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Sharks have several different processes that help them adapt to their environments. Some of these are thought to be found in all sharks, while others are specific to certain species.
There are seven species of Lamnifomes or "mackerel shark" that can keep their body temperatures above the water temperature, sometimes by as much as 12.8 degrees C. They have a special organ called rete mirable that allows the body to warm the colder, oxygenated blood coming from the gills, using heat produced by the muscles and organs. This allows the sharks to have greater speed and strength, and inhabit colder waters where there may be less competition for food.
A female hammerhead shark in captivity gave birth to a pup in 2001, even though she had not had contact with a male shark in 3 years. DNA tests confirmed that the offspring had no paternal DNA, making this a so-called "virgin birth." Scientists believe that this happens very rarely among sharks in the wild, and is a mechanism to ensure survival of the species even when mates are not available.
Sharks have special organs, called Ampullae of Lorenzini, that allow them to detect other creatures by the electromagnetic fields that they produce. This aids them in finding prey that is concealed under sand or in caves. Sharks have the greatest electrical sensitivity of any animal, though this can be a problem, as sharks are drawn to the electricity generated when salt water interacts with metal, which can lead to a confused shark attacking a boat.
Mammals, including human beings, have two types of sensory nerve cells: myelinated and unmyelinated. The unmyelinated neurons, called nociceptors, are those nerve cells that respond to pain. In human beings, 50 per cent of our nerve cells are nociceptors. However, a 1993 study found that only 1 per cent of neurons in two species of rays, (technically in the same family as sharks), were nociceptors. In the blackfin reef shark, 14 to 38 per cent of neurons were nociceptors. It may be that sharks do not feel pain at all, and if they do, it would be significantly different from the way that humans and mammals experience pain. This might be an evolutionary adaptation, as sharks and rays must keep moving in order to extract oxygen from the water, and therefore cannot stop and wait for pain to subside as a mammal would.
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