Have you ever imagined that there is an animal on Earth whose body is patched together from a variety of different animals, that can both lay eggs and breastfeed, that can swim in water and run on land, that has both stingers and inductors? It sounds like a monster from a fairy tale, or a mutant creature from a science fiction novel. However, such an animal is real in our world, and it is the platypus.
The platypus is a mammal that lives in Australia and Tasmania, belonging to the suborder Monotrenosomeae and is one of the most primitive mammals in existence. Its shape is very peculiar, it has a flat and broad beak, which is used to detect food under water; It has a thick and greasy fur that is used to keep warm and waterproof; It has a flat, broad tail that is used to balance and store fat; It has webbed and claws on its front and back limbs, and is used for swimming and digging earth; It has stingers on the inside of the male hindlimbs, used for self-defense and competition; It has inductors on both sides of the head that sense weak electrical signals in the water. These characteristics make the platypus look like it is a patchwork of ducks, otters, crocodiles, echidnas and electric eels.
The platypus is not only peculiar in appearance, but its reproductive methods are also very rare. It is the only group of mammals found that can lay eggs and has hatching behavior. Every spring, female platypus dig a 20-meter-long tunnel along the river bank and lay hay and leaves at the end of the tunnel to make a nest. She then lays one to three soft-shell eggs in the nest and incubates them in her warm belly for about 10 days. The hatchlings are very weak and helpless, only 15 cm long, without hair and eyes. The mother will use her own milk to feed the pups. Since the mother has no breasts and nipples, and secretes milk on both sides of the abdomen, the pups lie on the abdomen of the mother animal and lick and eat. It takes about four months for the pups to grow up and mature and leave their mother to stand on their own.
The reason why the platypus has so many peculiar and primitive characteristics is because it is an important and mysterious link in the evolutionary history of mammals. Mammals evolved from reptiles, but the process didn't happen overnight. In the evolution of reptiles to mammals, many intermediate morphological or transitional taxa have emerged that have common or similar characteristics of reptiles and mammals, and have different degrees or directions of evolutionary changes at different times. One of the most important and complex changes is the shift in reproductive patterns from oviparous to viviparous or semiviviparous (e.g. kangaroos).
Oviparous is when an animal reproduces offspring by laying eggs and relies on the yolk or the outside environment to provide nutrients and temperature to make the eggs hatch into larvae. Viviparity is when animals deliver nutrients and oxygen to their offspring through the placenta or other means, and give birth after they are developed and formed in the body. Hemiviviparous birth means that animals first develop in the body for a period of time and then produce immature or underdeveloped juveniles, and then put them in nursery bags or other protective structures to continue to mature.
These three reproductive methods have their own advantages and disadvantages, the advantage of oviparous production is that it can produce a large number of offspring, increasing the chance of survival, the disadvantage is that the egg shell is easily damaged or eaten by predators, and the yolk is limited, can not provide enough nutrition and oxygen for embryo development. The advantage of viviparity is that it can protect and nourish the embryo in the mother's body and make it fully developed, but the disadvantage is that it needs to consume a lot of energy and resources of the mother, and only a few offspring can be born at a time, increasing the risk of extinction. Hemiviviparousness is a compromise between the two, which protects and nourishes the embryo to a certain extent while reducing the burden and risk on the mother.
So, why do platypus still use the oviparous method? This is because platypus was one of the first mammals to diverge from reptiles, and its ancestors may have appeared at the end of the Triassic or early Jurassic. At that time, reptiles were still the dominant ones on the earth, and mammals were still in a weak position, only surviving on the fringes. The ancestors of platypus may have used the water as a refuge, searching for food and mates in the water, and digging holes at the water's edge to lay eggs. This can not only avoid the threat of predators such as dinosaurs on land, but also use the abundant resources in the water to survive. And, due to the lower oxygen content in the water, the oviparous way is also more suitable for embryonic development in the water.
This is probably how the ancestors of the platypus spent long and difficult years in the water, gradually developing their own unique and primitive characteristics. When dinosaurs became extinct at the end of the Cretaceous, mammals began to explode evolution and radiation, and a variety of new taxa and new characteristics appeared. The most important of these is the emergence and popularization of the viviparous or semi-viviparous birth method. These new mammals have improved their adaptability and competitiveness using viviparous or semiviviparous methods and have been successful in various ecological niches. The platypus, on the other hand, retained its oviparous way because it adapted to life in the water for a long time and did not follow the evolutionary steps of other mammals.
Therefore, the platypus has become a miracle through time and space, which has witnessed the evolution of mammals from oval to viviparous, and also shows the diverse and wonderful evolutionary results of mammals. The platypus is a very special and precious animal, which not only possesses many peculiar and original characteristics, but also many unique and advanced characteristics. It is not only an important and mysterious link in the evolutionary history of mammals, but also a wonderful and brilliant microcosm of mammalian diversity and adaptability. It is both a living fossil and a living miracle.
Currently found only in Australia and Tasmania, platypus are found in small numbers and are threatened by human activities and invasive species. We should cherish and protect this unique animal, so that it can continue to live and reproduce on this planet, so that it can continue to reveal to us the mysteries and wonders of the evolutionary history of mammals.