Australia has a population of 25 million, while kangaroos have 50 million kangaroos, which is a well-deserved kangaroo kingdom! What's even more bizarre is that there is a magical kangaroo in Australia, which can also be fertilized when pregnant, and can give birth to a second child after one child. Scientists call this phenomenon "embryonic diapause." In layman's terms, this kangaroo still mates and conceives three days before childbirth. This article will tell you in detail, how peculiar is this reproductive process?
Coat of arms of Australia
<h1 class="pgc-h-arrow-right" data-track="5" >What is this kangaroo? </h1>
This unique kangaroo is called the black-tailed kangaroo and is mainly distributed in the east and southeast of Australia. Like most Australian kangaroos, black-tailed kangaroos are non-endangered animals. Compared to other Australian kangaroos, the black-tailed kangaroo kangaroo is very unique. It is separately divided in biological species and belongs to the black-tailed kangaroo species of the genus Black-tailed Kangaroo.
The appearance of the black-tailed kangaroo is also very unique, and its name is closely related to its appearance. It has a distinct feature, that is, the back, claws, tail are all black, while ordinary kangaroos and black-tailed kangaroos are all brown or earthy red skin.
Black-tailed kangaroo
The black-tailed kangaroo is a small kangaroo. If you don't count the tail, the adult black-tailed kangaroo is between 66-85 cm long, which is taller than the newborn baby. The black-tailed kangaroo has a tail of 64-86 cm long, and it relies mainly on this long tail to maintain balance. Compared with most kangaroos, black-tailed kangaroos are not heavy, which is 10-21 kg weight.
Don't look at the small size of the black-tailed kangaroo, its strength is not weak. The black-tailed kangaroo has a powerful tail that it can use to attack enemies, and its hind legs are strong and explosive, and it can quickly escape from predators with it. Although the black-tailed kangaroo is very aggressive, it is a mild vegetarian. Unlike its distant relatives, the black-tailed kangaroo, although it has a strong sense of territory, does not have the desire to fight with its own kind. The black-tailed kangaroo has extremely simple food requirements, as long as it is a common leaf, bark and tender grass it can eat.
Fight against kangaroos
<h1 class="pgc-h-arrow-right" data-track="9" > the breeding of black-tailed kangaroos is very peculiar</h1>
The most amazing thing is the unique breeding method of the black-tailed kangaroo. Compared to many mammals and even kangaroos, black-tailed kangaroos breed in a way that can make people lose their eyes. The reproductive process of ordinary mammals is courtship - mating - breeding - breeding - birth, while black-tailed kangaroos can court - mate - gestate - reproduce - birth - fertilize again. Did you see that you were already surprised to open your mouth wide in surprise?
What's even more amazing is that the black-tailed kangaroo is not driven by animal instinct to have sex again when pregnant, and its rebreeding three days before pregnancy does not cause the previous cub to miscarry. For other animals, pregnancy and childbirth are like walking through the door, even for humans. And why black-tailed kangaroos are not afraid of pregnancy, scientists have been puzzled. The mystery was solved by an Australian team of researchers.
Black-tailed kangaroo with children
They scanned the abdomen of the black-tailed kangaroo with X-rays and found that there was a mystery under the ordinary "bag" of the black-tailed kangaroo. Unlike ordinary kangaroos, black-tailed kangaroos have two uteruses and matching ovaries and cervix. Having a double uterus isn't enough, black-tailed kangaroos can control the timing of egg discharge. Black-tailed kangaroos can secrete progesterone that inhibits egg release, which allows sperm to bind to the egg at the right time to form a fertilized egg. The sperm of male black-tailed kangaroos dormant in the second womb before binding, a phenomenon scientists call "embryonic diapause."
The structure of the black-tailed kangaroo womb is similar to that of the old double-barreled shotgun. The sperm is the bullet stuffed into the chamber, the egg is the hammer, and the black-tailed kangaroo is the hunter behind the shotgun. It decides when to press the bullet into the chamber of the gun, when to pull the hammer again, and when the hammer is pulled, the bullet will naturally pull the trigger at the right time.
Schematic of the working principle of a double-barreled shotgun
With progesterone regulating the time to re-conceive, female black-tailed kangaroos can safely feed their former cub, which she will put in a pouch for protection after the cub is born. Like other kangaroos, the black-tailed kangaroo's nursery bag is a type of leather bag that is supported by a bone.
Newborn kangaroo pups will try their best to climb into the female kangaroo's nursery bag, and the female kangaroo will protect it in the nursery bag. The inside of the pouch leads straight to the kangaroo's breast, and the kangaroo cub will intentionally look for the breast and suck the milk. In order to allow the cubs to get enough nutrition, kangaroos even evolved four nipples. Except that the kangaroo's four nipples were covered by the skin of the chest, and nothing could be seen from the outside.
Schematic of kangaroo breeding
Kangaroos evolved nursery pouches to feed their cubs as an improvement on their own deficiencies. Compared with ordinary animals, kangaroos have not evolved the "placenta", an important tissue that protects the fetus. Kangaroo pups produce in vitro when they are underdeveloped, which is similar to preterm babies in humans. How small are kangaroos pups when they are first born? As you might not guess, it's less than three centimeters long and its limbs are as thin as matchsticks.
Without any protection, newborn kangaroo pups can easily die prematurely. So, in order to protect their cubs, kangaroos have evolved nursery bags that can keep warm. The black-tailed kangaroo, on the other hand, was wiser than its own, evolving a uterus that could hold two parts of sperm and a body that could control the timing of conception. In this way, if the previous cub unfortunately miscarried or died during the gestation process, then he can get pregnant in a short period of time and give birth to his own cub.
The way kangaroos protect their cubs has aroused great interest among medical scientists. In 1984, two American doctors modeled on the female kangaroo nursery bag and invented a nursery bag for pregnant women with premature babies. This nursery bag allows the baby to stay close to the mother's body to conserve body temperature, while also sucking milk directly from the mother's nipples. Compared with the previous method of putting incubator protection, this method is more humane and greatly improves the survival rate of premature babies.
Kangaroo-style nursery bags
<h1 class="pgc-h-arrow-right" data-track="18" > learn to sprint from black-tailed kangaroos</h1>
Kangaroos can walk upright like humans, and their freed forelimbs will attack like humans. And its forelimb muscles are very developed, very suitable for boxing, Australia has professional boxers and trained kangaroos to fight in the ring. However, what many people don't know is that in addition to boxing, kangaroos can also sprint, and it is the black-tailed kangaroos that teach humans to sprint.
Prior to 1888, sports competitions were all started in a standing position, and this year australian sprinter Sharil observed the running posture of the black-tailed kangaroo and invented the "crouching" starting. American sprinter Thomas Burke used this style to win the 100-meter sprint at the 1896 Athens Olympic Games.
Crouch start
Unlike the running of human cognition, the running of kangaroos is actually more like the "jumping" of humans. The black-tailed kangaroo bends down before starting, keeping its belly almost pressed against the ground. Then the hind legs slammed hard, and the body rushed out of the ground like a bullet. Although Burke didn't know why black-tailed kangaroos could run so fast, it was easy to start with a squat position.
After analyzing the body structure of the black-tailed kangaroo, scientists found that the kangaroo squat start was scientific. Kangaroos are bulky and not very agile compared to other small animals. If you use an upright start, the speed is not strong. If you start with a crouching position, the kangaroo's center of gravity is reduced, and the forward impact can be greater. And when squatting, the hind legs can start on the ground, and the speed will naturally go up.
A black-tailed kangaroo ready to squat and run
At the same time, the leg muscle composition of kangaroos and humans is also very suitable for squatting start, scientists believe:
A squatting start elongates the gluteal muscles, quadriceps in front of the thighs, and the triceps behind the calves, leaving these muscle groups in a "tight" state before contraction. The elongation of muscles before contraction can improve the tension of the muscles and facilitate the ability to contract the muscles.
<h1 class="pgc-h-arrow-right" data-track="23" > conclusion</h1>
There are many animals in nature that have greatly helped human beings, and with their help, humans have solved many problems that have been unresolved for hundreds of years or even thousands of years. With the continuous progress of science and technology and the gradual deepening of the understanding of nature, human understanding and rational use of nature have become inevitable.