Deep-sea explorers at the Rebikoff-Niggeler Foundation have captured some of the first-ever footage of an anglerfish's deeply weird sex life, along with some of the first known footage of bioluminescence on an anglerfish’s filaments. Even the world's top marine biologists know relatively little about these ugly deep-sea critters, making this stunning footage all the more exciting.

As first reported by Science Magazine, it was filmed by husband and wife team Kirsten and Joachim Jakobsen using a manned deep-sea submersible vehicle called LULA1000, some 800 meters (2,625 feet) below the surface of the waters just off the coast of the Azores islands, Portugal.

The beautifully shot video shows a female Caulophryne jordani anglerfish, aka a Fanfin Seadevil, no larger than a grapefruit. On her side, there’s another small fish dangling from her – but this is no parasite, it's actually a male anglerfish mating with her.

When it’s time to get down to business, a smaller male of the species will bite onto the body of a female. Here, his body will fuse with the female and he will spend the rest of his days pumping her with sperm and leeching off her blood supply. Whatever floats your boat, I guess.

“I have spent hundreds of hours staring into deep waters, but this is one of the most amazing video footage I have seen to date,” Antje Boetius, a biological oceanographer at the Alfred Wegener Institute in Germany, said in a statement.

Along with this never-before-seen footage of a live mating pair, the marine explorers also captured evidence of the bioluminescence of the anglerfish’s filaments. Everyone knows the anglerfish has a lightbulb-like rod dangling in front of its face (you’ve seen Finding Nemo, right?) but this video shows an anglerfish covered in whisker-like filaments, all glowing with bioluminescence. Just like many species that live in the depths of the ocean, anglerfish use bioluminescence as a means to attract prey, see their prey, startle predators, and even attract mates.

“One can’t help but think these fin-rays form a network of sensory antennae, a kind of sphere of tactility around the fish – akin to cat whiskers – that functions to monitor the close presence of predators or prey,” added Ted Pietsch, a deep-sea fish researcher at the University of Washington in Seattle.

Scientists know very little about this elusive species, so this footage is rather exciting stuff. Anglerfish are built to cope with the extreme environment of the deep sea, so they rarely survive being brought up to the surface waters. This means that most of what we know about them comes from dead specimens that have been dragged up in fishing nets by accident.

You can learn about the Rebikoff-Niggeler Foundation's outstanding work right here.