Deep dive 3 min read
Male vs. Female Anglerfish: The Strangest Love Story in the Ocean
She's big, toothy and carries a lamp. He's tiny and bites onto her forever, until their bodies fuse into one. Welcome to the strangest relationship in the ocean.
Forget “till death do us part”. Some deep-sea anglerfish take commitment much further: the male bites onto the female and never lets go. Over time, their bodies fuse together, and he becomes a permanent part of her. It’s the strangest love story in the ocean, and possibly on the planet.
She’s the giant
The female is the anglerfish you know: a big head, a mouth full of needle teeth and a glowing lure on her forehead. Depending on the species, she can be anything from a few centimetres to over a metre long. She hunts, she glows and she’s in charge.
He’s tiny
The male is a completely different creature. In some species he’s under a centimetre long, which makes him one of the smallest vertebrates on Earth. He has no lure and isn’t much of a hunter. What he does have are big eyes and a superb sense of smell. His one job in life is to find a female in the vast, dark ocean, and to find her fast, before he starves.
Finding love in the dark
The deep sea is huge and almost empty, so bumping into the right partner is incredibly unlikely. Scientists think the female releases a chemical scent trail, and the male follows it like a bloodhound. When he finally reaches her, he doesn’t take any chances: he bites into her body and holds on.
He finds her, bites her and never lets go. Literally.
Two bodies become one
In some anglerfish families, what happens next is truly bizarre. The male’s lips and her skin slowly grow together. Their blood vessels connect, so he’s now fed by her bloodstream. Over time, he loses most of the parts he no longer needs, like his eyes and many internal organs. What’s left is mainly a sperm factory attached to her side, ready whenever she is.
And she doesn’t have to stop at one. Females have been found carrying several fused males at once. In the dark, lonely deep sea, it guarantees she always has a partner when it’s time to spawn.
Strange but trueNormally a body attacks anything foreign attached to it. A 2020 study found that fusing anglerfish have lost key parts of their immune system, which is why she doesn’t reject him.
Not every anglerfish does it
This fusion, called sexual parasitism, only happens in some families of deep-sea anglerfish. In other species the males attach only temporarily, or don’t attach at all and live independently. Scientists first discovered the fused males in the 1920s, and they were so tiny that the first researchers thought they were the female’s babies.
The verdict
Is it romantic? Creepy? A bit of both. Either way, it’s a brilliant solution to a very deep-sea problem: when partners are almost impossible to find, never let go of the one you’ve got. For more love lives that break all the rules, browse our Weird Reproduction collection.
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