Corals bred in public aquariums provide new opportunities for research and a healthy stock to establish in the wild, essential components of a thriving future for coral reef ecosystems, which are home to around 25% of all life in the oceans. of the earth. But the long-term success of these efforts depends in part on maintaining the genetic diversity of aquarium-bred corals, which leads to increased resistance to threats such as warming and ocean acidification. In a study published today in Marine Science Frontiersa diverse team of Steinhart Aquarium biologists and researchers from the California Academy of Sciences’ Coral Breeding Laboratory produce the first-ever pedigree, or “family tree,” for aquarium-reared corals and provide a list best practices for maintaining genetic diversity in aquarium-reared corals.
“Genetic diversity is what enables species to adapt to the myriad threats resulting from climate change,” says Academy curator Rebecca Albright, PhD, who founded the Coral Spawning Lab, one of the few facilities on Earth capable of successfully breeding corals. Albright’s work is an integral part of the Academy Hope for the reefs initiative, which aims to halt the decline of coral reefs this generation. “For facilities like ours at the Coral Spawning Lab, ensuring that each generation of corals is diverse allows us to conduct more robust experiments, which is a critical part of better understanding how corals can thrive on our changing planet. . For organizations that grow plantations, increased genetic diversity translates to a greater chance of survival in the wild.
For the study, the researchers performed genetic analyzes on the parents and offspring of two generations of Hyacinth Acropora the corals spawned in the Coral Spawning Lab in 2019 and 2020. Based on the similarities between the corals’ DNA, researchers were able to determine relationships between individuals, such as parenthood or siblingship.
“Corals are diffuse spawners, which means that multiple colonies release their sperm and eggs into the water simultaneously and there is no way to immediately tell which coral has spawned which offspring,” says Elora López-Nandam, PhD, Academy coral researcher and study author. “Amazingly, we found that only two of the four colonies that bred in 2019 raised 22 of the 23 offspring that survived to their 2nd birthday. This leads us to many new questions to explore how these two parents did so well, the answers to which could help us better understand coral reproduction more broadly.
“While successful coral spawning events demonstrate how closely we have been able to mimic natural ocean conditions, there are inevitably environmental pressures in aquariums that will differ from those in the wild and could select for certain traits in each generation of coral.”, explains López-Nandam. Therefore, in addition to relatedness, the researchers also sifted through the 450 million base pairs of DNA – if an organism’s genome is a book, the base pairs are the individual letters – of each of the corals sampled to find genetic differences between successive generations.
In particular, the researchers found 887 dots in the 450 million letter long code that appear to be different in aquarium-bred corals compared to those born in the wild.
“Many of the differences we found were in genetic pathways related to symbiosis with photosynthetic algae, which is how many corals get most of their energy,” López-Nandam says. “We hope to conduct future research in the Coral Spawning Lab to determine exactly what in an aquarium is causing these differences and how these genetic variations impact the overall fitness or health of corals reared in aquarium.”
Just as it takes a village to raise a child, the study authors note that it takes a unique cadre of experts to raise corals for such a study: from couscous-sized bundles of gametes to polyps. from the size of aspirin to breeding adults the size of a grapefruit.
“This type of collaboration between aquarist biologists and research scientists is rare,” says Lisa Larkin, Steinhart Aquarium biologist and study author. “There are very few places in the world where all these experts are housed in the same building, working together towards a common goal. The Academy is unique in that we can propel this type of research while having a major impact on coral conservation.
Larkin and his colleagues at the Steinhart Aquarium spend months monitoring water quality and tracking coral development to ensure they are healthy enough to spawn each year.
“Corals can be quite temperamental. They need a lot of energy to reproduce, and if they’re stressed, they’ll put that energy elsewhere,” says Larkin. “It takes months of careful attention to get them to the point where they are ready and able to reproduce.”
But, adds Larkin, the end result more than justifies the effort. “You tend to a coral for an entire year and when they finally spawn, you know you’ve done a great job. And as each spawn opens new opportunities for research like this applicable to coral conservation, the payoff is well worth it. »
Reference: Lopez-Nandam EH, Payne CY, Delbeek JC, et al. Kinship and Genetic Variation in Aquarium-Brought Fish Hyacinth Acropora corals. Forward Marine Sci. 2022;9. do I: 10.3389/fmar.2022.961106
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