Animals with 'night vision goggles'

Jonathan Amos Science correspondent

18 June 2018

A tarsier is known for its big, beady eyes, but it's only when you look at a skull of this diminutive South East Asian primate that you realise just how big they are.

Each one is the same size as its brain. They can't move their eyeballs; if they want to look to the right or left they have to turn their whole head. But the mere fact that tarsiers have these monster organs tells you one thing: vision is very important to them.

The animal is a master in the dark, able to see and snaffle insects and small birds even when it seems impossibly dark.

"Theirs is a monochrome world; the back of their eyes are packed with photoreceptor rods, not cones, so they can gather every last photon of light," explains Prof Geoff Boxshall from London's Natural History Museum.

"Their eyes are the animal world's equivalent of night-vision goggles."

Geoff is the science lead on a new exhibition opening at the NHM in July that will celebrate Life In The Dark.

There is an amazing diversity of creatures out there with some incredible tricks, to not only survive but also thrive in the absence of light.

The museum has pulled the best of them from its collections. Some you'll know but hadn't perhaps considered the genius of their adaptations - such as bats.

Some creatures will definitely be new to you because they've only recently been discovered. There's some truly bizarre stuff living in caves and in the deep ocean, for example.

Read on  

Frogs have unique ability to see color in the dark – Herp Digest

Science Daily, 2/28/17- Lund University, Sweeden

The night vision of frogs and toads appears to be superior to that of all other animals. They have the ability to see colour even when it is so dark that humans are not able to see anything at all. This has been shown in a new study by researchers from Lund University in Sweden.

Most vertebrates, including humans, have two types of visual cells located in the retina, namely cones and rods. The cones enable us to see colour, but they usually require a lot of light and therefore stop working when it gets dark, in which case the rods take over so that we can at least find our way home, albeit in black and white.

In toads and frogs the rods are a bit special, however. It was previously known that toads and frogs are unique in having rods with two different sensitivities. This has not been found in other vertebrates, and it is also the reason why researchers have long suspected that frogs and toads might be able to see colour also in low-light conditions. The new study was first in proving this to be true, and the results exceeded all expectations.

"It's amazing that these animals can actually see colour in extreme darkness, down to the absolute threshold of the visual system. These results were unexpected," says Professor of Sensory Biology Almut Kelber at the Faculty of Science, Lund University.

It was during the third of three experiments that the researchers discovered that frogs are able to use their rods to distinguish colour in extreme darkness. The researchers studied the frogs in a situation that is as serious as it is common, namely, when frogs need to find their way out in case they are trapped in conditions of complete darkness. This is potentially an everyday occurrence, taking place in dark dens and passageways on the ground. In such instances, finding the exit becomes crucial, which also means that the frog is inclined to make use of any sensory information that is available.

In the other experiments the researchers studied to what extent frogs and toads use their colour vision when searching for a mate or hunting for food. The results showed that the animals stop using their colour information fairly early when it comes to finding someone with whom to mate, whereas they continue to take advantage of their colour vision to select food in such low-light conditions that humans lose their ability to see colour.

"We have previously shown moths and geckos are also able to see colour in inferior light conditions compared to humans. However, frogs apparently have a unique ability to see colour in the dark," says Almut Kelber.

Story Source:

Materials provided by Lund University. Note: Content may be edited for style and length.

/story_source

Journal Reference:

            1          Carola A. M. Yovanovich, Sanna M. Koskela, Noora Nevala, Sergei L. Kondrashev, Almut Kelber, Kristian Donner. The dual rod system of amphibians supports colour discrimination at the absolute visual threshold. Philosophical Transactions of the Royal Society B: Biological Sciences, 2017; 372 (1717): 20160066 DOI: 10.1098/rstb.2016.0066

How early mammals evolved night vision to avoid predators

Date: June 20, 2016

Source: Cell Press

Early mammals evolved in a burst during the Jurassic period, adapting a nocturnal lifestyle when dinosaurs were the dominant daytime predator. How these early mammals evolved night vision to find food and survive has been a mystery, but a new study publishing June 20 in Developmental Cell suggests that rods in the mammalian eye, extremely sensitive to light, developed from color-detecting cone cells during this time to give mammals an edge in low-light conditions.

Cone cells are specialized for certain wavelengths of light to help animals detect color, while rods can detect even a single photon and are specialized for low-light vision. "The majority of mammals have rod-dominant retinas, but if you look at fish, frogs, or birds, the vast majority are cone-dominated--so the evolutionary question has always been, 'What happened?'" says Anand Swaroop, a retina biologist at the National Eye Institute, part of the National Institutes of Health. "We've been working for a long time to understand the fundamental mechanisms behind rod and cone development."

Previous work done by Swaroop and his colleagues showed that a transcription factor called NRL pushes cells in the retina toward maturing into rods by suppressing genes involved in cone development. "We began to wonder if, somehow, the short-wavelength cones were converted into rods during evolution," says Swaroop.

To investigate the origin of rods in mammals, Swaroop and his team examined rod and cone cells taken from mice at different stages of development. Details of an organism's embryonic development often reveal traits carried by its evolutionary ancestors; consider, for instance, how human embryos initially develop gill-like slits and a tail.

Continued … 

Deer night-vision cameras in Welsh forests as culling increases

The number of wild deer being culled in Wales has doubled in the past five years, according to officials.

It follows an explosion in deer populations, increasing by an estimated 25% a year in some parts of Wales.

The Forestry Commission in Wales (FCW) says about 1,000 have been shot over this winter.

The various breeds of deer have now become such a problem in Welsh woodlands that night-vision cameras will be used to monitor them.

The FCW said the new cameras would provide vital information about the movement of deer in forestry, where the animals can damage vegetation and trees.

David Jam, the FCW's wildlife management officer, said: "We base our culling on woodland impacts, so if we are getting high impacts in an area for a number of years and we are seeing a pattern there, then we need to increase the level of culling.

"When the woodland regenerates to a level where it can sustain a good population of deer then you can ease that culling pressure off.

"There is a balance - we don't just cull and cull and cull.

Read on:  http://www.bbc.co.uk/news/uk-wales-17004403

'Cat-Eye' Boy Video Said To Show Chinese Child Who Sees In Dark

According to a news reel from China, a young boy there possesses the ability to see in the dark. Like a Siamese cat's, his sky-blue eyes flash neon green when illuminated by a flashlight, and his night vision is good enough to enable him to fill out questionnaires while sitting in a pitch black room — or so say the reporters who visited Nong Yousui in his hometown of Dahua three years ago.

The footage of Nong and his strange-looking eyes originally surfaced in 2009; it got little attention at the time, but is now making a splash all over the Web. If the boy really does have a genetic mutation that confers night vision, then he would be an interesting subject for analysis by vision scientists, evolutionary biologists, and genetic engineers alike — but does he? 

The experts we shared the video with say Nong does have unusually colored irises considering his ethnicity, but he's not the next step in human evolution.

Night vision is made possible by a layer of cells, called the tapetum lucidum, in the eyes of cats and other nocturnal animals. This thin layer is a "retroreflector" — when a beam of light hits it, it reflects the light directly back along its incoming path. The reflected beam constructively interferes with the incoming light beam, amplifying the overall signal that hits the retina and enabling the animal to see in very low-light conditions. Retroreflection also causes cat eyes to flash when they are lit upon at night, and experts say Nong's eyes, if they are truly catlike, should do the same. [Red-Green & Blue-Yellow: The Stunning Colors You Can't See]

"It would be easy to test the boy’s eyes for retroreflection (eyeshine), which would be indicative of a tapetum lucidum," said Nathaniel Greene, a physicist at Bloomsburg University of Pennsylvania who has studied retroreflection.

Read on and see video:  http://www.huffingtonpost.com/2012/01/31/cat-eyes-boy_n_1244543.html