Yes indeed! Some sharks do lay eggs but not all of them exhibit the same behavior. Almost 40 percent of shark species lay eggs while the remaining 60 percent bear live young. Different species of sharks display different modes of reproduction. Therefore, some sharks lay eggs and some do not. Those sharks that lay eggs protect their eggs in a specialized jacket called egg capsule and leave them alone in the ocean without any care. The shape of each egg also differs; some are oval-shaped while others are like a ring. The baby shark is known as a pup. Now let’s discover more about sharks, their eggs and how the pups get nourished.
A Quick Guide To Sharks, Eggs And Pups | Do Sharks Lay Eggs
Sharks
Names of Sharks that lay Eggs: California Hornshark, Port Jackson shark, Catsharks; Zebra shark, Necklace Carpet shark, Swellshark,
Names of Sharks that give birth to live Pups: Whale sharks, Blue shark, Bull shark, Whitetip Reef sharks, Mako shark, Salmon shark, Lemon shark, Hammerheads
Sharks that lay eggs: 40 percent
Sharks that bear live young: 60 percent
Eggs
Name of the covering in which egg is enclosed: Egg Capsule or Mermaid’s Purse or Egg Case
Shape of Egg Capsule: Pouch or Screw
Size of Egg Capsule: 5 – 10 cm
Size of an Egg: 10 – 25 cm
Shape of an Egg: Oval or Circular
Number of Eggs in a Litter: 9 – 40
Incubation Period: 15 weeks
Pups
Size of pups after egg is hatched outside (Egg-laying sharks): 9 – 16 cm
Size of pups after coming alive from mother’s womb (Live-bearing sharks): 45 – 60 cm
Number of live pups in a Litter: 2 – 20
Gestation Period: 6 – 22 months
Egg Capsule | Do Sharks Lay Eggs
Those sharks that lay eggs are known as oviparous. An egg is usually encased in a solid pouch made up of leather. The leather pouch is known as egg capsule or mermaid’s purse. Egg capsule is composed of proteins called collagen and protects the embryo that is developing inside. This embryo gets nutrients from the yolk sac inside and as soon as embryo uses up all the nutrients, the pup breaks through the case into the water. The empty cases of egg capsules are often observed lying on seashore in that young ones are already hatched in water before the egg case lands onshore. Egg capsules have different shapes and sizes. For instance, the egg capsule of a bullhead shark is coiled nicely such that it is tucked perfectly inside the cracks. In this way, eggs are protected from potential predators.
There are some egg cases that are oval in size like egg capsules of zebra and bamboo sharks. While few capsules are oval, there are also some other egg cases that have a shape like purse like that of catsharks. Such cases have large tendrils attached at the end so they are easily tucked on sea floor or rocks under the sea. Egg capsule has small openings from both sides called slits. With the help of these slits, embryos get constant supply of oxygen from water as egg case regularly flaps its tail for ensuring water speed. The eggs are always deposited in pairs.
Sharks That Bear Live Pups
Not all species lay eggs and if truth be told, nearly 60 percent of shark species bear live young. So those species that do not lay eggs and instead give birth to live young are known as ovoviviparous. Such female sharks do not give off eggs and pups remain inside the mother’s oviduct until they are hatched. The embryos get nourishment from the fluids of egg yolk and also from the fluids produced by the inner surfaces of oviduct. The female shark’s ovary discharge eggs and these eggs arrive at oviduct while crossing ostium on their way. Typically, eggs are discharged in pairs into oviduct. Now the eggs get a thin egg casing (fine membrane) over them while crossing shell gland. There is a tube known as fallopian tube in which eggs are fertilized. The mother holds them in her uterus (womb) until the time comes. The gestation period may vary from few months to more than twenty months. The size may range up to 50 to 60 centimeters each.
References:
Florida Museum of Natural History. “Shark Biology”. n.d. Web. Accessed 25 Sept. 2014
Enchanted Learning. “Shark Reproduction”. n.p. Web. Accessed 25 Sept. 2014
Shark. “Mating and Reproduction of Sharks”. Shark Foundation. n.d. Web. 25 Sept. 2014
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