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Nature has come up with quite a few reproduction mechanisms. As a result, with the diversity of living beings themselves, the structure of their reproduction also changes.
One of the most popular ways to get offspring is by laying eggs. And the eggs themselves are so unusual that it's time to talk about them.
Shark eggs. The eggs of most of these formidable sea creatures, like those of the rays, have a very strange shape. It is also called the mermaid wallet. The egg is placed inside a thin capsule filled with collagen. At the same time, the fibrous reproductive deposits of sharks themselves are of an unusual square or rectangular shape, whose corners can be pointed. Outlines can often be of another, no less bizarre shape. Shark eggs are often washed ashore, usually the size of a human hand. But there is also a recorded record of 2 meters. After fertilizing the eggs, the shark leaves them at the bottom. There they lie, not needing maternal care, until the birth of the young. It happens that in some eggs several sharks are born. Nature makes it possible for us to light only one of them - the strongest eats the rest.
Octopus eggs. Octopus eggs are soft and half translucent. These tentacled creatures leave them on corals or rock ledges. Female octopuses lay hundreds of thousands of eggs at a time. But unlike sharks, these creatures do not abandon their offspring, staying close until they are born. After all, it is necessary to protect eggs from those who want to feast on defenseless food. Often this can last so long that hunger for survival will force the female to eat some of her eggs. And by the birth of little octopuses, they can only feed on tiny marine microorganisms such as plankton. Only when the cubs grow up do they begin to explore the seabed, leading an adult lifestyle. But for their mother, observing the eggs often becomes fatal - the weakened creature is usually eaten by some of the predators immediately after leaving the den. The female octopus does not have the strength to resist and fight for her life.
Fish eggs. What distinguishes fish from octopuses and sharks is the fact that most of their species do not mate at all. The female releases unfertilized eggs, or lays them somewhere. Then it's time for the male to work - he covers them with his "sperm". Nature has made it so that some males and females of the same species never even meet. At the same time, almost all fish, unlike the octopus, do not stay near their eggs in order to protect the offspring. In this case, the fry are given the opportunity to develop independently and hope that no one will eat them before birth. And at a time, a female fish lays millions of eggs, so even the coldest predator cannot destroy everything at once. However, eggs are sometimes laid even on unprotected surfaces, such as rocks. Often fish eggs generally drift right in the water, traveling hundreds of kilometers. This phenomenon is called ichthyoplankton and refers to the journey of fry even before they are born.
Bird eggs. Man is much more accustomed to dealing with bird eggs. Usually, females, like most reptiles, hatch their fertilized eggs. Parents protect their young up to the moment of their birth in a nest specially built for this purpose. But even after birth, the chicks are still helpless, needing the protection of their parents. In birds, the eggshell contains calcium carbonate, which is the main component in both pearls and sea shells. And for safety, nature has provided for a different color for bird eggs. It is curious that the eggs may be slightly deformed on one side, this is due to the constant pressure still inside the mother. But this property even turns out to be useful for some birds. Indeed, because of this, the eggs roll in a circle, and do not roll far out of the nest. When hatching, many birds create their own small world with a constant temperature. And there are some birds who do not want to hatch their chicks, throwing them to other, more trusting parents.
Dinosaur eggs. Despite the fact that these animals have long been extinct, scientists are faced with their fossil eggs. Tiny fossilized cubs are found there, which makes it possible to look back millions of years. It turned out that dinosaur eggs were of quite different shapes. Some resembled elongated spheres, there are those that look more like a pill. Some eggs were shaped like tears, and there were also round, like a sphere. Some species of dinosaurs laid many eggs and protected them, but there were also those who laid eggs and then did not bother with their protection. Scientists have been able to detect fertile deposits of a wide variety of forms. Almost all of them differ both in their shape and composition from those that are laid by birds and reptiles. Dinosaur eggs were much larger in size than any other living creature. The largest one found was about 60 centimeters high and 20 centimeters wide. At the same time, the shell of the egg contained tiny pores through which air entered the embryo. And in an egg that was too large, a thick shell was needed for strength, which made it difficult for air to reach the embryo.
Eggs of sea sponges. Although sponges and corals have little in common biologically with fish, they lay their eggs in a similar way. These creatures have no division into male and female sex. Each individual has organs for reproduction from both sexes. They release eggs and sperm into the water. And some sponges reproduce asexually, without organs for that. They simply release cells that grow into new individuals. For this, no fertilization is needed. Some sponges can multiply by simply dividing. Subsequently, each of them becomes a new independent organism. It is curious that the reverse process is also possible. Some types of sponges, after separation, can rejoin, turning into a new organism. If the body parts are placed at a distance from each other, then each sponge will simply begin to live its own life.
Insect eggs. Many insects have a rather respectful attitude towards the sperm of their male. The fluid obtained as a result of mating is stored later in the body to be used for subsequent fertilization. This is a very rational decision of nature, because not all males, for a number of reasons, are able to survive mating. Insects usually lay many eggs at once, sometimes building whole nests or unusual nurseries. And the eggs themselves can have a very unusual shape. In order to keep them from predators, insects have learned to mask well their future offspring. It also happens that eggs are laid even in water. Newborn insects already know how to live under water, only then they go out into the air. Many insects also know how to take care of laid eggs. For example, termites and ants maintain even a certain level of humidity around them.
Amphibian eggs. These amazing animals begin their life in water, only adults live on land. Amphibians also lay their eggs in water, often surrounded by a special gel. This substance holds things together. When the tadpoles hatch, they do not yet have limbs, but the gills are already present. They swim in the water like fish. But the tadpoles have no mouth yet; they absorb the remains of their eggs through the skin. Only over time, the lungs and limbs grow, the tail disappears, the mouth appears - this is how an adult is formed. Thus, the egg is not only a home for amphibians, but also food. Some frogs also tend to take care of their offspring if there is little water nearby.
Monotremes eggs. Biology suggests that monotremes descended from reptiles, being the ancestors of modern mammals. But today there are only two types of monotremes - echidnas and platypuses. These creatures are warm-blooded. They have hair and can even produce milk, which makes them mammals. But monotremes have a distinctive feature from mammals - they lay eggs. There is one more difference from reptiles and birds - even when the egg is inside the mother's body, it is provided with nutrients from it, just as it happens in mammals. Eggs in monotremes are small, spherical, and white. These creatures lay their future offspring in a burrow, and when they hatch, then even up to six months, the mother carefully looks after them and takes care of them. The platypus tries to keep the laid out eggs warm, for this he covers them with his tail. But the echidna simply covers the eggs with his body. But these animals feed the babies with milk, but not from the nipples. Nutrient fluid is secreted instead of sweat, feeding the newborn.
Viviparia. This term implies the birth of live babies. Sometimes they are in the egg until the very moment, but until they hatch inside their mother. This is quite rare in nature in fish, snakes, scorpions, cockroaches and other animals. For example, in seahorses, the female transfers her eggs to her male. He carries them until the children are born. But in mammals, as in higher beings, eggshells do not appear at all. The embryo is completely formed inside the mother's body, which, through the placenta, provides him with nutrients. Viviparia requires much more energy than an ordinary oviparous mother spends. Nevertheless, this method of childbearing allows much more complex creatures to be born, this is a step in evolution. Viviparia naturally forces parents to take care of their offspring and accustom them to life in a complex world, instilling the skills necessary for survival. In oviparous children, children already have all the necessary knowledge and skills for their future life in nature. But mammals have to learn everything. But these creatures are able to inhabit a much wider range of environments than they obey egg-laying animals.