The Prickly Deep Sea Anglerfish males become one with their female.
Anglerfish, a deep sea fish named for the spiny appendage on its head that it uses as bait to "fish" its prey, has an unusual mating habit. As it spends its time in the bottom of the ocean, finding a mate is a problem – but the species solved this evolutionary challenge beautifully.
At first, scientists were perplexed because they’ve never caught a male anglerfish. Also, all female anglerfish have a lump on their body that looks like a parasite. Only later did scientists discover that the lump is the remain of the male fish.
The tiny male anglerfish are born without any digestive system, so once they hatch, they have to find a female quickly. When a male finds a female, he quickly bites her body and releases an enzyme that digests his skin and her body to fuse the two in an eternal embrace. The male then wastes away, becoming nothing but a lump on the female anglerfish’s body!
When the female is ready to spawn, her "male appendage" is there, ready to release sperms to fertilize her egg.