Here’s an entertaining post about arthropods: Romanian cave sealed for 5.5 million years is full of strange creatures.
Why, yes, I bet it is. This is not the best article ever — I would have liked a much more complete survey of what kinds of critters were found in the cave and how they function metabolically — but we do get an idea of just how peculiar this little ecosystem is. I mean, it’s about as different from the normal ecosystem as deep sea vents.
The ecosystem relies entirely upon chemosynthetic bacteria that extract carbon from the air without the aid of light. The most numerous bacteria use carbon dioxide, and others get their carbon from methane. The bacterial film on the water and walls is where all the nutrients enter this ecosystem, and it’s the only known example of such a system. Small animals eat the slime, and larger animals eat them.
The atmosphere is poisonous, with only half the normal concentration of oxygen and very high levels of carbon dioxide and hydrogen sulfide. And of course because this was a completely sealed-off cave and is still basically sealed off, everything is blind and operates by touch (and, I would guess, probably scent).
Well, if you’re going to develop a lot of weirdness in a short time, arthropods will do it for you. I’m sure when the cave first got sealed off, die-off was considerable. But plenty of starting diversity, short generation times and tagmetization lead to a great ability for the species in a community of arthropods to evolve in weird directions quickly.