Quirks & Quarks

Pregnant male seahorses grow a placenta to nurture their young

The seahorse dads' kangaroo-like brood pouch undergoes a transformation when they get pregnant so it can supply oxygen and nutrients to their young.

Their kangaroo-like brood pouch undergoes a transformation when they get pregnant

Male seahorses turn their brood pouch into a placenta to deliver oxygen and nutrients to the babies they carry. (Jacqui Herbert)

Pregnant seahorse dads support the growth and development of their offspring by transforming the brood pouch in which they carry their babies into a placenta.

Seahorses are the only animals in which the males get pregnant and give birth instead of females. 

Scientists in Australia were curious about how the seahorse dads managed to supply oxygen to their babies inside their pouch.

Camilla Whittington, an evolutionary biologist at the University of Sydney, led the research, which was published in the journal Placenta. 

Seahorses are the only animals where males get pregnant and give birth instead of females. (Jacqui Herbert)

Her team found that as the pregnancy progresses there is a huge increase in the number of blood vessels going to the brood pouch. The tissue also becomes thinner and the surface of the pouch wrinkles so as to have more surface area. This makes it easier to supply oxygen to the developing young and remove carbon dioxide. 

Whittington said the biggest difference between a male seahorse brood pouch and the human placenta is that in humans, the parent's portion of the placenta comes from the mom's uterus, but in seahorse dads, it comes from his modified belly skin. 

Whittington told Quirks & Quarks host Bob McDonald that this is a fantastic example of convergent evolution, the phenomenon in which different species independently develop similar solutions to universal problems.


Produced and written by Sonya Buyting. Click on the link at the top of the page to listen to the interview with Dr. Camilla Whittington.

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