Seeing through the eyes of a crab

New research provides insight into the visual world of a crustacean

Date:  July 16, 2018

Source:  Society for Neuroscience

Crabs combine the input from their two eyes early on in their brain's visual pathway to track a moving object, finds new research published in JNeurosci. This study of adult male crabs from Argentina's Atlantic coast provides insight into the visual world of a crustacean.

The widely spaced eyes and visually guided behaviors of the crab Neohelice granulata suggest this highly social predator may compute visual parameters of moving targets by combining input from both eyes, but it is unclear where and how the two sources of visual information are merged and processed.

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Starfish on ocean floor found to have well developed eyes

February 7, 2018 by Bob Yirka, Phys.org report

A team of researchers from the University of Copenhagen and the Greenland Institute of Natural Resources has found that starfish living in the dark on the ocean floor have eyes on their arms that are similar to other starfish living near shore. In their paper published in Proceedings of the Royal Society B, the group describes their study of the unique sea creatures and what they learned about starfish vision.

Scientists have known for some time that some starfish that live near shore have compound eyes in the tips of their arms. In this new study, the researchers have found the same to be true for many types of starfish that live in the dark at the bottom of the ocean.

To learn more about starfish vision in places besides the shoreline, the researchers collected hundreds of specimens (representing 13 species) from depths ranging from shallow waters to 1,000 meters below the surface—all living in the North Atlantic near Greenland. They found that 12 of the species had compound eyes similar to those found in starfish near the shoreline—the one lone species without eyes was a burrowing starfish that lives relatively close to shore.

In all of those with compound eyes, the eyes were uncovered, the researchers report, and were located on the bottom side of the arm tip, which means the starfish bend the tips to use them, pointing the eyes at targets. Visual acuity and sensitivity to light varied among the species they studied.

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The Freaky Secret Hiding Inside a Scallop's 200 Glittering Eyes

By Rafi Letzter, Staff Writer | December 2, 2017 09:10am ET

Gaze into the fleshy maw of the scallop, and lo, the scallop will gaze back — its up to 200 eyes glittering and alien, giving no sign as to what they think of you in their endless hunt for particles of floating food.

Scientists have known since at least the 1960s that scallops use mirrors at the backs of their eyes to reflect light forward and project images onto their double retinas. That was the work of Michael Land, a pioneer in researching animal vision. But Land could never figure out what those mirrors were made of, or how they worked; he guessed that crystalline guanine was involved, but all the microscopic techniques of the era dehydrated the mirrored tissue, destroying his samples before he could study them.

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Genetic mutation in whale eyes may increase mortality risks

Date: October 24, 2016

Source: Florida Institute of Technology

Scientists have found that a genetic mutation in the eyes of right whales that hampers their ability to see in bright light may make them more susceptible to fatal entanglements in fishing gear, one of the major causes of death for this critically endangered mammal.

The study of this whale species, which numbers less than 500 individuals remaining in the Western Atlantic Ocean, may also help scientists better understand how vision works in other mammals, including people.

Florida Institute of Technology doctoral student Lorian Schweikert and her adviser, Michael Grace, professor of neuroscience and senior associate dean of science, worked with Jeffry Fasick, an assistant professor of biology at the University of Tampa, to characterize this newly discovered mutation in Northern right whales and Bowhead whales. Their results suggest that this mutation may seriously harm the whales' ability to visually avoid entanglement.

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What big eyes you have! Spider adaptation widened dietary net

A spider's unusually large and sensitive eyes help it catch bigger prey

Date: May 18, 2016

Source: University of Nebraska-Lincoln

Evolving the largest eyes among all known arachnids may have helped the net-casting spider add walking prey to its airborne menu of midnight snacks, says new research from University of Nebraska-Lincoln biologists.

Doctoral student Jay Stafstrom reached the conclusion after two months living out of a tent in a Florida state park, where he observed how the nocturnal species Deinopis spinosa hunted with and without the aid of secondary eyes roughly 2,000 times more light-sensitive than human eyes.

The net-casting spider earns its name by spinning a rectangular band of woolly silk to capture prey while rappelling upside-down from a single thread. When the time comes, the spider lunges forth and stretches the net to engulf prey in one fell swoop that lasts about one-thousandth of a second.

Stafstrom discovered that the spider snared prey about 3 1/2 times more often when relying on its massive secondary eyes than when those eyes were covered by vision-impairing dental silicone. But the effect seemed to depend on whether that prey traveled by leg or by wing.

While the silicone had no discernible effect on the species' ability to snag flying prey, it greatly reduced the odds of the spider capturing a crawling critter. Though one of every four specimens without the silicone blindfold would capture prey that walked their way -- roughly the same proportion that caught prey flying through their attack radius -- none managed to snare a walking meal while their vision was impaired.

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Crocodile eyes are fine-tuned for lurking

By Jonathan WebbScience reporter, BBC News

4 May 2016 

A new study reveals how crocodiles' eyes are fine-tuned for lurking at the water surface to watch for prey.

The "fovea", a patch of tightly packed receptors that delivers sharp vision, forms a horizontal streak instead of the usual circular spot.

This allows the animal to scan the shoreline without moving its head, according to Australian researchers.

They also found differences in the cone cells, which sense colours, between saltwater and freshwater crocs.

Published in the Journal of Experimental Biology, the findings suggest that although the beasts have very blurry vision underwater, they do use their eyes beneath the surface.

This is because light conditions are different in salt and freshwater habitats, but only underwater - and the crocodiles' eyes show corresponding tweaks.

"There's generally more blue light in saltwater environments, and more red light in freshwater environments. Animals tend to adapt to this," explained Nicolas Nagloo, a PhD student at the University of Western Australia.

He and his colleagues studied eyeballs from juvenile "salties" and "freshies", shipped to the university from a crocodile farm in Broome.

When they measured the light absorbed by single photoreceptors in the retina, they found that those of the freshwater crocs were shifted towards longer, redder wavelengths compared with their saltwater cousins.

Finding this skewed sensitivity in crocodiles was unexpected, Mr Nagloo said, because the famous predators were only semi-aquatic and did their hunting, feeding and mating on land.

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Moth eyes could lead to more efficient solar cells

March 6, 2015

Chuck Bednar for redOrbit.com – @BednarChuck

The compound lenses found in the eyes of moths have inspired a team of researchers to develop a new antireflective coating that could make solar cells more efficient than ever before.

In a recent edition of the journal ACS Nano, researchers at the Agency for Science, Technology and Research in Singapore explain that compound lenses found in nocturnal moth eyes helped lead to a coating that can also sharpen the view of solar cell image sensors.

Important non-reflective pattern

The moths ocular faculties contain micro lenses (ommatidia) which are patterned with nanoscale dome-shaped bumps that help reduce the reflection of light at multiple wavelengths, according to Gizmodo. These ommatidia make it possible for the moths to navigate in the dark.

“The ability to capture light and not let go is appealing in the world of solar cells because it can increase efficiency,” the website added. “So the team from Singapore has taken inspiration from the complex lens structure to create a process that stamps patterns over the surface of a material, replicating the antireflective effects of the moths’ eyes.”

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Humans and Squid Evolved Same Eyes Using Same Genes

By Malcolm Campbell, University of Toronto | May 06, 2014 11:59pm ET

This article was originally published at The Conversation.The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

Eyes and wings are among the most stunning innovations evolution has created. Remarkably these features have evolved multiple times in different lineages of animals. For instance, the avian ancestors of birds and the mammalian ancestors of bats both evolved wings independently, in an example of convergent evolution. The same happened for the eyes of squid and humans. Exactly how such convergent evolution arises is not always clear.

In a new study, published in Nature Scientific Reports, researchers have found that, despite belonging to completely different lineages, humans and squid evolved through tweaks to the same gene.

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New imaging system brings lobster-eye design down to scale

(Phys.org) —Scientists have long sought to emulate the fascinatingly structured compound eyes that allow lobsters to see their way along brackish seabeds. So far, it's worked only in huge X-ray devices used for astronomy.

However, a new artificial compound eye developed at the University of Wisconsin-Madison harnesses the concept to use the visible light spectrum, and at a much smaller scale. Its potential application areas range from medicine to astronomy to the military.

Hongrui Jiang, the Lynn H. Matthias Professor in Engineering and Vilas Distinguished Achievement Professor of Electrical and Computer Engineering at UW-Madison, announced the advance in a paper published April 24, 2014, in the journal Small. The lobster-inspired system represents a breakthrough in both optical imaging and micro-scale fabrication.


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Rats Have a Double View of the World

May 27, 2013 — Scientists from the Max Planck Institute for Biological Cybernetics in Tübingen, using miniaturised high-speed cameras and high-speed behavioural tracking, discovered that rats move their eyes in opposite directions in both the horizontal and the vertical plane when running around. Each eye moves in a different direction, depending on the change in the animal's head position. An analysis of both eyes' field of view found that the eye movements exclude the possibility that rats fuse the visual information into a single image like humans do. Instead, the eyes move in such a way that enables the space above them to be permanently in view -- presumably an adaptation to help them deal with the major threat from predatory birds that rodents face in their natural environment.

Like many mammals, rats have their eyes on the sides of their heads. This gives them a very wide visual field, useful for detection of predators. However, three-dimensional vision requires overlap of the visual fields of the two eyes. Thus, the visual system of these animals needs to meet two conflicting demands at the same time; on the one hand maximum surveillance and on the other hand detailed binocular vision.

The research team from the Max Planck Institute for Biological Cybernetics have now, for the first time, observed and characterised the eye movements of freely moving rats. They fitted minuscule cameras weighing only about one gram to the animals' heads, which could record the lightning-fast eye movements with great precision. The scientists also used another new method to measure the position and direction of the head, enabling them to reconstruct the rats' exact line of view at any given time.

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Doctor Pulls 5 Inches Live Worm From Man's Eye

The patient suffered pain for more than two weeks before he decided to go to the doctor because of eye irritation. He did not expect to experience a scene from a horror movie - from his eye was removed live worm 5 inches (13cm) long!


When Dr V. Seetharaman examined 75-year-old patient P.K. Krishnamurthy at Mumbai's Fortis Hospital this week, the eye expert was shocked by the highly unusual sight of the writhing parasite and had to operate speedily to remove it before serious damage was caused. Seetharman stated afterwards that: “It was wriggling there under the conjunctiva. It was the first time in my career of 30 years that I had seen such a case.”


The eye specialist removed the parasite in a 15-minute operation, making a small incision in the conjunctiva (the thin membrane around the eye) while Saraswati, the patient’s wife, looked on in horror.

According to doctor, there was a possibility that the worm, before it entered the bloodstream and to the eye, enters through a cut in the patient's foot or from eating raw or poorly cooked food.

The 5 inch long parasitic worm was alive for 30 minutes following the surgery, and was sent to the hospital’s microbiologists for identification.


Continued:  http://www.incredipedia.info/2012/07/doctor-pulls-5-inches-live-worm-from.html

Elephant-Nosed Fish Has Funky Eyes, Too

An unusual eye structure helps the strange-looking elephantnose fish see in their dim and murky habitat, a new study suggests.

These fish live in muddy rivers in central and west Africa, which are full of plant matter, mud and gas bubbles, even when it's light out. Living in such murky waters, the fish uses its trunk-like mouth extension (from which it gets its name) to sense electrical currents created by other fish.

"They were thought to be blind until a few years ago," study researcher Andreas Reichenbach, of Leipzig University in Germany, told LiveScience. When researchers got around to looking in these fishes' eyes, "it was a little bit of a surprise because its retina was very unusual."

Continued:  http://www.livescience.com/21257-elephantnose-fish-eye-sensors.html

Fossil Fish Eye Surprise: Small Structures Reveal Pigment

Tiny pebblelike structures found in a 54-million-year-old fossilized fish eye contain the natural pigment, melanin, a study reveals.

Similar structures show up regularly on fossilized feathers, hair and eyes, and in recent years, some scientists have suspected they contained melanin, a dark pigment found in the hair, skin and eyes of humans and animals.

This study, the first thorough chemical analysis of these microscopic structures, opens the door to better understanding the appearance and behavior of long-dead animals, said study researcher Johan Lindgren of Lund University in Sweden.

The presence of melanin alone does not reveal the color an animal displayed since other factors, such as other microscopic features, can also determine color. However, melanin is evidence of dark areas, such as bands on feathers, and the shapes of the melanosomes may correspond to some basic hues, such as gray, black or brown, according to Lindgren.

Continued:  http://www.livescience.com/20152-fish-eye-surprise-small-structures-reveal-pigment.html

Rock-eyed sea creature

This lined chiton, whose anterior end is to the right, lives about
50 feet below the water's surface near Whidbey Island, Washington.

Tuesday, April 19, 2011

A tiny sea mollusk uses eyes made of a calcium carbonate crystal to spot predators lurking above, researchers say of the first such rocky lenses found in the animal kingdom.

While scientists had discovered the hundreds of eye-like structures on the surface of this armored mollusk, called a chiton, decades ago, they didn't know what they were made of or whether they could actually see objects or just sensed light.

"Turns out they can see objects, though probably not well," said study researcher Daniel Speiser, who recently became a postdoctoral fellow at the University of California, Santa Barbara.

http://www.thedailystar.net/newDesign/news-details.php?nid=182144