To effectively save sharks it's important to not only understand where they reproduce but how and when so that vital protections can be established to conserve shark populations. So, for this post we're taking a deep dive into Shark Reproduction.
Sharks have outlived dinosaurs and many other of Earth's lifeforms with fossil records dating back 400 million years! With over 1000 different species of sharks and rays (more being discovered too!) there are three main ways in which they reproduce- let's break them down.
Did you know:
The Greenland Shark can live ~400 years but doesn’t reach sexual maturity until ~150 years! Sadly, many are killed before they are able to produce any offspring.
SHARK ANATOMY BASICS
How can you tell male from female sharks? Good news, it's easier than you may think.
Male sharks have very noticeable 'claspers', which are like an extra pair of rolled-up fins they use for mating; females do not have clasper fins. Additionally, male sharks tend to be smaller than females.
The male shark bites on to the female while he inserts and hooks one of his claspers into the female cloaca. The intimate moment leaves a bloody mark on the female shark. This is the reason why evolution has gifted the female shark with a skin that’s up to three times thicker than the male. Sharks also have magical healing capabilities, which allows the female to recover from her wounds in a matter of weeks.
REPRODUCTION METHODS
It is thought that female sharks make it easy for males to find them by giving out chemical signals (pheromones) when they are ready to mate.
oviparity (egg-laying) - Oviparous sharks lay eggs. Their eggs are protected in unique egg cases (varying species to species) which are sometimes referred to as “mermaid’s purses”. This method of reproduction is considered a 'primitive' form and more common in bottom dwelling species.
A female shark deposits egg cases hidden away from predators. These eggs are commonly found tucked in amongst rocky reef or kelp, attached to structures on the sea floor by tendrils to prevent them from floating away. Through slits along the egg, the developing pup continually moves its tail to oxygenate and/or increase water flow within the egg case.
Shark species that utilize this mode of reproduction include:
ovoviviparity -
Embryos develop within an egg which hatches inside the female’s body. No placenta is present in the uterus and the developing pup will then continue to be nourished via any unfertilized eggs and each other. Very few pups in a litter survive until birth as a result of sibling cannibalism.
Shark species that utilize this mode of reproduction include:
vivparity (live birth) -
Viviparous sharks give live-birth to pups, depending on the species litters range from 2-20+ pups at a time. The embryo receives nourishment from a yolk sac before the sac attaches to the wall of the uterus and forms a placenta. The young shark continues to receive nourishment directly from the mother’s bloodstream and waste products are transferred to the mother for elimination.
Viviparous species can be separated into two categories:
Placental (having a placenta, or true connection between maternal and embryonic tissue), or Aplacental (lacking placenta).
Shark species that utilize this mode of reproduction include:
DID YOU KNOW:
The Sandtiger shark (Carcharias taurus), in which the two largest embryos that were fertilized first, consume the other embryos of the litter (adelphophagy).
The ocean is still largely unexplored and many mysteries surround the various mating behaviors of sharks and rays. More research and more studies is needed on the topic of 'shark 'romance'. While tracking tags and data collecting technology improves and field work is funded we will be able to better understand how to save these animals.
WATCH 'n LEARN:
Did you know:
The average pregnancy is between 9-12 months. The Greeneye Dogfish has the longest pregnancy at 31 months!
Depending on the shark species, the location for mating and pupping varies. Many sharks migrate to breeding grounds annually or may have a rest period between mating for one or two years.
WATCH 'n LEARN:
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