Toastmasters: Sharks

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Status: Finished  |  Genre: Other  |  House: Booksie Classic
Sharks! Jaws! color blind???

Submitted: October 20, 2011

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Submitted: October 20, 2011

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It is unclear whether sharks have color vision despite having well-developed eyes and a large sensory brain area dedicated to processing visual information. Recently, Australian researchers found out that some, sharks may be color blind. The researchers from the University of Western Australia and the University of Queensland have been examining shark eyes under the microscope. They found that some shark eyes contain only one type of photoreceptor. In the retina of the eye, there are usually two different types of photoreceptor cells: cones and rods. Cones are used to distinguish colors while rods perceive the brightness or intensity of light, and respond to dim light. The rods are responsible for scotopic or dark vision. Humans have three cone types which are sensitive to blue, green and red light which allows us to see multiple colors. Out of the 17 different sharks studied 10 had no cones and the remaining 7 had only a single green-sensitive cone type making them monchromats and therefore potentially totally color blind. Color vision is not important in the marine environment where colors are filtered out because of the dim light. Everything is dark and shadowy and survival depends on distinguishing contrasts not colors. A few different types of sharks that are known to be color blind are the great white shark, which is feared by almost everyone and it was used as the antagonist in the movie JAWS, the Tiger shark, and the Bull shark. Sorry that I couldn’t find anymore color blind sharks. You can blame the internet for not giving me a list of them. Now I am going to give you some food for thought about what you should and should not wear around sharks. Several months ago, my friend and I were watching a show about sharks on Discovery Channel. The people on the show were testing the reactions of sharks to color.  They used three colors: Yellow, Red, and Black. Yellow scuba diving gear was placed on a mannequin who was put into a shark cage and lowered into the ocean to see what the sharks would do. The sharks only bumped the cage and left. The mannequin must have felt very lucky. Next they tried red and because it is the color of blood, they thought the cage would be attacked ferociously. The sharks were more aggressive but not ferocious. The last color they tried was Black, because that is the most common color to wear out in the ocean. When they put it on the mannequin and placed it into the cage, the sharks attacked it with no mercy whatsoever! As interesting as this is Dr. Hart’s study shows that the contrast against background rather than color per se may be more important for determining how the shark sees. He stated that this new research on how sharks see may help to prevent attacks on humans by designing swimming attire and surf craft that have a lower visual contrast to sharks and, therefore, are less 'attractive' to them.

For now according to the National Parks Conservation Association a more practical way to keep a shark from noticing you is:

Do not wear contrasting colors or flashy objects

Don’t swim at night, early in the morning, or early in the evening

Stay out of murky water

Avoid wadding or swimming in areas between sandbars and in waters that drop off steeply to greater depths

Never molest a shark of any kind, regardless of size

And the most important thing to remember. DO NOT. I REPEAT DO NOT. CARRY DEAD FISH WHILE SWIMMING OR DIVING!!!!!


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