phylum tardigrada

Phylum Tardigrada : 

Phylum Tardigrada By: Nik Nikolayev http://en.wikipedia.org/wiki/File:Waterbear.jpg

Presentation Overview : 

Presentation Overview Today we’ll be learning about a mysterious yet fascinating creature known as “water bear” or “moss piglet” because of the way it walks. By the end of the presentation, you should hope to be: Acquainted with the phyla by learning about their phylogeny, habitats and food sources Knowledgeable about some characteristics of the various species and what make them so remarkable. Informed about the debate about whether it is truly its own phyla or related to arthropods. Let’s get started!

Slide 3: 

http://upload.wikimedia.org/wikipedia/commons/6/65/Hypsibiusdujardini.jpg

Tardigrades : 

Tardigrades Whoa! What is that thing? It’s a microscopic, water-dwelling animal. They are very difficult to measure, an estimates range between 0.1mm to 1mm in size. They have two pairs of 4 legs on each side of their body, the body has 4 segments (excluding the head; which is a separate segment) and they have 4 to 8 claws on each foot. Tardigrades are currently in their own small yet distinct “subphyla” because they are not very well studied; though, there is some debate as to whether it is actually more closely related to arthropods. Either way, you can think of them as relatives of insects, crustaceans, and some nematodes (worms). http://plpnemweb.ucdavis.edu/NEMAPLEX/images/Tardigrad1.gif

Tardigrades : 

Tardigrades We have discovered two distinct types: Heterotardigrada and Eutardigrada. The Heterotardigrada are known as “armored tardigrada” because they have cuticle dorsal plates while the Eutardigrada do not, and they are known as “naked tardigrada,” and there are many variations in each one of these types. What type are these two? http://www.uni-duesseldorf.de/WWW/MathNat/Zoomorphologie/images/tardi1.jpg http://www.freewebs.com/invertebratezoology/Tardigrada.jpg

Tardigrades : 

Tardigrades There is currently debate regarding its classification because fossil evidence suggests that they are more than likely their own distinct phyla, but this does not eliminate the possibility of common lineage because recent genetic sequencing has suggested that they are more similar to arthropods than we previously thought (1). What do you think the results suggest? We know tardigrades are microscopic, and they live in water-rich environments, but how do they move? What do they eat? Where can they live? Before we answer these questions, let’s take a few minutes to watch some tardigrades in action and get familiarized with what they’re like in motion: http://tardigrades.bio.unc.edu/movies/

Specific Species : 

Specific Species From viewing the videos, you should be able to guess that they don’t have joints in their legs, hence the piggy waddle/bear-like gait!  Most tardigrades are herbivores, consuming microscopic phytoplankton and cyanobacteria. There are some carnivorous species though (2). Tardigrades are born with a full set of adult cells, so instead of relying on cellular division to grow (like humans do), they rely on hypertrophy, which is simply an enlargement of the current cells. http://merducle.timmy.fr/images/tardigrada-noir-blanc.jpg

Species Specifics : 

Species Specifics Their habitats range to some incredible extremes: they can be found anywhere from the top of the Himalayas (3), to 5km under the Antarctic ice sheet (4) and most places in between (5) including hot springs (6). It does not matter where they are on Earth because altitude has no effect on their survivability. Tardigrades have no respiratory organs because they are small enough to allow gaseous vapors to permeate their bodies. Hmm, what else can they resist… ? http://www.ok4me2.net/wordpress/wp-content/uploads/iceberg.jpg http://www.planetfear.com/images/cms/Ian%20Parnell/Himalaya%20Portfolio/Parnell%20Himalayan%20Portfolio%2011.jpg http://shangeothermal.com/images/Tahcharian_Hot_Springs.jpg

Species Specifics : 

Species Specifics This microscopic organism can: Survive when the pressure is as high as 87,020 pounds per square inch (7). Not only that, but they can also survive the vacuum of space and the intense solar radiation for at least ten days (8) and still produce offspring successfully. Survive in temperatures as unbelievably hot as 100*C/212*F (for one full hour, too! (9)), as well as freezing cold temperatures below -22*C/-7*F for several years, two weeks at -180*C/-292*F (10), and more than ten days at -270*C/-454*F during exposure to outer space. Survive around 1,000 times the radiation that would kill a human being (11) – and still reproduce successfully (12). Survive being soaked in 95% ethanol solution (13) as well as in boiling ethanol (14) with nearly 100% survival rates. http://www.wired.com/images_blogs/photos/uncategorized/2008/04/18/solarflare.jpg http://wsmweather.co.uk/wp-content/uploads/2009/06/hot-sun-thermometer.jpg http://www.geekwithlaptop.com/wp-content/gallery/iphone/radiation1.jpg

Species Specifics : 

Species Specifics It should not surprise you that tardigrades are classified as “extremophiles,” rare organisms that exhibit some unbelievably adaptive traits. How is all of this possible? Well, tardigrada are capable of going into a state known as “cryptobiosis” where no measurable metabolic activity occurs. Tardigrades are mostly water, so when faced with extreme conditions they can reduce the amount of water in their bodies from 85% to under 1% and enter what’s known as “ametabolic” states, where cellular activity can be completely stopped for extremely long periods of time. With zero exposure to water, they can survive around ten years in this state, where they are known as “tuns”. Over time, their resistance to these environments increases as water composition decreases… making it much harder to kill them  http://tardigrades.net/img/kumamushi/e-cryptobiosis.gif

Works Cited : 

Works Cited Giribet et al. "First molecular evidence for the existence of a tardigrada + arthropoda clade." Oxford Journals n. pag. Web. 24 Oct 2010. <http://mbe.oxfordjournals.org/content/13/1/76.full.pdf>. Suzuki, Atsushi C.. “Life history of Millnesium tardigradum doyere under a rearing environment.” Department of Biology, Keiko University. Web. 24 Oct 2010. <http://www.bioone.org/doi/pdf/10.2108/zsj.20.49> Beasley et al. “New records of tardigrades from China, with zoogeographical remarks.” Department of Biology, McMurry University. Web. 24 Oct 2010. <http://www.biollett.amu.edu.pl/biollett_43_1_2.pdf> Convey et al. “Exceptional tardigrade-dominated ecosystems in Ellensworth Island, Antarctica” British Antarctica Survey. Web. 24 Oct 2010 doi: 10.1890/04-0684 <http://nora.nerc.ac.uk/1729/> Glime, Janice M.  2007.  Bryophyte Ecology.  Volume 1.  Physiological Ecology. Ebook sponsored by Michigan Technological University and the International Association of Bryologists.   24 Oct 2010 <http://www.bryoecol.mtu.edu/>. Romano, Frank. “On Water Bears”. Jacksonville State University, Department of Biology. 24 Oct 2010. <http://www.jstor.org/pss/3496272> Seki, Kunihiro; Toyashima, Masato. “Preserving tardigrades under pressure.” Department of Biological Science, Kanagwa University. 24 Oct 2010 <http://www.nature.com/nature/journal/v395/n6705/abs/395853a0.html> Jönsson et al. “Tardigrades survive exposure to space in low orbit Earth” Current Biology - 9 September 2008 (Vol. 18, Issue 17, pp. R729-R731). Web. 24 Oct 2010 <http://www.cell.com/current-biology/retrieve/pii/S0960982208008051> Hengherr et al. “High-temperature tolerance in anhydrobiotic tardigrades is limited by glass transition. Universität Stuttgart, Department of Zoology. Web. 24 Oct 2010 http://www.ncbi.nlm.nih.gov/pubmed/19732016 Sømme et al. “Cold tolerance in tardigrada from Dronning Maud Land, Antarctica” Polar Biology Web. 24 Oct 2010 http://www.springerlink.com/content/u54213r144032257/fulltext.pdf Mole, R. H.“The LD50 for uniform low LET irradiation of man” British Journal of Radiology (1984) 57, 355-369 doi: 10.1259/0007-1285-57-677-355 Horikawa et al. “Radiation tolerance in the tardigrade Milnesium tardigradum” International Journal of Radiation Biology 2006, Vol. 82, No. 12 , Pages 843-848 (doi:10.1080/09553000600972956) Web. 24 Oct 2010 <http://informahealthcare.com/doi/abs/10.1080/09553000600972956> Higgins, Robert. “Life History of Macrobiotus Islandicus Richters with notes on other tardigrades from Colorado” Department of Biology, University of Colorodo. Web. 24 Oct 2010 <http://www.jstor.org/pss/3224022> Jönsson et al. “Trehalose in three species of dessication tolerant tardigrades” Department of Genetics, Stockholm University. Web. 24 Oct 2010 <http://www.bentham.org/open/tozj/articles/V003/1TOZJ.pdf>