Male seahorse pregnancy could be as complex as female pregnancy

New research by Dr Camilla Whittington and her team at the University ofSydney has found male seahorses transport nutrients to their developing babiesduring pregnancy. This discovery provides an opportunity for furthercomparative evolutionary research.

Seahorses and their relatives are the only vertebrates that have malepregnancy. The expectant fathers incubate developing babies inside a pocketcalled a “brood pouch”. We know a male seahorse can have more than a thousandembryos in the pouch at once but until now, researchers had limitedunderstanding of how the babies are fed during development.

“This work adds to the growing evidence that male pregnancy in seahorses couldbe as complex as female pregnancy in other animals, including ourselves,” saidDr Whittington, from the School of Life and Environmental Sciences. “Wenow know that seahorse dads can transport nutrients to the babies duringpregnancy, and we think they do this via a placenta. It’s not exactly like ahuman placenta though – they don’t have an umbilical cord, for example. Weneed to do further histological work to confirm this.”

Seahorses are emerging as important model species for understanding theevolution of live-bearing reproduction, said Dr Whittington.

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“We can draw some parallels between seahorse pregnancy and humanpregnancySeahorse dads seem to do some of the same things that human mums do,including transporting nutrients and oxygen to developing embryos, and immunemodulation to protect the babies from infection.”

The research published in Journal of Comparative Physiology B was led byUniversity of Sydney Honours student Zoe Skalkos in collaboration with DrJames Van Dyke at La Trobe University.

The study builds on previous genetic evidence suggesting that male seahorsesmight transport nutrients to developing embryos. This new study confirms, inthe first experimental evidence of ‘patrotrophy’ (nutrient transport from dadto babies). It also identified one of the classes of nutrients beingtransported: energy-rich fats.

“My team is using a range of techniques to investigate the biology of seahorsepregnancy,” Dr Whittington said. “We want to understand more about theseahorse pouch and the ways it protects and supports the baby seahorses.”

Honours student Zoe Skalkos, who led the research, said: “It’s really excitingbecause it’s a big step in understanding the relationship between dad and babyin male pregnancy.”

Key Points:

• Seahorses and their relatives are the only vertebrates that have male pregnancy. Dads incubate developing babies inside a pocket called a “brood pouch”.
• Male seahorses transport nutrients, including fats, to developing babies during pregnancy. The babies use these energy-rich fats for growth and development.
• The new results raise the question of whether seahorse embryos can influence how much nutrition they can get from dad while they are in the brood pouch.

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