Seahorse fathers give birth in a unique way, new research shows
In seahorses and pipefish, it is the male that gets pregnant and gives birth. Seahorse fathers incubate their developing embryos in a pouch located on their tail.
The pouch is the equivalent of the uterus of female mammals. It contains a placenta, supporting the growth and development of baby seahorses.
Seahorse dads provide nutrients and oxygen to their babies during pregnancy, using some of the same genetic instructions as mammalian pregnancy.
However, when it comes to giving birth, our research, published in Placenta, shows male seahorses seem to rely on elaborate behaviors and their unique body structure to facilitate labor.
How animals give birth
Labor is a complex biological process that in female pregnant animals is controlled by hormones including oxytocin. In mammals and reptiles, oxytocin induces contractions in the smooth muscles of the uterus.
Smooth muscle is found in the walls of most internal organs and blood vessels. This muscle type is not under conscious control. For example, your intestines are lined with smooth muscle, which rhythmically contracts to move food through your gut without you having to consciously control it.
In the human uterus (left), the entire outer layer is comprised of smooth muscle. The seahorse pouch (right) only has small smooth muscle bundles scattered throughout the outer layers of the pouch. Credit: Jessica Suzanne Dudley / VWR, Author provided