Freshwater Grumbletoads

While Apterra's freshwater ecosystems are dominated by the giants and specialists of the Ailoxichthyid family, grumbletoads are the small, inconspicuous generalists of lakes and rivers everywhere. Though they don't attain massive sizes or inhabit the harshest environments on the planet, they are the backbone of aquatic food chains. They help bring nutrients into the waterways through unlikely food sources, serve as meals for larger species, and experiment with odd body plans to escape competition with their normal-looking neighbors. 

The freshwater grumbletoads belong to the tribe Bufognathini, all descending from the Late Muricene Bufognathus. The species B. abeliensis (the estuarine grumbletoad) is the ancestor of modern forms like the Wormeater Grumbletoad (Vermiphagichthys). This is a voracious predator of gillywogs, tailtube worms, and the larvae of non-neotenic mosquitoes. It is especially fond of the protein-rich, slow-moving gillywogs, of which it eats hundreds per day. This is vital to insect diversity, as the Semperinfantids would quickly outnumber all other mosquitoes if their population wasn't kept in check. By reducing their numbers, the wormeaters ensure many different species can coexist.

Flyeater Grumbletoads (Culiciphagichthys) are the sister genus to the wormeaters. They are smaller than their cousins, at around 7-10 centimeters long, and feed on adult flying insects that get too close to the water. Female mosquitoes in the process of spawning are particularly vulnerable, as they must repeatedly approach the surface to lay their eggs. With dark brown scales on their backs, flyeaters blend in with the dark lakewater below, allowing them to get close to the fly undetected. When it swoops down to deposit an egg, the fish strikes, swallowing both the mother and her unborn offspring.

The Carrion Grumbletoad (Putrivorichthys) is the most basal of the estuarine clade, and it continues to lurk at the mouths of major rivers. Too slow to chase moving prey, it awaits the arrival of land animal carcasses from upstream. Though often already rotting and half-eaten by other scavengers, the tough stomach acid of the carrion-eaters allows them to extract whatever nutrition remains. Though they rely on chance to bring them a meal, certain areas sometimes provide a more regular food source. Those that live in the delta of the Founding Plains River will see the arrival of thousands of Muridiungulate corpses at the beginning and end of the dry season, as the grazers' migration leads them to cross the river twice a year in search of food. Those that fail to survive the crossing but aren't eaten by jaguarfish or stoutlings inevitably end up here, providing a feast for the local grumbletoads. 

The Snapping Grumbletoad lineage is characterized by a strong bite force, an affinity for shallow water, and a proportionally massive mouth and stomach capacity (even by grumblefish standards). The Grumblegrabber (Cervichirus) is a shining example of this strategy, feeding on animals its own size or larger. Its pelvic fins are directly on the underside of its body and fan outward in semicircular discs, allowing it to form a seal against surfaces. Unlike algae-eaters like the sucker eel, though, this genus uses its suction cup to hold onto prey, attaching to its belly or side before biting down with over fifty needle-like teeth. Death usually occurs by blood loss, after which the lifeless body is carefully maneuvered into the grumblegrabber's wide mouth and swallowed whole.

The Grumbullfrog (Bufops) is another snapper that waits at the water's edge. Like the original snapping grumbletoads, it ambushes smaller creatures drawn in by its insect-shaped lure. With the rise of other lake-dwelling predators, it's had to shift its diet away from fish and towards small terrestrial vertebrates. It sits in the mud, often for days at a time, with only its eyes above the waterline. Its pelvic and pectoral fins both have a fleshy, muscular base that allows them to jump vertically from a resting position, pouncing on any bird or mammal that gets too close. Its teeth are small and backward-pointing, and they serve only to help push the struggling animal down its throat. The prey dies a few minutes later from drowning in the grumbullfrog's stomach acid.

Not all members of the snapping lineage are carnivores; some use their strong bites to consume tough plant matter instead. The Seedeater Grumbletoad (Granivorichthys) eats nothing but large seeds and nuts, cracking them open with two pairs of chisel-like teeth. This high-protein food source lets them reach sexual maturity at 15cm long in just two months. In turn, their high rate of reproduction makes them an ever-available source of food for other fish, supporting grumblegrabbers, stoutling-morph jaguarfish, and many others year-round. 

The smallest of all grumblefish is the Glimmering Grumbleminnow (Monsamnichthys variatus). This is the only member of its genus, living in predator-free streams and pools on the slopes of Tepui Mons, with their numbers highest on the collapsed side. At just two centimeters in length, it's one of the only fish in its habitat, eating anything that can fit in its mouth. Its iridescent scales come in nearly every color, a trait found in both males and females. Only males possess a lure, which is no longer used to attract prey, but instead has become a display feature. Lures may be half the length of the male's body, and those with longer lures generally attract more females.