Seahorse Frequently Asked Questions / Why does the male seahorse give birth?

This is an interesting question, one that has a lot of possible answers. The first answer is sort of a question – why is it that females give birth? In mammals, we’ve evolved where the female has glands that produce food for the young, so it only makes sense that she be involved in the gestation and nurturing of the embryo. However, in non-mammalian  animals, the role of female as primary care taker is much more blurred, because after producing eggs or giving birth, there is no physical limitation to which gender takes care of the young. In fact, in many non-mammal species, the males take over the primary care of the young.

Ostriches  are a great example where the male takes care of the young. The female does lay the eggs, and helps with incubation, but the male cares for and defends the chicks. This is “role-reversal” is not much of a reversal at all – because non-mammals have more options for rearing the young, it’s common for males to take over the job of rearing the young to protect his genetic investment. This happens in insects,  fish, amphibians, and birds. It’s downright common in fish  [pdf].

Seahorses have just taken this paternal care to the next level. They have evolved to have a pouch that actually encloses the eggs, and have tissue that performs the functions similar to a placenta. The female still lays eggs, but they are deposited directly into the males pouch. Females help out in an additional way though – they produce more eggs than can be fertilized. The male then absorbs those eggs, and gains nutrients from them for both himself and his growing brood.

Posted in: Reproduction