Why there is no 'walking with tentacles'...

Tentacles are cool: they look sleek, effective, a bit mysterious, and also slightly repulsive, particularly when covered with lots of suckers and slime. It is no wonder that science fiction illustrators equipped their creations with tentacles when something like the above-mentioned criteria were called for. And longer ago monsters like the 'Kraken', a giant octopus, were the staple monster of heroic tales.

As an aside, it is interesting to speculate why exactly the boneless movements of an octopus evoke fascination as well as revulsion (not in me, but certainly in many people). The explanation might be that their body scheme is so completely different from ours that it is difficult for us to comprehend what is going on when they move. (there are neurons in the motor areas of our brain that respond when we see body parts moving in other people; I would predict that their response is less as a body scheme departs more from ours). But that is not the point here. Let's take it as a given that tentacles create interest, so it would be nice to design some creatures that walk on tentacles.

Those who really know their cephalopods might say that there is no need to design animals walking on tentacles, as they already exist. Indeed; here they are. But those are 'walking' underwater, and I want animals walking on dry land.

Before anyone thinks of the loophole that land animals could quite well walk on tentacles in a very light gravity, I will accede the point. But I want animals walking on dry land in an Earth-like gravity.

Some among you might now think of ballonts (see earlier entries) that are starting to evolve back to a terrestrial life again, so they can walk with their bodies partially suspended from a balloon. To stop that, and lighter than air parts are now declared officially out of the question. The demands put on this design are to walk on tentacles in an Earth-like gravity on dry land, without any unfair ballooning aids.

I will count the solution of having a very very large number of legs as a possibility, but it doesn't sound energetically efficient. So try to design the biomechanics in such a way that the animals could actually work.

Has this been done? Well, yes. In fact, I designed one many years ago (in 1982...), turning one tentacle in a slug-like foot, leaving the others free. It was the Jellyshell, and here is part of its description:

"Without any apparent reason they will suddenly set out towards the beach. Many specimens crawl ashore more or less simultaneously, move around for a while on the beach, leaving trails of glistening slime behind them. These mysterious maneuvers last for several hours; afterwards they return to the water and take up their normal habit of slithering and algal grazing. They will not be seen on land for weeks on end; then you will suddenly encounter dozens of their trails on the beaches, left during one of their forays. Just why they come on land, and why they glide and slither there in their slow and solemn way, no one knows."

But having one slug-like foot doesn't really count as walking, so I guess that one does not count. Dougal Dixon did one several years later: the 'Coconut Grab' (found in 'The New Dinosaurs' from 1988). Here it is (click on it for a full scale depiction; it is fairly large). I think the book is still to be found, and I definitely recommend it.


That comes much closer to 'walking on tentacles', but not close enough: as the description says, the grab draws itself along the ground with four of its legs, and crawling doesn't count as walking.

So the only ones I know of that really count are the evolved cephalopods in 'The Future is Wild': the megasquid especially. This was a television series that featured some speculative evolution. The megasquid is a gigantic descendent of squid (probably octopuses, come to think of it), and it walks upright on its eight columnar tentacles. The program does have some comments on how the legs actually work, and these make it clear that the tentacles are properly boneless, as they should be. Here is a frame taken from the program.


I have my doubts though; is the proposed bimechanical explanation sufficient, or, to be more precise, would evolution leave it at that?

But first some explanations are needed about what makes a tentacle into a tentacle; but that's for another installment.

Ballonts II

(No, there is no 'Ballonts I', but there is an entry on 'The Interplanetary Zoo III', and that could have been called 'Ballonts I').

I guess that ballonts could do with a bit more attention. Let's start with a small illustration of their physics. I made the point that ballonts work better in heavy gases, meaning that you need a smaller gasbag to lift a given mass in a heavy than in a light atmosphere. Or, you can lift a heavier load with the same volume of gasbag; same principle. So here is a mixomorph larva. Its gasbag, as well as the gas, are supplied by the parent. The larva merely floats suspended from the gasbag. There is complete painting of them, by the way). It floats around passively until it lands, and then the larva can wiggle around for some time to find a suitable spot to root in, and there it remains for the rest of its life. Of course only one of these sketches depicts the real larva: the middle one. The one with the spindly larva shows the consequences of a light atmosphere, and the other one is its hypothetical heavy air cousin.



Playing around with this principle results in a series of organisms from different planets. At the top right you will find a ballont from a light atmosphere. With its large gas bag it is reduced to floating at the mercy of the winds. It does not even have any limbs for transverse movement, as these would be futile. Going down and to the left the gasbag gets progressively smaller. These animals live in heavy, soupy atmospheres. Locomotory limbs, i.e., wings, begin to appear, and these progress from thin weak flaps to sturdier shapes. At the end, just above the gray line, the difference in density between the gas and a fluid isn't very large anymore, so the animal takes on some characteristics of aquatic animals, such as wings that are almost flippers.

The gray line is literally a watershed; below it, we are dealing with fluids, and the shift in density is so large that the gas bag can be extremely small. In fact, it is hidden inside the animal, and is now known as a swim bladder. Gasbag or swim bladder, wings or flippers, they are the same things, really.

The Interplanetary Zoo III

More Edd Cartier! Once again, you can see that there were some really good aliens 50 years ago.

This time, it's a ballont. A what? You heard, a ballont. Or perhaps the word is new to you, as well it might be, seeing I invented it. It is meant to describe all lifeforms that fly, or float as the case may be, due to being lighter than air. All heavier-than-air flyers are labeled 'avians', even if they do not look particularly like Terran birds. Terran insects are avians too in exobiological jargon, like it or not.

Do ballonts make any physical sense? At first glance, they might not, seeing how on Earth man made balloons have to be enormous to lift just one human up into the air. Could such a design be made out of living tissue? In that case the lifting gas inside, no matter whether it is a light gas or hot air, would have to be supplied by the animal. That is no mean feat, and would probably require a significant energy expenditure, requiring heavy organs, making it impossible to lift them, etc. Even if the sac itself were made of dead tissue, not requiring any energy, and if the lift would be generated passively, for instance by being kept hot in some way by the sun (by being pitch black perhaps?) there still is the problem that there is virtually no way to move against the wind.

No, the thing is to adapt the circumstances rather then the organism. Would you consider a fish as a ballont? Probably not, but you would be wrong conceptually (you would be literally right, as fishes do not fly in air). If the fish has a swim bladder, it manages to float passively in the sea; it does so because it, as a whole, is just as heavy as water. And yet the fish itself, with its bones and its muscles, is made of material heavier than water. It is the swim bladder that is much much lighter than water, being filled with air. The combination allows the lifting forces supplied by the swim bladder to balance the sinking forces due to its heavy body: the fish floats...

The reason why fishes work and ballonts do not (really) resides in differences in mass: the fish isn't much heavier than water, but its bladder is much lighter than water. That's why a small bladder can lift a big fish in water. For a human in a balloon, the human is much heavier than the air, while the contents of the 'bladder', the balloon, are only a bit lighter than the air. Hence, an anormous balloon is needed.

The lesson is that ballonts will work better in heavy gases. That's why SF authors have them floating in gas giants. In the Furaha universe, ballonts in gas giants are so ubiquitous that people are completely bored by them. "Oh no, not another documentary on ballonts..."

Having ballonts on a terrestrial planet, a Gaean such as Furaha, that is a novelty. On the website there is I think as yet only one, on the splash screen. I am afraid to do the math, as I am afraid I will have to strike them from creation, and I rather like them.

Look at Cartier's ballont. You can see he understood the metabolic difficulties of the design: the limbs are frail and light, and most of the animal is in fact no more than a sac. You could probably work out the heaviness of its atmosphere by comparing the volume of the sac with the mass of the rest of the body. Fairly heavy, I would say; definitely not living on a Gaean.

Texturing the planet

Finally the work of making a texture for Furaha is nearing completion.

After ample deliberation I decided upon places for likely deserts, based on some understanding of Earth's climate system. I did receive help, but in the end I confess there was lots of guesswork. It was good to have that major hurdle out of the way, as I could then concentrate on creating the texture itself.

To do that, I needed to become more used to Photoshop (never mind 'proficient'). In the end I took published maps of Earth (NASA's 'Blue Marble' series), and I cut bits and pieces out of these maps, and pasted them, with some rotation if necessary, on my new map. I used some of Photoshop's tools to bridge the borders between these pieces with believable intermediaries. That took some time, mostly because I was learning this as I went along.

Having done that, it was time to create some shallow seas, done by lightening a few pixels here and there near some coasts. And there we are! The real texture is much bigger than shown here, by the way. It is probably much too light, but that was handy during construction to see what I was doing. Compared to the Blue Marble pictures, this texture is much too bright, so it will probably has to cross over to 'the dark side' before I post it on the website.

Click to see in a bigger window

That's not all though, I also worked on a programme to cover part of the land with snow and ice, depending on the season. You can see the result for Earth below. I can of course do it for Furaha, but the advantage of doing it with Earth is that the result at least allows an idea of how well it all works. The programma works by taking the distance from the nearest pole (latitude) as well as elevation into account. These are combined in such a way that the chances of snow cover are bigger as you come nearer the pole and as you get higher up.
The same is true for the Earth: mountain tops may be covered in snow when there is no snow at all in the surrounding valleys, and the nearer you get to the equator the smaller the chances of finding a snow-covered peak are.
Where the program goes wrong is in forgetting about precipitation: the definition of a desert is a place with very little precipitation; and when there is no rain or snow, you do not get an ice cover, no matter how cold it is. The Tibetan plateau may be such a place: there should be no snow, but the programme puts it there. Oh well; that can be edited.

Click to see in a bigger window

What's left? Well, rivers, lakes, sea ice that changes with the seasons, seasonal changes in the colours of the land due to plant life, etc. Much to do yet...

The Interplanetary Zoo II

It's time to bring another of Edd Cartier's wonderful drawings back(I've found about 10, so we haven't run our yet)

Now thís is really an odd design. People who design alien lifeforms often try to get away from the shapes we know to enhance the alien nature of their designs. I have my doubts how far you take take that line of thinking, because biomechanics will work the same all over the universe. If you wish to swim, streamlining is efficient, given certain characteristics of size, density of the fluid, etc., etc. Leave that as it may be for the moment, and approach the problem from a different angle: perhaps an alien design works as such if you cannot immediately work out what the general build of the animal is. If you wonder 'how does this thing work?', then the designer may be onto something.

Like the previous one, this creature seems to have a rotund body slung between two walking limbs. The limbs divide in separate parts, but that is nothing novel: our legs also end is toes, and the prototypical arthropod limb also is 'biramous', meaning it has two branches. But this one is slightly different, in that the split into 'toes' happens fairly high op the limb itself, so the 'toes' take on an aspect of legs themselves. They seem capable of somewhat independent motion. If our legs would split into two separate 'leglets' at the level of our knees, would we say that we had two lower limbs or four?

Never mind, but the point is that this is a shape that takes some study before you start to see how it works. As such, it's delightfully alien.

Rhinogradentia III

The previous post on the Rhinogradentia mentioned the book by one 'Karl D.S. Geeste' entitled 'Stümpke's Rhinogradentia'. It turned out that Geeste and Stümpke are in reality one and the same person, who in real life is called Gerolf Steiner. This puts the interview, in which Geeste questions Stümpke about how the Rhinogradentia came into being, in a new light: in essence the interview is an autobiographical style figure. There are only a few pages about the early history of the Rhinogradentia in the book, but they have something to tell.

The overall feeling you get from the Rhinogradentia is one of good uncomplicated fun, without any cynicism or sarcasm. There is hardly even irony. It is all extremely good-natured. Even the responses to letters Steiner received from people who had failed to get the joke, or who felt that scientist should never joke in such a way, show a great deal of respect for the sentiments of the senders, even when these were rather dour. And yet, the circumstances during which the Rhinogradentia were conceived were not nice at all. The following is from 'Stümpke's Rhinogradentia (Fischer Verlag 1988, pp 64-67).

The project started by chance early in 1945, in Darmstadt, in the western part of Germany. Germany was not yet beaten but Darmstadt was occupied by Americans. There was nothing to eat, so Steiner had even tried frying snails with the last 10 grams of fat. He found that the mucus of the snails made the snails stick in his throat, so he was unable to eat them, and cried for being so hungry. Steiner, bombed out of his own home, lived in a room in a house in the outer parts of the city, less damaged by bombing than the city centre. He had some paper and some pencils there, that had survived the bombing. One day a student who wished to become a zoologist shared some asparagus with Steiner; this was a wondrous great gift. He wished to do something in return, and decided to make a drawing for her; something not too serious, but uplifting, and with a zoological theme. And that's how the Nasobem was born. Because he liked the drawing himself, he made another one for his own amusement. And later another one, etc.

By itself this story is not that surprising or that moving. But there are a few sentences describing what life was like in the suburbs of this ravaged city. These tell their own story and make you wonder how Steiner managed to evade cynicism or despair. For those who can read German, the original text follows first, followed by my translation. I tried to stay close to the original text.

"Ein bisschen satt zu essen zu bekommen, gehörte zu diesem Beglückenden ebenso wie später die Frülingsblumen oder die schönen Chorgesänge der freigelassenen Russen, die plündernd durch die Gegend zogen. Dazwischen hörte man das irre Schreien vergewaltigter Frauen, die sich -ausgebombt- in ihre Gartenhütten einquartiert hatten."

"To be able to get a bit to eat so you didn't feel so hungry anymore was one of the things that made you happy, just as much as spring flowers later did, or the beautiful choir singing of the freed Russians, who wandered through the countryside, plundering as they went. In the midst of this you heard the mad crying of raped women, who, having been bombed out of their homes, had found shelter in garden sheds."

What a contrast.

Locomotion in the game 'Spore'

'Spore', for those few who do not yet know, is a long-awaited computer game in which the player must design and guide a creature from life in some warm pond to a space-faring civilization. While there may not be that much overlap between those who play computer games and those who are interested in exobiology, 'Spore' should hold some interest for either party.

A few weeks ago a part of the game was introduced on its own: the 'Creature Creator'. If you type that into Google with 'spore' along, you will find it in no time. There is a free trial version as well as an inexpensive complete version. The 'creator' allows the user to stick various bits and pieces together to design interesting animals. The parts can be rotated, scaled, etc., and the animal can be coloured to great effect. The program works very smoothly. The resulting animals have a characteristic cartoonish shape and mode of movement to them, so I recommend playing with the trial version.

There are many things you cannot control, however. For instance, you can control the thickness of a body segment, but this works fro all dimensions of that segment. It would be hard to depict a very flat animal with this program, at least so it seems to me now. Another thing that had me puzzled was how the programmers dealt with movement: you can stick on predefined limbs, and then the animal will walk all by itself. I was interested in how the programmers had solved the problem of gait. The Furaha site contains a page on various gaits, and those who have read that will know that there are many different gaits, that all depend on the number of limbs. To see what would happen, I designed a simple animal with a sausage-shaped body, and stuck on up to five pairs of limbs.

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Let's start with the simplest design, a biped, with just one pair of limbs:

By the way, the video catch mode is built into the program; very neat! As you can see, the phase difference between the legs is exactly 50%, or indeed what you would want a walking bipedsuch as ourselves to do. I haven't sen anythingresembling gait controls, and if there aren't, there will be no way to get a kangaroo-like gait. That's a pity in a way, but I guess the complexity of gait control might confuse many players. To keep the number of videos down, I will not show you a tetrapod gait. It turns out there is only one, and it is a trot: the left fore and the right hind leg move in unison, and opposite to the other pair. Again, only a trot, so no walk, pace or gallop! Perhaps a walk could be added in the future: having a slow and a fast gait might make the species involved more interesting to look at, and it can't be very difficult to put in.

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Now, let's increase the number of legs to three; what gait will that give us?

It's a tripod walk! Nice one. The right front, left middle and right hind legs move together, in phase opposite the remaining pair. You can also view this as the phase changing by 50% as you go from to first to the second pair of legs, and from the second to the third pair.

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And now, of course, four or five pairs of legs. The result follows:

Well, well, the programmers decided to stop following that pattern, and now all legs on one side simply move together (except during turns, and designing a neat way of turning must have taken some thought). Using five pairs had exactly the same effect. Again, there is no way to control the gait, so there is no way to obtain the nice rippling effect successive small phase differences have on the general feel of how a centipede moves.

While I would like to see more control over body shapes and gait, let me stress how much fun it is to play around with this program. It really does what it sets out to do extremely well. In fact, the programmers even foresaw that some players would develop animals without any legs at all: even then you get movement of a sort. And oh yes, stride freqency seems to go down as body size goes up. I'm impressed.