Glerrings

Glerrings (Lumenichthyidae) are a family of bioluminescent livebearers found across all of Apterra's oceans. The basal glerring condition is that of a small, shoaling sea-minnow that can be found by day in the mesopelagic zone and by night much closer to the surface, relying on its light-emitting organs to confuse and distract predators. Some modern genera live a lifestyle only slightly changed from that of their ancestors. One such example is the Gaslight Fish (Retrolumenichthys), a cosmopolitan group that, at first glance, seems like nothing more than a slightly larger version of the first glerrings. However, this genus has one unique feature that sets it apart from the rest of its family. When threatened, the fish flashes its lights in a wave pattern that travels from its snout to the tip of its tail. With luck, this diversion can trick visual predators into doubling back, chasing a phantom fish that appears to be traveling in the opposite direction from the glerring. 

More derived glerrings have conquered the deep sea over the past four million years, radiating into a variety of shapes and strategies. The loss of some or all of the body scales is a common trait among non-shoaling Lumenichthyids, as many have independently adopted a flexible, eel-like body. This category includes species like the Glowgulper (Lumenochasma elongatus), a deep-sea predator that hunts with an extended lure made out of the first dorsal fin ray. This ray, tipped with a light-producing nodule, arcs over the face and hangs in front of the mouth at rest, luring in other animals up to twice its own size. Its folded, leathery belly distends greatly, and its exceptionally powerful stomach acid neutralizes the glowgulper's prey before it can struggle enough to deal serious damage from within. The fish then retreats to a rocky hiding place on the seabed where it can wedge itself and wait until its meal has digested.

The largest of the glerrings, measuring up to a meter long, is the Laser Eel (Lumenops patiens), an abyssopelagic generalist whose prey ranges from Pelagarthrid isopods to large tailtube worms to other fish. It stuns its target using the densely-packed light organs that cover its face, then grabs hold of the smaller animal before it can get its bearings. When performed correctly, this maneuver has a success rate of over 90%, but in order to accomplish it, the eel first has to sneak up on its prey. This is no easy task, as many sea creatures have electroreceptors that can sense the large fish as it approaches through open water. The laser eel must therefore approach slowly, propelling itself with undulations of the dorsal and anal fins but keeping its body stiff and immobile. This greatly reduces the eel's electrical signal, making it appear like a much smaller fish. A patch of dim light-producing tissue on its caudal peduncle adds to the illusion, keeping the victim's attention while the head begins to snake closer. In a quarter of a second, it's all over; the laser eel's head lights up with an intensity sharp enough to utterly disorient its meal, which soon thereafter finds itself vacuumed into the giant glerring's needle-studded jaws. Here it is held securely while the eel thrashes its head in every direction, reducing the unfortunate creature to a mess of chum and broken pieces of shell or bone.