Anglerfish

Deep deep down in the sea, where the sun literally don't shine, a tiny male anglerfish sniffs out the lady of his little anglerfish dreams. When he finds her, he does what any rational anglerfish would do: chomps down hard and hangs on for dear life, never ever ever letting go, ever. In fact, so lasting is the anglerfish's love that the two literally start to become one: their skin fuses and they share a blood supply. Until death does them part -- no wait, actually, even death doesn't part their bodies. That's dedication, people.