It could always be worse!!!
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 meters down, it metamorphs. 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.
The large fish is the female. That small thing that is attached beneath the tail fin? THAT is the male.