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.
Fascinating!! I never really thought of a fish's swim bladders as being equivalent to an atmospheric beast's balloon. This makes me wonder- is there any plausible evolutionary path that might cause an aquatic animal to eventually take to the air, or is the gap between fluid and gas just too big? What other way might a ballooning creature develop?
ReplyDeleteHalf a balloon isn't useful, or even a smaller one in a light atmosphere like Earth's- unlike say, an eye. A more primitive eye might only be able to detect light and dark, but it is useful- and successive generations of organisms develop still more complex and useful eyes to gain still more of an advantage. But you can't imagine a ballont starting out with a smaller, less capable balloon- it needs a full fledged one from the outset just to float in an a terrestrial style atmosphere. Could this be why we don't see any real life ballonts on Earth? Or is there a plausible line of evolution for these beasties, which simply hasn't happened on Earth by chance?
Hello Christopher,
ReplyDeleteA new comment on an old post... Now I get a message for every comment that is posted, but do you too? If not, I am answering this for nothing. Anyway, your thoughts came up in later posts and discussions, to the effect that it would be very difficult to have small ballonts. This raises problems for raising young, but those can be solved. How to get ballont evolution going is still problematic though.
No- I don't get a message when you reply to my comments, but I check back here occasionally. So you didn't answer for nothing. (:
ReplyDeleteI read about the difficulty with ballont breeding, but it seems pretty solvable. The ballonts may have a sessile life stage in which "medusas" bud off after growing large enough. Dougal Dixen's Sulfuria ballonts bud off small ones when the young have grown large enough to fly- this approach could work, too. The key is that the baby ballonts need a little time to grow large enough to fly before they and the parent go their separate ways. I will look into the life cycles of jellyfish etc.- they have a sessile life stage, if I recall correctly.
The ballont evolution problems seem somewhat less tractable. My biggest concern is the big gap between the swim bladder and any sort of balloon that can fly in a light atmosphere- it makes a jump from water to air seem quite unlikely, or at least more unlikely than the jump from water to land. After all, many organisms float in water, from fish to kelp, but we haven't seen any atmospheric beasts or balloon plants evolve on Earth.
As I asked before, a primitive eye that can only detect light and dark is useful, but a balloon to small to float in an atmosphere is not- so how do these beasties jump from, say, a sea jelly to a hydrogen exhaling flying beastie? A convincing answer to this question would make a great detail in a SF 'verse!!
I'd imagine a ballont might start out with an inflatable pouch for the purposes of intimidation or sexual selection, and with escalation these pouches would grow larger and more dramatic, with an additional coincidence of the material being something lighter than the atmosphere. :o Sexual selection is a fairly easy cop out for difficult situations like this.
ReplyDelete*yes I am going through your old posts, sorry if you already solved this later on*
Heh! After seeing Ymedron's comment I might as well ad my own, naturally with the same disclaimer.One way for life to develop with the ballont strategy would be if it developed its very multicellularism in atmosphere. I don't know how exactly that should work out, but there are plenty of bacteria and other life forms living in Earth's upper atmosphere. It would have make a little sense for them to gather together as other life has; and even in the smallest clusters, they probably immediately need to worry about staying lighter than air. So they could begin trapping hydrogen on a very small scale, and eventually create full-fledged multicellular ballonts.
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