While we wish a ‘Happy Father’s Day’ to all the scuba diving, freediving, and ocean-loving dads out there, we also want to give a big shout out to some of the most unique and incredible dads that call the underwater world home – male seahorses. Out of the entire animal kingdom, male seahorses (and their close relatives, pipefish and seadragons) are the only males in the world that undergo pregnancy and give birth to their offspring.
If being able to change color, being able to move their eyes independently of one another, and having a prehensile tail weren’t enough, the fact that male seahorses get pregnant and give birth is sure to leave you in total awe of these strange and fascinating fish.
Although male seahorses carry the eggs, they don’t make them. After the male and female seahorses spend time courting, the female actually deposits her eggs inside the male’s pouch, at which point he fertilizes the eggs inside the pouch. Instead of growing their baby seahorses inside of a uterus like human moms do, seahorse dads carry their babies in a pouch that provides oxygen and nutrients, as well as regulates temperature, blood flow, and salinity for the developing eggs. Depending on the species, male seahorses typically carry the eggs for two to four weeks, and give birth to between 100 and 1,000 babies at one time. Like human moms, seahorse dads give birth through energetically costly muscular contractions.
Seahorses, and their close relatives, pipefish and seadragons, belong to the family Syngnathidae. While male seahorses are the only ones that hold developing eggs in a true pouch, male pipefish and male seadragons carry developing eggs attached to an area on the underside of their bodies, supplying nutrients and oxygen through a placenta-like connection.
Scientists theorize that the males in the Syngnathidae family have evolved to carry the babies because it gives the species the ability to create more babies quickly, thus better chances of species survival. While the male is bearing the young, the female can prepare more eggs to implant in the male soon after he has given birth. Additionally, this method of reproduction seems to distribute the energy costs of the entire process more evenly between the male and female.
While seahorse dads really go the extra mile to give birth, there is no parental care offered to their tiny offspring once they are born. However, due to the protection during pregnancy that seahorse dads provide, the survival rate of baby seahorses is actually fairly high compared to most other species of fish which abandon the eggs immediately after fertilization.
While male seahorses are putting in a lot of effort to keep their species thriving, unfortunately there are many human-caused threats facing seahorse populations worldwide. Legal and illegal trade of dried seahorses for souvenirs as well as for medicinal purposes, wild capture of live seahorses for the aquarium trade, and accidental bycatch of seahorses in shrimp fisheries are the primary reasons why seahorse populations are at risk worldwide. Ocean-lovers around the world can help create a brighter future for seahorses by not contributing to or supporting these harmful actions.
Want to help seahorse populations while you dive? Download the iSeahorse App to upload your seahorse photos to a database of seahorse images from around the world. This Project Seahorse initiative allows divers to act as citizen scientists, helping to provide vital information that contributes to a better understanding of, and the conservation of these incredible fish.
While male seahorses, pipefish, and seadragons don’t exactly win dad of the year, the fact that they are the only male animals in the world that get pregnant and give birth definitely deserves some recognition.