Thetownend.com

"The Deep Sea Angler fish lives thousands of
    feet below the surface of the ocean where there
    is little food or light. Life is hard and lonely
    for the young male angler fish as it slowly sinks
    from the surface where it grew up. At about a
    thousand metres down, it metamorphoses. It
    gets big teeth, big eyes, and loses its
    digestive tract.

    In this state, it has only one chance of
    survival: having sex. In the distance, he spies
    a dim light. He is in luck, it is a single
    "unattached" female! The male, who is only a
    fraction of her size, grabs hold of her with
    his teeth. Over time, his skin and blood vessels
    start to fuse with hers. His skin gets tougher,
    his eyes start shrinking, and any unnecessary
    organ wastes away. He is now totally reliant
    on her and in fact, is part of her. The male
    has become simply a source of sperm