Final answer:
GloFish, which are genetically modified zebrafish, express fluorescent jellyfish proteins and glow under ultraviolet light. They have been engineered for scientific purposes but are also popular in the aquarium trade.
Step-by-step explanation:
The type of fish that expresses fluorescent jellyfish proteins and glows in the dark are the GloFish, which are a genetically modified version of the zebrafish. These fish were engineered to express the green fluorescent protein (GFP) originally found in jellyfish, allowing them to glow under ultraviolet light. The purpose of the modification was originally for scientific research, to easily identify transgenic individuals and to study gene expression. However, GloFish have since become popular in the aquarium trade. None of the other fish listed, such as angelfish, guppies, or tetras, naturally express the jellyfish proteins that cause bioluminescence.