Watch: Deep-Sea Anglerfish Caught Mating In Incredibly Rare Video

Anglerfish are those deep-sea dwellers that we see once in a blue moon. They live hundreds to thousands of feet underwater and barely come up to the top to give a glimpse of their lifecycle.

Everything we know about the monstrous look of the creatures — their massive heads, fang-like teeth, beady little eyes, and long, bioluminescent whisker-like filaments — has either come from dead specimens caught in the nets or a handful of deep-sea clips.

But now, thanks to an incredibly rare video captured by wildlife filmmakers Kirsten and Joachim Jakobsen and reported by Science Magazine, we know a little more about the anglerfish, particularly how it mates.

In August 2016, the husband and wife duo was exploring deep-sea habitat near Portugal's Azores Islands when they found a pair of anglerfish mating some 2,600 feet underwater.

Though they were about to end the five-hour long dive, the intriguing form of the six-inch long creatures, with thread-like filaments and beady eyes, prompted them to follow them around and capture the whole thing on camera.

Later, deep-sea animal researcher Ted Pietsch took a close look at the video and identified one of the strange animals in the video as a female member of Caulophryne jordani species, aka fanfin angler, which was involved in a close mating arrangement with a much smaller male — something that has never been observed in the past.

According to biologists, the pair in the video was involved sexual parasitism — an inter-dependent mating process in which a dwarf male anglerfish bites into the female in order to fuse permanently with it. Once this bond is formed, the male receives protection and essential nutrients from female’s circulatory system and provides sperm in return for spawning.

Scientists have witnessed dead males fused with lifeless females in the past but this is the first time the whole process was captured on camera. It is also worth noting in some anglerfish species, female can incorporate up to eight males in the same way.

"I've been studying these [animals] for most of my life and I've never seen anything like it," Pietsch told Science Magazine while describing the unprecedented find. "You can see how rare and important this discovery is. It was really a shocker for me."

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