NOVA: And what about male pregnancy?
AV: Well, we tend to think of parental care as being the responsibility of the female, but that’s because we’re mammals. In birds, if you think about it, both parents usually care for the young. And in fishes, people are often surprised to learn that usually the parental care is given only by the male. Now parental care in fishes usually involves just guarding the eggs, fanning the eggs, making sure they get enough oxygen and they’re clean. The seahorses are the most extreme example of fathers providing the care that we know in the animal world. Because they guard the eggs all right, but they guard them on their body. They also provide oxygen through a capillary network in the pouch, and they also transfer nutrients, and they control the pouch environment so that it changes during the pregnancy to become more like salt water. This then is an extreme example, but presumably instead of producing many small young, the seahorses produce fewer, but better developed and larger young.
