The reproductive role where male seahorses carry and give birth to offspring is called male pregnancy.
During courtship, the female seahorse deposits dozens to thousands of eggs into the male’s specialized brood pouch. Fertilization occurs as the eggs enter the pouch, where they become embedded in its tissue. The male then incubates them until they develop into miniature seahorses and expels the young through muscular contractions.
The pouch is more than a passive container. It supplies oxygen, regulates salinity and other conditions, transports waste, and can provide embryos with nutrients such as lipids and calcium. This unusual arrangement occurs among seahorses and some of their relatives in the fish family Syngnathidae, including pipefishes and seadragons.
“Paternal guarding” is broader parental behavior and does not specifically describe carrying embryos. “Oviparity” means laying eggs, while “marsupial care” is not the standard term for this seahorse reproductive system. Seahorse young receive no prolonged parental care after birth, so the male’s pregnancy ends when he releases the fry.