Ailox Lake Mosquitofish

Situated in the middle of the long, winding land-bridge that connects the continents of Ailuropia and Loxodia, a great lake rolls with waves reaching almost four meters during a thunderstorm that's been battering the shores all day. It is over 65,000 km2 in area, comparable to Earth's Lake Victoria. It lies in the middle of a massive belt of pseudoforest that stretches thousands of kilometers in either direction, forming a continuous temperate zone across the northern continents. Ailox lake, like all of Apterra's freshwater ecosystems, is a refuge from the deadly red tide. That's not to say any of its inhabitants have ever seen the sea; their ancestors never adapted to become salt-tolerant, finding the pristine fresh waters of the lake a more suitable home.

The largest fish here, and one of the largest on Apterra as a whole, is Gambusia cultridens, a sharp-toothed hunter with an appetite for other mosquitofish. It patrols the deeper parts of the lake, which may reach 100 meters in depth. It generally attacks from below and exhibits a drab counter-shaded pattern, with a white belly and dark silvery-gray dorsal regions. As the apex predator of this habitat, it faces no outside threats whatsoever, but intraspecific fighting is ferocious. Without flashy patterns, the only way males can prove their fitness is through battle. In some smaller cousins of this species, these are purely display fights, but these livebearers take things up a notch, nipping at one another's fins, tearing off the scales of their opponent, and occasionally even killing each other. The 30-centimeter fish has a trout-like shape, cutting through the water with speeds unmatched by other carnivores.

Scavengers also have a significant presence here. Serving a similar role as (though not closely related to) G. bradymelanocisor, the Mud-Mosquitofish (G. sublacustris) sifts through the silt and plant debris on the lake bottom, gulping down anything large enough to be worth its time. Any stirred-up organic debris too small for the twelve-centimeter livebearer to eat is thus made available to invertebrate filter-feeders such as copepods and certain specialized mosquito larvae. This species, known as Ae. polymensinfans, is one of the scattered remnants of Aedes semelparosus. In fact, while all the other descendants of the short-lived culicids are on the decline and sure to die out over the next handful of centuries, this population is thriving. They live similarly to their ancestors, with further adaptations that promote a long larva stage, with some remaining in their immature form for up to four months. By building up their reserves of food, adult males can live to reproduce several times, though they still exhaust themselves to death in the process. 

These and various other larval mosquitoes form the basis of many species' diets. Some have evolved to become more efficient swimmers, resulting in an arms race that produced Gambusia salionatus, a small insectivore that hunts with intense bursts of speed, catching any inattentive larvae before they have a chance to react. The young of other mosquitoes have responded to predation pressure by burrowing into the soil; not only do mud-mosquitofish occasionally snack on them, but G. lutophagus specializes in seeking out the buried bugs.

Not all the inhabitants of this lake are meat-eaters, though. Algivores swarm the shoreline, as green algae grows in abundance throughout the shallows. One species, Gambusia herbicisor, even goes out of its way to find rotting grass, as none of its congenerics have the hardware to break it down. This species has a mouth full of small, rasping teeth, perfect for shredding away at the stalks and blades that are bound to wash into the lake during the ongoing storm. This is a meager living, for theirs is not a diet rich in calories. Its reduced size - in most individuals, less than 1.5 centimeters - allows it to subsist on this food source, but results in higher levels of predation, especially for fry. They have an innovative solution to this issue, though: after giving birth, females hold their clutch of 5-10 young in their mouth cavity for up to a week, ensuring they remain safe as long as she does.