A water flea, hatched from an approximately 700-year-old dormant egg
Scientists successfully hatched tiny aquatic animals from dormant eggs that had been lying on the bottom of a lake for around 700 years. The resurrected water fleas, known scientifically as Daphnia pulicaria, could be the oldest animal eggs to ever to be brought to life. The animals, which scientists also extracted DNA from, serve as a living time capsule. They can be used to study how these species have adapted to their changing environments over time, particularly as a result of human disturbances.
"The chemistry of those lakes has been carefully documented for decades," Carl Zimmer of the New York Times explains, "making it possible to see how changes in pollution levels affected the water fleas." Specifically, researchers looked at the amount of phosphorus in South Center Lake in Minnesota over the last 1,600 years, the age represented by the sediment core that scientists, led by Lawrence Weider from the University of Oklahoma , extracted from the lake in 2009 (the oldest hatched eggs from this core that they were able to revive seem to be around 700 years old).
The concentration of phosphorous remained steady, at low levels, for the first 1,500 years, but began to increase in the mid-1800s as a result of "intensifying agricultural activities," the study found. "That environmental shift coincided with a drastic change in the genes of the water fleas," Zimmer writes. "As phosphorus flooded the lake, a previously rare strain emerged and took over." The researchers found that older Daphina, those that existed before European settlement, were not able to regulate their phosphorous intake the same way as Daphina that were just decades-old. This tells us that Daphina changed how they used phosphorous in response to more of it becoming available, evolution in action. "The new research adds to a growing number of studies indicating that humans are influencing the evolution of wild species," Zimmer writes.