Male Seahorses Give Birth: What Role Does Courtship Play in This Animal Species’ Pregnancy?

In aquatic animals like pipefish and seahorses, the male gets pregnant and gives birth. Seahorse fathers specifically are incubating their developing embryos in a pouch found on their tails.

As a ScienceAlert report specifies, the pouch is equivalent to a female mammal's uterus. It contains a placenta that supports the development and growth of baby seahorses.

Essentially, seahorse dads offer nutrients and oxygen to their babies during pregnancy, utilizing some of the genetic instructions as "mammalian pregnancy."

Nonetheless, when it comes to giving birth, the new study reveals that male seahorses appear to depend on elaborate behaviors and the unique structure of their body to facilitate labor.

Giving Birth Among Animals

Labor is a multifaceted biological process that, in pregnant female animals, is regulated by hormones, including "oxytocin." In reptiles and mammals, oxytocin generates contractions in the smooth muscles of the uterus.

Specifically, there are three main muscle types smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle is located in the walls of most internal organs, as well as in blood vessels.

Cardiac muscle, on the other hand, is particular to the heart, not to mention also under involuntary control.

Meanwhile, skeletal muscle is located throughout the body and attaches to bones through tendons, allowing body movement. According to the Placenta study, this muscle type is under conscious control.

Seahorse Fathers Giving Birth

The research team from the University of Sydney and the University of Newcastle set out to identify how labor works in male seahorses.

The team's genetic data suggested that seahorse labor may be akin to labor in female mammals.

A study conducted in 1970 also revealed that when non-pregnant male seahorses got exposed to the fish edition of oxytocin known as "isotocin", they expressed behaviors similar to labor.

As a result, the study investigators forecasted seahorse males would use oxytocin-family hormones to regulate the process of giving birth through contracting muscles inside the brood pouch.

Courtship and Male Seahorse Pregnancy

Seahorse courtship is an intricate process. Males open and fill their pouch with water by bending forward and contracting their bodies, forcing water into the pouch before dancing with the female.

Similarly, while in labor, male seahorses bend their body toward the tail, pressing and relaxing. Such a pressing behavior is accompanied by short gaping of the pouch opening, with a set of whole-body jerks.

This movement and pouch opening enable seawater to flush through the pouch. Both the jerking and pressing continue.

And, as they do, the pouch opening is getting slowly bigger, and groups of seahorse babies are being ejected with every movement. Essentially, hundreds of babies are ejected in a short period.

The study findings suggest that contractions of the large skeletal movements stimulate the opening of the pouch for courtship and birth found close to the opening.

Opening of the Seahorse Pouch

As indicated in The Conversation, where this report first came out, the researchers propose that the muscles control the opening of the seahorse pouch, enabling the seahorse fathers to control their young's expulsion at the end of pregnancy consciously.

Future electrophysiological and biomechanical studies are needed to analyze the force needed to contract such muscles and test if they indeed control the opening of the pouch.

Related information about seahorse fathers giving birth is shown on National Geographic's YouTube video below:

Check out more news and information on Animals in Science Times.