Tuesday, 20 October 2009

More on spidrids and tripods

I have been playing with my Matlab octapod program a bit more. The program proved to have a bug (sorry about that pun, but it seemed inescapable). I eradicated it...

First, here's one for Anonymous. It is a tripod walker with two legs moving in phase and one acting on its own. In this case, the leg moving on its own is the front one rather than a hind one. Please note that the hind legs do not just move in a pure front-to-aft direction, but swing in a circle. That's a result of their radial design. At any rate the body should swing to kep the centre of gravity balanced over the legs, but that hasn't been programmed in yet.

And just for fun a leggy spidrid. NOT a spider! A SPIDRID!


Simon said...

Hi there.
I've been a big fan of your project for a while now - especially some of your musing on radial symmetry and tetropters. I've been playing around with radial symmetry in alien critters now, and I've got kind of an odd question for you. How do the spidrids defecate? You can't really do the top of the head anus like a starfish. Does the mouth do all the work, like in jellyfish?
Check out this sketch. Here's the ideas I've been playing with.


Sigmund Nastrazzurro said...

Hi Simon,

I like your sketches. Drawing animals with radial symmetry takes some getting used to, doesn't it? Your sketches work quite well in getting the idea across that this is simply the way these beings are built.

As for defaecation; hm, well, yes, your question calls for some on the spot thinking. The idea of a combined mouth/ anus might work and need not necessarily lead to infections. After all, rabbits eat their own faeces, don't they. But still, I prefer having the two ends of the digestive tract separate. This might force some bilateralism into the design, or else there should be multiple mouths and/or multiple anuses.

j. w. bjerk said...

At least with earth-life, it seems that having more than one kind of symmetry in a creature is common.

Vertebrates are bilateral on the outside, but inside (i believe) they are usually not strictly bilateral. Snakes for instance usually have one lung shrunk to nearly vestigial size.

Echinoderms at an early stage of development are bilaterally symmetrical.

I could be wrong, but it seems like only the simplest earth organisms (jellyfish, worms, etc) don't cheat at least little on their primary pattern of symmetry.

Furaha wouldn't necessarily be the same, but i think you have plenty of justification if you broke the pattern of symmetry a little.