Since more than 200 million years, sharks foam the oceans of the whole world. This fish without bones is an excellent predator very important for the marine chain food. With more than 400 species, they are all different by their size, their shape, their color and their life habits.
Nature creates a "perfect creature" through the shark : fast, effective, well adapted to its environnement and master hunter. Many parts of its anatomy inspire high technology creations (like the boat hull)
The shark is a very old animal. Its forefather swam 400 millions years ago in the oceans. The modern forms of sharks appeared 200 millions years ago and didn’t change a lot until today. It means that sharks are older than dinosaurs!
Each fin has a define role which permit the shark to swim easily in different environments:
- pectoral fins : are like a rudder to change direction
- back fins : balance the shark’s body
- pelvic fins : are next to the sexual organs
- and finally it has a small anal fin
The shark is an excellent predator with a strong jawbone. It can eat some crustaceans or hunt turtles and seals. With its teeth, it can catch, cut, dig out or hold its preys.
Shark’s mouth structure is very interesting. The shark has about one hundred teeth in different levels. Each species has a special teeth shape adapted to their preys. They aren’t fixed to the bones of the skull like humans. The jaw seems to a movable carpet: when the shark loses a tooth it’s replaced by another one in the precedent level inside the mouth.
Do you know the five senses? Touch, smell, taste, hear and sight. They are very important to discover the world around us by different ways. We know how understanding a lot of tiny details from our environment.
Sharks have these 5 senses and 2 others:
Ampullae of Lorenzini : it is an electrosense. The shark can feel the other animals by some small organs in its nose. It can identify the earth movements and the different currents.
The lateral line: is very important for all the fish. They can feel the oceans’ movements, vibrations and pressures.
The shark’s skin is very rough, like the rays’ skin. Made by a lot of little teeth called “dentils”, they pierce the epidermis. These dentils are different for each species and gender. They restrict the rubbing of the water and allow the shark to swim quicker.
To identify a male from a female it is quite easy. Between the two pelvic fins, the male has two appendices called “claspers”. They have the same role as a penis and the shark uses only one of the two during the impregnation. The clasper is a transformed pelvic fin and can contain a bone (like a spine). Testicles are internal. The female has a genital orifice called cloaca.
Sharks have three kind of reproduction:
Oviparous: some sharks lay eggs. Each egg contains one embryo. These eggs are made in keratin (like nails and hairs). During its development the purse’s yolk nourishes the baby by the umbilical cord.
Viviparous: some sharks have babies like mammals. Embryos develop themselves into the female’s uterus. They are nourished by a placenta. When they were born, they look like small adults and are totally independent.
Ovoviviparous: the most common for sharks. The gestation time is the longest with 2 years maximum. Each embryo develops itself into a purse in the mother’s uterus. They are fed by an independent yolk.
In any case shark is a fish and not a mammal. It doesn’t feed babies and doesn’t look after them. Young sharks look like adults and are totally independent from their parents.
Reproduction at SEA LIFE Paris
The Nursehood (Scyliorhinus stellaris) is a small shark that lives next to Atlantic Ocean coasts. Easy to recognize with its brown blotchy skin, it eats crustaceans and mollusks on the ground. Our Nursehounds lay eggs inside the tanks. If most of them are empty, some contain a precious shark embryo. It will develop during about 8 months. You will admire baby nursehound during your visit in the central area to the centre.
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- There are more than 300 species of sharks in the world but only 5 potentially dangerous for humans
- They have 7 powerful senses to recognize preys from predators: view, sight, smell, touch, taste, electrosense (organs in their nose permit to feel the electric field from other creatures) and lateral line (to identify currents and water pressures)
- Some of sharks have to swim to breathe because the muscles of their gills are too weak to pump water by themselves
- The nursehound (Dina’s species) is a small friendly shark found in the northeastern Atlantic Ocean
- It is oviparous and lays the famous “Mermaid Purses”, some keratin thick-walled egg cases, two at a time, from March to October.
- The nursehound is nocturnal and spend day time inside small holes in rocks and swim into deeper water at night to hunt.
Would you like to learn more about sharks? : Read the program of animations