When scientists began pulling anglerfish from the deep ocean, they noticed something odd—all of the specimens were female, and many of them had small parasites attached to their bodies. And when they studied the fish in detail, the story got even odder—the “parasites” were actually the missing males.

Deep-sea anglerfish are some of the strangest creatures in the oceans. To attract prey, the females wave around a small “lure”—a pod filled with glowing bacteria. They have a wide mouth filled with sharp teeth, and a stomach that can hold a meal that’s twice the size of the anglerfish herself.

But the male-female relationship may be the strangest feature of all. Females range from a few inches to a few feet long—at least 10 times the size of the males, and sometimes much more. That’s one of the greatest differences among any animals on Earth.

It’s hard to find mates in the blackness of the deep ocean. So a male is born with a great sense of smell, which it uses to sniff out a female. And when he finds one, he latches on with his sharp teeth. He produces an enzyme that dissolves his mouth and the mate’s skin. The male then “feeds” off the mate’s blood. His only job is to fertilize the eggs when the female spawns.

In most cases, the male grabs its mate and never lets go—it really is “’til death do us part.” But the female can carry multiple mates at the same time. The record is an even dozen—one more oddity for this unusual deep-sea fish.