Harvard Researchers Classify Microorganism Species, Tardigrade

Harvard researchers identified a new fossilized species of tardigrade — known as “water bears” — scientists reported in an Aug. 6 paper in “Communications Biology.”

Researchers used confocal laser microscopy to classify two previously discovered tardigrade fossils, identifying one as a new species. Tardigrades are eight-legged micro-animals believed to have been around for at least 500 million years.

Javier Ortega-Hernández, a Harvard Organismic and Evolutionary Biology professor and one of the study’s authors, said the results are groundbreaking.

“The study represents the most precise estimate for the origins of tardigrades that the data will allow today,” he said.

While Ortega-Hernández said he believes there are hundreds of fossilized tardigrades, only four have ever been found.

The tardigrade fossils examined in the study were first identified in 1964, but were difficult to classify using traditional methods because of their size and the opacity of the amber that encased them.

According to Ortega-Hernández, the size of the new species was “highly problematic” because it was “only a few microns in length.” The study’s use of confocal laser microscopy — which involves shooting a laser beam into a fluorescent sample — allowed researchers to capture more specific anatomical details, leading to the new classification.

“For the type of tardigrades that these are, the claws have basically all the information,” Ortega-Hernández said. “So that is why it was really necessary to obtain these very, very fine morphological details and to make as many comparisons as possible with what we know about tardigrades today.”

Marc A. Mapalo, a Ph.D. candidate in the OEB department and co-author on the study, said he creates songs about breakthroughs in tardigrade research. In 2021, Mapalo published a song online after he classified a new tardigrade fossil in a piece of amber from the Dominican Republic.

Pushpalata Kayastha — a genomics researcher at the University of North Carolina, Chapel Hill who was not involved in the research — said that the breakthrough will provide insight into tardigrades’ unique ability to survive extreme conditions such as desiccation, radiation, and the vacuum of space. This phenomenon is known as cryptobiosis.

“Cryptobiosis didn’t come into existence recently,” Kayastha said. “This is something they’ve had since they have stayed on this Earth, so it will help us understand the mechanism.”

The findings also further analysis of evolutionary divergence from common ancestors. According to Ortega-Hernández, the data from the tardigrades provides fossil evidence for evolutionary events such as the Cambrian explosion, from which many new organisms — including mollusks, arthropods, and vertebrates — emerged.

Moving forward, the researchers hope to examine tardigrade miniaturization.

“We are trying to find the fossil evidence that is going to really be the smoking gun, to show that that is really the case,” he said.