Water Fleas Adapt to Climate Change Using Genetics

Climate change is forcing all sorts of species to change their ways. For example, certain tropical lizards have swiftly learned to deal with the heat, shape-shifting plants are physically changing their appearance, and crabs are going into survival mode. Now, new research shows that when it comes to water fleas, they are using genetics to adapt to climate change.

The water flea Daphnia, a zooplankton organism typically found in shallow ponds and lakes, normally reproduces asexually by cloning itself. But in difficult living conditions - during food shortages or heat waves, for instance - these fleas switch to a different type of procreation: they mate and lay dormant eggs. These eggs are in fact encapsulated embryos that are resistant to harsh conditions. Remarkably, a dormant egg can remain in the sediment of a pond for dozens of years and still be able to hatch.

So biologists from KU Leuven, Belgium, compared "resurrected" water fleas - hatched from 40-year-old eggs - with more recent specimens to find out how they evolved amidst a changing climate.

"When water fleas reproduce asexually, their offspring is genetically identical to the mother. But when they mate, this results in genetic variation. The genetically fittest water fleas - the ones that are best adapted to the environment - survive and lay dormant eggs," biologist Aurora Geerts explained in a statement.

"When we hatch the dormant eggs of water fleas from the past and compare them with the contemporary population," she continued, "we can reconstruct the evolutionary changes that occurred in that population and examine how they have adapted to the rising temperature of the water in which they live."

The biologists decided to use dormant eggs from Felbrigg Hall, a shallow lake in England, where both the water flea population and changes in lake temperature are well-documented. It's also a site that has seen some serious climate changes. For example, over a period of 40 years the average temperature near Felbrigg Hall has risen by 1.15 degrees Celsius, and the number of heat waves has tripled.

"This causes stress to animals that live in such shallow water," Geerts said.