Glassbelly
Glassbellies are tiny, squishy, bottom-of-the-food chain omnivores. With their lack of defenses, they survive much as mice do: through camouflage, skittishness, nocturnality, fast maturation and prolific breeding. They also have the neat trick of fleeing into water to escape land-bound predators. They are often found along streams and ponds at night, hidden in the undergrowth, flickering like fireflies in the evening.
Physiology
Compared to its ancestor, its skin is thicker and more strongly pigmented, especially on its back. Although this increases its ability to withstand UV light, it is still more susceptible to sunburn and drying out than most land organisms. This, along with its breathing system working best in moist air, restricts it to the darker, cooler hours of the evening, night, and early morning.
Like a frog, a Glassbelly breathes through both its skin and the lining of its mouth. Like certain river turtles, it can also breathe through its other end: the four sphincter-equipped vents on its backside. Although both of its breathing methods are passive, its small size, simplicity, high-oxygen environment, and relatively slow movement means that is no problem. While its back end and tail contain a system of thirty sacs that exchange air and water, this is used only for movement and water regulation, not breathing.
Its eyes are not much bigger, but are slightly more sophisticated. The ribbed walls of its stomach are more muscular, and feature little strontium-reinforced bumps. Although it can grind up its food somewhat, it can only digest highly digestible, small items.
Relative to their ancestor, Glassbellies have longer, more well-defined legs. A Glassbelly’s legs are largely hydraulic, with little actual muscle. The little muscle it has is concentrated in the bases of the legs. Its arrangement of limbs makes it highly maneuverable: it can even move well if flipped upside-down. It can climb weak slopes and large flora, if the bark is rough enough and the slope is gentle. (e.g., fallen logs) Glassbelly feet, tipped with strontium-reinforced claws, feature sucker-like pads that help it walk and climb.
It lopes along in a gait somewhere between a frog and a gecko, dragging its tentacle-like tail. When chased, it speeds up into an awkward hop-like gait. While its movement is slow and awkward compared to other organisms of its environment, it’s faster than its ancestor. As its back legs are held out in a more horizontal, lizard-like way than its front legs, it makes a unique track pattern on mud. Most of its limbs are identical in structure, though its upper and lower front legs are largely used for digging.
Its water-dwelling larvae (0.6 mm at birth) take on blobby, superficially Carpotesta Luceremundare-esque forms, but lack lights. The larvae grow fast, eating tiny microbes and detritus, as well as aquatic Scale Knightworm larvae when they are big enough. They metamorphose in the water, approximating its lineage’s course of evolution from simple aquatic filter-feeders to amphibious, eight-legged organisms. At roughly 2 cm, they become amphibious, short-legged, shorter-tailed versions of the adult forms, and transition to the adult diet.
Behavior
It's pretty dim: most of its behavior is reflexive. Nonetheless, it has a denser nerve net than its ancestor, which is very close to the outer tissue of its stomach. Smelling predators makes them flee someplace dark and enclosed.
If mature, healthy and in the breeding season, if it sniffs certain Nitroadora/Continentadora chemicals from a puddle, it will use its dangling forelimb to dig into and expand the puddle. Then, it will flash its lights in a certain slow sequence. This invites other Glassbellies to go to the puddle and breed. It largely reproduces sexually now. Strangely, this is predicated on physiological stresses: captive Glassbellies who live predator-free with all the food they need reproduce only asexually. Conversely, injured, diseased, or cold-stressed Glassbellies always reproduce sexually.
While unable to “sleep” in the typical sense, as it lacks a true brain, the Glassbelly enters a dormant state during the daytime. It rests in little scrapes underneath dense flora or burrows made by other fauna and contracts its mouth, reducing oxygen absorption but also reducing water loss.
Glassbellies prosper in the South Glicker Monsoon Forest during the wet season, but their ability to breed is often greatly lowered in the dry season. They also find it more difficult to hide in scrapes under flora, if they can’t find the burrows of other fauna. Although their numbers drop with each dry season, the Monsoon Forest keeps getting re-colonized by more Glassbellies from the neighboring biome.