The tardigrades, also called water bears, are known as the most resistant living beings. Almost indestructible, they are able to survive freezing, dehydration, lethal radiation doses to us, or even the vacuum of space. A new study seems to have hit its weak point.
The work is carried out by the Department of Biology of the University of Copenhagen, Denmark. They explain that resistant microscopic invertebrates may be vulnerable to long-term exposure to rapidly rising temperatures associated with climate change.
We knew that when extreme conditions arise, tardigrades can enter what is known as cryptobiosis, a “reversible ametabolic state” by which the body contracts its body, retracts its legs and reorganizes its internal organs to dry.
This state is capable of allowing the tardigrade to fight environments that lack oxygen, have high levels of toxic concentrations or see extreme temperature changes. However, extremely high temperatures over a long period of time can be with the “Achilles heel” of these living beings, even in their dried state. The more temperatures are maintained, the lower the chances of survival of tardigrades.
The truth is that a 2018 study found that a species of Antarctic tardigrade, Acutuncus antarcticus , could be at risk of extinction due to climate change. Now we have a second species, the Ramazzottius varieornatus , who has demonstrated a similar weakness. According to biologist Ricardo Neves, from the University of Copenhagen in Denmark and author of the study:
The samples used in this study were obtained from the roof gutters of a house located in Nivå, Denmark. We assess the effect of high temperature exposures on active and dried tardigrades, and also investigate the effect of a brief period of acclimatization on active animals.
The results showed that for active tardigrades that were not acclimatized to higher temperatures, the population reached a mortality rate of 50 percent after 24 hours only 37.1 degrees ° C. A brief acclimation period two hours 30 ° C, followed by two hours at 35 ° C, raised this mortality threshold to 37.6 ° C. That is, acclimatization seems to improve the survival rate.
On the other hand, the dried tardigrades could withstand much higher temperatures. A 50 percent mortality rate was observed after 24 hours at 63.1 ° C, and additional experiments revealed that the creatures will die much faster when temperatures are even higher. According to Neves:
From this study we can conclude that active tardigrades are vulnerable to high temperatures, although it seems that these creatures could acclimatize to rising temperatures in their natural habitat. Dried tardigrades are much more resistant and can withstand much higher temperatures than active tardigrades. However, exposure time is clearly a limiting factor that limits your tolerance to high temperatures.
The researchers say that the reason could be because high temperatures can destabilize the proteins that are essential for the cryptobiotic survival of tardigrades. In fact, it seems that extreme heat can alter that state of extreme latency they get, particularly when a tardigrade does not have time to acclimatize to their new environment.
” Global warming is already having harmful effects on habitats around the world and, therefore, it is important to understand how the increase in temperature can affect existing and almost indestructible animals such as tardigrades, ” the researchers conclude the job.