Why does the male seahorse carry the baby

While inside the pouch, the male supplies nutrients to his developing embryos, before giving birth to up to 1, babies. Embryonic development requires oxygen, and the oxygen demand increases as the embryo grows. So too does the need to get rid of the resulting carbon dioxide efficiently. This presents a problem for the pregnant male seahorse.

In egg-laying animals — such as birds, monotremes , certain reptiles and fishes — the growing embryo accesses oxygen and gets rid of carbon dioxide through pores in the egg shell.

For animals that give birth to live young, a different solution is required. Pregnant humans develop a placenta, a complex organ connecting the mother to her developing baby, which allows an efficient exchange of oxygen and carbon dioxide it also gets nutrients to the baby, and removes waste, via the bloodstream. This improves the efficiency of oxygen and nutrient delivery to the fetus. Some sharks, like the Australian sharpnose shark Rhizoprionodon taylori develop a placenta with an umbilical cord joining the mother to her babies during pregnancy.

Many live-bearing lizards form a placenta including very complex ones to provide respiratory gases and some nutrients to their developing embryos. Our previous research identified genes that allow the seahorse father to provide for the developing embryos while inside his pouch. Our new study shows that during pregnancy the pouch undergoes many changes similar to those seen in mammalian pregnancy.

We focused on examining the brood pouch of male seahorses during pregnancy to determine exactly how they provide oxygen to their developing embryos. By viewing the seahorse pouch under the microscope at various stages of pregnancy, we found that small blood vessels grow within the pouch, particularly towards the end of pregnancy. This is when the baby seahorses called fry require the most oxygen. These changes improve the efficiency of transport between the father and the embryos.

Interestingly, many of the changes that occur in the seahorse pouch during pregnancy are similar to those that occur in the uterus during mammalian pregnancy.

The male can deliver babies in the morning and get pregnant again the same day. The female expends her energy making more eggs rather than carrying fertilized ones.

Creating new life takes a lot of energy, which factors into another theory as to why male seahorses carry the babies. When the females create the eggs, she uses her energy to fill the egg casings with nutrients to help the babies mature.

This takes some of the stress off the dad. He provides a safe and environmentally controlled environment for his babies, but the mom gives them some food. Depending on the species, seahorses can deliver from five to more than 1, babies at a time.

Unfortunately, only about five out of every thousand survive to adulthood. The babies are so tiny that they can't eat the same plankton food as their parents, so their choices are limited. Also, they tend to get carried away by ocean currents before they can latch onto rocks or other secure objects with their tails, becoming part of the zooplankton other animals eat. Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue.

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