Saturday, 28 August 2010

Adding oddity (alien plants II)

Click to enlarge

I don't write often on alien plants, for a simple reason: there seem to be few of them. I wrote about the -real!- plant life on the island Socotra once, shown you Furahan swamps and showed a few images from the British comic strip Dan Dare. My main post on alien plants was devoted to a computer-generated video. The firm that made it produced another one, as I learned from a site called dexigner.com. The images shown here and the video are taken from that site (the video quality on the site is very good). In fact, there I learned that the previous one was called 'Sixes Last'; there are so many copies of it on the Internet that it is not hard to find it, but it is hard to trace its origin. The 'new' one dates from 2006 and is a commercial for an alcoholic drink. I have nothing against that; in fact, C2H5OH plays quite a role in Furahan biochemistry. As 'advertisement' is not exactly a synonym for 'accuracy', do not expect much in the way of plausibility. Then again, the film does not try to be accurate, just intriguing and humorous. It succeeds well, I think. The computer-generated bits seem to be added to real footage, which may explain why the images look very real.

Click to enlarge

The second reason to show it is to discuss the problem of how to design odd plants. I have this worrying idea that the basic plant design may not allow much creative freedom, at least not if the definition of plant is not stretched too much. The main ingredients of the definition may be photosynthesis and being sessile, with some -arbitrary- limits in that the plants in question are multicellular and that they are land plants. Photosynthesis needs light, and the best way to get much light is with a large area, i.e. thin shapes. Needles are good but planes are better. Basically a blanket-like shape with roots to pick up minerals and water is all you need. But if the blanket gets too large it may be torn by the wind, and an easy way to avoid that is to distribute wind stress over many small leaves. Growing towards the light avoids being in the shadow of other plants. Branching systems and leaves seem unavoidable, and any alien plant with those will look like an Earth plant.

What can be done is to alter the relative sizes of plants: thick stems, enormous leaves, etc. and giving them odd colours. But there are usually reasons for these proportions as well as for colours, so there is no total freedom here. The simplest way to add oddity may be to add elements of animals: give the plants eyes or mouths. That is what happened in the earlier video as well as in the present one. Eyes are there to tell an organism about its environment: where is the prey, where is the predator, are there good-looking potential mates around, etc. Acquiring information is only useful if you can act on it, and the main limitation here may be the sessile lifestyle. Sessile life forms can certainly be interesting; there are quite a few sessile predators: think of anemones. But there may be a limit on how well developed their sense organs and brains can become. Why have fine eyes and precise grasping arms when your reach remains frustratingly limited? Wouldn't an animal that can do the same things but that can move around be vastly more fit in the evolutionary sense? You may counter that by saying that it may be enough to outperform the dumb and blind types of sessile organisms. In evolutionary biology traits always seem to cost something. The price to pay may be a metabolic one: eyes, muscles and particularly brains are very expensive in terms of energy.

In that sense, high class eyes are jetset organs, reserved for high flyers only. So the puzzle remains how to increase the oddity of alien plants...



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Wednesday, 18 August 2010

Strandbeesten and mantis shrimps

Actually, 'Strandbeesten and stomatopods' might have sounded better, but would be even more incomprehensible, and a blog is supposed to attract readers, not frighten them away. Based on how many readers were attracted by previous posts, I should probably use 'The Future is Wild' and particularly 'Avatar' a lot more often in post titles (and no, Furaha was NOT modelled on Avatar; it is much older). Right; now that I've got that out of the way, back to the strandbeesten.

I discussed Theo Jansen's imaginative mechanical walking machines before on this blog. Literally the word is Dutch for 'beach beasts'. If you do not know about them, read that entry and visit Mr Jansen's site, or just enter 'Theo Jansen' into Google or YouTube. His work came up in this blog because of my interest in animal locomotion. The problem he faced was how you can get a foot to move backwards along a straight line when on the ground, after which it has to be lifted, moved forward and put down again for the next step. For real animals this is not a big problem, as the various segments of a limb are all controlled by a nervous system telling each segment when to do what. As Jansen's devices lack a brain, he needed a purely mechanical system to achieve this sort of motion. In the end he came up with an intricate series of interconnected bars: if you start with a rotary motion of one bar, another bar, ending in a foot, produces a suitable movement. Very clever indeed. Such series of connected bars are called linkages. You can take a good look at his design on this particular site, which shows other linkages as well. When I wrote that post I had never seen a single strandbeest yet, and that has now been rectified. Mr Jansen works not that far from where I live, so it was a matter of time before I could visit one of his demonstrations nearby. This was the case last June, on a very cold and windy day. I will show a few videos I made that day.

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This is a tiny strandbeest, of which there were three. If its sail is perpendicular to the wind direction, the little beast may walk with the wind. I tried pushing it forward as well, and found that it is not in fact that easy to move. While the 'beesten' are quite light, their joints were harder to move than I had expected. There is no lubrication, but the main problem seems to be that the entire shape deforms enough to put shearing forces on the joints. One result of this is that the poor beest tends to topple over. But never mind that, they are an amazing sight.

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Here is a larger one following one of Mr Jansen's assistants.

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And this is the major species present at the occasion. Not only did it have two bodies or trunks, an enormous number of legs, but also two waving membranes at the top that I think were designed to help propel it. These sails were reefed that day however, and the force of the wind on the body was enough to prod the beast onwards. Aren't they wonderful?

In my previous post I wondered how often linkages occurred in biology, but did not look up the matter. I have done a bit of research now, and found that there are quite a few examples. Fish jaws are probably the best-known example (see below). Other structures, such as sheep hocks and human knees are also counted as so-called four-bar linkages. In a four-bar linkage four stiff bars are linked together in a sort of circle by pivots. If you hold one bar still, and move another one, the remaining two must move in a fixed way. What that way is depends on how exactly they are connected. I felt that regarding the human knee as a four-bar linkage is bending the rules a bit, as two of the bars are ligaments rather than stiff bars. If you include connected series of bones as well as ligaments there are lots of linkages in biology; what I was looking for was linkages of bones involved in locomotion, but I have not yet seen any. Presumably a system with more mechanical freedom but with a smart nervous system to control it is simply superior. Still, the other ones are interesting.

Click to enlarge; Wainwright et al, Integr Comp Biol 2005; 45: 256-262

Here is an example of what fishes do with a four-bar linkage. The source is mentioned in the caption, and the colours are my addition. Fish use this kind of mechanism to move their jaws forward and to enlarge the volume in their mouths, sucking in water as well as their prey. There is at least one Furahan animal with a similar arrangement, and those are 'Fishes' too. The jaws of the sawjaw are connected, all four of them, by bars linking them to the neurocranium in a kind of circular linkage.

So where are the mantis shrimps, everyone's favourite Terran alien? When searching for linkage mechanisms I found that there is a four-bar mechanism in their 'raptorial appendages' as well! I like that: somehow you expect animals that not just spear or club their prey but can see depth with just one eye to be special in other respects as well, and mantis shrimps never seem to let us down when it comes to, well, weirdness.

Click to enlarge; Patek et al; Nature 2004; 428: 819

Here is a figure from the journal Nature, no less. The first author, Sheila Patek, has a lab where she studies all kinds of biomechanically interesting things, most notably mantis shrimps. Have a look, as there are quite a few videos and photographs. Under 'multimedia' you will find an inspired lecture she gave on 'TED', where she explains the striking mechanism of stomatopod raptorial appendages. Very interesting. She is not the only one interested in stomatopods either; here is another enthusiast.

So now you know why strandbeesten and stomatopods end up in the same post: they are connected by linkage (I could not resist that one). I guess both also score very highly when it comes to their ability to evoke a sense of wonder.



PS. This is post #100!

Sunday, 8 August 2010

Warren Fahy's "Fragment"

Predators resembling mantis shrimps, insect-like life forms whose wings are placed in a radial design, and covers of books that do not exist...

You might think that this is the Furaha site I am talking about, and indeed it could be. But the same characteristics also describe another speculative playing field, and that is "Henders Island".

'Fragment' is a novel
by Warren Fahy that came out last year. I have never discussed any of the large number of interesting life forms in written science fiction before; the reason is simply that I have a strong predilection for visual matters. 'Fragment' is accompanied by a website with quite a bit of visual material. Some of the images there are printed in the book as well.

I will not describe the story in any detail; if you like an adventure story along the lines of Crichton's 'Jurassic Park', you will like this book as well. The story begins with a camera crew stumbling upon an unexplored island. 'Unexplored' means except for a captain Henders a few centuries ago, who noted its existence. The island is the remnant of a former continent, where life went through its own evolutionary process regardless of mainstream evolution. You might think that that is what islands are for, in fact. The Galapagos islands, definitely a breeding ground for somewhat original shapes, are 5-10 million years old, and Madagascar, the home of lemurs and some of the oddest trees in existence, has been isolated for some 100 million years (or so Wikipedia says). It makes sense to think that longer isolation allows further separation between island and mainland life forms, giving rise to the dictum that 'weirdness waxes with time'. Well, Henders Island has been isolated since the Precambrian...


Click to enlarge; copyright Warren Fahy and Company

The resulting life forms cannot even be categorised in modern terms. Above is a Henders rat attacking a poor mongoose, let loose by scientists to see how well 'normal' animals fare against Henderian ones (the Henderian ones kill them in minutes). This 'rat' has a ringlike internal skeleton that seems to have developed from a crustacean (?) exoskeleton. They have fur, give birth to live young, have blue blood, have interesting eyes (mantis shrimps again), a second brain with its own eyes on its back. One of their 9 limbs is really a tail; the first two pairs of limbs are adapted to catch prey ('hypercentaurism').

Click to enlarge; copyright Warren Fahy and Company

This is a Henders wasp, one of the radially symmetrical flying life forms. It seems to have five wings, which means it will not be easy to develop a wing 'gait' that does not produce a wobble in flight. The wings stick out but do not seem to move to and fro as frantically as you might expect. They are quite a bit like my tetropters; that's convergent speculation, all over again. Previous posts on tetropters started here and continued here, here and here. (By the way, I have solved the major hurdles of producing smooth tetropter flight animations, but there is still quite a bit to do.)
Click to enlarge; copyright Warren Fahy and Company

Life on Henders Island is so extremely aggressive and efficacious in eating anything anywhere anytime that the rest of the Earth had better watch out. Step on land and you will be stung, bitten into or simply turned into shish kebab in a few minutes. You cannot even trust the 'plants'! Interestingly, the book contains discussions between the protagonists whether or not an ecosystem can flourish without any clear distinction between herbivores and carnivores. I suppose I am one of the doubters: if anything that can be eaten will be eaten in a matter of minutes, you wonder how anything can live long enough to grow large. And there are large animals; above is a spigre with a human for scale. Large animals may be fairly immune to attacks from animals half their size, but they are not so to insect-sized or smaller animals.

Click to enlarge; copyright Warren Fahy and Company

Small Henderian animals are certainly dangerous; above is a disk ant, a radially symmetrical animal, like a spidrid, but much nastier. Disk ants carry their own young that carry their own young etc, so there is a cascade of nastiness. The book describes how they bore their way into flesh and open a leg to the bone in a matter of seconds; a bit too quick, I thought: movement takes time, certainly on a miniature scale. But what keeps them from devouring a spigre? I do like the disk ant's movement: it can walk as any decent radial animal should, but can switch to rolling on one side. Likely? Probably not. Fun? Definitely!

Reading the book gave me a distinct feeling that the author had a film in mind, and indeed Mr Fahy wrote me that a film is 'definitely now in the works'. I suppose that that is why so much visual material has been developed. Because I like to credit the artists where possible, I asked him for their names, and here they are: Daren Bader, Steven Olds, Ron Lemon and Michael Limber.

I guess we now wait for the sequel and for the film. I do hope that the movie makers will pay more attention to how animals move than the designers of Avatar did. If you read 'Fragment', it is clear that the author likes his creations and thought a lot about their biology; that's a very good starting point.