Male pipefish get “pregnant,” and Atlantic slippersnails change sexes as they grow. Researchers are now uncovering how and why these bizarre sex strategies occur.
There is some recent research about the intricacies of some of the weirder animal sexual strategies, including but not limited to, the pipefish. These male pipefish "get pregnant" as the females pass the eggs off into their brood pouch. But more interesting, they can either care for the eggs diligently, or fail to take good care of them, resulting in fewer viable offspring.
Here's the article I found
Here's the original paper in Nature about pipefish