The male angler fish, a deep-sea denizen, takes monogamy very seriously. Anglers live so far under the surface that light is virtually shut out of their world. So these fish have evolved a lantern, a little bioluminescent bulb-on-a-pole they use to attract prey, and, perhaps, to find each other. Even with the aid of the lantern, though, it can be tough to find a mate that far down. So when they stumble upon a female, male anglers form an actual, not just metaphorical, bond. They bite into her, fuse blood vessels, and then dissolve away until the males exist mainly as a hypothalamus and sack of
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