No Such Thing as a “Typical” Shark—Shark Diversity, Part 3

Frilled, Leopard, Coral Catshark

Here’s some other shark adaptations:

• Swell sharks can inflate their stomachs with water, increasing their diameter by up to 3 times their normal size. This sudden size increase can startle predators or  help the shark to wedge itself in a crevice on a reefbed, making it hard for predators to remove it.
• Juvenile Nurse sharks prop themselves up on their side fins and curl the fins under themselves to create a false cave that unsuspecting crabs seek refuge in. The sharks promptly eat any tricked crabs.
• The way an Epaulette shark’s side fins are attached to its body allow it to maneuver its fins in a type of “walking” motion over coral and rock beds.
• All sharks have light cartilage skeletons and large oil filled livers to boost their buoyancy since they don’t have swim bladders like bony fish. Sand tigers, though,can  use their stomach like a swim bladder. They swallow surface air and hold it in their stomach, giving them enough buoyancy to hover mid-water.
• Horn sharks have sharp, protruding spines positioned in front of each dorsal fin. The horns act an anti-predator defense. Divers have witnessed larger sharks engulfing smaller Horn sharks, only to immediately spit them out.
• Mackerel sharks (Whites, Threshers, Makos, ect…) have a specialized circulatory system that positions the arteries that carry blood warmed by muscle activity next to the arteries that pass cool blood from the gills. Heat is transferred from the warm to cool blood. Being warm blooded increases the speed and strength of muscle contraction and allows the sharks to venture into colder water without becoming sluggish.
• There are six “river” sharks with osmoregulatory adaptations  that live solely in fresh water. Bull sharks can freely move between fresh and salt-water habitats. Some other species of sharks, like Lemon sharks, are able to tolerate the low salinities of estuaries and river mouths areas.