The number of eggs that a male can carry varies from a few dozen in the short-snouted seahorse (Hippocampus hippocampus), to almost 650 in the speckled seahorse (Hippocampus erectus) with a huge pouch. The eggs, with a maximum diameter of 3 mm, will hatch within the brood pouch and the embryos will remain there until the end of their development.
At the end of this gestation (from a few days to 2 months) the young seahorses are expelled. Wedged on a support, on the bottom, the male expels them in small groups, by successive contractions. Once all out the pocket is absorbed. This moment is exhausting for the male who will need some time to regain his physical condition.
Measuring barely 5 mm long, the little ones will try to find a support to cling to, sometimes to their brothers and sisters from whom they will still have to free themselves without getting tangled. They will then begin to pick up any food that comes their way, if it suits their tiny mouths.
The courtship of a couple of seahorses resembles a slow and graceful dance which begins at the foreplay after which male and female will be entwined, cheek to cheek and tails tied. The female will then press her belly against that of the male and after several successive shivers that run through both of their bodies, the male will then half-open his incubator pouch into which the female will introduce her spawning tube and dump her eggs. These are fertilized during transfer.
Once the eggs have been laid, the pouch closes and the female leaves to rest. Then begins the work of incubation and protection, the responsibility of the male. The walls of the pocket thicken and become vascularized. This placenta brings oxygen and secretes a nutritive liquid necessary for the development of the embryos.
The young will grow in their mother's womb, safe from predators. During this intra-uterine development, the embryos feed on yolk and then on a liquid containing mucus, fat and proteins, it is a kind of uterine milk secreted by the mother. The gestation period is between four and twelve months. A litter can consist of up to seven pups that are less than 15 cm wide. We know that the male reaches sexual maturity when the width of his disc reaches twenty centimeters.
This species of ray is ovoviviparous: the females do not lay eggs and give birth directly to already formed specimens. During incubation there is no direct connection between mother and child through a placenta. Put simply, the fetus feeds on the yolk of its egg, but develops inside the mother's body.
The breeding season lasts about four months, from May to August. The male clings to the female by biting one of her wings then stays on her in order to proceed to copulation. With one of his two pterygopods he will penetrate the female and disseminate his sperm inside her. This is called internal fertilization.