Please select your home edition
Edition
Southern Spars

Are sharks colour blind? Why NOT to wear black swim gear

by Springer Science+Business Media/Sail-World on 20 Jan 2011
Are sharks color blind? DPI Victoria .
Sharks are unable to distinguish colors, even though their close relatives rays and chimaeras have some colour vision, according to new research by Dr. Nathan Scott Hart and colleagues from the University of Western Australia and the University of Queensland in Australia. And this leads to the question -when you dive off your sailing boat to cool off or go snorkelling, should you be wearing pale blue swimmers and wetsuits?

Their study shows that although the eyes of sharks function over a wide range of light levels, they only have a single long-wavelength-sensitive cone* type in the retina and therefore are potentially totally color blind. Hart and team's findings are published online in Springer's journal Naturwissenschaften – The Science of Nature.

'This new research on how sharks see may help to prevent attacks on humans and assist in the development of fishing gear that may reduce shark bycatch in long-line fisheries. Our study shows that contrast against the background, rather than colour per se, may be more important for object detection by sharks. This may help us to design long-line 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,' said Prof. Hart. While it is probably safer to swim in the same waters as a shark than it is to drive a car, the news is food for thought for all prudent sailors, many of whom spend a considerable amount of time off their yachts in water sports, sometimes in shark-infested seas.

Sharks are efficient predators and their evolutionary success is thought to be due in part to an impressive range of sensory systems, including vision. To date, it is unclear whether sharks have color vision, despite well-developed eyes and a large sensory brain area dedicated to the processing of visual information. In an attempt to demonstrate whether or not sharks have color vision, Hart and colleagues used a different technique - microspectrophotometry - to identify cone visual pigments in shark retinas and measure their spectral absorbance.

They looked at the retinas of 17 shark species caught in a variety of waters in both Queensland and Western Australia. Rod cells were the most common type of photoreceptor in all species. In ten of the 17 species, no cone cells were observed. However, cones were found in the retinae of 7 species of shark from three different families and in each case only a single type of long-wavelength-sensitive cone photoreceptor was present. Hart and team's results provide strong evidence that sharks possess only a single cone type, suggesting that sharks may be cone monochromats, and therefore potentially totally color blind.

The authors conclude: 'While cone monochromacy on land is rare, it may be a common strategy in the marine environment. Many aquatic mammals - whales, dolphins and seals - also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution, in other words, they acquired the same biological trait in unrelated lineages.'

*There are two main types of photoreceptor cells in the retina of the eye. Rod cells are very sensitive to light and allow night vision. Cone cells also react to light but are less sensitive to it. Eyes with different spectral types of cone cells can distinguish different colors. Rod cells cannot tell colors apart.

ReferenceHart NS et al (2011). Microspectrophotometric evidence for cone monochromacy in sharks. Naturwissenschaften – The Science of Nature; DOI 10.1007/s00114-010-0758-8
PredictWind.com 2014Mariners Museum 660x82Naiad/Oracle Supplier

Related Articles

MAPFRE set the Volvo Ocean Race bar with overall Leg Zero victory
Newer teams know they have more work to do, but there are still plenty of positives to take from the progress they made Charlie Enright’s Vestas 11th Hour Racing became the third team to grab a victory from four stages in Leg Zero – a series of pre-race qualifying stages for the next edition of the round-the-world race – as they sneaked ahead of MAPFRE in the early hours of Wednesday morning.
Posted on 16 Aug
Volvo Ocean Race – MAPFRE seal overall Leg Zero victory
ast-improving Vestas 11th Hour Racing took the stage win with the shortest Distance to Finish at 0430 UTC. The decision to call a halt to the racing came late on Tuesday night as the stage had become a drifting contest, with the teams making a series of expensive gybes in a bid to find some wind, and latest ETAs predicting that the boats would not reach Lisbon until well into Thursday.
Posted on 16 Aug
Volvo Ocean Race – What the skippers say
What a start to 2017-18 Leg Zero has given us! It's been exciting, intense, frustrating – and a great form guide We had an email a couple of hours ago from Race Control saying that the forecast was no wind at all and they decided to shorten the race which I think is a good decision because this Leg Zero was already becoming quite long and we are looking forward to finish and have a good rest.
Posted on 16 Aug
Volvo Ocean Race - MAPFRE invest in west – and it's looking best
With the exception of Sun Hung Kai/Scallywag, fleet remained close together to the east of front throughout the night With the exception of Sun Hung Kai/Scallywag, the fleet remained close together to the east of the front throughout the night, experiencing light northeasterly winds as they sailed down wind towards Cape Finisterre.
Posted on 16 Aug
2017-18 Volvo Ocean Race - Leg Zero - Light wind as calms continue
The fleet restarted on Monday morning from the south coast of Brittany in the same order they finished yesterday The fleet restarted on Monday morning from the south coast of Brittany in the same order they finished yesterday, so it was no surprise to see MAPFRE and Vestas 11th Hour Racing take an early lead.
Posted on 15 Aug
2017-18 Volvo Ocean Race - And they're off!
The fleet restarted fourth and final stage of Leg Zero at 0615 UTC on Monday – with boats spread just over five minutes The fleet restarted the fourth and final stage of Leg Zero at 0615 UTC on Monday – with the boats spread just over five minutes apart from front to back.
Posted on 15 Aug
Volvo Ocean Race – MAPFRE continue Leg Zero dominance in final stage
Extended periods of extremely light weather meant that the Saint-Malo to Lisbon leg had to be split into two parts. As expected, the Volvo Ocean 65s stayed tightly bunched on the first of those, a drag race towards Le Grand Lejon. Vestas 11th Hour Racing were neck-and-neck with MAPFRE for the lead, with the Spanish side just pipping them to the line.
Posted on 13 Aug
Volvo Ocean Race – MAPFRE win qualifying sprint
MAPFRE had a lead of seven nautical miles when they crossed the finish line off the French sailing city of Saint-Malo. Team Brunel took second place in their first race sailing with new recruit Peter Burling, the Olympic gold medallist and America’s Cup winning helmsman, whose signing was announced just hours before the fleet's departure from England's south coast.
Posted on 11 Aug
Volvo Ocean Race – Leg 0 start
The third stage of the Volvo Ocean Race 'Leg 0' kicked off at 1300 GMT today from Plymouth. The third stage of the Volvo Ocean Race 'Leg 0' kicked off at 1300 GMT today from Plymouth.
Posted on 10 Aug
Volvo Ocean Race - Sailing superstar Peter Burling joins Team Brunel
The Kiwi joins his long-time sailing partner – and now Volvo Ocean Race rival – MAPFRE's Blair Tuke Olympic gold medallist and America’s Cup winning helmsman Peter Burling is joining Team Brunel for the 2017-18 edition of the Volvo Ocean Race. The signing of the world’s most in-demand sailor is a major coup for Brunel skipper Bouwe Bekking – and sets up what should be a compelling rivalry with Burling’s long-term sailing partner Blair Tuke
Posted on 10 Aug