Most coral reefs produce by a sexual process. About 25 percent of corals are hermaphrodic. 75 percent of corals are gonochoristic. Both hermaphrodic and gonochoristic corals have types that reproduce sexually or asexually. Corals predominantly produce sexually, or by the method of gametes (eggs) and sperm.
Gonochorists are species that sexually reproduce offspring that are of a determinate sex which never changes. Most mammals are gonochorists. Sex of the offspring is mostly genetically determined, but can be determined by other mechanisms, such as responses to temperature or chemicals in the environment.
A hermaphroditic species contains the reproductive organs of both male and female. Each partner in the sexual reproduction can act in either the male or female role.
SEXUAL: SPERM AND EGGS
Sexual reproduction can be by means of broadcasting both the gametes (eggs) and sperm and letting the water currents transport them, once the eggs are fertilized. The fertilized eggs become a microscopic larvae called planula. The planula head toward light by a process called photaxis, until they grow, then go in search of viable soil to live in. Several thousand of these are formed annually by a good sized colony to ensure that the survival of the colony is safe.
Synchronous spawning occurs when the entire colony, and even multiple species of coral in an area broadcast their gametes and sperm at the same time, based on lunar cycles or light cycles. This increases the odds of the gametes and sperm actually meeting up with each other and forming planula.
Brooders live in areas of high wave action, strong currents or other activity. They are not able to form coral reefs and go with the flow, gaining the name of ahermatypic coral. Brooders can store the gametes for weeks, then release the sperm when conditions are best, not being tied to the need for synchronous, or timed spawning.
ASEXUAL
Asexual reproduction in corals is accomplished by growing genetically identical polyps. The polyps can develop by budding where a new coral grows out of the head of the parent. Then the new coral develops the mouth, stomach and tentacles. Intertentacular budding is when the bud forms in the oral disc and is the same size as the parent polyp. Extratentacular budding is when the offspring forms at the base of the polyp and is smaller than the parent.
Asexual reproduction continues in its variety with longitudinal and transversal splitting reproduction. In longitudinal reproduction the colenteron, or stomach and mouth of a polyp divide and two new polyps develop, complete with tentacles, but with a need to grow their own exoskeletons and other parts.
In transversal asexual reproduction, an adult polyp splits into the top, or oral disc and the bottom or basal disc. Each part must then grow the rest of it’s parts to make a whole.
Asexual fission occurs when some polyps are able to break away and form a new colony.
Other forms of reproduction, where polyps can form new colonies include bailout, where a polyp escapes to start a new colony; and fragmentation, where colonies can re-establish themselves in new soil after natural disruptions, such as storms.
Learn more differences between sexual and asexual
