Anglerfish

Anglerfish are a diverse group of fish species, many living in the deep sea, best known for a modified fin ray that projects above the mouth like a fishing rod tipped with a fleshy, often luminous lure used to attract prey close enough to be engulfed by the fish's large mouth. In several deep-sea anglerfish species, males are dramatically smaller than females and, in the most extreme cases, permanently fuse onto a female's body as a parasitic mate, sharing her bloodstream and providing sperm on demand in an environment where finding a mate in the vast, dark ocean is otherwise a formidable challenge. Anglerfish are ambush predators, relying on camouflage and their lure rather than active pursuit to capture prey, and deep-sea species remain poorly studied due to the difficulty of observing them in their extreme habitat.