Friday, 5 May 2017

Kwals 2: from universal back to local

Since the last post I have busily worked on some two-page spreads, one of which shows an advanced kwal. Each spread probably takes about 25 hours of work: there is an animal to design, one 6000 x 4200 painting to do, text to write, a silhouette to design and paint, a map to be made, and often an additional illustration to do. If I ever produce a book again, I will write it as normal people do, not paint it...

Anyway, designing the kwals proved less than easy. In the previous post I designed kwals with central valves to let in water on the upstroke, but when I sat down to design species built on that concept, I was became less and less satisfied with it. It seemed biologically possible, possibly plausible, but not painterly pleasant. So here is what happened next.

Click to enlarge; copyright Gert van Dijk

This is a quick sketch of a 'gatkwal'. It is still very much like Earth's jellyfish, with its single bell at the top of the body, with tentacles dangling below it, in part from the edge of the bell, and in part from the central body below the bell. The major departure here is the hole in the bell, meant to let water stream through on the upstroke. Obviously, the water has to stream right through, meaning the body must not block the hole. So there are spokes connecting the bell to the body underneath. Of course, this comes about embryologically as a hollow cylinder with secondary fenestrations in its sides. Same thing, really. Here there are six spokes, meaning that the gatkwal has six-sided symmetry, representing a doubling compared to the prototypical three-sided radial kwal design (we'll get to that).
   When the bell contracts, it sends down a rotating torus of water, as happens with Earth's jellyfish (see the previous post).

Click to enlarge; copyright Gert van Dijk
While I was thinking about the three radial 'pie slices' that make up a kwal, I started pulling on the edges of the bell, which then together no longer formed a nice circular edge, but a three-lobed shape. Take that idea and separate the lobes more and more until they are fully separate. We now have a kwal with three bells instead of one. The first stages of these trikwals are not shown here, but the finished painting is about one such, the 'tribune' ('Tribunus vacans'). The musculature of the bells had to evolve: rather than only having circular muscles to squeeze the bell together, there is now a more complex arrangement to control movement in the 'longitudinal radial' as well as 'transverse radial' directions. And those in turn necessitated rods of less compressible material (the 'chordae') embedded in the jelly to give the muscles something to work against. With all these changes, kwals became less like jellyfish with every step. This is ironic, as they started as supposedly 'universal' shapes. By now that are probably quite specifically Furahan. Just as well, I guess.
  Anyway, here is the 'klapkwal', in which the three bells have evolved some more: each bell has two halves that fold together as they are lifted up, but open as they are driven down. It is here shown during an upstroke. It looks a bit like a plant, but that is because the context is missing: you have to imagine it drifting through the ocean.

Click to enlarge; copyright Gert van Dijk
Here is another advanced kwal, which is as yet nameless. Its bells have evolved to beat slowly through the water. In this case they are supple on the upstroke but less so on the downstroke, which is shown here. Mind you, this is probably as far as the design can go: it is tempting to speculate how far kwal evolution can move towards quicker or more efficient propulsion. The problem is that the rest of the design may not allow this. The biggest obstacle is probably the way kwals feed, which is by dangling tentacles in the water and waiting until something edible blunders into them. The elaborate tentacles offer considerable resistance to movement. This is not a real problem at low speeds, but does form a major hindrance at high speeds. To move quickly, kwals would have to acquire a different feeding mechanism. The conversion would have to happen in small steps, as this is how evolution works: it is like rebuilding your house a bit at a time, while you keep living in it. But designing a whole new feeding mechanism is more like tearing down the house before you can rebuild another one. Unfortunately, that leaves you with nowhere to live.
  So these 'rowing bells' may be the most advanced feature kwals will ever possess. Still, give them another 100 million years or so, and let’s see what happens.    


Anonymous said...

Absolutely amazing work! Perhaps the kwals could retract their tentacles when they are not feeding? Alternatively, they could release a cloud of toxin similar to squid ink to increase their area of effect. This would require a more developed sensory input since this would be an active hunting method compared to passively swimming and waiting for something to hit your tentacles, but even Eart jellyfish have developed rudimentary eyesight to detect UV light.

Can't wait until the next installment!

Sigmund Nastrazzurro said...

Anonymous: I very much like the idea of toxin secreted in the water. There might be a disadvantage in secreting a possibly expensive substance (metabolically, that is) without certain success when sticking and stinging cells provide a very precise response. But I can see a local release of toxins if a prey is struggling, and an overall release if the kwal itsel is in danger. I think I will put that in the kwal body plan. Thank you!

Keavan Ѳ said...

Though the tentacles of jellyfish do create a fair amount of drag, cephalopods too have tentacles, and squid seem to be able to swim quite quickly in spite of that. Admittedly, yes, cephalopod tentacles work differently​, but a gradual evolutionary switch from many sticky, dangling tentacles, to a few muscular, grabbing tentacles doesn't sound so far-fetched to me.

Anonymous said...

so much excellent ideas in text and picture. kudos to you.

the Klapkwal leaves act like fins, makes sense. the spiralling "roots" remind me of some aquatic carnivorous plants here on Earth.

I imagine some of the Klapkwal's relatives might enlarge the leaves while reducing the stems, letting themselves be propelled by the water currents. others might try to bury their leaves under the sand, leaving only the roots and a bit of the body exposed.

keep up the great work.


Sigmund Nastrazzurro said...

Keavan: As it is, the kwal tentacle system is like the jellyfish one; there are fleshy tentacles ('oral arms') hanging under the body, but also lots of thin ones, that in jellyfish hang from the bell but in kwals project sideways from the body lobes. but you are right; by concentrating on the 'oral arms' it should be possible to do away with the other tentacles, and that would reduce drag. That would indeed make it possible for kwals to develop quicker forms. And then better eyes, brains, etc... Hmmm.

Rodlox: thank you. The fact that I have not shown much work in the past few years does not mean I have not kept on working. Any time I spend on blogging detracts from the time I can spend on The Book. However, every now and again I feel the need to write a blog, though (just have a look at the new post on rings). Thank you for these ideas. Kwals will probably take two two-page spreads: one to introduce the group, one to depct one species. But with all these ideas, perhaps I should give them another two pages...