In zoos, strange things like single mothers without a partner often occur. Last February, eggs were found in the stomach of a leaf fish in the state of North Carolina, USA. But the fish had no partner. Charlotte has spent most of her life at the North Hendersonville Area Aquarium. The fish has not mated with a male mate of its species in the last eight years. Yet mysteriously eggs were found in the stomach of the fish. The aquarium and shark lab scientists were surprised by this.
In addition, last year in Costa Rica, a girl named Coquita, who had been single for 16 years, laid crocodile eggs. There is also a child from it. Mystery has also been created around this incident. However, scientists say that although the matter may seem strange to humans, the phenomenon of such reproduction without sexual intercourse is not unknown in animals.
The crocodile was unaccompanied for 16 years at the Parque Repatilandia zoo in Costa Rica. Meanwhile, in 2018, the cockatiel laid some eggs. Later, an egg is found to contain a mature crocodile embryo. Being alone for so long, the crocodile had no chance to come in contact with its male mate. Even so, the fact that he got the embryo into an egg gave rise to mystery.
Scientists are talking about fin theory in case of leaf fish. They say there are two white spots on Charlotte’s fins, indicating that a shark in the tank met Charlotte. Because some suspicious bite marks were found on Charlotte’s body. Such marks may be a sign of the shark’s sexual behavior.
But this would be an unusual occurrence. Because, it will create a hybrid of shark-shaplapata fish. Rather than theorize it, scientists believe it may be the result of the rare phenomenon of reproduction from fertilized eggs without sexual intercourse (parthenogenesis). The Greek word parthenos means ‘virgin’ and genesis means ‘creation’. In this process, an egg develops into an embryo without being fertilized by a sperm. A partner has no role to play here.
Scientists explained the reason for the first time in a research report published in the journal Biology Letters on June 7. They believe that crocodiles, like some other animals, are capable of reproduction through parthenogenesis.
Parthenogenesis is a fairly common phenomenon in insects, such as flies. But parthenogenesis is rare in vertebrates. In 2001, a captive bonnethead shark was the first to give birth in this process. Since then, sharks and reptiles have seen more incidents of this.
Read also : How do calm dolphins become dangerous shark attacks?
Exactly why parthenogenesis occurs remains a mystery. Some scientists say this is the last attempt to produce a child through female reproduction.
Molecular biologist Kevin Feldheim has used genetics to study shark populations and sexual behavior at the Field Museum in Chicago. The goal of evolution, he says, is to release genes. There is no chance that a female animal separated from a male animal will produce offspring through sexual reproduction.
In 2008, Feldheim studied a phenomenon of parthenogenesis in zebra sharks at the Shade Aquarium in Chicago. First, he had to rule out the possibility of untoward incidents among aquarium animals.
“There was no direct evidence of male sex with the female animal,” Feldheim stated. But there was no camera in that tank. He also said that finding out the parentage of sharks can be very complicated. Because some female sharks can store sperm for months after sex.
So how does pregnancy happen in zebra sharks? Feldheim replied, through parthenogenesis.
In most cases of animal reproduction, eggs are produced by a process called meiosis. Where cells divide, genetic material and other cellular processes are shared between them. This process creates polar bodies. Normally, these polar bodies are reabsorbed by female animals. However, parthenogenesis mimics sexual reproduction by allowing one of these polar bodies to fertilize an egg and form a viable embryo.
But it’s a different process for cloning, says Cady Lyon, a scientist who studies sharks, skates and rays at the Georgia Aquarium. But it has flaws.
“The cells used in this are not carbon copies of the mother,” said Cady Lyon. Because both the egg and the polar body contain parts of the mother’s genome, the offspring are less genetically diverse than their mother.’
Asexual reproduction is advantageous in some species. For example, the majority of whiptail lizards in Mexico and California are female. They reproduce asexually. This species has developed an unusual way of maintaining its genetic diversity through parthenogenesis by doubling the number of chromosomes in the eggs of asexually reproducing female lizards. This has some advantages, which help the species settle in new areas and protect against sexually transmitted diseases.
But it has some disadvantages. Not naturally subject to mate choice, their DNA in this process acquires more deleterious genetic mutations through parthenogenesis than through sexual reproduction.
Not all species can adapt to parthenogenesis like whiptail lizards, Feldheim says. The offspring of shark parthenogenesis are short-lived, rarely reaching sexual maturity.
Scientists study the survival chances of animals born through sex and parthenogenesis. In one study, parthenotes (born through parthenogenesis) live less than a year on average. These animals behave in ways that weaken their chances of survival; Such as unilateral swimming, turning, headstand and feeding difficulties.
This research team included Cady Lyon. He said he wasn’t surprised to see evidence of parthenogenesis in leeches; However, Charlotte’s case did not solve all the mysteries surrounding the incident.
The history of the ‘virgin birth’ of animals
Scientists have known for more than a century that some animals are capable of laying fertile eggs without having sex with a partner. Warren Booth, a researcher at Virginia Polytechnic Institute and State University in the United States, has been researching parthenogenesis for more than a decade. He said, first scientists discovered this in pigeons.
Later, the presence of parthenogenesis was observed in various other animals including snakes. This type of reproduction has also been observed in birds, lizards, turtles and sharks. To that list has been added crocodiles.
The researchers believe that after female animals lay eggs without a partner, they should be tested to see if they are fertile. But Warren Booth thinks that most of the embryos produced by parthenogenesis are very sick or weak.
This is not the case in humans or other mammals, Booth said. Because, in their case, certain genes are needed from both the girl and the boy to form the embryo.
According to researcher Warren Booth, this does not occur naturally in mammals. Researchers have successfully produced mice through the process of parthenogenesis in the laboratory. But for this they had to edit a lot of genes. They have to transfer genes in due time.
According to this American researcher, crocodiles and birds may have acquired such abilities from dinosaurs. Although there is no way to prove this definitively without dinosaur DNA.
Sources – Taken from BBC, New Scientist and CNN
