Not too long ago, I made a wishful post, wherein Chapel leads Vash through an abandoned SEEDS ship that is embedded into the earth. While walking, he makes mention of a discover he and Conrad have made while exploring.
"December was no different. However, if you’ve learned anything from the settlements that eventually dug their own wells, this planet has a subterranean water supply. This area is firm enough to build upon safely, but underneath, the underground caverns below were large enough that when this ship crashed, instead of crumpling against the ground, it smashed clear through into the system of caverns. The ship, amazingly, has remained watertight this entire time—a testament to its construction. And curiously, if you go down to the lower levels and look out and turn on the floor lights, you can actually see sandworms In the water. They swim. Who knew?"
Sandworms are a large, intelligent, telepathically communicating species in Trigun, located on the planet Gunsmoke. But what do they do? What do they eat? Namely, atop all of this, WHAT THE FUCK IS GOING ON?
No, seriously—as far as species go, you have the telepathic sandworms, the hive-minded insects, and those Tomas/Thomas jumbo kiwi birds that trot around. Thanks to Knives, you also have humans and Plants of the Bulb and Independent varieties.
But sandworms are HUGE. All the rest of the species are fairly small. And the Thomas kiwis are the next largest creatures on that planet, and they’re not going to make a very hearty meal for a predator that size. And considering their intelligence, if they wanted to, the sandworms could hunt humans, surrounding their cities and destroying all lines of travel. When people tried to leave, they could attack.
Except they don’t. They do attack, but it’s not organized. Their attacks on humans aren’t examples of hunting. These things are eating something and it’s not topside.
While intelligent, their eyes are small, so they probably rely on things like hearing to locate prey. If someone goes tromping around on the dunes, any attack that occurs is most likely MUCH like a shark attack on a human—a case of mistaken identity.
Citing my examples from the anime, because I’m still missing chunks of the manga, in one of the final episodes, we see Milly helping in the digging of a well. This is important because it establishes that there is naturally occurring water on Gunsmoke—it’s just underground.
As well, in an episode previous to that, you have the little shit and his poor trafficked dancing-girl girlfriend who want to run away together from the caravan they live with and be free. Unfortunately, the caravan is stuck outside a geyser field, trapping everyone for the time being.
—STOP THERE, FORGET THE LOVEBIRDS. PAY ATTENTION TO THE GEYSERS.
Check what the fuck wikipedia says:
Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma. Generally, surface water works its way down to an average depth of around 2,000 metres (6,600 ft) where it contacts hot rocks. The resultant boiling of the pressurized water results in the geyser effect of hot water and steam spraying out of the geyser’s surface vent (a hydrothermal explosion).
Ergo, we’re talking some deep, deep water, here. Deep enough that you can build on the surfaces over top them. And with volcanic activity and a mass of water, subterranean or not, that means somewhere down there, you’re going to get hydrothermal vents!
And a HUGE amount of life just FLOURISHES around those things! Have you ever researched black smokers? Do it, bitch.
But with volcanic activity on the planet and the chance for vents like that to occur in the subterranean seas, you have a very good start of an explanation on why a planetary ecosystem that seems so limited from the surface can actually support such huge creatures.
The answer is that Gunsmoke actually has a mind-blowingly large biosphere, just the mass of it is underground. The vents feed the smaller organisms, who feed bigger ones, who feed bigger ones, who feed the sandworms!
And even the term ‘sandworm’ would be a misnomer!
Look at this shit!:
See the nubbly little legs on it’s underside? Those are built for crawling and pushing through sand and grit while burrowing. However, look at that flappy shit closer to its head. Nothing there lends indication that they’d be useful while burrowing. You’re looking at FINS.
Heck, look at the SHAPE of the body. Like any eel or serpent/snake, it’s built for swimming, possibly in the to-fro style you see in sea snakes. As well, having small eyes works not only for an in-ground creature, but one that lives in near complete darkness in deep water. With a thick-plated body, it can withstand high pressures underwater.
This is a creature suited for both aquatic and terrestrial life.