A new species of ‘indestructible’ water bear has been found fossilised in a chunk of amber dating back 16 million years.
Tardigrades, also known as water bears and moss piglets, have been around for 500 million years and are known for surviving five mass extinction events, the vacuum of space, and even for coming back to life after spending years frozen in the Arctic.
Researchers at the New Jersey Institute of Technology and Harvard University studied the third ever documented fossilised tardigrade, which they found to be an entirely new species.
The tardigrade frozen in time within a Dominican amber chunk is just half a millimetre long and has been identified as a relative of today’s tardigrade.
The specimen dates back to the Miocene period and according to the study is a new genus and species that they named ‘Paradoryphoribius chronocaribbeus’.
They confirmed that it is a member of the modern tardigrade superfamily, Isohypsibioidea.
Phil Barden, the senior author of the study and assistant professor of biology at New Jersey Institute of Technology, said: “The discovery of a fossil tardigrade is truly a once-in-a-generation event.
“What is so remarkable is that tardigrades are a ubiquitous ancient lineage that has seen it all on Earth, from the fall of the dinosaurs to the rise of terrestrial colonisation of plants.
“Yet, they are like a ghost lineage for palaeontologists with almost no fossil record. Finding any tardigrade fossil remains is an exciting moment where we can empirically see their progression through Earth history.”
Marc A Mapalo, a graduate student at Harvard’s Department of Organismic and Evolutionary Biology who contributed to the study, said: “At first glance, this fossil appears similar to modern tardigrades due to its relatively simple external morphology.”
He went on: “However, for the first time, we’ve visualised the internal anatomy of the foregut in a tardigrade fossil and found combinations of characters in this specimen that we don’t see in living organisms now.”
The unique features allowed the researchers to place the tardigrade in a new genus and explore the evolutionary changes that the species has experienced during its multi-million-year existence on our planet.
Water bears are well known for their bizarre appearance and incredible self-preservation capabilities.
They are able to survive extreme conditions by curling into a dehydrated ball and entering a self-induced state of suspended animation known as cryptobiosis in which their metabolism is almost entirely stopped.
Unearthing fossilised water bears is especially complicated because of their tiny size.
Barden said: “In fact, Pdo. chronocaribbeus was originally an inclusion hidden in the corner of an amber piece with three different ant species that our lab had been studying, and it wasn’t spotted for months.
“This particular model of fossilisation helps explain the patchy fossil record.
“Fossil amber with arthropods trapped inside is only known from 230 million years ago to the present … that’s less than half of the history of tardigrades.”
“We are just scratching the surface when it comes to understanding living tardigrade communities, especially in places like the Caribbean where they’ve not been surveyed.”
Prior to this discovery, only two definitive tardigrade fossils had ever been formally studied and both were found in Cretaceous fossil deposits in North America.
Barden said: “This study provides a reminder that, for as little as we may have in the way of tardigrade fossils, we also know very little about the living species on our planet today.”
The researchers hope that their discovery will encourage more people to take closer looks at amber samples which might contain the next piece of the puzzle in the long history of the water bear.
The study was published titled ‘A tardigrade in Dominican amber’ in the Proceedings of the Royal Society B: Biological Sciences on 6th October.
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