Men, be glad you're not an anglerfish.
In some deep-sea anglerfish species, like the needlebeard seadevil, the tiny male bites into the female, who is often 10 times his size, and soon begins to disintegrate, melting and fusing into her until he’s nothing but testes—a sperm supply she’ll use to fertilize her eggs.
All well and weird, but how, @Raakxhyr asked Weird Animal Question of the Week on Twitter, do those coveted sperm get to the egg?
The action all happens outside their bodies, says Marah J. Hardt, author of Sex in the Sea: Our Intimate Connection with Sex-Changing Fish, Romantic Lobsters, Kinky Squid, and Other Salty Erotica of the Deep. Males release sperm and females release eggs, which are then fertilized in the water.
But it's unclear which fish—the female or the parasitic male—controls the sperm release. “Given that his tail end is protruding,” he may release sperm at the time she releases her egg, Hardt says. (Related: "Hot Water: The Bizarre Sex Lives of Ocean Creatures.")
Lest we stereotype the anglerfish, note that not all their males are so clingy. In some species, like the striated frogfish, males and females come together and release sperm and egg into the water.
In others, like the humpback anglerfish, males attach to females but let go after fertilization.
Evidently even anglerfish have heard that Frozen song.
Parasitic anglerfish aren’t the only animals that perform creative coupling.
- Male squid give females sperm packets called spermatophores, which they stick onto the female using either a tentacle, "technically called a hectocotylus," or “a terminal organ, which is like a giant penis,” Hardt says. Once stuck—on the mantle around the head—the sperm burrow into the skin. After that, their route is a mystery, though Hardt says females of some species have sperm receptacles that may pass the eggs or grab them as needed.
- Dragonfly sperm scrapers are a unique tool in the reproduction game, says University of Arizona entomologist Katy Prudic. Male dragonflies have two sets of genitals and move sperm from the testes into the penis. Before mating, however they use their penis to scrape out the sperm of any prior mating before delivering their own. (Read more about the weird world of dragonfly sex.)
- “A Greek tragedy” is how Prudic describes the fate of the male Adactylidium mite, which technically becomes a dad while still inside his mother's body. The mother mite hatches up to nine eggs inside her body, and usually only one is male. This broody bunch [ha!] lives inside and feeds on mom. Once matured, the females mate with their brother, then cut a hole in mom’s dead body and leave, while the male dies (presumably of exhaustion and/or embarrassment).
- Osedax worms live in the deep sea, where they feed on whale bones. Their growth is stunted, so males look “like prepubescent worms but with fully developed testes,” Hardt says. They live inside the females and “ejaculate through the top of their heads, releasing sperm right near the opening where the female's eggs come out.” (See "New Species of Naked Bone-Eating Worms in Antarctica.")
You make the joke. We’re way too classy to do it.