Fanggob
Unlike its filter-feeding ancestor, the Fanggob is a carnivore. It lures in prey with flashing lights and a fishy odor. (caused by trimethylamine) When its prey enters its mouth, it quickly seals up the entrance with its “teeth”, contracts its outflow vents to prevent escape, and starts secreting digestive fluids. If it smells (or “tastes”) prey is above it, but the prey hasn’t entered within several seconds, it will suddenly burst up with jets of water to capture small prey just above it, locking it inside in one motion. Although it is usually still as a statue, once it has captured prey, it quietly swims up like a balloon, avoiding predators that roam the slope.
The fangs of its mouth are not sharp: these are simply stiff, modified lip structures. While its ancestor’s lips were entirely outside epithelium, the Fanggob’s fangs are made of both outside and digestive epithelium. The fangs close up its mouth as it contracts its lips. The “fangs” in its stomach are not made of the same material, though they are analogous structures.
The downwards-pointing “fangs” within its stomach make it hard for climbing organisms to climb out, and despite being translucent, its red body and stomach make it hard to see in the twilight zone. Its stomach is made of tougher material than most of its relatives, what with swallowing live, intact prey. Its four reproductive chickpea-shaped glands are farther away from the bottom of its stomach, to avoid injury from struggling prey. The glands are normally encased with two layers of somewhat leathery epithelium that further protects them, and they exist within a vestigial stage until it has a big meal.
Its eyes have keener vision than their small size would suggest. While it has poor image resolution, it is sensitive to light and can detect yellow, red, blue, and green.
The larvae start out as small, globe-shaped filter-feeders, similar to Carpotesta luceremundare, which feed by a simple, ribbed, sticky membrane. The membrane becomes a pocket, and then an outright stomach. For a while, its tooth-lips are just a ring of useless prickles.
Juvenile Arsnoots sometimes wander inside, tempted by the odor, only to be captured. Their mothers often rip open the Fanggob in time to rescue their young, and occasionally devour the Fanggob too.