significance and has great scientific value for studying biological evolution. What do we think Seppin is? The strangest lizard in the world? It can tell us a lot about the evolution of reproductive strategies. ?
Why is this discovery so exciting for scientists? We know that on the earth, since the emergence of spontaneous reproduction, the initial way of reproduction is oviposition, and it is the kind of egg without amniotic membrane, which is only suitable for reproduction in water.
Hard-shelled eggs evolved under the pressure of primitive fish ancestors living in the ocean in order to adapt to the dry environment on land. These fish are the ancestors of reptiles.
Reptiles have ruled the earth for hundreds of millions of years. All the existing mammals on the earth evolved from the original reptile ancestors, but this evolution occurred about 654.38 billion years ago, which is very far away from us.
Why do reptiles change their reproductive strategies and become viviparous? This problem has always been a difficult problem in biological evolution and a theoretical guess.
Therefore, the discovery of Saiphos equalis has become a transitional species from oviparous reptiles to viviparous mammals, and it is a living species, which is more valuable than any transitional fossils found.
It can explain a key link in biological evolution for us.
There are several explanations for why Saiphos equalis laid eggs and gave birth to live babies in the same pregnancy:
There is a theory that this is a kind of. Risk hedging? In other words, the ability to switch between spawning and viviparous can provide it with the advantage of survival and reproduction in an unpredictable environment.
For example, if the weather is cold or dry and there is no hidden nest to protect the eggs, it is a better strategy to choose viviparous and let the cubs mature and be born.
If you are often threatened by predators during the breeding period, if you still have a baby at this time, it will hinder the female's action and face the risk of being hunted. At this time, laying eggs in a hidden nest in advance can improve the survival rate.
Another explanation is that this kind of Saiphos equalis was originally a viviparous strategy, but it vomited a nest of eggs early because of some changes and stimuli in the environment.
But these three premature eggs also hatched healthy babies. If so, it shows that this phenomenon often happens in the wild, and future generations can survive anyway.
Scientists still don't know the process of evolution and the future results. However, this discovery means that Saiphos equalis, a transitional organism, may evolve into oviposition or viviparous in the future.
Generally speaking, viviparous animals evolved from oviparous ancestors, and few animals evolved in the opposite direction. That is to say, there is atavism, which indicates that Cefoping is likely to be completely transformed into viviparous in the future.