Natures wonders: night hunting giant spider eyes (Introduction)

by David Turell @, Wednesday, May 18, 2016, 18:34 (1244 days ago) @ David Turell

These spiders cast a net at night to catch moving prey. Their giant eyes really help the process:

http://phys.org/news/2016-05-giant-eyes-net-casting-spider-nocturnal.html

"To prove the theory that the big eyes evolved to help with night foraging, the researchers started by video-taping several of them as they went about their activities in their natural environment. Then, they captured some samples and applied dental silicone over the single pair of big eyes (net-casters, like other spiders have eight eyes altogether, the others eyes are much smaller) temporarily blinding those eyes. The research pair then recorded the activities of the spiders as they tried to survive without benefit of their huge eyes.

"In studying the results, the researchers found that the blinded spiders were much weaker hunters when their big eyes were covered. Removing the eye covers allowed the spiders to regain their former skill levels.

"In a second test, the researchers conducted a similar experiment, except they did it in a controlled environment in their lab. In studying the results, the researchers found almost identical results.

"The research pair suggest their study shows that net-casting spiders use their huge eyes to hunt walking prey at night; they allow for catching prey in near dark conditions—prey which is very often much larger than they would catch with their net only. They noted also that the partially blinded spiders were just as adept at dealing with prey that was caught in the web, which adds more credence to the idea that the evolution of the large eyes, was strictly to allow the spider to catch larger prey while hunting during the nighttime—which the researchers also note, is a much safer time to hunt as there are far fewer predators out looking to eat them."

Comment: This is real improvement for night stalking spiders. I do not view this as added complexity.


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