The reproductive system of coral is inside the polyps.

The sexes are normally separate. Are both sexes of polyp present in one colony, or are individual colonies composed of polyps of the same sex? The maturation of the male cells takes place over one year. It starts at the beginning of summer. On the other hand, the maturation of the female gonads takes place over 2 years. This begins slowly the first year and is completed at the beginning of the second year (Vighi, 1972).

Once liberated by the male polyp, the spermatozoids swim to the female polyp. Fertilisation takes place inside the polyp. The young larva, known as a planula , develops for 20 or 30 days inside the polyp before going out into the open sea : so the red coral is viviparous. Larval emission takes place from July to the beginning of October, according to the depth.

The larvae swim for 4 to 15 days, at first upwards, looking for the roof of the grotto. If they don't find a substrate here, they swim downwards, until they find a suitable one for their metamorphosis, the mechanisms and control of which are totally unknown. It seems that the larva does not react to light, suggesting that the distribution of red coral with respect to light, results either from the absence of suitable sites for metamorphosis in lighted zones or else from a growth problem of the young colonies (due to competition with algae, for example).

Following metamorphosis, the young larva begins to build-up its structure: a new coral colony is born. The sexual maturity of the first polyps is attained after about 2 years. It seems that growth of the young colonies is rapid at first and slows down after a few years.