Unveiling Survival Adaptations of Tardigrades Beyond Anhydrobiosis

Aside from the already known anhydrobiosis, which is the ability of some animals to survive without water, and the transformation of tardigrades into tuns, which is their dehydrated forms curled into a ball, it is still a question how they remain insignificantly affected by extreme conditions while they exist in their tun form. How do they hold out against environments that should be more than sufficient to disintegrate or to transfigure their bodies? One theorized answer is the production of trehalose - a simple sugar - that coats them like armor through the process vitrification.

Trehalose prevents the denaturation of protein and preserves moisture when the animals are under stress.

Many lower forms of life, such as shrimp and insects like grasshoppers, bees, locusts, and butterflies that exclude mammals, produce trehalose when they are under stress in order to prevent the denaturation of their proteins. However, trehalose seems insufficient, and Research has proven that many species of tardigrades produce only very little trehalose.

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Instead, they produce specific proteins that interact with their environment to shield them. These proteins and the amounts produced vary depending on the species, making other species tougher than the others. Another fact that seems to violate the laws of life is how tardigrades retain only 0.01% of their metabolism while they are tuns and quickly "resurrect" once hydrated. Their relatives and relationship to other species are also a mystery that can trace their origins and evolutionary pathways once figured out and studied.

Yoshida, et al. (2017) studied and compared the genomics of two tardigrade species, which are the Hypsibius dujardini and the Ramazzottius varieornatus.

To do so, they first cultured the two species, which they bought from Sciento. They fed the animals with Chlorella vulgaris and incubated them at 18°C and 22°C respectively. Soon after, they dried them for a few hours until they reached anhydrobiosis. More than 90% of the samples recovered, and genomic DNA was later on extracted from the remaining samples. DNA purification came soon after and sequencing and mapping commenced. The genes that underwent horizontal gene transfer were determined and analyzed. The genes that react to facilitate anhydrobiosis were also studied and genomic alignment was done to finally establish the relationship of the two species.