In brief: Seahorses exhibit male pregnancy and are thus valuable comparative models for the study of the physiology and evolution of pregnancy. This study shows that protein is transported from fathers to developing embryos during gestation, and provides new knowledge about paternal contributions to embryonic development.
Abstract: Syngnathid embryos (seahorses, pipefishes and seadragons) develop on or in the male in a specialised brooding structure (brood pouch). Seahorse brood pouches supply nutrients, including lipids, to developing embryos (patrotrophy). We tested the hypothesis that proteins, vital for gene regulation and tissue growth during embryogenesis, are also transported from father to embryos, using the Australian pot-bellied seahorse, Hippocampus abdominalis. We used dry masses and total nitrogen content to estimate the total protein content of newly fertilised egg and neonate H. abdominalis. Neonates contained significantly greater protein mass than newly fertilised eggs. This result indicates that paternal protein transport to developing embryos occurs during H. abdominalis pregnancy. This study is the first to show paternal protein transport during pregnancy in seahorses, and furthers our understanding of paternal influence on embryonic development in male pregnant vertebrates.