“Have you ever seen a shark egg before?” was a question asked to me by a nine-year-old who was trying to convince me that sharks were mammals. I couldn’t answer the question immediately, so he laughed at me in the most humiliating way possible. Anyways, thanks to that annoying little boy, I found an amazing topic to share with you.
First of all, I will give you some information about how sharks reproduce. There are four different ways that sharks reproduce: viviparous, ovoviviparous, asexually and oviparous. I know they all sound the same, let me explain.
Viviparous Reproduction
This type of reproduction has many similarities with the way mammals give birth. The eggs develop in a womb and they have placenta and all. The only difference is that the sharks will hatch inside the womb. These sharks also have an umbilical cord that provides oxygen and nutrients to the babies so they have belly buttons just like humans!
Ovoviviparous Reproduction
This type is very similar to viviparity. The eggs again hatch inside the womb but there is no placenta this time. There is an egg sac that provides only oxygen to the fertilized eggs. The shark pups will get the nutrients from the yolk sac until the egg hatches. But after the sharks are out of their eggs, the only way to take the essential nutrients is to consume the other shark fetuses and their yolk sacs which insures the survival of the fittest.
Asexual Reproduction
This type of reproduction is very rare to occur. The cells placed close to each other are called adjacent cells. It is possible for an adjacent cell to fertilize the egg, so when this happens, the shark reproduces asexually. The baby shark’s DNA is exactly the same with its mother’s DNA. But this reproduction has only been documented when there are no available males. Some animals like birds, Komodo dragons and snakes can also reproduce this way.
Oviparous Reproduction
This reproduction type is the most interesting one for me because it is the reason the fabulous shark eggs are formed. Oviparous reproduction is when a shark lays eggs in a deposit in the water. About 40% of sharks are oviparous. The shapes of the eggs are so unique that people often call it “mermaid’s purse”. Sadly, most eggs don’t survive because they are left unprotected. They are either eaten by predators, or they are washed up on the shore. That’s why the sharks that reproduce this way lay many eggs.
As far as I know, there are four main shapes of shark eggs. Let’s take a look at them.
This is a horn shark’s egg. It looks really rigid but actually it is like plastic. Horn sharks put their eggs between the rocks so this shape probably makes it easier to put them there.
(You can see this egg with more details by clicking this link: https://vm.tiktok.com/ZM2SK8mrd/)
These are the eggs of a cat shark. The curly tendrils at each end make it easier for the eggs to stay where they are laid.
I couldn’t find any information about which shark’s egg this is, but its shape is really cool.
This is the egg of the Australian ghost shark.
If I had seen these eggs two months ago, I would have thought they were either alien or dragon eggs. Now we all know these “mermaid purses” are shark eggs.
Resources and credits:
The first picture is drawn by Ketrina Yim (@ketrinadrawsalot on Facebook).
Special thanks to that nine-year-old for giving me this idea.
The websites I got the information from:
https://scubashackcoz.com/shark-reproduction/#:~:text=There%20are%20four%20different%20ways,oviparous%2C%20ovoviviparous%2C%20and%20asexually.
https://www.australiangeographic.com.au/topics/science-environment/2018/08/the-weird-world-of-shark-eggs/