The purple Dendronephtya australis, or the purple cauliflower soft coral, is now considered an endangered species. It was also almost fully eradicated across the Port Stephens estuary and by the coastline.
This is a tragedy as the coral helps protect young snappers and the White's seahorse, which is also endangered. There has also been minimal knowledge regarding the matter, which, in turn, has hampered efforts for recovery.
Understanding Coral Sex Life Could Be Key to Recovery
Now, researchers have recently discovered the reproductive mechanisms of the coral. In a recent study, they used in-vitro fertilization (IVF) to create a lab coral. The coral was also successfully brought to the wild.
The sex life of corals is generally quite complicated, as there are a couple of ways for them to "do it." The gender of these corals also varies.
Coral reproduction is typically asexual. This meant they could genetically duplicate themselves in a process often involving shedding polyps that may link to reefs and form different colonies.
The process is commonly used for restoring corals. The fragments or cuttings are taken from adult colonies and kept inside the lab. New corals are then brought to the wild. Such a process is not simple for soft corals.
Several corals are hermaphrodites as they may carry both female and male reproductive organs. Others form fully male or female colonies, while some swap and mix their sexes.
The process of spawning involves sperm and egg release. Broadcast spawning takes place when eggs and sperm get expelled into a water column, while brooding takes place when eggs undergo fertilization within colonies and are released in the form of larvae.
However, until scientists get to observe the sex life of an individual species, this matter remains private and mysterious.
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Chance Discovery
The scientists were raising lab-grown coral clones from fragments when they observed something odd. Small orange dots could be found inside some corals. These dogs were bigger than the coral food, which was also orange, fed to the creatures.
They then discovered that these dots were unfertilized eggs. Half of the scientists' fragments had eggs. Given the small sperm count, they needed to sacrifice some of the coral fragments for their contents to be inspected closely under a microscope. Doing so enabled the scientists to discover that the other half of the fragments were bearing sperm.
They then gathered fragments from one male and one female donor colony. They then had a chance to discover the gonochoric nature of the purple cauliflower soft coral. This means that its colonies are either female or male.
The researchers observed over the coming weeks that females released their eggs during the neap tide when the Moon is half-full, of summer months.
IVF on Corals
The researchers then used IVF to fertilize the harvested eggs. Within a few hours, cell division happened, while mobile larvae grew in the next week.
The larvae started becoming polyps from its eighth day. In a few weeks, 280 babies were produced from a few fragments.
Since this IVF discovery, the researchers have replicated the techniques. They transplanted hundreds of babies and released thousands of larvae to Port Stephens. Initial findings reveal that some of the IVF corals survived their first 18 months and even performed better than fragments that were asexual.
The researchers plan to implement the IVF program, hoping it may boost the general population of this endangered species.
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