Curiosity 7 of 10
7. In seahorses, it is the male who gets pregnant
In seahorses, the father carries the young until birth. The female deposits her eggs in a pouch on the male's belly, and it is he who gives birth weeks later.
A pouch that works like a womb
During mating, the female transfers the eggs to the male's incubation pouch, where they are fertilized. Inside, the embryos are protected and receive oxygen, and the male controls the environment of the pouch, including the salt content of the water, while they develop.
Gestation lasts two to four weeks, depending on the species and the water temperature. At the end, the male contracts and releases the young, which swim away right away and fend for themselves. Depending on the species, anywhere from a few dozen to more than a thousand young can be born at once.
Why did nature divide the work this way? One hypothesis is that, with the male handling the pregnancy, the female can prepare a new batch of eggs in the meantime, so the pair can have more offspring per season.
Swimming is not the seahorse's strong point. It moves upright, beating a small fin on its back dozens of times per second, and it is one of the slowest fish known. To avoid being carried off by the current, it wraps its tail around algae and corals.
Did you know? The close relatives of the seahorse, such as the pipefish and the leafy seadragon, also have male pregnancy. In the leafy seadragon, the eggs are attached under the male's tail, without a closed pouch.
