Darwinian Crestgills
Darwinian Crestgills split from their ancestor and diversified into a burrowing worm-like niche throughout Darwin, coexisting with the more terrestrial Shed Knightworms. They depend on water to respire, and thus they live underground where they are constantly moist much like Terran earthworms. Similar to a Terran earthworm, they emerge from the ground during rain, but also like a Terran earthworm they do not do this to avoid drowning, contrary to popular belief. Instead, when they emerge above ground in the rain, it is because it is much easier to flop about on the wet surface than to dig through mud. In addition to consuming detritus, they will also opportunistically prey on juvenile Knightworms which have become stranded in their burrows after rain.
Darwinian Crestgills have developed an “upper lip”, a section of skin which causes them to look like they have jaws. In reality, it is only tough skin used to dig; its effect of covering the mouth serves as protection, and it easily bends out of the way when the mouth is inverted to feed.
Darwinian Crestgills range in color through varying shades of brown, and have brightly colored mouths and undersides of variable color. Their undersides are also highly reflective, catching even small amounts of light for maximum effect. When attacked, they invert their mouths and start flipping and squirming about, their bright colors catching the light and potentially startling the predator long enough for them to escape. This color is usually bright yellow, green, or blue, but in dry regions where wildfires occur they may also come in fiery patterns. Being small creatures, they evolve fast and speciate readily, so there are far too many species to list beyond general trends; polar and temperate species hibernate over winter, and those in dry regions are found more commonly among roots and decaying flora where there is more moisture.