Tardigrades Discussion Practice

Discussion 5 Guide NAME: Wesley Beals Directions:    Read the article BEFORE answering the questions. Each question will refer to the indicated aticle This assignment should be a “deep dive” into the material. It will take time to do. Møbjerg and Neves, 2021: 1. What two strategies do organism do to cope with harsh conditions? Organisms have two strategies to deal with harsh conditions. They can either 1) stay active metabolically and help adapt to the changing environment by changing physiologically or 2) enter a state of metabolic suppression in which the metabolism enters a reversible standstill until conditions improve enough to survive in the environment. 2. Describe the five survival strategies that tardigrades use to survive. The five survival strategies are Anhydrobiosis, osmobiosis, cryobiosis, anoxybiosis, and chemobiosis. In anhydrobiosis, osmobiosis, and possibly chemobiosis, there is the formation of a tun in which the tardigrade pulls in its legs and rolls up into a ball until conditions all in response different things such as water loss, too much osmotic pressure, or presence of environmental toxins. The tun appears as a defense for it to survive. In anoxybiosis, the body becomes elongated and turgid and in crypbopsis, the body of the tardigrade partially contracts in response while shutting down a little so that it can survive. 3. What stressors trigger tun formation in tardigrades? The stressors that trigger tun formation are a lack of water in the environment, an increase in osmotic pressure, or an increase in environmental toxins that can each cause harm to the tardigrades. 4. Why are active tardigrades not as tolerant to heat? What evidence supports this? It has been suggested that tardigrades are not tolerant to heat because too much heat, denatures proteins and other essential macromolecules necessary for them to function. Even in the tun state there is a limit to the amount of heat that tardigrades can be exposed to over a certain period before it causes damage and ultimately dies. Through testing, scientists have found that for some species that range in which tardigrades cannot survive is about 29-37 degrees Celsius. In tun it can go as high as 83 degrees in an hour. 5. How do Tardigrades stabilized their bodies on a physiological level? And on a cellular level? Because the tardigrades lack an internal respiratory or circulatory system, they stabilize their internal environment through fluid to transport solutes and keep their shape. They regulate the constant influx of water through excess water that can be expelled through osmotic means. When forming the tun the muscle protein filaments that lock into place when the tun is formed as well as other cytoskeleton things help with stabilizing the filaments. 6. Why are physiological and molecular studies been difficult with tardigrades? The study of tardigrades is difficult for a couple of reasons such as they are small, have a small amount of DNA, or small amount of RNA. With each of these things, scientists have studied many other things to better understand tardigrades such as genomics, proteomics, and transcriptomics. 7. Describe the cell transport mechanisms that tardigrades have. Discussion 5 Guide They have a couple of transport mechanisms. They have membrane pumps, numerous solute carriers, ion channels, and aquaporins. With each there are a few specifically mentioned in the article such as, H ion pumps as well as Na/ K ion pumps which provides the driving force of the transport of organic waste out of the cells such as nitrogen waste through carrier proteins or channels. Each of these are similar among different species. 8. Why would scientists use transcriptomic data to study tardigrade cell physiology? Scientists use all this transcriptomic data because of the small amount of DNA and RNA that is found in tardigrades which can make it difficult to determine structures in the cell. Despite the fact that not much is known about the cell’s physiology, looking through the transcriptomic data has given rise to many discoveries and helped us better understand tardigrades. 9. What bioprotectants do tardigrades use? Describe the three main types. One of the main bioprotectants is the disaccharide, such as sucrose and trehalose. Each of these helps act as molecular stabilizers that replace water and protect different cell structures during extreme water loss. Another protein is the different heat shock proteins that help stabilize structures in the cell for periods of time in hot conditions and even repair proteins damaged by the heat. The last one listed is lots of antioxidant defense that help protect the DNA and the structures associated with the DNA and even repair in in the event of hydroxyl radicals which helps in survival. delBarco-Trillo, 2019: 10. What is the hypothesis of this review? The two questions that the author asked and attempted to answer were first, is there a consistent decrease in tardigrade populations in urban areas versus non-urban areas and second, if the similarities in cities tardigrade populations can be explained by distance between the cities. With each of these questions, the author attempts to shed light on urban adaptation and provide more avenues for study. 11. What was the prediction of this review? The author made the prediction that there is a decline in the number of urban tardigrade species as compared to rural tardigrades and that each of these species was different than the adjoining rural tardigrades. With each of these predictions, there is the underlying question of why is it that these populations are declining and that is not something that is really predicted by the author only summarizing speculation that has been given by others. 12. What were the findings of the reviewed studies? During the review of the different studies, it was found that there was about a 50% decrease in tardigrade diversity in every single city as compared to rural areas. This shows that the prediction that tardigrades in the cities are generally less diverse than other populations when you control for other variables in sampling and places found. In addition, there was a positive correlation between the distance and diversity of tardigrades which means that cities that are closer together generally have similar species of tardigrades 13. What possible explanations are there for these findings? According to the article, possible reasons for the decrease in tardigrade diversity could be linked to many different factors and it is difficult to determine which is entirely accurate. The Discussion 5 Guide common answers to the decline of each of these species could be the fact that compared to nature, cities have a few different factors such as higher pollution, lower pH, lower humidity. Each of these factors make it difficult for certain species to survive while others are more likely to adapt to the changes. Another factor is the fact that there could be sampling errors that tainted the results in some way. In addition, for the similarity in species between close cities, the possible explanation is that to further expand the range of a species, there needs to be already established territory around the city and with that it helps tardigrades enter the city. 14. What advantages are there to using tardigrades as study organisms? Tardigrades are intriguing study organisms because of many factors. One of the major factors is the fact that they are hard to kill and survive in really challenging environments such as no water, extreme heat, extreme cold, high radiation, and many more. In addition, they are easy to sample and transport across countries without much challenge and with each of these things they can provide keen insight into the challenges but also the successes in colonizing an urban environment. 15. How did the author select articles to review? What criteria were used to exclude articles? The author did some initial searches in the Web of Science and put in the terms of Tardigrade, water bear, city, and urban and the author found 73 articles initially. The author reviewed each of the articles to see if the article reported the number of tardigrade species in the urban setting. Most did not because most only included the rural samples and not any urban ones. Another excluding criterion was if the article did not list the different species found. After sifting through the articles, the author was left with 10 and with these, he did his analysis. 16. What critiques of the methods did delBarco-Trillo list? How would these different methods impact the results? The one main critique that is listed is the fact that number of studies about the subject are low as well as sample sizes being small which make it challenging to make accurate estimates of tardigrade species across many cities. The author noted that with sample sizes being small it makes it difficult to find out the effect of variables on the many different areas of the studies. In addition, the statically small sample makes it difficult to make claims about why these the results are the way they are. In addition to small sample sizes, the author noted that sampling effort was lacking in each of the studies. He speculated that there is a high possibility that there could be small populations that with a not through sampling could prevent those populations from being counted dragging down the results some. In addition, tardigrades in urban areas could have lived in different areas compared to rural tardigrades which could also have lowered the number of species represented in the city as compared to the rural areas. 17. Describe the statistical tests that delBarco-Trillo used. The author reported all the results using mean + standard deviation and then used many different tests to help determine the usefulness of and the statical significance of the data that he found. The paired t test was used to measure difference in tardigrade richness by either looking at the number as a whole or the number of species divided by samples analyzed. Mantel tests were used to determine the similarities between tardigrade species and the distance between cities looked at. Lower distance values meant more similar species. 18. What did this review conclude about urbanization on tardigrade species richness? Discussion 5 Guide This review concluded that despite the small sample size, the results were consistent enough to show a pattern of a clear decrease in the tardigrade species richness in urban areas. With this, the author then gave many possible reasons for the decrease and those are listed above. The author noted that close cities also share similar populations of tardigrades and with those things it show that there is some effect with the urbanization of some cities. 19. What eusynanthropic species does the author list? Other animal species that the author lists are the pigeons, Norway rat, moss or ferns. All of these besides the tardigrade species that are there in the cites. 20. Describe the future studies delBarco-Trillo suggests be undertaken to further investigate this topic. The author describes and says that one of the main things that could be studied further is the morphological and genetic adaptation that allow tardigrades to survive in the urban environment. Along with that is the study into how these species adapt to different levels of urbanization and more specific collection techniques to get a better understanding of the types of tardigrades that live in the cities.