Recognizing a Tardigrade’s DNA for Human Evolution
Principles of Ecology
Florida Atlantic University
What would it be like to have superpowers or withstanding UV radiation that is lethal to humans? Tardigrades, which are more commonly known as water bears, come from the Panarthropoda animal clade, that combine with other phyla such as Arthropoda and Onychophora (Stone, 2014). These species are distinguished for their tolerance in extreme conditions a human being cannot survive. Water bears are able to survive in conditions of being without water, air, and in space. Also, they can even repair their own DNA. Yet for these species, it is an aspect they have evolved into, making them the unique species they are today. There are three important details of tardigrades to note, because they will help scientists evolve those same traits in humans. Comprehending tardigrades responses to changes in extreme conditions and how it helps them survive, could help humans survive similar conditions. Also, understanding a water bear’s DNA and how it repairs itself to bring a tardigrade back to a normal condition is also important to know. Furthermore, acknowledging the different types of DNA used in their genomes to help them survive is considered as well in this research. Thus, isolating tardigrade genes that can help them survive in extreme conditions could help humans also survive or adapt to inhabitable conditions as well.
Tardigrades have different characteristics or states that have been recognizable in the range of 250 years (Schill, 2010, pg. 856). Water bears enter a ‘cryptobiotic’ state which allows their metabolic activity to come to a halt, and has their body go through different morphological changes. These morphological changes range from anhydrobiosis (dehydration), cryobiosis (extremely low temperatures), anoxybiosis (lack of oxygen), and osmobiosis (high salt concentrations) (Bingemer, 2016, pg. 857). Their freezing point for tardigrades range from -22 to -180 degrees C on the Celsius scale, (depending on their water concentration in their bodies) and survive a lethal dose of 50% (LD50) of UV radiation (Stone, 2014). Scientists have also discovered how these creatures can maintain life support in outer space. On a space mission, (BIOPAN 6/Foton-M3 mission in 2007) tardigrades along with nematodes and rotifers, were sent into low earth orbit and were exposed to space vacuum along with space radiation (Acta Physiologica, 2011, pg. 414). Out of the different tardigrade species only the M. tardigradum was known to be the most resistant along with its embryos in the trenches of space (Acta Physiologica, 2011, pg. 414). Furthermore, of their unique adaptations, there are other traits that bewilder our minds and have scientists wanting to know more, and that is desiccation. Desiccation is the state of being without water or extremely dry. Not all tardigrades, but certain species dry up and come back to survival after 20 years such as the Echi-niscus testudo (Acta Physiologica, 2011, pg. 414). Tardigrades are the unique species that are evolving as the years go by and knowing their adaptations are important keys to notate for the human evolution.
Along with surviving these extreme conditions, there is another aspect of tardigrades and that is they can repair their own DNA. Water bears repair their DNA after the extreme conditions and morphological changes their bodies go through. When certain tardigrades were exposed to an experiment of UV radiation there was a final test to go through. They were cultured in an area that exposed them to different light exposures. One was placed in complete darkness and the other was placed in a more well-lit environment. The different environments in which they were placed was to acknowledge the differences of their DNA to see if it is light dependent upon repair or not (Horikawa, 2013, pg. 9). After 18 hours there was an escalation of the phrA gene, which inferred to be a gene used for DNA repair. In addition, there was no difference in dark or well-lit conditions when it came to the repair of DNA concluding light did not make an impact into their repair (Horikawa, 2013, pg. 9). In addition to restoring their DNA they are able to transfer genes from other species into their own genome sequence, which is known as horizontal gene transfer (HGT) (Boothby, 2015, pg. 15,976). In a study conducted by Boothby, there was a confirmation of physical linkage with plants, fungi, and Archaea. The foreign genes in tardigrades have become the adaptation that have supplemented, expanded, and replaced the genes of this phyla within their own genome sequence (Boothby, 2015, pg. 15,976).
This is just one of the few astonishments found in the tardigrade, and scientists come to conclude how important it is to understand their science and DNA to use towards human evolution. There were some Japanese scientists that saw various genes that appeared to help for repair in certain areas. One example was a tardigrade known as R. varieornatus, that when it was exposed to extreme conditions four gene copies were present known as MRE11, which helped to repair the breakage of a double-strand DNA (R. S. Harikumar, 2017, pg. 903). Besides having different types of genes present in their DNA upon repair, there were also other genes that seemed to be less of or missing completely. The gene is known as ß-oxidation (R. S. Harikumar, 2017, pg. 903). The part behind this gene missing can give an explanation to why they are preserved in better forms in morphological changes. When ß-oxidation is not present, it gives the cellular anatomy of tardigrades a greater sustainability when preserving themselves through any changes such as desiccation (R. S. Harikumar, 2017, pg. 903).
There is plenty more research that can be conducted to explore the potential connection between tardigrades’ DNA and evolution in human beings. This shows how tardigrades have become a unique species in our science books and help us understand the world around us. One day applying HGT into our human development can create a better tomorrow for humans. Thus, concluding, if humans were to understand tardigrades and applying it to our evolution it can make the human race more likely to survive the ever-changing Earth environment.
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Bingemer, J., Hohberg, K., ; Schill, R. O. (2016). First detailed observations on tardigrade mating behaviour and some aspects of the life history of Isohypsibius dastychi Pilato, Bertolani ; Binda 1982 (Tardigrada, Isohypsibiidae). Zoological Journal Of The Linnean Society, 178(4), 856-862. doi:10.1111/zoj.12435
Boothby, T. C. (2015, December 29). Evidence for extensive horizontal gene transfer from the draft genome of a tardigrade
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Horikawa, D. D. (2013). Analysis of DNA Repair and Protection in the Tardigrade Ramazzottius varieornatus and Hypsibius dujardini after Exposure to UVC Radiation.
Møbjerg, N., Halberg, K. A., Jørgensen, A., Persson, M., Ramløv, H., ; Kristensen, R. M. (2011). Survival in extreme environments – on the current knowledge of adaptations in tardigrades. Acta Physiologica, 202(3), 409-420.
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