Sharks kill each other from the womb

The sand tiger shark fetuses take over each other to gain the right to live in the womb.

With an average body length of 2.5m, sand tiger sharks (Carcharias taurus) are distributed throughout the world. We live in the waters near the coast. In the US, people often see them near sandy beaches and call them "sand tiger sharks".

During the reproductive period, females in the sand tiger shark always mate with many males. Pregnancy of sand tiger shark lasts nearly a year. They usually give birth to two babies after each pregnancy.

Sand tiger sharks must destroy each other to gain the right to live right from the moment
they are also in the form of embryos in the womb. (Photo: National Geographic)

Livescience reported that marine biologists of Stony Brook University in the United States analyzed embryos in the womb of sand tiger sharks (Carcharias taurus) in various stages of development. They initially noticed that the number of embryos in the shark's abdomen was up to 12. They were the product of many fathers. But the number of embryos decreases with time because the largest embryos swallow the remaining embryos. At the end of pregnancy, only two embryos exist in the uterus, including the largest and another. It is worth noting that the two embryos often have the same DNA, meaning they originate from a father.

"In some species, the struggle for paternity does not only take place when males compete with each other to mate with children, but also continue to the fetal development , " Demian Chapman , a member of the research team said.

The research team said that the process of killing each other between embryos reduces the number of children. Thus, sand tiger sharks produce healthier babies than other sharks. In addition, the fact that two embryos originated from a father showed that large embryos could recognize "him" or "em" with their father so they did not destroy. Thus, the sharks mate with many males, but only one "guy" has the opportunity to transmit genes to the next generation.