She concedes, though, that many of the specific consequences have yet to be studied. In oysters, as Payton explains, this response could negatively affect their health, possibly making the animals more vulnerable to disease over the long term. For example, the oyster equivalent of a mammal gene that helps make melatonin is usually expressed more at night, but the researchers observed that the gene stayed highly active during the day, disrupting the natural circadian rhythm. ![]() And while oysters have certain genes that typically turn “on” during the day and others that turn on at night, exposure to nighttime light virtually eliminated the difference. In the control tank, oysters were most active in the middle of the day and started to close when the lights went out.īut exposure to artificial light at night caused the oysters in the other four tanks to stay open at inappropriate times, with activity peaking in the early evening. The team fitted half the oysters in each tank with electrodes to determine when the animals opened their shells-something oysters do to feed, breathe, and mate. Tran’s colleague and co-author, the marine scientist Laura Payton, explains that shell movement is really the only oyster behavior that can be observed. The researchers compared these oysters’ behavior with that of their counterparts in a control tank that experienced complete nighttime darkness. In the recent study, Tran and his colleagues put four tanks of oysters in different rooms and exposed each to a different intensity of artificial light at night. Read: Scallops have eyes, and each one builds a beautiful living mirror While other bivalves, such as scallops, have eyelike organs, oysters may use specialized cells on their skin to detect light, though scientists have yet to definitively identify the cells or figure out exactly how they might work. It’s especially remarkable, Tran says, when you remember that oysters don’t have eyes-at least not in the conventional sense. The results of the experiment, which were recently published, found that artificial light at night can disrupt oyster behavior and alter the activity of important genes that keep the animals’ internal clocks ticking.ĭamien Tran, a marine scientist at the Paris-based French National Centre for Scientific Research and one of the study’s authors, was surprised that even the lowest level of nighttime light that the team tested-“below the intensity of the full moon,” he says-was enough to throw off the oysters’ circadian rhythm. The dim glow simulates the light pollution that plagues many marine species-even in natural habitats. Each morning, the lights come up slowly, carefully mimicking the rising sun, but at night the test groups’ rooms never fully darken. ![]() ![]() In several quiet rooms in a marine lab in southwest France, dozens of Pacific oysters sit in glass tanks, quietly living their oyster lives. ![]() This article originally appeared in Hakai Magazine.
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