The glowing lure on a female anglerfish, called the esca, does not produce light from the fish's own cells. Instead, it houses colonies of bioluminescent bacteria that emit a blue-green glow through a chemical reaction involving luciferin and the enzyme luciferase. The fish and the bacteria have a symbiotic relationship: the bacteria receive nutrients and a protected home, while the Black Seadevil gets a living lantern to attract prey in the pitch-black deep ocean. Recent research has also shown that anglerfish can control the brightness of this lure by regulating blood flow to the esca, essentially dimming and brightening the light on demand.

Male Melanocetus johnsonii are born with highly developed olfactory systems specifically designed to track down females by detecting pheromones in the vast darkness of the deep sea. Once a male finds a female, he bites into her flesh and releases an enzyme that begins dissolving the skin at the attachment point, fusing their tissues together. Over time, the male's organs degenerate until he becomes a permanent reproductive appendage of the female, sharing her circulatory system entirely. This extreme biological adaptation, known as sexual parasitism, is thought to have evolved because finding a mate in the vast, dark deep ocean is so incredibly rare that once a meeting occurs, it is evolutionarily advantageous to never let go. A single female Humpback Anglerfish can carry multiple fused males at once.

In November 2014, researchers at the Monterey Bay Aquarium Research Institute captured the first-ever video footage of a live Melanocetus johnsonii, the Black Seadevil, swimming at approximately 600 meters depth in Monterey Canyon using a remotely operated vehicle. The footage revealed the fish's haunting, otherworldly appearance in real life: the glowing lure pulsating in the darkness, the translucent black body, and the enormous mouth. The video was released publicly and went massively viral, garnering millions of views within days and spawning countless memes, news articles, and social media reactions. For most people, it was their first time seeing a live anglerfish behave naturally in its actual habitat, and the sheer strangeness of the creature captivated audiences globally. It firmly established the angler fish as an internet icon.

The Humpback Anglerfish inhabits depths between approximately 200 and 1,500 meters, a zone characterized by near-freezing temperatures, crushing water pressure, and complete or near-complete absence of sunlight. These fish are highly adapted to these extreme conditions. When accidentally caught in trawling nets and brought to the surface, Melanocetus johnsonii specimens typically do not survive due to the dramatic decompression and temperature change. Their soft, gelatinous bodies, adapted to withstand immense pressure, deteriorate rapidly outside their natural environment. This is why undamaged specimens are incredibly rare in museums and scientific collections, and why the 2014 live video footage was so historically significant for marine science.

The anglerfish became a beloved internet meme for several overlapping reasons. Its physical appearance, a round, dark body with enormous terrifying teeth and a glowing light dangling from its head, looks almost like a cartoon villain brought to life, making it inherently memeable. The viral 2014 MBARI footage introduced it to a mainstream audience, and science communicators quickly embraced it as a way to illustrate bizarre evolutionary biology. The story of male anglerfish permanently fusing to females became a darkly comedic metaphor that spread widely across social media. Additionally, the Black Seadevil became closely associated with deep-sea horror aesthetics popular in internet communities, appearing in everything from horror art to wholesome plushy merchandise. The combination of scientific strangeness, visual uniqueness, and that perfect balance of terrifying and adorable made the angler fish a permanent fixture of internet culture.