Ancient tardigrades in amber reveal secrets of their 150-million-year evolution

Scientists have uncovered new details about ancient tardigrades preserved in amber. Using advanced imaging techniques, researchers examined four rare specimens, some dating back nearly 150 million years. The findings shed light on the evolutionary history of these resilient microscopic creatures. Tardigrades, often called water bears, first appeared over 541 million years ago, long before the Cambrian period. Their ability to survive extreme conditions, known as cryptobiosis, may have developed around 420 million years ago.

Four tardigrade specimens were found trapped in amber, but only a few have been studied closely. Researchers used confocal fluorescence microscopy to analyse two species: Beorn leggi and Aerobius dactylus. The latter was identified for the first time.

The study revealed key differences in their anatomy. Aerobius dactylus has noticeably longer claws on its rear legs, suggesting a unique evolutionary path for these limbs. Both species share claw features with the Hypsibioidea superfamily, hinting at a common ancestor.

Genetic evidence also shows that heterotardigrades and eutardigrades split into separate groups around 500 million years ago. This divergence helps explain the variety of tardigrade species seen today. The research provides clearer insights into tardigrade evolution, from their ancient origins to their survival strategies. By studying well-preserved amber specimens, scientists have pieced together how these creatures adapted over hundreds of millions of years. The findings also highlight the importance of advanced imaging in uncovering details from fossilised remains.