Male seahorses can get pregnant
Seahorses reproduce in an unusual way: the male becomes pregnant. Pipefishes and seahorses are the only species in the animal kingdom to which the term "male pregnancy" has been applied.
The male seahorse has a brood pouch in which he carries eggs deposited by the female. The mating pair entwine their tails and the female aligns a long tube called an ovipositor with the male's pouch. The eggs move through the tube into the male's pouch where he then fertilizes them. The embryos develop in ten days to six weeks, depending on species and water conditions. When the male gives birth he pumps his tail until the baby seahorses emerge.
The male's pouch regulates salinity for the eggs, slowly increasing in the pouch to match the water outside as the eggs mature. Hatched offspring are independent of their parents. Some spend time developing among the ocean plankton. At times, the male seahorse may try to consume some of the previously released offspring. Other species (H. zosterae) immediately begin life as sea-floor inhabitants (benthos).