A new study published in the journal Nature Communications Biology has revealed fascinating insights into the evolutionary history of tardigrades, also known as “water bears”. These microscopic creatures are famous for their ability to withstand extreme conditions such as temperature, pressure, and radiation, thanks to a process called cryptobiosis.
Researchers from the Museum of Comparative Zoology at Harvard University examined two fossils of tardigrades found in ancient amber pebbles in Canada. The fossils, estimated to be 84-71 million years old, were analyzed using high-contrast microscopy to reveal previously unseen details of their claws, leading to a more precise taxonomic classification.
The study, led by Harvard University graduate student Mark Mapalo, identified a new genus and species of tardigrade called Aerobius Dactylus, as well as revising the classification of the previously described species BEORN Leggi. Both fossils were placed in the supra-family Hypsibioidea, prompting a reevaluation of the evolutionary tree of these remarkable organisms.
The findings suggest that cryptobiosis may have emerged in tardigrades during the Carboniferous period, approximately 359-299 million years ago, predating the mass extinction event known as the “great extinction” by about 50 million years. The ability to enter cryptobiosis likely played a crucial role in the survival of tardigrades during this catastrophic event, in which 96% of marine species and 70% of terrestrial life forms went extinct.
Despite being present on Earth for hundreds of millions of years, fossil evidence of tardigrades is extremely rare, with only four known fossils preserved in amber. The discovery of these fossils provides valuable insights into the evolution of tardigrades’ unique survival strategies and may unlock new secrets about their remarkable resilience.
Mapalo hopes that the study will encourage further research into fossil tardigrades, noting that there is still much to learn and discover about these intriguing creatures. The study underscores the importance of understanding the evolutionary history of tardigrades and the role of cryptobiosis in their survival over millions of years.