INTERESTING FACTS ABOUT SHARKS
The dark upper part and light lower part of sharks’ skin helps them to blend in with their surroundings and camouflage them from predators and prey – this called counter-shading. Image (c) Morne Hardenberg
Some species of shark (e.g. Great Whites) cannot survive if they stop moving because they don’t have the necessary muscles to pump water through their mouth and over their gills, but as long as they keep swimming, the water moves over their gills and keeps them alive. This is known as ram ventilation.
Sharks have between 5 and 7 gill slits on the sides of their heads.
Sharks have the same five senses we do – sight, smell, taste, hearing and touch. However they are also able to detect pressure waves in the water from struggling fish. These waves are picked up by their lateral line, a thin line which runs down the length of the shark and is filled with small pressure sensors which helps them detect the movement and direction of an object. They also have the ability to detect the electromagnetic fields emitted by their prey (their electrical sensors are called ampullae of Lorenzini). Image (c) Shark Shield
Most sharks hunt at night or during the evening. Sharks have different hunting strategies e.g. great white sharks attack their prey from below, while species that live on the ocean floor will bottom-feed. Some sharks attack schooling fish e.g. thresher sharks, and others swim through the ocean with open mouths, filtering plankton and krill, e.g. whale sharks.
Most shark species live for 20-30 years but some, such as the spiny dog fish and whale shark, can live for over 100. The maximum recorded age of a great white shark is approximately 70 years old. The age of a shark is determined by the number of rings in their vertebrae, where one year of grow equals one ring, much like the rings in a tree. Image (c) Canadian Shark Research Lab.
Ragged tooth sharks engage in two forms of intrauterine cannibalism; the first one involves the consumption of smaller, weaker embryo’s by the strongest one. This continues until there are only two developing embryo’s in the mothers uterus, one on either side, which enables them to grow much larger than they would have had they been sharing their food and space with multiple siblings. Oophagy is the other form of cannibalism that ragged tooth sharks participate in while in the womb and occurs when the developing embryos eat the mother’s unfertilized eggs. Image (c) Renee Blundon