Australasian Science: Australia's authority on science since 1938

Male Seahorse and Human Pregnancies Are Alike

Seahorses are famed for being part of the only family in the animal kingdom in which the male is responsible for pregnancy. What hasn’t been known until now is the degree to which male seahorses nourish and protect embryos in their brood pouch during the 24-day gestation period.

A study published in Molecular Biology and Evolution has reported that male seahorses play as much a part in nurturing embryos during pregnancy as female mammals. Previously their role, other than as a pouch provider, was largely a mystery.

“Seahorse babies get a lot of nutrients via the egg yolk provided by their mothers,” said Dr Camilla Whittington of The University of Sydney, “but the pouch of the fathers has also evolved to meet the complex challenges of providing additional nutrients and immunological protection, and ensuring gas exchange and waste removal”.

Whittington and colleagues found that male seahorses are able to deliver nutrients to their developing embryos, particularly energy-rich lipids and calcium to allow them to build their tiny skeletons. It is likely that these nutrients are secreted in the brood pouch and then absorbed by embryos.

The researchers also conducted the first RNA sequencing study – monitoring how much genes switch on and off – across the full course of pregnancy in any animal, and found that gene expression in male seahorses and humans change in similar ways during the course of the pregnancy.

“Regardless of your species, pregnancy presents a number of complex challenges, like ensuring you can provide oxygen and nutrients to your embryos,” Whittington said. “We have evolved independently to meet these challenges, but our research suggests that even distantly related animals use similar genes to manage pregnancy and produce healthy offspring.”

Whittington said that the similarities between seahorse, mammal and lizard pregnancies revealed in the study warrant further investigation to determine whether the evolution of animal pregnancy across all species is more similar than previously thought.