Lauren Huey stares at an oyster’s gonads.
Her computer shows a picture of oyster tissue preserved and stained in pink and purple hues. Huey, a Virginia Sea Grant graduate research fellow at the Virginia Institute of Marine Science (VIMS), differentiates the gonads, a thick, dark pink ring of eggs, from the rest of the oyster. She’s tracking changes in gonads of Chesapeake Bay oysters over the past 30 years to investigate their tolerance to a disease that has been plaguing them since the 1980s.
Perkinsus marinus, a parasite that causes a disease called Dermo in oysters, was first found in the Chesapeake Bay in 1949. Its presence intensified in the 1980s, contributing to the oyster’s severe decline. While Dermo still causes mortality in some Chesapeake Bay oysters—and most oysters in the Bay are infected by Dermo—they seem to be recovering from historically low numbers.
This might be because the oysters have become more tolerant to Dermo. To check this hypothesis, Huey is going through an archive of oyster tissue. Since the 1960s, VIMS researchers have collected and preserved cross-sections of oysters from Chesapeake Bay. These samples are housed in rooms of wall-to-wall drawers packed with glass slides, each containing a thin slice of oyster tissue.
This archive enables Huey to look at oyster gonads sampled from the James River from 1988 to the present. Which is why she’s peering so intently at the gonads on her computer screen. The number of eggs a mature female oyster produces indirectly reflects its tolerance to Dermo, because eggs tell scientists about an animal’s energy budget. When an oyster makes more eggs, it suggests the oyster is more tolerant to Dermo—because it’s devoting less energy to fighting off Dermo and can spend it on making more eggs instead.
For every year, Huey must analyze between 15 and 20 oyster samples, which takes a couple of hours. First she inspects every sample under a microscope to count the number of eggs. Then she takes a picture of the slide so she can use a computer program to calculate how much of the oyster overall is taken up by gonads.
“Looking at a single oyster, they’re all sort of the same and it’s kind of tedious,” Huey admits. So far, she’s looked at 307 individual oysters spanning 21 years. (In the process, she’s also listened to 21 audiobooks, and numerous short stories, mostly by Edgar Allen Poe and Ray Bradbury.) “But when you put them all together, it tells this story.”
