Saturday, 19 May 2012

Archives IV: once and future rusps

The archives of the Institute of Furahan Biology contain the evolutionary lineages of almost all Furahan animals, in the form of sketches that show how the animal and its depiction evolved over time, before their shapes were frozen in the form of a painting. Well, that is how it seemed: as I have started reworking my paintings digitally, evolution has suddenly leapt ahead again. Sometimes I also revisit old designs again; rusps are an example.

Click to enlarge; copyright Gert van Dijk

Rusps feature on the 'walking with rusps' page on the main Furaha site (on the 'land' page). The image above shows the first ever sketches of 'rusps'. (Their name is inspired by how Dutch children may have difficulty with the word for caterpillar, and end up saying 'rusp' instead of 'rups'.) As you can see, rusps have multiple legs and are protected by a strong carapax. My notes alongside the sketch stated whether such presumably slow animals could survive in an environment of agile large animals. But I also noted that sea urchins are bright nor fast, but do quite well. Such considerations made me add stings, evolved from stings alongside the body through poisonous hairy plumes into mean-looking fore and aft tentacles equipped with poisonous barbs. Their bodies are segmented, and there are multiple eyes on the front and back; in fact the lower rusp also has secondary eyes along the body. The reason there is a tentacle at both ends had to do with my wish to protect the animal. I have always been surprised by the inability of earth's animals to protect their rear end well, a weakness exploited with great success by predators such as lions and hyenas. Of course, this 'active rear' design, with eyes, a tentacle and the corresponding neural circuitry, represents a departure from Earth patterns, where no large animal has a 'split brain' to this degree. It reminds me of the claims for a 'secondary brain', such as was once implied for stegosaurs? Such a design goes against the theme of 'cephalisation', and I am not at all certain that it could actually work. Then again, I see no definite reason why it could not.

Click to enlarge; copyright Gert van Dijk

I almost immediately wished to make them bigger, at least elephant sized. Here is another early sketch, showing how a large rusp crosses a stream sunk into the ground. Animals such as elephants have great difficulty in doing so, as they cannot jump at all and dislike steep inclines. I thought that rusps would have the advantage of being able to use their long bodies: they can hold the front part of their body in the air at some energetic cost until they are able to find a foothold on the other side.

Rusps probably evolved from millipede-like ancestors. In contrast to Earths arthropods these ancestors were obviously equipped with respiratory and circulatory systems allowing adaptations for large bodiess. They were also endoskeletal, for similar reasons. The carapax is not a part of the skeleton, but simply an outer protective covering; it is leathery rather than hard.

Click to enlarge; copyright Gert van Dijk

The top image shows one from a low viewpoint, a trick that by itself suggests large size, as viewers often assume a viewing point at eye level. What you can also see is how the legs move in a sort of ripple, with adjacent legs moving a bit out of phase with the ones in front and behind. That is the usual gait of Earth's millipedes and centipedes, by the way (this is also animated on the main Furaha site). The sketch in the middle show transverse sections, illustrating my thoughts on their possible body shapes. I did not want their legs knocking into one another, so I thought that successive pairs could be offset to the left or the right, giving each room to move. To evoke an atmosphere of large size, I played with the idea of making them high and narrow rather than wide and squat. If you take a good look at elephants and many dinosaurs you will see that they are often relatively narrow. I also played with the site of attachment of the legs: underneath the animal or along its sides? The sketch at the bottom shows a resulting rusp of the narrow type. I rather like their tentacles, but realised that they woud pose biomechanical problems: holding them horizontally with muscle power alone would be as comfortable and efficient as humans holding their arms horizontally in the air all day: try to do it for 10 minutes...

Click to enlarge; copyright Gert van Dijk

Rusps only made it to a painting once, a detail of which is shown above. But even on that painting they were in the middle distance. One of the reasons they never received their own painting was that I had problems in finding a suitable design. With their long horizontal bodies they present a somewhat passive shape. One solution would be to show them from the front with a considerable degree of foreshortening, such as in the images above, or I could show only a part of their body, such as in the 'fording a stream' design above. But there were other problems as well, such as the relative positions of the legs, the 'active rear' with its corollary 'split brain', and of coarse the tentacles, that cannot just be held in the air horizontally like that. For a structure held up with muscle power only, such a position is virtually impossible; just try to hold your arms with extended elbows horizontally in the air for 10 minutes, and you will find out why...

Click to enlarge; copyright Gert van Dijk

I keep coming back to rusps, and above is a recent study done with Vue Infinite. Here, too, the successive legs are offset resulting in a double track on each side. It has as a disadvantage that the hip joint is not directly above the foot. As a painting it results in a rather sedate view, but the well-lit afternoon sunshine could make up for that. Rusps ought to look grandiose, and perhaps a design like this brings that out.


video


video

The one thing I am not worried about at all is the leg pattern. The two animations are newer 3D versions of rusp locomotion. The essence of centipede or millipede locomotion is that there are successive phase differences between successive legs. Depending on whether a leg is either just ahead or behind in its cycle compared to the leg behind it, the legs tend to clump together either on the ground or in the air. The effect is that the movement appears to ripple either forwards or backwards along the animal. For centipedes and millipedes the choice seems to depend on how far sideways the legs are held. In rusps, the legs are always held vertically, so leg tangles have to be avoided in another way. Possible solutions are of course to make the legs shorter, place them further apart, or, as I wrote above, to have their feet offset. On the other hand, the animation shows that manipulating the phase differences can avoid leg entanglement quite well, so the simplest solution is probably the best one. In short, there seems to be little need to offset the legs.

Click to enlarge; From: Steven Vogel. Comparative biomechanics. Princeton Oxford 2003

Click to enlarge; from:Klein et al; biology of the sauropod dinosaurs. Indiana University Press 2011

As for the tentacles, some further thought suggested a solution. Sauropod necks and tails are very long structures held out horizontally in positions that at first glance seem impossible. This is possible because they are not tentacles but trusses: there are bones resisting compression at the bottom and tendons to withstand pulling forces at the top. With a design like that, rusps whips could function and wreak havoc on any hexapod predator foolish enough to enter the rusps' range of motion, at its front or back. Rusps whips will not curve in three dimensions as gracefully as they do in the sketches above, but will be a bit stiffer. Expect the cross section of future rusp whips to be narrow and high.

The next diversion into the archives will explain the relation between rusps and major Gruber, a creation of the late Moebius, a French grand master of bandes dessinées (comics).

14 comments:

j. w. bjerk said...

Your concerns about painting a Rusp in a dynamic pose could be met by curving their bodies in a "C" or "S" shape. That way you can show detail at either end also.

Petr said...

Wowie! New blogpost! =)

Spugpow said...

Finally, we delve into rusps! I've been eagerly awaiting this day.

I think the bicephalisation makes sense, since a rusp must have a much wider turning radius than a similarly-sized elephant or dinosaur: a rusp being attacked from behind would be forced to pitifully chase its own tail in pursuit of the predator. I wonder if this means that they're just as comfortable walking backwards as forwards? There are probably optimization issues with the legs, but it's an interesting idea.

I think making the whips into trusses is a smart idea. I wonder if there could be a flexible portion at the end with a bony weight attached, to act as a flail?

How diverse are the rusps? Are there smaller, arboreal rusps (by analogy with sloths, which were both giant browsers and arboreal leaf eaters), or pig-like rusps, or burrowing rusps even?

Evan Black said...

Great work, as usual!

I agree that, in general, rusps would likely be depicted with more passive behavior, majestically roaming the fields in what look like family groups. But I also think that the stream-bridging rusp shows quite a dynamic moment in the creature's life. It may not be much of a deal for animals that can slide down one side and climb up the other (like us) but, properly explained, human observers could certainly empathize with the strain this creature is experiencing at the captured moment. I think it would make an excellent painting.

One thing the talk of the rusps' whips made me think of was biological hydraulics. Perhaps, when not in use, the whips could be drained of supporting fluid and hang limply and partially retracted. A threat would prompt a rapid tumescence and the whips are ready to go. However, I wonder if the pressure needed to make the whips ready for defense would be too slow to properly react to a threat. A spider uses a kind of hydraulic system in its own locomotion, and spiders are usually quite nimble, but perhaps there's a scaling issue here, and at the size of the rusps this biological mechanism just won't cut it.

I can also see some relatively effortless diversification into different niches, such as what Spugpow suggested. Whips could be fashioned into a sort of digging probe for roots, or maybe even to burrow. At small scales, rusps could even potentially climb trees with offset batteries of clawed feet. Of course, there may be skeletal structures at work that may prevent rusps taking these niches. For example, we haven't seen anything demonstrating the flexibility of the rusp's body. How tightly could they turn? Could there be niches with a more flexible body, or all they all doomed to a wide turning radius?

Sigmund Nastrazzurro said...

j.w.bjerk: That is a good idea. Their ability to curve sideways is limited, but it should be enough to help show their bodies.

Petr: thank you.

Spugpow: 'bicephalisation' is a nice word. I'll use that if you do not mind. Mind you, the front and read end are not equal: only the front end has a mouth, and the posterior eyes, whip and brain are subservient to the frontal one. Rusps do not walk backwards with ease.
I haven't worked out what is on the end of the whips. For large rusps, a strong hide with perhaps a club should be enough, but I will keep barns on the smaller ones.
I hadn't thought about diversification in much detail yet. There are certainly rusps the size of pigs. I had not considered arboreal forms at all, but it is interesting to think what that would need; probably something looking a lot like Earth's millipedes.
The sauropod book I used had a chapter on how long necks enlarge the volume that can be reached for feeding, and that would make sense for a rusp as well, so the whips could act like an elephant's trunk, at least in some species.

Evan: do hydraulics work well at large sizes? I do not know, but now that you have put the idea in my head, it probably will stay there for a while (perhaps a post some day; biological hydraulics should be fun).
Having settled on an endoskeleton, the question arose how to do so. I first considered two chains of bones on each side connecting to the leg bones. But in order to get any lateral bending at all, these chains would have to be harmonica-like. The other solution is a central chain of bones (making it a vertebral column) from which bones project sideways to connect with the legs. Right now I feel like combining these ideas. Anyway, for a rusp to bend, the legs will come closer together on one end and separate on the other. With that in mind, do not expect rusps to be flexible enough to bite their own tails.

Petr said...

I have to confess, I've written that comment even before reading the post itself.
In an answer to your reply, if you are considering a club on the tentacles of some rusps, what about some spikes in a yet another species? I would imagine the hairs/quills could fuse to form horns or spikes.

On another note, I would definitely enjoy reading something about animal hydraulics!

Keep up the great work!

rodlox said...

Perhaps have some rusps coil or curl their whips against their backs/sides, and it whips away from the body only when needed to.
(might lead to "handedness" in rusps, granted)

Evan Black said...

In a sense, there is already a sense of chirality, or "handedness" to the rusps: as explained, the front neurology of the bicephalization has dominance over the rear.

The coiled whip sounds like an interesting idea too. Why not rest the limb on the body when not in use? I bet some species could even use combinations of methods discussed in this post and its comments. A flexible, curled up whip could tumesce in the face of danger and use the full advantage of reach and control that the hardened length provides.

Sigmund Nastrazzurro said...

Rodlox and Evan,

Intriguing ideas! There is also a possibility of folding a whip in zigzag fashion rather than curling it. There would need to a surface to rest it on though...
Sauropod tails could probably be kept in the air nearly passively, by the use of an elastic tendon at the top. With such a design, there would be a neutral position that requires no muscle activity to maintain. Of course, movements sideways and up and down deviations do require muscle activity. But even so, I like the idea of the whips being withdrawn in some fashion when not needed. I think that concept will be part of the 'future rusp'.
I think I will post an additional unplanned post on rusp skeletons this weekend.

Zerraspace said...

I realize that there are not yet answers to all these questions, nevertheless I would like to ask them on behalf of my brother (whom I mentioned earlier regarding this same topic), who seems to be regarding possible niches for these animals. Amongst other things, how strong are rusp tentacles (can they lift any weight or apply any pressure)? How flexible do you intend them to be (do they possess any dexterity or bending capability)? Are there are any species with boneless tentacles, more similar to those of cephalods than bone whips? Lastly, how is it that they breathe (spiracles, trachea, lungs - although I'm assuming the latter)?

He also asked if there were any tree-climbing rusps, feeling that smaller species with longer legs could benefit in this department from their number of limbs. I referred him to the grouillard, although its eye system and lack of anterior whip led me to doubt this classification. Is it indeed a rusp?

In an attempt to offer rather than just ask, could some species use boneless tentacles that simply inflate? If their only task is to whip predators and many depend on poison anyway, I do not see that they require any load-bearing ability. As for dealing with the matter of cephalization, could you potentially use an annelid-like organ system, where every body segment is practically a copy of the ones before internally and externally?

Zerraspace said...

I had already sent this but the comment disappeared shortly after posting it. With any luck, my inquires may now be received.

I realize that there are not yet answers to all these questions, nevertheless I would like to ask them on behalf of my brother (whom I mentioned earlier regarding this same topic), who seems to be regarding possible niches for these animals. Amongst other things, how strong are rusp tentacles (can they lift any weight or apply any pressure)? How flexible do you intend them to be (do they possess any dexterity or bending capability)? Are there are any species with boneless tentacles, more similar to those of cephalods than bone whips? Lastly, how is it that they breathe (spiracles, trachea, lungs - although I'm assuming the latter)?

He also asked if there were any tree-climbing rusps, feeling that smaller species with longer legs could benefit in this department from their number of limbs. I referred him to the grouillard, although its eye system and lack of anterior whip led me to doubt this classification. Is it indeed a rusp?

In an attempt to offer rather than just ask, could some species use boneless tentacles that simply inflate? If their only task is to whip predators and many depend on poison anyway, I do not see that they require any load-bearing ability. As for dealing with the matter of cephalization, could you potentially use an annelid-like organ system, where every body segment is practically a copy of the ones before internally and externally?

Sigmund Nastrazzurro said...

Zerraspace: Firstly, I do not understand why your first message disappeared; I did not delete it.

How rusp whips work was also discussed by others here. As I wish to have meagrusp, the whips need load-bearing capability. Note that the main load they need to carry is their own weight! Secondary loads are branches plucked from trees and bushes.
Tentacles (here defined as an appendage without bones, operating under muscle power only) would not work for large rusps. I do not think it would make much sense for small rusps to have a completely different structure in their whips then for large rusps, so they all have a skeleton in the whips. All whips are flexible, but for large rusps whips are more flexible laterally than upwards of downwards; small rusps have much more leeway.

- Rusps have lungs; the grouillard is not a rusp.

- As for inflatable tentacles, that resembles Evan's idea of hydraulic whip movement. For the reason I explained above rusp whips do not work that way, but it is a big world, and I like the idea, so...

Zerraspace said...

It appears that I'm somehow deleting my own comments when I look over them and I apologize for cluttering the blog. I had just wanted to communicate my brother's response; it appears he had quite a brainstorm after your reply. If I may repeat his message:

"You mentioned the idea of tree climbing rusps. A creature with 24 limbs would be an excellent tree climber. I had considered rusps with specialized limbs, using elongated ones for locomotion through the trees, and shorter ones for gripping, allowing them to hang upside down from braches or to easily grip onto vertical surfaces, like tree trunks or sharp rock faces. I think smaller Rusps with slightly longer legs would do well on mountains.

One of my questions wasn’t how rusps breathe, but from where! [I apologize on his behalf... ]

I had a few ideas for swimming rusps. They could do this in many ways, including:
• Swimming in a manner similar to a shrimp, by beating rows and rows of legs to swim.
• They could undulate (unlikely)
• One of their whips developed into a tail that can beat up and down to swim.

I had a question about how strong rusp whips here, and about how flexible. I had an idea for a fishing rusp, which would use long whips to strike fish, poisoning them, and allowing them to drag the fish back onto land and into the rusp’s mouth. Also, if the tentacles were strong enough, they could assist a tree climbing rusp, similar to a monkey’s tail.

Thus, I suggest many different rusps. Perhaps in arctic areas, giant, seal rusps that walk across the ice, burrow through to swim, and survive by eating fish and other oceanic creatures. Because of many limbs with padded feet, rusps would be stable on ice, and giant ice rusps could exist. Perhaps there could be “Raccoon” rusps, which are omnivorous, and can look anywhere for food, by climbing, fishing, swimming, and digging. There could be “Monkey” rusps, or “Gorilla” rusps, which care gentle, tree climbing giants. There could be “Otter” rusps, which swim for food.

This is all for now! I hope these are acceptable!"

If this annoys you, I will attempt to condense any future responses before referencing. I thank you for your time (and I think he does too).

Sigmund Nastrazzurro said...

Zerraspace: The idea of rusps in various environments is growing on me. I had not though much about that as I needed to work out some biomechanical odds and ends first, but I think most of those are solved now (see a post later today...).

The respiratory inlet and outlet openings are at the front of the animal.

As for swimming, I suppose the easiest way for a rusp to do so is to use a walking movement under water (that works for large mammals too).

The whips are strong enough to topple or hurt a predator, and to grab branches. They are also strong enough to support your idea. In fact, I once drew something that did that; in hindsight it was nearly a rusp...

As I said, I am warming to the idea of rusps everywhere. The larger ones are herbivorous but will eat carcasses now and then. I suppose that could evolve into omnivory.