Seahorse Male Pregnancy as a Model System to Study Pregnancy, Immune Adaptations, and Environmental Effects

Seahorses, together with sea dragons and pipefishes, belong to the Syngnathidae family of teleost fishes. Seahorses and other Syngnathidae species have a very peculiar feature: male pregnancy. Among different species, there is a gradation of paternal involvement in carrying for the offspring, from a simple attachment of the eggs to the skin surface, through various degrees of egg coverage by skin flaps, to the internal pregnancy within a brood pouch, which resembles mammalian uterus with the placenta. Because of the gradation of parental involvement and similarities to mammalian pregnancy, seahorses are a great model to study the evolution of pregnancy and the immunologic, metabolic, cellular, and molecular processes of pregnancy and embryo development. Seahorses are also very useful for studying the effects of pollutants and environmental changes on pregnancy, embryo development, and offspring fitness. We describe here the characteristics of seahorse male pregnancy, its regulatory mechanisms, the development of immune tolerance of the parent toward the allogeneic embryos, and the effects of environmental pollutants on pregnancy and embryo development.

Automated summary

Seahorses, along with sea dragons and pipefishes, are a type of teleost fishes belonging to the Syngnathidae family. The peculiar feature of male pregnancy is found in seahorses and other Syngnathidae species. This paternal involvement in carrying for the offspring ranges from simple attachment of eggs to the skin surface to internal pregnancy within a brood pouch, similar to mammalian uterus. Seahorses serve as an excellent model to study the evolution of pregnancy, as well as the immunologic, metabolic, cellular, and molecular processes of pregnancy and embryo development. They are also valuable for investigating the effects of pollutants and environmental changes on pregnancy and offspring fitness.