Island scientist explores the past and future of oysters
They could be considered the dinosaurs of the dining table. With an evolutionary history dating back many millions of years, members of the family Ostreidae — the bivalve mollusks known most commonly as oysters — have over the eons developed a special talent for both confounding predators and delighting palates, both human and otherwise.
“Oysters are well designed for survival,” said Bill Wardle, a marine scientist and recently retired Texas A&M University at Galveston professor, as he held up a large, 50 million-year-old shell discovered in an East Texas fossil deposit. By counting the layers of shell, Wardle estimates that this particular oyster, whose life dates back to a time when the Gulf of Mexico extended as far north as Dallas, lived to be about 30 years old.
Oysters themselves predate this particular specimen by millions of years, however. Today’s oysters are descendants of Cambrian-era clams that appeared about 540 million years ago. As time passed, offshoots began to diverge and about 300 million years ago, mussels appeared, then a couple of million years after that, scallops and oysters began to grace the globe.
Humankind was much later in coming to the show, and most likely discovered the edibility of these hard-shelled bivalves by watching other animals crack or whack them open before lapping up the luscious, nutrient-packed innards. Middens — those prehistoric garbage dumps scientists explore for clues to ancient lifestyles — indicate that our ancestors were enjoying oysters at least 10,000 years ago, at the end of the last ice age.
With their high nutritional content and ability to filter as much as 1 to 2 gallons of water an hour, oysters are not only good for the person but good for the planet. Oysters also do a very good job of providing themselves with food and shelter.
“Adult oysters usually eat very well because the sea is always providing abundant quantities of the plankton on which they feed,” Wardle said. “Shelter is not a problem either because they secrete their own protective home of hard shell affixed to a solid foundation.”
Donning waterproof boots, Wardle waded out to the Sydnor Bayou oyster reef in the back of his Galveston Island home to further explain how oysters build their communal reefs.
“Although we refer to oyster ‘beds,’ oyster communities are built vertically,” Wardle said. “Oysters set up housekeeping on top of other oysters, resulting in high-rise condominiums that provide a solid footing for not only future generations of oysters, but for other animals such as mussels to establish their homes as well.”
Fascinated with the sea since his boyhood in coastal Virginia, Wardle’s lifelong relationship with marine life has included his earning a doctoral degree from Texas A&M University at Galveston and working with the world-renowned marine biologist Sammy Ray, as Ray conducted his ground-breaking and internationally impactful research on oyster disease.
“Dr. Ray’s research was some of the earliest that sought to investigate interactions of the environment with oyster and reef health,” Wardle said, adding that in those early days of his career, his wife, Aline, also joined him in Ray’s basement lab at the university’s original Fort Crockett campus.
“A third person was needed, so I became that person,” Aline Wardle said. Her involvement meant she also brought along the bassinet cradling the couple’s infant son.
“We all had a job,” Aline Wardle said. “Bill would shuck the oysters, Dr. Ray would excise the tissues he wanted to research, I would place the samples into test tubes and baby Gregory would sleep.”
Despite their long and intense scientific relationship with oysters, the Wardles both still enjoy them gastronomically, and their favorite preparation is none at all.
“We prefer them raw on the half-shell,” Aline Wardle said.
The island’s abundance of oysters was among the major delights she discovered after moving to Galveston from Paris, France.
“I wrote back to my family at home that I had found paradise — that here you could just go out in the water and collect oysters to eat,” she said. “Today, of course, that is not safe to do, but back then it was totally acceptable.”
Despite today’s challenges with pollution and the resulting need to ensure oysters for human consumption come from a reliable source, Wardle is optimistic about the future of Galveston’s most popular bivalve population, although he feels more regulations are necessary.
“Oysters are at their most vulnerable in their first two to three weeks of life, as they mature from fertilized eggs into the larval and veliger larval stages,” he said as he carefully opened an oyster to point out its organs and explain their functions.
“Gradually, the shell, mantle and gills develop, then at about four months of age, they all mature into males first, then — as they get to be around 3 inches in size — they change into females and remain female thereafter.
“On the bright side, not only can oysters live as long as 20 years, but each female is capable of releasing as many as 20 million eggs each season to await fertilization by a generation of younger males. With such odds in their favor, as long as we provide an appropriate firm-based place for them to settle and good water quality, they can go on forever.”