Researchers have made groundbreaking discoveries about ancient and extinct species of tardigrades, also known as “water bears,” thanks to high-powered microscopy tools. The findings shed new light on the evolution of these incredibly resilient creatures.
Tardigrades are one of the oldest and most enduring species on Earth, with some experts tracing their earliest ancestors back 500 million years to the Cambrian Period. Today’s tardigrade species likely evolved between 155-66 million years ago alongside dinosaurs during the Cretaceous Era.
What sets water bears apart is their ability to enter cryptobiosis, a state of suspended animation where they can survive extreme conditions like outer space, boiling hot volcanic vents, and freezing cold temperatures. This remarkable adaptation allows them to withstand radiation-laden environments, making them one of the most resilient species on the planet.
Despite their impressive survival skills, scientists have long wondered how and when water bears evolved to be so tough. To investigate this question, researchers from Harvard University’s Museum of Comparative Zoology studied 72-83 million-year-old amber containing two ancient tardigrade fossils.
Using advanced microscopy techniques, the team created high-definition composite images of the fossilized tardigrades, revealing previously unknown details about their physical characteristics. By comparing these ancient species with modern water bears, researchers were able to determine that at least two separate groups of water bears evolved cryptobiosis at distant points in the past.
The findings also confirmed that Beorn leggi and Aerobius dactylus, two extinct species of tardigrades, belong to the same superfamily group. This critical fossil calibration point provides new insights into the origins of water bears and their remarkable resilience.
While only four tardigrade fossils have been discovered, researchers are optimistic that future findings will shed even more light on the evolutionary journey of these incredible creatures.
Source: https://www.popsci.com/science/extinct-tardigrade-pictures/