When Anglerfish mate, they melt into each other and share their bodies forever. If a male finds a female, he latches on and fuses to her, losing his internal organs until they share a blood stream. He lives the rest of his days like this, releasing sperm when she releases eggs.
A male will bite onto his lady friend, then fuse his face to her body. He lives the rest of his days like this, releasing sperm when she releases eggs. That little bump at the back of her belly? That’s her husband.
Teen movies are, at their core, veiled studies in evolutionary biology, with young men and women coming to sexual maturity and either giving into or resisting what is arguably an animal’s sole purpose on this planet — to find a mate. Some decide to wait until they’re married, others lack the desirable traits to even get that far, and still others succeed and consequently have to put off college for a while.
But if the deep-sea anglerfish happened to have the cognitive and physical capabilities required to produce its own such films, there’d be decidedly fewer plot twists. Every single movie would go a little something like this: Boy meets girl, boy bites girl, boy’s mouth fuses to girl’s body, boy lives the rest of his life attached to girl sharing her blood and supplying her with sperm. Ah, a tale as old as time.
The over 300 extremely varied species of anglerfishes inhabit everything from shallow to super-deep waters, and are so named because they are fish that fish for fish using lures, which are actually highly modified spines of dorsal fins that have migrated to their snouts. But among the 160 deep-sea species, only some 25 engage in the aforementioned biting-fusing-mating, what is known as sexual parasitism. In this group, the diminutive male looks like an entirely different species, lacking the female’s enormous jaws and characteristic lure.
This is because he doesn’t need to hunt. He only exists to attach to a female, and according to evolutionary biologist Theodore W. Pietsch of the University of Washington, mates are so scarce down here that it might be that only 1 percent of males ever find a female. The rest starve to death as virgins — unfortunate guys in a sea that doesn’t have plenty of other fish.
But it isn’t for lack of trying. The male has the biggest nostrils in proportion to its head of any animal on Earth, according to Pietsch. These sniffers are paired with extremely well-developed eyes, “so we think that it’s kind of a dual approach,” he said. “The female emits a species-specific smell, a pheromone, and the male searches out based on that, and then when the male gets close enough, the eyes can be used to distinguish the female of the correct species.”
And with two dozen other species of anglerfishes that engage in this manner of reproduction, the male had better be damn sure he chooses the right one. Luckily, the female puts on the red blue light — in the form of glowing bacteria living in her lure. Incredibly, some 90 percent of species in the deep utilize such bioluminescence.
“The bait out there is not only an organ of luminescence, but structurally it’s species-specific,” said Pietsch. “Every species of these 160 forms within this group, they have a pattern of filaments, and pigment patterns, and probably also light flash patterns, like fireflies. And they separate themselves out that way so that males can find females,” distinguishing “the tiny little differences between the structure of the bait.”
Once the male closes in, he bites onto the female, usually her belly, and their tissues fuse together to permanently join the pair in incredibly unholy matrimony. The male’s eyes and fins atrophy away, and here he will live out the rest of his life nourished by her blood, still breathing with his own gills and, importantly, still producing sperm.