Sharks are cartilaginous fish, that is, their skeleton is made up of cartilage instead of bone. They are characterized by being large predators and by their great variability, since 375 different ones have been found.
They include from the smallest to the largest species such as the whale shark, which although its only diet is based on plankton, can reach 18 meters.
Most species, especially large ones, are endothermic, that is, they regulate their temperature depending on the environment in which they live.
Below I explain how sharks are born and I encourage you to also read this article on What a Shark is like.
Shark life cycle
As we have already said, there are approximately 400 different species, and each one has a different life cycle. But you can generalize to all the same functions. Sharks can live between 18 and 25 years.
How sharks are born:
To begin with, reproduction is given. This occurs when the male’s pterygopodium inserts into the female’s opening.
Later, depending on the shark we can also find different developments of the embryo; it can be viviparous, oviparous or ovoviviparous:
- The oviparous is about laying the eggs, which usually contain a protective sac.
- In the viviparous way, females have a placenta that nourishes the little one inside their body before it is born at the end of gestation.
- Finally, the ovoviviparous is to lay and care for the eggs inside the body of the female, before the young are born alive and fully developed.
After being born…
The shark takes between nine months and two years to develop depending on the species and its complexity.
Also the number of offspring depends on the species, since there are some that can only produce one at a time, and others can produce 100.
They usually weigh between 18 kilos and measure 1.5 meters. Once they are born, they swim away from their mother; otherwise they will most likely eat their own young. Once it is born, it is ready to survive on its own, hunting thanks to its instincts.
The sharks are feeding and growing. Depending on the species and the years they live, they take less or more time to reach sexual maturity. But once they arrive, they continue to grow until they die, albeit more slowly.
How do sharks reproduce?
Before reproducing, sharks carry out a series of mating rituals, which vary according to the species. But there are some traits that they all have in common, such as synchronized swimming, color change, and the bites they do.
The bites are usually by the males, so that the females are stimulated and copulate more quickly or to hold on. They usually occur 30 days before ovulation. The smaller shark species do their mating by curling up their bodies. In the largest species, it is formed by orienting head to head in a parallel way.
Sharks, unlike most other bony fish where the females lay their eggs outside and the males lay the sperm, forming the less secure embryo there, but a greater number of them, these have an internal reproduction, where they will produce less eggs, but instead, more protected.
Once the eggs have formed internally within the body of the female shark, they can develop in three different ways depending on the species we are talking about. The different developments are:
Oviparous development.
It is produced when the shark lays its eggs on rocks or algae due to the hardness of the shell, therefore, they will resist the attack of predators. These eggs are usually rectangular in shape. The female incubates the eggs until they hatch. Once she hatches from her eggs, they will feed on the yolk of the egg.
Viviparous development.
These pups are fed from the placenta in the female shark’s uterus, and when the pups are fully formed, they give birth. There are some species where the female releases a substance, uterine milk, for the fetus to feed on.
This type of development is considered the most developed in the animal world, and thanks to this, some of the largest known species are produced, as is the case of the blue shark.
Ovoviviparous development.
In this case, the shark also gives birth and they keep the egg in their uterus. The difference with viviparous development is that they are fed with the substances found in the egg of the uterine sac.
In these cases, there may be intrauterine cannibalism. He means that some of the offspring “eat their brothers.” It occurs because one of the embryos has used up all the food from its egg and needs to feed, so it eats the food from unfertilized eggs, therefore it does not eat its siblings, but only looks for food to be able to continue with life.
An example of this can be seen in the bull shark, where the mother has two wombs, and although she has many eggs, only two young are born. These embryos develop to the point where their teeth erupt, and they begin to eat other embryos and unfertilized eggs.
The good thing about this is that these pups come out with a very high level of development, so much so that they can measure up to a meter in length at birth.
Although in most cases this production requires the intervention of a male, documented cases have been found where the female conceives an offspring without the intervention of a male. This may be due to the fact that there are certain species in which, after their first gestation, the females store sperm from the males in order to continue reproducing when necessary without the help of a male shark.
How sharks are born:
Once the males expel their sperm inside the female, their function ends. It will be the female alone who will take care that the embryos that are produced grow or are safe.
Shark gestation can vary depending on the species, but will last between 6 and 24 weeks. For example, the gestation of the Dogfish shark is one of the longest, and not only of sharks, but almost of vertebrates, since it lasts 2 years.
As we have already said, there are three types of developments, therefore, depending on the development they have, they will be born in one way or another. It should be noted that most of the species are oviparous, and that there are still species that we do not know what development they have, as in the case of the whale shark. Then we find a third of sharks that reproduce viviparous.
Once the young are born, they separate as quickly as possible from their mothers, and will have to survive from predators and feed themselves. This task becomes easier the greater their length at birth, and therefore, the more they develop inside the mother. And this is how sharks are born and grow into adults.
