A new species of tardigrade – microscopic animals that resemble a cross between a pig and a bear – has been discovered in 16-million-year-old Dominican amber.
Tardigrades – also known as water bears or moss piglets – are renowned for their hardiness. In 2007, some were sent into orbit and became the first known animals to survive the vacuum of space.
Molecular studies suggest that tardigrades originated about 500 million years ago, but their microscopic size and tendency to rapidly decay after death makes their fossils hard to come by. Until recently, only two fossilised species had been found.
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But that was before sharp-eyed ant researchers detected an interesting speck in an otherwise insect-filled amber specimen mined in the Dominican Republic.
Viewing the speck under a microscope, at the New Jersey Institute of Technology in Newark and his colleagues were surprised and excited to recognise the plump, barrel-like shape of the tardigrade and some of its four pairs of clawed feet.
“In the case of tardigrades, it’s just their extreme sort of ancient nature of the group, coupled with the rarity of the fossils, that makes any physical evidence of their time on Earth really exciting,” says Barden. “They’re like a ghost lineage.”
Barden’s team passed the specimen on to tardigrade experts at Harvard University, where investigated it under transmitted light and confocal laser scanning microscopy.
Mapalo captured remarkable micrometre-level details of the 559-micrometre-long tardigrade and its characteristic claws, which are 20 to 30 times finer than a human hair, he says. He also noted that the animal has distinct differences in its tube-shaped mouth and swallowing structures compared with the two other recognised fossil species – the 78-million-year-old Beorn leggi, detected in Canadian amber in 1964, and the 92-million-year-old Milnesium swolenskyi, identified in amber from New Jersey in 2000.
But Mapalo also found that the new tardigrade has claws that are so similar to those of modern tardigrades that the new species could be classified in the same superfamily, Isohypsibioidea. The research team decided to name it Paradoryphoribius chronocaribbeus based on the Greek word óԴDz (“time”) due to its age and “Caribbean” due to its location.
Amber-embedded tardigrade fossils are probably far more common than researchers realise because they just look like dust to the naked eye, says Mapolo. “We would like to ask people working with amber to just be careful, because they might have a tardigrade in their specimens which could help us tardigradologists to better understand how these [animals] evolved,” he says.
Proceedings of the Royal Society B
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