Sharks are amazing creatures that have existed on this planet for over 400 million years; which is 50 million years longer than trees.
These astonishing fish have a reputation for being much deadlier to humans than they actually are, but make no mistake: their evolutionary success is indeed due to the fact that they are incredible apex predators. These guys are pretty intense in a lot of ways, including reproduction.
1. For sharks, lovemaking is anything but gentle.
When a male shark finds a female he wants to mate with, he makes his intentions very obvious. The male nips the female on her body to let her know what is about to happen, and then flips her upside down, clamps down on her pectoral fin to hold her in place, and he goes about his business. Sometimes, the males can even draw blood.
Not exactly a gentle courtship.
No, as it turns out, the females actually don't enjoy the process.
2. Some female sharks will avoid unwanted advances from males by hiding in shallow waters.
Because the mating process is really hard on the females, they don't want to have sex any more than they have to. During the mating season, females can be found much closer to shore because the water is more shallow. This gives the males less of an opportunity to turn them over for sex, resulting in fewer injuries for the female.
When it does come time for the females to want to mate, they are better able to cope with the process because of certain evolutionary adaptations.
3. Females have literally evolved thicker skin to protect themselves from males.
The mating process does leave noticeable scars and pits in the female's skin, which is much thicker than that of males. Females are generally much larger than the males, which minimizes the damage the male shark is capable of inflicting on them.
The size difference is an example of sexual dimorphism, and is fairly common throughout the animal kingdom. Because females require more resources to bear offspring than males who just crank out sperm cells, the ladies typically need to be bigger.
As if the way the male sharks get the attention of the females isn't intense enough, their actual reproductive organs are pretty scary themselves.
4. Male sharks have claspers, which is kind of like a double penis.
Only one of the claspers is used at a time, and the males insert it into the female's cloaca (vagina-like organ). However, that's not the end of the story. The clasper has spurs that come out sort of like a fish hook to hold the organ in place until the male has successfully inseminated the female. Ouch.
Not all sharks go through this, though.
5. Some shark species are able to avoid this traumatic process by reproducing asexually.
Some captive female sharks have been known to lay unfertilized eggs, which are then able to develop into babies. This asexual process is known as parthenogenesis and isn't just seen in sharks and other fish, but in reptiles, certain insects, and even birds as well.
It's assumed that females resort to this when there isn't access to a male (or one that the female deems as suitable). Researchers haven't seen this one performed in the wild yet, so there's no telling how common of practice it may be for sharks. At any rate, it's a lot more gentle than the alternative.
So what happens after the sharks mate?
6. Shark pups have intense sibling rivalry and can even cannibalize each other in the womb.
Competition for food and resources is pretty fierce for shark pups, and for some, the struggle begins before they are even officially born.
While many sharks lay eggs, some shark species develop offspring inside the mothers and give birth to live pups. The pups that emerge first will eat his or her siblings, taking out the competition for the mother's resources. However, one female shark can have offspring from several males at once, and those with the same father don't generally eat each other. Instead, they'll gang up on those with other fathers, and take them out.
This life cycle is not for the faint of heart.
[Header image: iStockphoto/Amanda Cotton]