Study

Facts and fiction about long-term survival in tardigrades

Jönsson, K. I.; Bertolani, R.

Journal of Zoology, 2001

Peer-reviewednarrative reviewlaboratory

What they did

A critical examination of the published claims for extremely long survival in the desiccated state, tracing each to its original report and assessing the evidence behind it.

Studied in: Tardigrada
Sample size: critical review of long-term anhydrobiosis reports

The frequently cited figure of survival for over a century traces to a single unreliable observation of movement in a museum specimen, which was not a demonstration of revival. Well-documented survival in the desiccated state is on the order of years rather than decades, with a small number of credible reports approaching a decade.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Long-term anhydrobiotic survival in tardigrades is real but has been substantially overstated in secondary literature, and the extreme figures do not survive examination.

How NatureHQ reads it

A paper whose title says what it does, and it is unusually valuable because the claim it corrects is still repeated constantly. "Tardigrades can survive dry for a hundred years" descends from somebody seeing a leg twitch in a museum specimen — which is not revival, and was never reported as revival. Years, credibly. Decades, occasionally and with better documentation since. A century, no. The interesting question underneath is that survival declines with time in the tun, which means the state is not suspended animation so much as very slow decay.

Limitations

A review of others' reports, constrained by how those reports were documented.
Later work has extended credible survival times somewhat, so the specific figures have moved.
Species differ substantially, and much of the older literature does not identify species reliably.