Tiger Sharks-SY

Tiger Sharks

Tiger Sharks (Galeocerdo tigrinus) are one of the biggest sharks, capable of reaching over 5 m in length. They are commonly found in tropical waters, around the Pacific islands.Tiger Sharks are apex predators, meaning that they are on the top of the food chain. They are solitary and nocturnal hunters, feeding on a wide variety of prey; ranging from crustaceans to dolphins. However they are considered as near threatened species due to finning and fishing by humans. The name tiger shark was given to this type of shark due to the dark stripes similar to a tiger down its body, which fade as the shark matures.

Thermoregulation

Tiger Sharks are ectotherms meaning that they depend on their external environment to maintain their body heat. Therefore a drop in the water temperature would result in a drop in their core temperature. Therefore they rise to the top of the ocean, where the water is warmer and are able to be heated up by the sun to increase their body temperature. By doing so digestion is aided, the muscles are able to work harder, their heart beats better and metabolism is boosted. Conversely in order to lower their body temperature they sink to lower regions, where the water temperature is lower.

They also display behavioural thermoregulation, as they choose specific habitats or behaviours based solely on the water temperature. An example of this is rising to the top at night (when it is safer) to digest food faster using less energy and also feeding and breeding in shallower and thus warmer waters.

Thermoregulation in homeothermic sharks However some sharks e.g. great white shark are homeothermic, meaning that their body temperature is always slightly higher than that of the water of their environment. They generate the extra heat by increasing the rate of respiration in the strip of red muscle that runs along the center core of the fish's body which is surrounded by the rete mirabile, a web of veins and arteries. Some sharks have the ability to keep certain areas of their body (such as their eyes and brains) warm so even in colder temperatures they are able to work at their best.