Test tube coral could be a way to save corals – 02/03/2024 – Science

It was a new moon night, in 2019, when researchers went looking for little packages in tanks near the Brazilian sea. The objects of attention were packets of sperm and eggs recently released by endangered brain corals. Accompanied with the aid of head torches, they were captured and then frozen.

Years later — and a pandemic in between —, test-tube coral babies, from those captured sperm, were born, raising hope for yet another mechanism to recover suffering coral populations around the world.

According to Leandro Godoy, a researcher at UFRGS (Federal University of Rio Grande do Sul) who led the test-tube coral project, this type of research is still in its early stages.

For insemination, the first necessary step was sperm freezing. And then the difficulties begin.

“She [a célula] is frozen in time. It’s alive, but it doesn’t have any kind of chemical reaction,” says Godoy. “It’s one thing to put a piece of meat in the freezer. But keeping a cell alive in liquid nitrogen, at -196°C, that’s the challenge.”

One of the problems, according to the researcher, is the large amount of water inside cells, which, when freezing, forms ice crystals that end up rupturing and killing the cell. Therefore, it took years to understand the structure of brain coral sperm (Mussismilia harttii) he was working with (which is four times smaller than sperm from corals from other regions, such as Hawaii and Australia).

To prevent the formation of crystals, researchers had to look for so-called cryoprotectants, which, generally speaking, take the place of water inside the cell — and are toxic, which requires testing with different types of substances and dosages.

The target corals of the research were the Mussismilia harttii, endemic to Brazil and on the IUCN (International Union for Conservation of Nature) red list of threatened animals. Furthermore, these corals have a very short reproduction period: new moon nights from September to November — hence the mention at the beginning of the text.

Around 10 to 15 hours before the moment of reproduction, members of the Instituto Coral Vivo dived in the Recife de Fora Marine Park region, in Bahia, and — with authorization from competent bodies — collected some coral colonies and took them to tanks that maintained suitable conditions for the animals.

In nature, the little packets — which carry both sperm and eggs; the species is hermaphrodite—mentioned at the beginning of the report, they hatch when they reach the surface of the ocean, says Godoy. For research, as soon as they were released by the corals, researchers collected them in tubes, where they would then hatch.

After the collections and the start of work, Covid-19 came. The researchers basically had to interrupt work in the UFRGS laboratories, and the sperm were frozen for more than two years because of the health crisis.

Freezing was a challenge and thawing — with the help of a water bath — was also a challenge, a moment in which ice crystals can also form and in which losses are expected.

With the ideal thawing process deciphered, the time has come for researchers to finally see if they can reproduce the Mussismilia harttii with frozen semen.

In short, frozen sperm were placed together with eggs in a tube, which was then shaken and then taken to an aquarium. “Two or three hours later we can follow the embryonic development. It’s very fast. From one day to the next the larvae are born”, says Godoy.

To verify that the process had actually worked, the researchers used fresh sperm as a kind of control group.

According to Godoy, the results were practically the same for both frozen and fresh sperm.

The next step in the life of corals is to settle in some location. Inside the aquariums, scientists placed a tile to hold the larvae that will become corals. In this case, the settlement rate was also very close between the two groups of sperm analyzed.

With around R$168,000, the project, financed by the Grupo Boticário Nature Protection Foundation, managed to create the first coral semen bank in the South Atlantic Ocean, according to the foundation. The initiative lasted from 2019 to 2022.

Godoy highlights that, from now on, he needs more funding for the next steps, which include trying to freeze eggs —a process, according to him, much more complex— and larvae, monitoring the growth of the corals that were born and trying to take them to the ocean to understand their ability to rebuild the population of a given area.

The UFRGS researcher estimates that around half a million reais will be needed, over a period of four years, for these next steps.

Status of corals in the world

By now, you may already know about the sensitivity and importance of corals. If you don’t know, no problem. In short, there is great concern about the situation of corals in the world, which have faced high mortality and bleaching.

There are estimates that indicate that the planet has lost around half of its corals since 1950. And the climate crisis only worsens the current and future situation of these living beings — this may still surprise some people, but, yes, corals are animals. According to a 2022 study, more than half of the world’s corals could be under inadequate environmental conditions, even in the best possible climate scenario — which, it seems, will not occur.

“Coral reefs are the most threatened ecosystem in the world as a whole. They are extremely threatened precisely because they are so sensitive to any environmental change”, says biologist Janaína Bumbeer, project manager at Fundação Grupo Boticário.

The biologist points out that conservation alone is no longer enough, requiring restoration initiatives, such as replanting, and the search for test tube corals.

Bumbeer remembers the importance of corals for marine biodiversity. “We are talking not only about the conservation of some species, but also about food security, tourism and coastal protection,” she says.

A recent survey by the Grupo Boticário Nature Protection Foundation estimates that tourism to coral reefs generates around R$7 billion per year — such tourism, of course, needs to be conscious so as not to harm these living beings.