Unlike humans and most mammals, pregnancy in seahorses occurs in males. In a new study conducted by researchers from the University of Sydney, male seahorses were found to exhibit similar features to humans during pregnancy.

Viviparity or live birth has been altered more than 150 times in vertebrates or animals with backbones and thus has become a good model in studying changes in complex traits. Syngnathid fishes such as seahorses exhibit a one of a kind type of viviparity as pregnancy among these species occur in males. These animals have developed brooding pouches that serve as a specialized tools for protecting their offspring, facilitating gas exchange and osmoregulation, and providing nutrition to their embryos. These pouches are different among the syngnathid species and thus are also good aspects of study. However, the modifications that happen in terms of genetics and physiology, as well as the extent to which male seahorses nourish their offspring, have not been clearly identified.

The researchers performed the study by utilizing a profiling technique to investigate the genes during the different gestational stages of Hippocampus abdominalis, which is a species of seahorse that has the most intricate pouch structure. They then identified the changes that occurred in the genes linked to the different functions of the brood pouch, including nutrient transport, structure remodeling, immunological protection, conception and parturition.

The findings of the study, published in the journal Molecular Biology and Evolution, show that the role of male seahorses in terms of providing adequate nutrition to their embryos may be comparable to that of female mammals such as humans. The species are able to specifically provide calcium for bone growth and energy lipids. According to the study, these nutrients are likely secreted in the pouch and absorbed by the embryos. The gene expression changes that occur in male seahorses and humans are also similar.

"Surprisingly, seahorse dads do a lot of the same things human moms do," says Dr Camilla Whittington, co-author of the study from the University of Sydney, School of Biological Sciences.

Although different species exhibit a whole range of diverse mechanisms during pregnancy, this study was able to discover that even if the species are quite distant in relationship, similar genetic changes may still occur in order to grow healthy babies. Further investigations are needed, particularly those that tackle the evolution of pregnancies across animal species to detect more similarities than previously perceived.

Photo: Sylke Rohrlach | Flickr