The Cycle of Cyann

The title should more properly be 'Le Cycle de Cyann', as this is a series of 'bandes dessinées' (the word 'comics' does not seem appropriate) by Bourgeon and Lacroix that does not seem to have been published in English. I have no idea why, but there have been arguments with the first publisher, Casterman. The series started in 1993 in a magazine called 'A Suivre' ('To be continued'). Strangely, I did not find any good websites to direct you to, not even at the two different publishers responsible for the albums: Casterman and Glénat. Amazon in the UK and the USA only have entries for French and German versions, but amazon.fr will at least show you all the album covers. The series revolves around a rather attractive headstrong young woman called Cyann. Driven by the hope to find a cure for a disease ravaging her home planet she discovers that the priest class on the planet have kept a portal system hidden from the population, that allows travel through space. The system is largely derelict, and many worlds have been out of touch for so long that they have forgotten their common ancestry, and developed their own customs, architecture, etc. The reason to mention the series here is that the authors are rather good at making up entire planets, with ecologies, etc, along with peculiarities of their human inhabitants that really seem to belong in that ecology. Cyann's home environment is humid and tropical, and the inhabitants are accordingly dressed scantily. Except that this makes sense, it allows Bourgeon to draw attractive women, something he seems unable or unwilling to forgo anyway. There are lots of plants and animals in the series, and you can tell that much attention has gone into their design. Anyone interested in the background of the series should pick up a copy of 'La Clé des Confins', that is not a story by itself, but a companion volume explaining the worlds Cyann travels on. Here I will introduce just a little sideshow from the first album (La Source et la Sonde). The two main protagonists have camped outside and are waking up. The next page starts as follows:

Click the image to enlarge it

We are treated to part of a food web in just a few frames: there are floating seed heads, that are of coarse ballonts (see earlier entries in this blog to learn more about ballooning animals). The balloon sac is opened by some avian to get at the seeds, while a ground-living animal has another way of getting at them: it jumps up to get at them, and its hind legs seem specifically well-developed for this purpose. But make sure you look at the background as well: there are interesting plants, there is a city with intriguing architecture, the heroine is lying on the ground, etc. And all this is just a sideshow for the main action. I think I will post some more morsels of this marvelous universe every now and then.

Why there is no 'walking with tentacles'... (4)

So the 'Walking Tentacle, Mark II' developed last time has a stack of elements able to withstand compression and still has considerable amount of freedom, with its many ball-and socket joints. In fact, I was tempted to elevate it to the level of a 'Working Solution' and to keep it in the Furaha universe. There are several things it cannot do that a completely muscular tentacle can do, and that is to lengthen or to shorten at will. It also still takes lots of muscle force just to keep it in place.

There are some interesting refinements to be considered. One thing I came up with is that the surface of the joints is now completely smooth, not obstructing movement in any way. But suppose that the surface could somehow be made to become less smooth if needed. Perhaps with small elements under the surface that can be raised to make the surface coarse-grained. If you do that on both sides of a joint's surface, the friction will become much larger, so the joint would need less muscle force to stay in place. That would be the Mark IIb...

But a much more likely development would be to reduce the number of movable elements. Simply lengthening the compressive elements inside the tentacle would solve many problems: there are fewer areas of motion, hence fewer places where muscle force is needed. The concentric muscle cylinders can go, as they are replaced by muscles spanning one or two joints.

But consider the nature of this Mark III 'Walking Tentacle' looks like: it is a series of elements made of strong material able to withstand compressive forces, and movement is effected by muscles pulling at these elements, causing them to rotate at some places only: yes, the Mark III 'Walking Tentacle' is a leg, and that's why there's no 'Walking with Tentacles': they evolved into legs...

Here it is, with just two muscles (click to enlarge)

Why there is no 'walking with tentacles'... (3)

Last time I argued that using tentacles to walk on would require wasteful amounts of energy. To withstand bending forces you would need very high pressure inside the tentacle in order to keep it stiff enough (the principle is called a muscular hydrostat by the way). The first big disadvantage that this generates is that you need a lot of power , and the second is it the high pressure puts a large strain on the circulation.

So let's do some creative evolution to work around these problems. A tentacle differs from the balloon animal in the last post in that the inside of the balloon is filled with air while the tentacle is filled with muscle cells, i.e., basically water. For walking purposes we need something well able to withstand compressive forces. The first thing I can see happening is compartmentalization. With compartments inside the tentacle, you could have high pressure in one compartment and lower in another. The next step is to have some organ inside each compartment that is built to withstand compressive forces. Evolution might start with specialised muscle cells, that no longer contract actively, but simply form an elastic blob that is fairly stiff, and less easily deformed than the cells.

Click to enlarge

They could have a shape as shown above: a more or less cylindrical sac filled with a jelly-like substance. Perhaps its wall is non-elastic, or perhaps there are strong fibres in there, running from one side to the other. Let's call this a 'corpus gelatinosus centralis (CGC)', or, in Latin-less days, a compression blob. Whatever the solution, the blob holds its shape, and if you stack a number on top of one another they can carry weight. It will still need lots of muscles on the outside to keep the stack balanced. Three layers are shown, but that is just a rough idea. The arrangement costs less energy to keep upright, controlling it still costs lots of energy. It might just allow an animal to fumble around on shore, so perhaps this is a credible 'Walking Tentacle, Mark I'.

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Click to enlarge

Evolution will not stop there, however. The next step is shown above. The CGC's have evolved, and now fit rather well together. The top half of each is spherical and fits in a depression in the bottom part of the next one. This arrangement ensures that pressures can be safely transferred down the stack of CGC's, called the 'columna corporum gelatinosorum (CCG)'. Take care here, as you can get lost easily in anatomical jargon. The spherical joints between the blobs allow movement in all directions, so from the outside the limb still has many characteristics of tentacles. The material of the blobs has evolved as well; they no longer simply keep their shape by virtue of tension fibres inside the blobs, but the gelatinous mass is now also crisscrossed by calcareous spicules that withstand compression forces directly.

Circling the blobs the various layers are still there, but with two innovations. The first is that there are now ligaments as well as muscles that attach to one blob and connect it to the next one in the line. These are crucial in fine tuning the positions of each pair of blobs, while the outer muscle layers do the brunt of the work in moving the tentacle. The second new item is that the layer of circular fibres has atrophied, as it is hardly needed anymore: it's job was mostly to generate a high tension, but those are now to a large extent taken care of by passing the forces through materials that withstand them.

I guess I should have put these refinements in the figures, and perhaps I will, at a later date. But this concludes the 'Walking Tentacle, Mark II'.

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As for Mark III, I wonder if anyone sees where this is going; we are on the way to evolve a walking tentacle, and yet the thread is entitled ' Why there is no 'walking with tentacles'...

Why there is no 'walking with tentacles'... (2)

Well, it took a while to write a new chapter. The reason is called 'work'.

Anyway, to continue with the 'Not walking on tentacles' subject, I made some illustrations with Vue Infinite, shown below. Let's have a look at a typical tentacle.

(Click the image to enlarge it)

This particular one is almost entirely made up of muscle cells (also called muscle fibres). the fibres are the red elongated structures. I played with images of mammalian striated muscle cells to form a reasonably realistic texture. The first thing to remember is that muscle fibres can only pull; they cannot push! So, if we want to use a tentacle as a leg, pushing against the ground, we will have to devise a way to push with elements that can only pull. Normal legs, with skeletons, work because the two jobs are separated: the muscles pull on the bones and the bones do the pushing.

Back to the tentacle: it is almost entirely made of muscle cells, except for the very centre, where I have put in an artery, a vein and a nerve (these have the customary colours found in medical textbooks: the artery is round and red, the vein is rather floppy and blue, and the nerve is solid and yellow). No bone, of course; it wouldn't be a tentacle if there was one!

The muscle cells are arranged in concentric layers, and the muscle fibres are arranged in different directions in different layers. The innermost layer has its fibres running lengthwise. If they contract, the tentacle will shorten. It will also become thicker, as the total volume of the tentacle will not change; after all, the whole thing is largely water, and water is incompressible. You can also have the fibres of that layer contract on one side only; if that happens, the tentacle will bend. You do not have to have this happen along the entire length, so the bend can happen anywhere. Already our tentacle can move in various directions.

The outermost layer has its fibre running transversely. If these contract, they will squeeze everything inside. Having nowhere else to go, the tentacle will become thinner, and therefore longer. The two other layers were added to add a bit of complexity and dexterity: their fibres run diagonally, so they will tend to twist the fibre. They also have compressive as well as shortening effects. Playing with these layers and fibres should allow the tentacle to move in just about any way you can think of.

There is no particular need to have the layers arranged just so. In fact, there might be another lengthwise layer on the outside, and there are various other things you can think of. As it stands, the tentacle can pull quite well. By activating the circular fibres the tentacle will become longer; isn't that the same as pushing? Well yes, but not with any great force. What we have so far is something like the human tongue, and you can push it out of your mouth, or against your teeth. But you can't do push-ups with it.

(Click the image to enlarge it)

To understand why, look at the balloon animal shown here. Its 'legs' sacs of air, and the only reason they hold their shape is because the sac under pressure. If we do the same for the tentacle, and tighten the outermost layers of the tentacle over its entire length, the inner bits of the tentacle would be under pressure, with the same result: a structure with enough tension to hold its own shape. But you cannot put any weight on a balloon animal: the legs buckle.

With that as a given, the simplest solution is to increase the pressure tremendously, so the leg/tentacle will not buckle so easily. That seems to be the solution chosen for the 'megasquid' in 'The future is wild'.

But that is so wasteful! The tension has to be built with continuous muscle force, and that eats energy. In contrast, to stand on bones the only energy you need is to keep them from buckling at the joints, and if you balance them right, all you have to do is a balancing trick rather than a brue force approach. A second problem is that the pressure inside the tentacle would be very high, and that creates big problems for getting any blood to the muscle cells. Blood pressure in the tentacles would have to be even higher than tissue pressure to force any blood through, and that in turn puts heavy strain on the heart, or hearts, come to think of that. More energy, more engineering problems. Anything with bones would run rings around such silly squids.

I think walking on tentacles requires more than a very thick tentacle; it needs evolution to keep the costs down. More on a possible solution next time...

Just some tree designs

Real life has a habit of getting in the way of more creative endeavours, so any trusty reader will have to wait a bit for me to write some more on how not to walk on tentacles. Meanwhile here are a few trees I have been working on, which perhaps also counts as creative work. They are designed with XFrog, and rendered with Vue (links in the appropriate section of the website). As always, click on the images to enlarge them.



First, this might either be called a Thistle Tree or a Galactère. It's surprising how quickly the number of polygons rises: this version weighs in at over 1.1. million polygons, and I don't think the ratio of leaf size to tree size is good yet: the leaves should be smaller in relation to the tree, but that is the quickest way to get really high polygon counts.


Here is the same tree shot from underneath, which perhaps helps to understand how it got its names. You can get away with much rougher leaves for long distance shots, but if you want to get in close you need detail.



And just for fun a Mollum, that is rather unlikely to make it through the utterly unnatural selection process determining continued survival on the planet Furaha, also known as Nu Phoenicis IV...

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.