The seahorse is the only creature where the male becomes pregnant. The female inserts a nipple-like appendage into the male and releases her eggs into his stomach. He then discharges his sperm over them, and once the eggs are fertilized, his belly takes on the rounded shape.
For the mouthbrooder catfish, which lives off Mozambique, fertilization takes place in the female’s mouth. She releases her ova into the water and then turns round and swallows them. When the male swims by, she opens her mouth to swallow his sperm as well. The young fish remain in the mouth until they have absorbed their egg yolk.
Since the female bedbug has no sexual opening, the male drills his own vagina, using his curved, pointed penis as a drill. The male then inserts his sperm and the blood-sucking female feeds on some of it when blood is in short supply.
The female praying mantis eats her partner after sex. During copulation, the larger female hooks her deadly arms around him and begins nibbling away at him, but his sex drive is so strong that he can carry on even while being eaten.
The male swamp antechinus, a mouse-like marsupial from Australia, is the only mammal which dies after mating. The males dedicate their lives to a round of non-stop copulation until they literally drop dead. The majority die of starvation because they have no time to feed between sex.