Tag: biology

Spider Eyes are Nature’s Marvels

Now I do not exactly remember where and how I started my journey down this rabbit hole. But the deeper I went the more interesting it became. It was a great learning experience. I’m clearly not an expert. Here I share the understanding I developed of the spider eye over the few hours of exploration. For this I referred to various sources all of which are mentioned in the links. And if you know more or would like to add something interesting to the article please let me know in the comments below.

The  first thing about spider eyes is that 99% of spiders have 8 eyes. A little less than 1% of them have 6 eyes. In some fringe species there are 4, 2 or no eyes at all. Apparently, based on the pattern these eyes are arranged in, on their cephalothorax (let us mortals call it the ‘head’ to make things simple), the family to which the spider belongs can be determined. Some blessed human, made the following schematic to help us do exactly that. In case you ever feel the need to do so, here it is:

And in much greater detail, right here.

For their small size and the limited number of photocells, spider eyes, especially the jumping spider’s (Salticids) eyes perform surprisingly well. Their resolution is better compared with larger mammals than with insects. In the human world a camera of such standards this would simply be an engineering miracle. You will understand why I say that soon…

In the image above if you locate the family Salticidae, you will see those two large eye in the front which are particularly very interesting. These are called the principal eyes (or anterior median eyes) and are the ones that allow high resolution vision. So much that the spider would be able to resolve two spots on a screen 20 cm away from the spider, sitting just 0.12 mm apart from each other. An acuity of about ten times that of a dragonfly – 0.04°.

The brain of this spider, show in blue in the image below is pretty big for its size. The proportion of the volume of brain to body is more or less similar to that of human beings. The brain of Salticids also have a rather large region dedicated for visual processing.

The principal eyes we are talking about are in the shape of elongated tubes as seen below, in the front of which is a hard lens and at the other end is a layer of photocells. Inside the tube, near the retina is another little lens which moves back and forth along the tube like a telephoto lens system. These elongated tubes are like the tubes of a binocular which allow for a higher resolution using a small package.

However the downside of such a tube like architecture is that it limits the field of vision. Here’s how that problem is dealt with.

The front part, with the big corneal lens is fixed. It has a long fixed focal length. The farther end where the retina is located, is connected to these muscles shown in red. These muscles allow for the tube’s farther end to move around in several degrees of freedom to make quick movements and scan a larger image in its head, one small field of view at a time.

In the video below you can see the retinal end of the black tubes moving around inside the translucent exoskeleton of the spider as the spider forms a high resolution complete image of its surroundings, one small field of view at a time.

If you peer deep into their eyes you will see a dark (black) when you are looking into the small retina. However when the farther end of the tube moves, you see a honey brown color with spots. This is the inner wall of the tube that you are seeing in the following video.

Then the retina itself is another biological marvel. Unlike our single layered retina, the Salticid’s retina is made up of four layers. The four layers are arranged one behind the other. This lets the nature pack more photocells in a smaller area and also helps the spider see in color as different colors (different wavelengths) with different refractive indices are focused in different planes.

Counting from the rear end, the spider uses different layers of retina to obtain different colors of the image. The retina’s layer 1 and 2 to get the green color (~580 nm – 520 nm wavelengths), blue color using the layer 3 (~480 – 500 nm wavelengths) and layer 4 for ultraviolet (~360 nm).

An important detail in the above image reveals how spiders manage to keep focus on different objects at different depths, in focus. The layer one has photocells arranged in a step fashion, with varying distance from the lens which makes sure that all objects are focused on at least one part of the layer 1.

The other problem of distance estimation which matters a lot for jumping spiders is again solved rather elegantly by the same apparatus. Humans use their stereo vision – two eyes which are far apart to estimate distance. Other animals move heads to do the same but I’m not getting into that.

Jumping spiders employ a completely different algorithm, utilizing degree of blur cues. For which the second layer plays a crucial role. The second layer would have received a sharp blue image, but they are not sensitive to blue light like I mentioned above. The green they detect is rather blurred at that plane. It turns out that the amount of blur depends on the distance of the object and helps the spider determine the depth by processing the amount of blur in the image. Hence allowing it to jump and hunt accurately.

If you are a university student with free access to journals, I think a quick look at the paper titled: “‘Eight-legged cats’ and how they see – a review of recent research on jumping spiders,” will help you delve into greater detail.

Psst: Someone has it uploaded on research gate for free access for I don’t know how long: here.

Please leave a comment below to let me know your thoughts on this, or if you have any ideas for future posts. I plan to reward the top commentators every month so do not forget to say something.

Jellyfish Stings and The “Pee on it” Myth

By Anupum Pant

I haven’t been ever stung by a jelly fish, but from how Destin says it in the video, and other people I’ve seen getting bitten, tells me that it is something no one would want to experience in their life. If you did not know, the sting is awfully painful.

A jelly fish uses venom, not poison. They are two different things. Which means that a jellyfish stings you and uses extremely tiny hypodermic needle like things to inject toxins in your body.

But doesn’t jellyfish seem like a bunch of jelly floating around with no visible prickly parts? how does something so soft actually go about inserting something sharp into your skin?

Turns out, on the surface of those long tentacles these fish have, there are microscopic organelles called nematocysts which it uses to sting you. Even a tiny brush with those tentacles can trigger them. The more interesting part is that these tiny needles act very fast, and like I said, they are also very tiny. So, to see them you need a really high frame-rate camera attached to a microscope.

That is exactly what Destin does in the video below. It’s fascinating to see those tiny stingers do their work so fast under a microscope. Not many get a chance to see something like this.

Just FYI. In case you ever end up getting bitten by a jellyfish, please don’t ask your friend to pee on it. There’s a word going around that this helps, but in reality it doesn’t. In fact it can make it worse. Instead try washing it off with sea water. And then use a credit card to scratch the sting to remove any nematocysts stuck in your skin.

Don’t believe me? Please watch this…

Biological Darkmatter

By Anupum Pant

To most of us, looking at things from a distance, it often seems like the age of exploration is over. It seems like there’s not much left to be discovered. Only a few who strongly believe that the age of exploration is far from over, and work hard to keep exploring, end up finding new things.

Take for instance the part of ocean that remains unexplored and unseen by human eyes today. According to NOAA’s website this unexplored part is about 95%, even today!

In fact, it is estimated that 96% of the universe is made up of some mysterious thing (called the dark matter) which we haven’t even started to figure yet.

If you think that is taking it too far, we don’t even know our bodies completely yet. Just last year (in 2013) a new body part in the human body was discovered!

Nathan Wolfe, a biologist and explorer, talks about how most (as much as 40-50% of it) of the genetic information found in our own gastrointestinal tracts doesn’t classify under any kind of biological form we have ever known – Not plant, animal, virus, bacteria or fungus. Biologists call it the biological dark matter.

genetic information

There are unknowns all around us and they are waiting to get discovered.

Nightvision Eye Drops

By Anupum Pant

A deep sea dragonfish, or specifically Malacosteus niger, has a special pigment in its eyes which helps it see better in the deep  dark sea. This pigment, isolated from the eyes of this dragonfish, in the year 1990, was found to be a derivative of Chlorophyll.

The marine biologist Ron Douglas of City University London, who was able to isolate it then, found that the pigment gave this fish an ability to absorb red light. Of course It did seem abnormal to find a chlorophyll derivative inside an animal’s eye. Moreover, the animal had learned to use it to enhance its vision! At that time it was conjectured that the chlorophyll came to the fish through some bacteria, and it somehow found a way to put it to good use.

A couple of years later (in 2004) an ophthalmic scientist at Columbia University Medical Centre read about it and started testing the derivative on other animal’s eyes. Recently, by using it on mice and rabbit eyes, the researcher has been able to enhance their night vision, by enhancing their eye’s ability to absorb red light.

It is highly possible that, in the near future, the pigment could somehow be made safe for human eyes, and be used to enhance their nightvision. Soon a better nightvision could be as easy as ingesting a pill, or using eye drops made out of this derivative. How great would it be for the special ops team! Of course, the U.S. Department of Defence is very interested, and has started funding his research now.

[Read more]

Evolution of Eggs

By Anupum Pant

Eggs come in a variety of shapes, sizes and colours. Birds, a major group of creatures that descended from reptiles have, for several years, continued to evolve the design of their eggs for millions of years now (not consciously, through natural selection).

Eggs could have been cube shaped. In that case they would have been very difficult to lay. Also, they would have been weakest at the centre points of a face of the cube. Hence, eggs didn’t end up being squarish.

While most eggs have evolved to, well, an egg-shape, some eggs like those of some owls are nearly spherical in shape. But oval and pointy eggs do have an advantage of sort.

Spherical eggs tend to roll easily, and if laid somewhere near a cliff, they’d roll away, never to be seen ever again. Oval eggs normally tend to roll in circles. Usually, they roll in big circles. Still dangerous for birds who perch on cliffs most of the time.

Of all the eggs, the egg of a common guillemot bird is probably the most incredible – in the sense that it has a design that doesn’t let it roll down cliffs very easily.

Common guillemots are sea birds and they normally like to perch on cliffs. To add to the danger of their precarious perching places, they usually perch on such cliffs with a huge group. Also, they don’t even make nests.

Had their eggs been shaped like those of owls, they would have easily gotten knocked by someone from that huge group of perching birds, perching on precarious cliffs. So, their eggs have evolved to survive these conditions.

This is how their eggs look like. They are very awkwardly shaped. But when it rolls, thanks to natural selection, it rolls in very small circles! They don’t fall off cliffs easily. Wonderful!

common guillemot egg

First seen at [io9]

Bizarre Starfish Wasting Syndrome

By Anupum Pant

Up in the Washington state a videographer and also a diver, Laura James noticed a couple of  dead Starfish on the coast one day. The dead bodies looked like something mysterious had happened. There were broken bodies and splats all over the place as if the fish had been zapped by a laser.

Laura videographed some of the tens of thousands of starfish bodies all over the north america’s pacific coast. No one was sure what was actually happening. And then there were reports of these mysterious starfish deaths from all over the west coast of North America.

For some time, only the sunflower starfish were thought to be affected by this. However, on further investigation, it was found that almost 12 different species of starfish were dying mysteriously all over the west coast (and some on the east coast too). When this was confirmed to be an epidemic of some sort, they started calling it the sea star wasting syndrome and notified the scientists.

Ben minor, a western Washington university professor of biology started collecting sea stars at the coast. They found a number of normal sea stars. Later when the search continued a pile of sea star arms and twisted parts of them were found at different places. Some of the live starfish were collected and were studied in the laboratory.

It was confirmed that the starfish which were affected by this epidemic experienced twisting arms and lesions first and then the arms crawled away in different directions, tearing the body of a starfish apart. All of it in under 24 hours. This bizarre disease then left a spill of inside parts of the fish and broken body parts all over the place.

No one knows for sure what causes this bizarre disease among the sea stars.

Seeing Your Own Eye Blood Vessels

By Anupum Pant

Blind spots are fine and I’ve known for years how to spot your own blind spot. You can make 2 spots on a paper separated by 4-5 inches, close your right eye and look at the right side spot with your left eye. If you do that and move forward or backward ( and rest at about 15 inches from the surface you drew on), you’d find a point where your left eye’s peripheral vision would not render the left side spot. You’d have found your blind spot.

But there is something more interesting, I never knew. You can actually see the blood vessels of your eye, with your own eye. Here’s how…

Take a sheet of paper (or card), and poke a pin hole in it. Then close one eye and holding paper close to your eye, jerk around the paper in little circles. At the same time, make sure you are looking at a bright white area through that hole. You could open up MS paint, make the whole canvas white and stare at it through the hole. Try to focus on the white screen and not the paper (or card)…

The video probably explains it better.

The Amusing Kiwi Beaks

By Anupum Pant

Kiwis have a fairly long beaks, but technically they have the shortest beaks of all birds. There’s a very funny reason for that.

Kiwis can’t see too well. However they have an exceptionally good sense of smell, thanks to their nostrils which are at the tip of their beaks.

According to another research done recently, Kiwi beaks have specialized sensors at the tip which help them to sense tiny vibrations. Combining both the exceptionally good sense of smell and the ability to detect minute vibrations using their beaks, kiwis are able to find creepy crawlies moving under a layer of mud.

Now, they have long thin beaks, physically. And at the end of the beak there are nostrils.

Officially the convention to measure the beak of a bird dictates that the measurement be done from the end of the tip to the nostril. And since Kiwis have nostrils at the tip, the distance from the tip of their beaks to their nostrils is very less (negligible). That distance is also, technically, according to the convention, the length of their beaks.

So, Kiwis officially have the shortest beaks among all birds, even if they physically have fairly long beaks.

A Mean Creature from the Sea

By Anupum Pant

Stone fish is a bizarre looking creature, 15-20 inch sized, weighing about 5 pounds, is covered in dark patches and has ugly pimple like things all over its body. It’s found in the coastal regions of the Indian ocean and the Pacific ocean and likes to sit in between coral reefs and stones most of the time. The fish can survive outside of water for a whole day.

The fish is well-known as the most venomous fish. The most surprising thing about it is that it can be held in bare hands and you still won’t get poisoned.

However, a part of this fish can leave you dead in minutes. The fish has very sharp needle like things inside of skin sacks on its back, which when stepped on, are designed to inject an extremely powerful toxin into your body. The toxin is known to cause severe pain, paralysis and tissue necrosis. These venom spines can refill in about a week. Watch spines go in the video I’ve attached below…

A Man-Made Leaf

By Anupum Pant

Julian Melchiorri, a graduate student from Royal College of art, claims to have fabricated the first ever man-made biological leaf which absorbs water & carbon dioxide, just like a leaf does, and produces oxygen.

It looks like a promising first step towards enabling longer distance space travel – in a way that the artificial leaf made by him could be used to supply oxygen in micro-gravity, in which terrestrial plants have a hard time growing.

The artificial leaf he made for his project involves extracted chloroplasts from plant cells laid on a matrix of silk protein.

The “first man-made biological leaf” could enable humans to colonise space from Dezeen on Vimeo.

Weather Reporting Leeches

By Anupum Pant

Of all the creatures in the whole wide world, you’ll be surprised to know that leeches have played a fairly important role in the history of weather forecasting. An incredibly bizarre device invented by Dr. George merry weather, in the 19th century, called the tempest prognosticator, was basically a barometer powered by leeches.

Dr. George Merryweather, aptly named, was a surgeon by profession who was a lot into leeches. Since barometers were already being used for a long time then, to indicate approaching storms, he knew that air pressure was crucial in determining weather. However, Dr. Merryweather, an ingenious man, hell-bent on doing things the different way, had a different plan in his mind.

In his profession, he came across medicinal leeches all the time. In course of time, with a keen ability to notice details, he noticed that leeches were sensitive to electrical variations in the atmosphere.
He noticed a peculiar behaviour among these creatures. He observed that the leeches often started squirming around in a chaotic manner before a storm arrived.

Putting this practical knowledge to use, and experimenting with a number of designs, Dr. Merryweather devised a contraption. It consisted of 12 pint-sized bottles arranged in a circle. Each of which contained a leech in one-and-half-inch deep rain water. The top of every bottle had a tube into which the leech could crawl and disturb a mechanism, which in turn would activate a hammer to hit a bell – indicating that a storm is coming.

When a storm would come, the leeches were expected to crawl up the bottle, into the little pipe and activate a Heath-Robinson like mechanism which would make a hammer hit the bell. When the leech had completed its job it would fall down into the water and the hammer would go back to its place.

However, a number of times the leeches would give a false alarm. That was the reason he decided to use a jury of 12 leeches. And said,

The more of them that rang the bell, the more likely it was that a storm would be on its way.

If you ever go to Devon, you must take some time out to visit the Barometer World Museum to check out a full-scale working model of this device. Or you could go to the Whitby Museum in North Yorkshire to see the other working model.

Ants and Their Friends

By Anupum Pant

Background

If you consider the habits, social organization, communities, network of roadways, possession of domestic animals, and counting skills of ants, they are not very different from humans. Yes, ants even domesticate animals. And we’ve talked about their counting skills in the past. Then, I came across a very interesting experiment sir John Lubbock decided to do on ants.

Experiment

He had in his captivity a number of varieties of ants living in different colonies. One day he saw a group of ants feeding on honey together. He picked twenty five of them and managed to intoxicate them by some method, others were left there, feeding on honey.

Next, he picked twenty five other ants of the same species, from a different colony and intoxicated them too. He then placed all of these 50 intoxicated ants near the honey, in the path which the ants were using to move to and fro from the honey.

He watched them for hours and it was an amazing thing he found. The twenty five ants which belonged to the same colony of ants that were feeding on honey were treated much differently by them, than the other 25 ants of the same species that belonged to a different nest! Somehow they were able to identify the ants of their own nest – differentiate friends from strangers.

Twenty out of the twenty five friend ants (which belonged the same nest) were carried by the honey feeding ants to their home. While about 18 of the other intoxicated stranger ants were picked up and thrown into water.
There were just 5 friend ants which were thrown into water (probably accidentally) and 6 stranger ants which were carried back to home (probably accidentally, again)

Nevertheless, most ants were correctly identified as friends and strangers. Moreover, I think their reaction to drunk friends and drunk strangers was so much like what human beings would do!

Next Experiments

In an experiment which he did later, the researcher tried separating friend ants (of the same nest) for about 4 months. And when they met after 4 months they were able to clearly identify each other. They caressed each other with their antennae.

In other experiments when he introduced a stranger ants in a nest, the strangers were evicted immediately and sometimes even killed.

There are a couple of other interesting experiments he has mentioned in his article here. Do read it whenever you find time. [link]

This Tiny Sponge is Probably Set to Change The World

By Anupum Pant

Background

Things absorbing water from the air is nothing new. Hygroscopic substances – or substances which have ability to attract and hold water molecules from the surrounding environment – have always been around. Coffee powder for instance is one great example – leave the dry coffee powder in the open and it will turn into a mushy matter within hours. Thanks to the moisture present in the air that it absorbs.

Hygroscopy in Nature

In the nature too, hygroscopy – the ability to extract water from thin air – has some peculiar functions. One fantastic example is the seed of the needle-and-Thread grass. This seed, with the help of a hygroscopic awn attached to it, can twist and untwist the screw like structure by releasing and absorbing moisture from the air. This way, it is able to dig its way into the ground. But that’s just one of the many examples of how hygroscopy is all around us. Here’s another one…

Thorny devil – an Australian lizard – lives in the arid scrubland and desert that covers most of central Australia. It has a hard time finding water in this dry place. So, blessed by the evolutionary forces of nature, the lizard has developed tiny hygroscopic channels between the spines on its back. These channels, working in tandem with a capillary action mechanism, are able to draw water from the air. Then their precise design makes the water move into the mouth of the lizard. Fascinating!

Other Ways

Although not exactly using hygroscopy, the Namib desert beetle, also does something similar – drawing water from thin air. Unlike the hygroscopic grooves of the thorny devil’s back, the desert dwelling beetle has developed some patterns on its hard wings which help it in drawing water from the air. These patterns include an array of  hydrophobic and hydrophilic materials which are able to trap water from the foggy morning air and are able to channel it to the beetle’s mouth.

The Nanotube Sponge Mat

This particular beetle’s hard wings with magical patterns on it, intrigued a couple of researchers. They took cue from this natural material and were able to create an artificial mat which could absorb water from the air.

nanotube sponge

Although we do have commercial Atmospheric Water Generators (AWG) which can harvest water from the air and supply drinking water, the sad thing is that these things run on electricity. This new mat that was fabricated recently, using an array of carbon nano tubes sandwiched between hydrophilic and hydrophobic layers, doesn’t need any electricity to extract water.

This mat they’ve fabricated is smaller than your thumbnail, but it still works, and is able to extract about 1/4th of it’s weigh in water within a few hours. The researchers are working on it to make it more efficient. [more information] [Original Paper]

A couple of years back a US based startup, NBD Nano, was inclined on developing a water bottle based on the same Namib desert beetle principle. The much touted water bottle, they said, would be able to fill itself! I’m not sure where their project is headed today, but an auto-filling water bottle sure would be a product just too cool to not own by every kid at school!

Needless to say, it would probably make a huge difference by lowering greatly the number of people who don’t find clean drinking water every day – Just for the record, about 1/7th of the world population didn’t have access to clean water today.

A Massive 3200 Year Old Tree in a Single Picture

By Anupum Pant

If there’s one place I’d like to visit, it is the part of California where you find giant sequoia trees. The Giant forest is one such grove in the western Sierra Nevada of California. It is home to five of the ten most massive trees on the planet.

With a tree trunk measuring 36.5 feet in diameter, the Giant Sherman in the Giant forest grove, is the largest of the trees in this grove. It is 275 feet tall! (and yet there are taller trees in existence – Hyperion – again in California, which is about 379 feet tall)

While the President tree, 3200 years old, is another one of these Giant sequoia. It has seen hundred generations of humans pass by. Throughout its life it has survived a number of storms, fires, winters, earthquakes, and climate changes. And even today it grows faster than most other trees on the planet, adding one cubic meter of wood every year.

Its trunk measures around 27 feet in diameter.  In height, its topmost point measuring at 247 feet, is slightly shorter than the Giant Sherman. Still, the tree is massive. Its huge branches hold about 2 billion needles (leaves), which is more than any other tree on earth.

It is so huge that until recently it hadn’t been captured in a single photograph (excluding satellite shots and other such smart ideas). A team from National geographic magazine joined scientists to study and photograph the tree.

the president tree

[Video] Stunning Animation of How HIV Works

By Anupum Pant

Sorry, it was the FIFA WC finals, my favourite team (Germany) won, and I was too excited to write a lot today. So I searched my notes for something interesting to share quickly.

I found this 3D medical animation that I had bookmarked a long time from now. It is an animation of how the HIV replicates. It’s one of those videos with a lot of jargon where not everyone would understand what’s really happening, unless they are a lot into biology. If you are not, then I’d suggest muting the sound (don’t actually) and just watching the biological machines at work.

Still, it is amazing to see how things work at a very very tiny level and it’s an immense pleasure to appreciate how little biological machines work around in bodies to accomplish so much.

Moreover, it makes me very happy that we’ve come so far in science to understand so many things that we are now able to make mesmerizing animations of the extremely complicated and seemingly abstract biological mechanisms.

Script, Storyboard, Art Direction by: Frank Schauder, MD
Animation: MACKEVISION
Publicity: Dr.Rufus Rajadurai.MD. | D.DiaDENS