#thisispearl Nov. 2021 - Page 9

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Sustainability Corner with Douglas McLaurin-Moreno

Pearls in the Web of Life, Part III

"Many pearl oysters are called mother-of-pearl oysters because they give birth to pearls, but many small and frail creatures likely regard these mollusks as mothers entirely because of the shelter and nutrients they provide."

In our last entry we learned that the outsides of pearl oysters act as small ecosystems, but now we will dive deeper into the oysters themselves. This pattern of oysters acting as ecosystems repeats itself in a kind of Hermetic understanding of the “as is above, is below” law, but with different actors involved. And, if you ever had the opportunity to stare into a live and open pearl oyster, you would begin experiencing a calmness that emanates from these animals, as if staring into an encased, fleshy orchid or a peaceful womb. And it is this protective environment that some unusual creatures are searching for.

Many pearl oysters are called mother-of-pearl oysters because they give birth to pearls, but many small and frail creatures likely regard these mollusks as mothers entirely because of the shelter and nutrients they provide, just as many people call our planet Mother Earth. Who are the dwellers of this small, motherly environment? Well, there are just a few, and each variety of pearl oyster will be able to house its own unique species in a unique biological association known as commensalism: species that live on another one without causing damage to their host.

One of the most bizarre of these is the Pearl Fish (Carapus), a serpentine-shape and almost translucent fish that loves living inside pearl oysters of the genus Pinctada. These slow and frail creatures require a place to hide from predators, and pearl oysters offer them quite a large and luxurious nacreous apartment. Little is known of these reclusive Carapus fishes, which are easily identified due to their unusual dwelling habits, including in the crevices of starfishes, other bivalves and—quite oddly—inside the anus of sea cucumbers. It is easy to imagine why they would prefer pearl oysters, isn’t it?

Carapus ultimately find an oyster, find a mate, produce their offspring, and live out their “pearl dream,” but when they die, their tiny corpses will start decaying, and most are expelled from the host pearl oyster. On some occasions something truly special happens: the pearl oyster coats them with mother-of-pearl, thus they become nacreous mummies or one of the most striking natural blister pearls you have ever laid eyes on.

These small nacreous coffins become an enduring testament to the lives of these rare inhabitants of our seas. All life is important to keeping an adequate balance, and pearl oysters—as you have been able to ascertain with these last entries—are a key player in many marine environments, not only due to their main biological function but also to protect and nurture so many other minor players.

Douglas McLaurin-Moreno is a biochemistry engineer with a master’s degree in sustainability and natural resources management as well as a university professor, PAO instrstructor, and a founder of the Sea of Cortez pearl brand, the first commercial marine pearl farm in the entire American continent.

Black-lipped oysters (Pinctada mazatlanica) in the wild have occasionally been found to contain unique natural blister pearls comprising the remains of Carapus dubius or “Pearl Fish.” The photo of the shell on the left can be seen on display at the Mina El Edén Rock and Mineral Museum in Zacatecas, México, and the one on the right was photographed at the American Museum of Natural History in New York City.

Photos courtesy McLaurin-Moreno