What do Voldemort and tardigrade fossils have in common? They’re both almost impossible to kill and even more difficult to find. Until now, that is. A team of NJIT and Harvard University researchers reported the discovery of a new tardigrade fossil －the third to ever be found.
Tardigrades are microscopic eight-legged animals that have been occupying an outsize proportion of science headlines in the last few years. They’re resistant to radiation, have come back to life after freezing, can withstand starvation and are currently used for quantum experiments. For microorganisms, tardigrades are pretty active, too! They dance and move their legs around under the microscope. They’re interesting little animals that can teach us a lot about the extreme conditions under which complex life can survive.
These ‘water bears’ are ubiquitous, observable in marine, freshwater and terrestrial environments. There are over 900 observed species, and the phylum’s history is ancient, stretching back 500 million years. So, why have their fossils been so hard to locate?
“The tardigrade is the tip of the iceberg for the things that we hope to find by studying amber,” commented Dr. Phil Barden, assistant professor of biology and the senior author of the study. Fossilization usually involves sediments replacing the bone of an organism, but the grains are too large to preserve a tardigrade. Therefore, all three tardigrade fossils to date have been found in amber. “They elude most people looking for them because they’re as small as a speck of dust.”
This specimen is the youngest to date and the best-preserved at only 16 million years old; the others found were 78 and 92 million years old. The amber that preserved this tardigrade was found and refined in the Dominican Republic.
“This paper was a really great example of collaboration,” said Barden. Several parties were working on this discovery. Barden trimmed and prepared the fossil in addition to providing context on the amber. Harvard graduate student and tardigrade expert Marc A. Mapalo helped analyze and diagnose the tardigrade along with his advisor Javier Ortega-Hernandez, an assistant professor and paleontologist at Harvard.
The tardigrade was first imaged and then compared to other species that exist today through a statistical analysis and phylogenetic reconstruction－essentially rebuilding its family tree to see where it fits in. After these processes, the matters that the finding addressed include why tardigrade fossils are so rarely seen and why they’re found in amber. Because the fossil was only the third found, it can lead to a better understanding of modern tardigrades and more accurate calibrations for the age of tardigrade lineages.
Another interesting application lies in biogeography. “Because this is such an ancient group, tardigrades can be used to understand how organisms move over the plant over periods of time,” added Barden.
The geological development of the Caribbean, where this fossil was discovered, is not very well understood. Yet by comparing tardigrade species there today with this fossil and any others that can be found, the migration of these animals can be used to understand the development of Caribbean islands.
“There are hypothetical land bridges that would have connected North and/or South America to the Caribbean, but we don’t know for sure that this happened,” Barden explained. “So, these animals are the best way to understand what the geology was like in the past.”
However, many questions remain, including a more complete history of the evolution of this phylum — the group of descendants. As tardigrades have become key to several scientific advancements, this discovery may spur other paleontologists to look more closely at their amber pieces.
“The exciting thing about amber fossils is that you never know what will turn up and what stories it will tell or what questions it will answer,” said Barden. “For us at NJIT, the next steps are to continue collaboration and fieldwork and collect more fossils.”
Dr. Barden’s evolutionary biology lab primarily focuses on ants preserved in amber and uses these, and other data points, to understand how natural patterns formed and predict what will happen next. To learn more about the lab’s work, visit bardenlab.org.
