For millions of years Sharks have been known to survive using their very effective sensory organs. They are not just good at smelling their prey and blood, but also have well developed external eyes and a significant area in the brain suited to vision. But now scientists have found that sharks might be color blind.
A recent study conducted on retina of 17 species of sharks including Tiger sharks and Bull sharks, caught off the coasts of eastern and western Australia, has raised doubts , on whether sharks are color blind.
In living beings, two types of light sensitive cells occur in retina. Rod cells and Cone cells: while the former assists in measuring brightness of objects, the later cells are believed to distinguish colors.
Researcher Nathan Scott Hart, of University of Australia and his colleagues used a technique called ‘Microspectrophotometry’, to scan retina of Sharks, to ascertain if there were pigments linked to rod and cone cells. Rays and Chimeras, considered to be close relatives of Sharks, also were studied earlier, using the above said technique, and were found to have color vision.
He found that of the 17 species of Sharks studied, though rod cells were found in all the species, cone cells were not observed in 10 of the 17 species. Only one type of cone cells was found in the remaining seven species.
What the findings suggest is as rod cells were found in all species, Sharks have a broad range of view in different light levels. But species that do not have cone cell could not identify distinct colors.
Shark biologist Michelle Mc Combe, of Harbor Branch Oceanographic Institute, Florida Atlantic University, says that,
“We can’t say hands down if sharks are color-blind yet, as there are over 400 different shark species. But these findings are excellent, and a surprise, and definitely should spur more work.”
The researchers however noted that color-blindness could be possible among sharks just like other oceanic predators like Dolphins, Seal and Whales who may not find much use of the color distinction particularly in a permanently ‘Blue Green’ environment. Sharks especially can also smell blood miles away, and that they may not need to know that blood is Red.
The researchers are hopeful that if the discovery holds true, it could be significant in saving endangered shark species.
“Our study shows that contrast against the background, rather than color per se, may be more important for object detection by sharks,” study co-author Hart said.
“This may help us to design longline fishing lures that are less attractive to sharks, as well as to design swimming attire and surf craft that have a lower visual contrast to sharks and therefore are less attractive to them.”
Over 8 million Sharks are killed every year accidentally, off the coasts of Africa only. If the researchers are right about color blindness, this could help save shark attacks on humans and also significantly reduce millions of untimely Shark deaths. – Atula, Staff Writer