23. The Mariana Trench is home to a surprisingly large variety of life forms. Among these is a horrifyingly ugly fish that dangles a bioluminescent fleshy bulb in front of its head to lure prey. What fish is this?
From Quiz Diving Deep - The Secrets of the Mariana Trench
Answer:
Anglerfish
The bioluminescence is a result of a symbiotic relationship with some of the deep-sea bacteria. One of the most incredible things about this fish is that it can survive over one hundred megapascals (~14,500 PSI) of pressure without having its bones crushed (for it is a vertebrate). Also fascinating is the mating process for the anglerfish. Since finding a mate would be nearly impossible in the inky darkness, male anglerfish have evolved so that after birth, their heightened olfactory senses lead them to a female, at which point they attach themselves to the female and integrate with her body. Then, whenever the female is ready to reproduce, she has a mate already waiting.
Aside from the anglerfish and the also-bioluminescent viperfish, most of life forms down in the trench are invertebrates, and many are bacteria.
Note: The three incorrect choices are real fish, and quite a sighto! I encourage you to Google them.